- 28 Oct, 2021 22 commits
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Kirill Smelkov authored
In 959ae2d0 (lib/zodb: Add patch to ZODB.Connection to support callback on connection DB view change) we added patch for ZODB.Connection to support callback when database view of the connection changes. At that time the patch was working for ZODB5 and ZODB4 was TODO. Let's add support for ZODB4 (both ZODB4 and ZODB4-wc2) now. As a reminder: ZBigFile + WCFS client integration will use this callback to keep WCFS connection in sync with ZODB connection. Preliminary history: kirr/wendelin.core@533a4cfa X onResyncCallback for ZODB4
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Kirill Smelkov authored
This patch logically continues previous change `bigfile/virtmem: Introduce "mmap overlay" mode` and exposes mmap-overlay functionality to Python: if PyBigFile backend provides .blkmmapper PyCapsule the mmap-related methods will be extracted from it and passed on through to virtmem - see _bigfile.h for details. ZBigFile will use this to hook into using WCFS.
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Kirill Smelkov authored
with the intention to later use WCFS through it. Before this patch virtmem had only one mode: a BigFile backend was providing loadblk and storeblk methods, and on every block access loadblk was called to load block data into allocated RAM page. However with WCFS virtmem won't be needed to do anything to load data - because loading from head/bigfile/f mmaped through OS will be handled by OS directly. Thus for wcfs, that leaves virtmem only to handle dirtying and writeout. -> Introduce "mmap overlay" mode into virtmem to handle WCFS-like BigFile backends - that can provide read-only base layer suitable for mmapping. This patch is organized as follows: - fileh_open is added flags argument to indicate which mode to use for opened fileh. BigFileH is added .mmap_overlay bitfield correspondingly. (virtmem.h) - struct bigfile_ops is extended with 3 optional methods that a BigFile backend might provide to support mmap-overlay mode: * mmap_setup_read, * remmap_blk_read, and * munmap (see file.h changes for documentation of this new interface) - if opened with MMAP_OVERLAY flag, virtmem is using those methods to organize VMA views backed by read-only base mmap layer and writeout for such VMAs (virtmem.c) - a test is added to exercise MMAP_OVERLAY virtmem mode (test_virtmem.c) - everything else, including bigfile.py, is switched to use DONT_MMAP_OVERLAY unconditionally for now. In internal comments inside virtmem new mode is interchangeable called "mmap overlay" and "wcfs", even though wcfs is not hooked to be used mmap-overlaying yet. Some preliminary history: kirr/wendelin.core@fb6932a2 X Split PAGE_LOADED -> PAGE_LOADED, PAGE_LOADED_FOR_WRITE kirr/wendelin.core@4a20a573 X Settled on what should happen after writeout for wcfs case kirr/wendelin.core@f084ff9b X Transition to all VMA under 1 fileh to be either all based on wcfs or all based on !wcfs
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Kirill Smelkov authored
This patch follows-up on previous patch, that added server-side part of isolation protocol handling, and adds client package that takes care about WCFS isolation protocol details and provides to clients simple interface to isolated view of bigfile data on WCFS similar to regular files: given a particular revision of database @at, it provides synthetic read-only bigfile memory mappings with data corresponding to @at state, but using /head/bigfile/* most of the time to build and maintain the mappings. The patch is organized as follows: - wcfs.h and wcfs.cpp brings in usage documentation, internal overview and the main part of the implementation. - wcfs/client/client_test.py is tests. - The rest of the changes in wcfs/client/ are to support the implementation and tests. Quoting package documentation for the reference: ---- 8< ---- Package wcfs provides WCFS client. This client package takes care about WCFS isolation protocol details and provides to clients simple interface to isolated view of bigfile data on WCFS similar to regular files: given a particular revision of database @at, it provides synthetic read-only bigfile memory mappings with data corresponding to @at state, but using /head/bigfile/* most of the time to build and maintain the mappings. For its data a mapping to bigfile X mostly reuses kernel cache for /head/bigfile/X with amount of data not associated with kernel cache for /head/bigfile/X being proportional to δ(bigfile/X, at..head). In the usual case where many client workers simultaneously serve requests, their database views are a bit outdated, but close to head, which means that in practice the kernel cache for /head/bigfile/* is being used almost 100% of the time. A mapping for bigfile X@at is built from OS-level memory mappings of on-WCFS files as follows: ___ /@revA/bigfile/X __ /@revB/bigfile/X _ /@revC/bigfile/X + ... ─── ───── ────────────────────────── ───── /head/bigfile/X where @revR mmaps are being dynamically added/removed by this client package to maintain X@at data view according to WCFS isolation protocol(*). API overview - `WCFS` represents filesystem-level connection to wcfs server. - `Conn` represents logical connection that provides view of data on wcfs filesystem as of particular database state. - `FileH` represent isolated file view under Conn. - `Mapping` represents one memory mapping of FileH. A path from WCFS to Mapping is as follows: WCFS.connect(at) -> Conn Conn.open(foid) -> FileH FileH.mmap([blk_start +blk_len)) -> Mapping A connection can be resynced to another database view via Conn.resync(at'). Documentation for classes provides more thorough overview and API details. -------- (*) see wcfs.go documentation for WCFS isolation protocol overview and details. . Wcfs client organization ~~~~~~~~~~~~~~~~~~~~~~~~ Wcfs client provides to its users isolated bigfile views backed by data on WCFS filesystem. In the absence of Isolation property, wcfs client would reduce to just directly using OS-level file wcfs/head/f for a bigfile f. On the other hand there is a simple, but inefficient, way to support isolation: for @at database view of bigfile f - directly use OS-level file wcfs/@at/f. The latter works, but is very inefficient because OS-cache for f data is not shared in between two connections with @at1 and @at2 views. The cache is also lost when connection view of the database is resynced on transaction boundary. To support isolation efficiently, wcfs client uses wcfs/head/f most of the time, but injects wcfs/@revX/f parts into mappings to maintain f@at view driven by pin messages that wcfs server sends to client in accordance to WCFS isolation protocol(*). Wcfs server sends pin messages synchronously triggered by access to mmaped memory. That means that a client thread, that is accessing wcfs/head/f mmap, is completely blocked while wcfs server sends pins and waits to receive acks from all clients. In other words on-client handling of pins has to be done in separate thread, because wcfs server can also send pins to client that triggered the access. Wcfs client implements pins handling in so-called "pinner" thread(+). The pinner thread receives pin requests from wcfs server via watchlink handle opened through wcfs/head/watch. For every pin request the pinner finds corresponding Mappings and injects wcfs/@revX/f parts via Mapping._remmapblk appropriately. The same watchlink handle is used to send client-originated requests to wcfs server. The requests are sent to tell wcfs that client wants to observe a particular bigfile as of particular revision, or to stop watching it. Such requests originate from regular client threads - not pinner - via entry points like Conn.open, Conn.resync and FileH.close. Every FileH maintains fileh._pinned {} with currently pinned blk -> rev. This dict is updated by pinner driven by pin messages, and is used when new fileh Mapping is created (FileH.mmap). In wendelin.core a bigfile has semantic that it is infinite in size and reads as all zeros beyond region initialized with data. Memory-mapping of OS-level files can also go beyond file size, however accessing memory corresponding to file region after file.size triggers SIGBUS. To preserve wendelin.core semantic wcfs client mmaps-in zeros for Mapping regions after wcfs/head/f.size. For simplicity it is assumed that bigfiles only grow and never shrink. It is indeed currently so, but will have to be revisited if/when wendelin.core adds bigfile truncation. Wcfs client restats wcfs/head/f at every transaction boundary (Conn.resync) and remembers f.size in FileH._headfsize for use during one transaction(%). -------- (*) see wcfs.go documentation for WCFS isolation protocol overview and details. (+) currently, for simplicity, there is one pinner thread for each connection. In the future, for efficiency, it might be reworked to be one pinner thread that serves all connections simultaneously. (%) see _headWait comments on how this has to be reworked. Wcfs client locking organization Wcfs client needs to synchronize regular user threads vs each other and vs pinner. A major lock Conn.atMu protects updates to changes to Conn's view of the database. Whenever atMu.W is taken - Conn.at is changing (Conn.resync), and contrary whenever atMu.R is taken - Conn.at is stable (roughly speaking Conn.resync is not running). Similarly to wcfs.go(*) several locks that protect internal data structures are minor to Conn.atMu - they need to be taken only under atMu.R (to synchronize e.g. multiple fileh open running simultaneously), but do not need to be taken at all if atMu.W is taken. In data structures such locks are noted as follows sync::Mutex xMu; // atMu.W | atMu.R + xMu After atMu, Conn.filehMu protects registry of opened file handles (Conn._filehTab), and FileH.mmapMu protects registry of created Mappings (FileH.mmaps) and FileH.pinned. Several locks are RWMutex instead of just Mutex not only to allow more concurrency, but, in the first place for correctness: pinner thread being core element in handling WCFS isolation protocol, is effectively invoked synchronously from other threads via messages coming through wcfs server. For example Conn.resync sends watch request to wcfs server and waits for the answer. Wcfs server, in turn, might send corresponding pin messages to the pinner and _wait_ for the answer before answering to resync: - - - - - - | .···|·····. ----> = request pinner <------.↓ <···· = response | | wcfs resync -------^↓ | `····|····· - - - - - - client process This creates the necessity to use RWMutex for locks that pinner and other parts of the code could be using at the same time in synchronous scenarios similar to the above. This locks are: - Conn.atMu - Conn.filehMu Note that FileH.mmapMu is regular - not RW - mutex, since nothing in wcfs client calls into wcfs server via watchlink with mmapMu held. The ordering of locks is: Conn.atMu > Conn.filehMu > FileH.mmapMu The pinner takes the following locks: - wconn.atMu.R - wconn.filehMu.R - fileh.mmapMu (to read .mmaps + write .pinned) (*) see "Wcfs locking organization" in wcfs.go Handling of fork When a process calls fork, OS copies its memory and creates child process with only 1 thread. That child inherits file descriptors and memory mappings from parent. To correctly continue using Conn, FileH and Mappings, the child must recreate pinner thread and reconnect to wcfs via reopened watchlink. The reason here is that without reconnection - by using watchlink file descriptor inherited from parent - the child would interfere into parent-wcfs exchange and neither parent nor child could continue normal protocol communication with WCFS. For simplicity, since fork is seldomly used for things besides followup exec, wcfs client currently takes straightforward approach by disabling mappings and detaching from WCFS server in the child right after fork. This ensures that there is no interference into parent-wcfs exchange should child decide not to exec and to continue running in the forked thread. Without this protection the interference might come even automatically via e.g. Python GC -> PyFileH.__del__ -> FileH.close -> message to WCFS. ---------------------------------------- Some preliminary history: kirr/wendelin.core@a8fa9178 X wcfs: move client tests into client/ kirr/wendelin.core@990afac1 X wcfs/client: Package overview (draft) kirr/wendelin.core@3f83469c X wcfs: client: Handle fork kirr/wendelin.core@0ed6b8b6 fixup! X wcfs: client: Handle fork kirr/wendelin.core@24378c46 X wcfs: client: Provide Conn.at()
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Kirill Smelkov authored
Via custom isolation protocol that both server and clients must cooperatively follow. This is the core change that enables file cache to be practically shared while each client can still be provided with isolated view of the database. This patch brings only server changes, tests + the minimum client bits to support the tests. The client library, that will implement isolation protocol on client side, will come next. This patch is organized as follows: - wcfs.go brings in description of the protocol, overview of how server implements that protocol and the implementation itself. See also notes.txt - wcfs_test.py brings in tests for server implementation. tWCFS._abort_ontimeout had to be moved into nogil mode into wcfs_test.pyx to avoid deadlock on the GIL (see comments in wcfs_test.pyx for details). - files added in wcfs/client/ are needed to provide client-side implementation of WatchLink - the message exchange protocol over opened head/watch file - for tests. Client-side watchlink implementation lives in wcfs/client/wcfs_watchlink.{h,cpp}. The other additions in wcfs/client/ are to support that and to expose the WatchLink to Python. Client-side bits are done right in C++ because upcoming WCFS client library will be implemented in C++ to work in nogil mode in order to avoid deadlock on the GIL because client-side pinner thread might be woken-up synchronously by WCFS server at any moment, including when another client thread already holds the GIL and is paused by WCFS. Some preliminary history: kirr/wendelin.core@9b4a42a3 X invalidation design draftly settled kirr/wendelin.core@27d91d47 X δFtail settled kirr/wendelin.core@c27c1940 X mmap over under pagefault to this mmapping works kirr/wendelin.core@d36b171f X ptrace when client is under pagefault or syscall won't work kirr/wendelin.core@c1f5bb19 X notes on why lazy-invalidate approach was taken kirr/wendelin.core@4fbdd270 X Proof that that it is possible to change mmapping while under pagefault to it kirr/wendelin.core@33e0dfce X ΔTail draftly done kirr/wendelin.core@12628943 X make sure "bye" is always processed immediately - even if a handleWatch is currently blocked kirr/wendelin.core@af0a64cb X test for "bye" canceling blocked handlers kirr/wendelin.core@996dc6a8 X Fix race in test kirr/wendelin.core@43915fe9 X wcfs: Don't forbid simultaneous watch requests kirr/wendelin.core@941dc54b X wcfs: threading.Lock -> sync.Mutex kirr/wendelin.core@d75b2304 X wcfs: Move _abort_ontimeout to pyx/nogil kirr/wendelin.core@79234659 X Notes on why eagier invalidation was rejected kirr/wendelin.core@f05271b1 X Test that sysread(/head/watch) can be interrupted kirr/wendelin.core@5ba816da X restore test_wcfs_watch_robust after f05271b1. kirr/wendelin.core@4bd88564 X "Invalidation protocol" -> "Isolation protocol" kirr/wendelin.core@f7b54ca4 X avoid fmt::vsprintf (now compils again with latest pygolang@master) kirr/wendelin.core@0a8fcd9d X wcfs/client: Move EOF -> pygolang kirr/wendelin.core@153e02e6 X test_wcfs_watch_setup and test_wcfs_watch_setup_ahead work again kirr/wendelin.core@17f98edc X wcfs: client: os: Factor syserr -> string into _sysErrString kirr/wendelin.core@7b0c301c X wcfs: tests: Fix tFile.assertBlk not to segfault on a test failure kirr/wendelin.core@b74dda09 X Start switching Track from Track(key) to Track(keycov) kirr/wendelin.core@8b5d8523 X Move tracking of which blocks were accessed from wcfs to ΔFtail
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Kirill Smelkov authored
Use ΔFtail.Track on every READ, and query accumulated ΔFtail upon receiving ZODB invalidation to query it about which blocks of which files have been changed. Then invalidate those blocks in OS file cache. See added documentation to wcfs.go and notes.txt for details. Now the filesystem is no longer stale: it provides view of data that is uptodate wrt changes on ZODB storage. Some preliminary history: kirr/wendelin.core@9b4a42a3 X invalidation design draftly settled kirr/wendelin.core@27d91d47 X δFtail settled kirr/wendelin.core@33e0dfce X ΔTail draftly done kirr/wendelin.core@822366a7 X keeping fd to root opened prevents the filesystem from being unmounted kirr/wendelin.core@89ad3a79 X Don't keep ZBigFile activated during whole current transaction kirr/wendelin.core@245511ac X Give pointer on from where to get nxd-fuse.ko kirr/wendelin.core@d1cd128c X Hit FUSE-related deadlock kirr/wendelin.core@d134ee44 X FUSE lookup deadlock should be hopefully fixed kirr/wendelin.core@0e60e9ff X wcfs: Don't noise ZWatcher trace logs with "select ..." kirr/wendelin.core@bf9a7405 X No longer rely on ZODB cache invariant for invalidations
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Kirill Smelkov authored
FileSock is bidirectional channel associated with opened file. FileSock provides streaming write/read operations for filesystem server that are correspondingly matched with read/write operations on filesystem user side. WCFS will use FileSock to implement exchange over .wcfs/zhead and, later, head/watch files. Some preliminary history: kirr/wendelin.core@b17aeb8c X Change FileSock to use xio.Pipe which is io.Pipe + support for IO cancellation
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Kirill Smelkov authored
ΔFtail builds on ΔBtail and provides ZBigFile-level history that WCFS will use to compute which blocks of a ZBigFile need to be invalidated in OS file cache given raw ZODB changes on ZODB invalidation message. It also will be used by WCFS to implement isolation protocol, where on every FUSE READ request WCFS will query ΔFtail to find out revision of corresponding file block. Quoting ΔFtail documentation: ---- 8< ---- ΔFtail provides ZBigFile-level history tail. It translates ZODB object-level changes to information about which blocks of which ZBigFile were modified, and provides service to query that information. ΔFtail class documentation ~~~~~~~~~~~~~~~~~~~~~~~~~~ ΔFtail represents tail of revisional changes to files. It semantically consists of []δF ; rev ∈ (tail, head] where δF represents a change in files space δF: .rev↑ {} file -> {}blk | EPOCH Only files and blocks explicitly requested to be tracked are guaranteed to be present. In particular a block that was not explicitly requested to be tracked, even if it was changed in δZ, is not guaranteed to be present in δF. After file epoch (file creation, deletion, or any other change to file object) previous track requests for that file become forgotten and have no further effect. ΔFtail provides the following operations: .Track(file, blk, path, zblk) - add file and block reached via BTree path to tracked set. .Update(δZ) -> δF - update files δ tail given raw ZODB changes .ForgetPast(revCut) - forget changes ≤ revCut .SliceByRev(lo, hi) -> []δF - query for all files changes with rev ∈ (lo, hi] .SliceByFileRev(file, lo, hi) -> []δfile - query for changes of a file with rev ∈ (lo, hi] .BlkRevAt(file, #blk, at) -> blkrev - query for what is last revision that changed file[#blk] as of @at database state. where δfile represents a change to one file δfile: .rev↑ {}blk | EPOCH See also zodb.ΔTail and xbtree.ΔBtail Concurrency ΔFtail is safe to use in single-writer / multiple-readers mode. That is at any time there should be either only sole writer, or, potentially several simultaneous readers. The table below classifies operations: Writers: Update, ForgetPast Readers: Track + all queries (SliceByRev, SliceByFileRev, BlkRevAt) Note that, in particular, it is correct to run multiple Track and queries requests simultaneously. ΔFtail organization ~~~~~~~~~~~~~~~~~~~ ΔFtail leverages: - ΔBtail to track changes to ZBigFile.blktab BTree, and - ΔZtail to track changes to ZBlk objects and to ZBigFile object itself. then every query merges ΔBtail and ΔZtail data on the fly to provide ZBigFile-level result. Merging on the fly, contrary to computing and maintaining vδF data, is done to avoid complexity of recomputing vδF when tracking set changes. Most of ΔFtail complexity is, thus, located in ΔBtail, which implements BTree diff and handles complexity of recomputing vδB when set of tracked blocks changes after new track requests. Changes to ZBigFile object indicate epochs. Epochs could be: - file creation or deletion, - change of ZBigFile.blksize, - change of ZBigFile.blktab to point to another BTree. Epochs represent major changes to file history where file is assumed to change so dramatically, that practically it can be considered to be a "whole" change. In particular, WCFS, upon seeing a ZBigFile epoch, invalidates all data in corresponding OS-level cache for the file. The only historical data, that ΔFtail maintains by itself, is history of epochs. That history does not need to be recomputed when more blocks become tracked and is thus easy to maintain. It also can be maintained only in ΔFtail because ΔBtail and ΔZtail does not "know" anything about ZBigFile. Concurrency In order to allow multiple Track and queries requests to be served in parallel, ΔFtail bases its concurrency promise on ΔBtail guarantees + snapshot-style access for vδE and ztrackInBlk in queries: 1. Track calls ΔBtail.Track and quickly updates .byFile, .byRoot and _RootTrack indices under a lock. 2. BlkRevAt queries ΔBtail.GetAt and then combines retrieved information about zblk with vδE and δZ. 3. SliceByFileRev queries ΔBtail.SliceByRootRev and then merges retrieved vδT data with vδZ, vδE and ztrackInBlk. 4. In queries vδE is retrieved/built in snapshot style similarly to how vδT is built in ΔBtail. Note that vδE needs to be built only the first time, and does not need to be further rebuilt, so the logic in ΔFtail is simpler compared to ΔBtail. 5. for ztrackInBlk - that is used by SliceByFileRev query - an atomic snapshot is retrieved for objects of interest. This allows to hold δFtail.mu lock for relatively brief time without blocking other parallel Track/queries requests for long. Combined this organization allows non-overlapping queries/track-requests to run simultaneously. (This property is essential to WCFS because otherwise WCFS would not be able to serve several non-overlapping READ requests to one file in parallel.) See also "Concurrency" in ΔBtail organization for more details. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Some preliminary history: kirr/wendelin.core@ef74aebc X ΔFtail: Keep reference to ZBigFile via Oid, not via *ZBigFile kirr/wendelin.core@bf9a7405 X No longer rely on ZODB cache invariant for invalidations kirr/wendelin.core@46340069 X found by Random kirr/wendelin.core@e7b598c6 X start of ΔFtail.SliceByFileRev rework to function via merging δB and δZ histories on the fly kirr/wendelin.core@59c83009 X ΔFtail.SliceByFileRoot tests started to work draftly after "on-the-fly" rework kirr/wendelin.core@210e9b07 X Fix ΔBtail.SliceByRootRev (lo,hi] handling kirr/wendelin.core@bf3ace66 X ΔFtail: Rebuild vδE after first track kirr/wendelin.core@46624787 X ΔFtail: `go test -failfast -short -v -run Random -randseed=1626793016249041295` discovered problems kirr/wendelin.core@786dd336 X Size no longer tracks [0,∞) since we start tracking when zfile is non-empty kirr/wendelin.core@4f707117 X test that shows problem of SliceByRootRev where untracked blocks are not added uniformly into whole history kirr/wendelin.core@c0b7e4c3 X ΔFtail.SliceByFileRev: Fix untracked entries to be present uniformly in result kirr/wendelin.core@aac37c11 X zdata: Introduce T to start removing duplication in tests kirr/wendelin.core@bf411aa9 X zdata: Deduplicate zfile loading kirr/wendelin.core@b74dda09 X Start switching Track from Track(key) to Track(keycov) kirr/wendelin.core@aa0288ce X Switch SliceByRootRev to vδTSnapForTracked kirr/wendelin.core@588a512a X zdata: Switch SliceByFileRev not to clone Zinblk kirr/wendelin.core@8b5d8523 X Move tracking of which blocks were accessed from wcfs to ΔFtail kirr/wendelin.core@30f5ddc7 ΔFtail += .Epoch in δf kirr/wendelin.core@22f5f096 X Rework ΔFtail so that BlkRevAt works with ZBigFile checkout from any at ∈ (tail, head] kirr/wendelin.core@0853cc9f X ΔFtail + tests kirr/wendelin.core@124688f9 X ΔFtail fixes kirr/wendelin.core@d85bb82c ΔFtail concurrency
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Kirill Smelkov authored
ΔBtail provides BTree-level history tail that WCFS - via ΔFtail - will use to compute which blocks of a ZBigFile need to be invalidated in OS file cache given raw ZODB changes on ZODB invalidation message. It also will be used by WCFS to implement isolation protocol, where on every FUSE READ request WCFS will query ΔBtail - again via ΔFtail - to find out revision of corresponding file block. Quoting ΔBtail documentation: ---- 8< ---- ΔBtail provides BTree-level history tail. It translates ZODB object-level changes to information about which keys of which BTree were modified, and provides service to query that information. ΔBtail class documentation ~~~~~~~~~~~~~~~~~~~~~~~~~~ ΔBtail represents tail of revisional changes to BTrees. It semantically consists of []δB ; rev ∈ (tail, head] where δB represents a change in BTrees space δB: .rev↑ {} root -> {}(key, δvalue) It covers only changes to keys from tracked subset of BTrees parts. In particular a key that was not explicitly requested to be tracked, even if it was changed in δZ, is not guaranteed to be present in δB. ΔBtail provides the following operations: .Track(path) - start tracking tree nodes and keys; root=path[0], keys=path[-1].(lo,hi] .Update(δZ) -> δB - update BTree δ tail given raw ZODB changes .ForgetPast(revCut) - forget changes ≤ revCut .SliceByRev(lo, hi) -> []δB - query for all trees changes with rev ∈ (lo, hi] .SliceByRootRev(root, lo, hi) -> []δT - query for changes of a tree with rev ∈ (lo, hi] .GetAt(root, key, at) -> (value, rev) - get root[key] @at assuming root[key] ∈ tracked where δT represents a change to one tree δT: .rev↑ {}(key, δvalue) An example for tracked set is a set of visited BTree paths. There is no requirement that tracked set belongs to only one single BTree. See also zodb.ΔTail and zdata.ΔFtail Concurrency ΔBtail is safe to use in single-writer / multiple-readers mode. That is at any time there should be either only sole writer, or, potentially several simultaneous readers. The table below classifies operations: Writers: Update, ForgetPast Readers: Track + all queries (SliceByRev, SliceByRootRev, GetAt) Note that, in particular, it is correct to run multiple Track and queries requests simultaneously. ΔBtail organization ~~~~~~~~~~~~~~~~~~~ ΔBtail keeps raw ZODB history in ΔZtail and uses BTree-diff algorithm(*) to turn δZ into BTree-level diff. For each tracked BTree a separate ΔTtail is maintained with tree-level history in ΔTtail.vδT . Because it is very computationally expensive(+) to find out for an object to which BTree it belongs, ΔBtail cannot provide full BTree-level history given just ΔZtail with δZ changes. Due to this ΔBtail requires help from users, which are expected to call ΔBtail.Track(treepath) to let ΔBtail know that such and such ZODB objects constitute a path from root of a tree to some of its leaf. After Track call the objects from the path and tree keys, that are covered by leaf node, become tracked: from now-on ΔBtail will detect and provide BTree-level changes caused by any change of tracked tree objects or tracked keys. This guarantee can be provided because ΔBtail now knows that such and such objects belong to a particular tree. To manage knowledge which tree part is tracked ΔBtail uses PPTreeSubSet. This data-structure represents so-called PP-connected set of tree nodes: simply speaking it builds on some leafs and then includes parent(leaf), parent(parent(leaf)), etc. In other words it's a "parent"-closure of the leafs. The property of being PP-connected means that starting from any node from such set, it is always possible to reach root node by traversing .parent links, and that every intermediate node went-through during traversal also belongs to the set. A new Track request potentially grows tracked keys coverage. Due to this, on a query, ΔBtail needs to recompute potentially whole vδT of the affected tree. This recomputation is managed by "vδTSnapForTracked*" and "_rebuild" functions and uses the same treediff algorithm, that Update is using, but modulo PPTreeSubSet corresponding to δ key coverage. Update also potentially needs to rebuild whole vδT history, not only append new δT, because a change to tracked tree nodes can result in growth of tracked key coverage. Queries are relatively straightforward code that work on vδT snapshot. The main complexity, besides BTree-diff algorithm, lies in recomputing vδT when set of tracked keys changes, and in handling that recomputation in such a way that multiple Track and queries requests could be all served in parallel. Concurrency In order to allow multiple Track and queries requests to be served in parallel ΔBtail employs special organization of vδT rebuild process where complexity of concurrency is reduced to math on merging updates to vδT and trackSet, and on key range lookup: 1. vδT is managed under read-copy-update (RCU) discipline: before making any vδT change the mutator atomically clones whole vδT and applies its change to the clone. This way a query, once it retrieves vδT snapshot, does not need to further synchronize with vδT mutators, and can rely on that retrieved vδT snapshot will remain immutable. 2. a Track request goes through 3 states: "new", "handle-in-progress" and "handled". At each state keys/nodes of the Track are maintained in: - ΔTtail.ktrackNew and .trackNew for "new", - ΔTtail.krebuildJobs for "handle-in-progress", and - ΔBtail.trackSet for "handled". trackSet keeps nodes, and implicitly keys, from all handled Track requests. For all keys, covered by trackSet, vδT is fully computed. a new Track(keycov, path) is remembered in ktrackNew and trackNew to be further processed when a query should need keys from keycov. vδT is not yet providing data for keycov keys. when a Track request starts to be processed, its keys and nodes are moved from ktrackNew/trackNew into krebuildJobs. vδT is not yet providing data for requested-to-be-tracked keys. all trackSet, trackNew/ktrackNew and krebuildJobs are completely disjoint: trackSet ^ trackNew = ø trackSet ^ krebuildJobs = ø trackNew ^ krebuildJobs = ø 3. when a query is served, it needs to retrieve vδT snapshot that takes related previous Track requests into account. Retrieving such snapshots is implemented in vδTSnapForTracked*() family of functions: there it checks ktrackNew/trackNew, and if those sets overlap with query's keys of interest, run vδT rebuild for keys queued in ktrackNew. the main part of that rebuild can be run without any locks, because it does not use nor modify any ΔBtail data, and for δ(vδT) it just computes a fresh full vδT build modulo retrieved ktrackNew. Only after that computation is complete, ΔBtail is locked again to quickly merge in δ(vδT) update back into vδT. This organization is based on the fact that vδT/(T₁∪T₂) = vδT/T₁ | vδT/T₂ ( i.e. vδT computed for tracked set being union of T₁ and T₂ is the same as merge of vδT computed for tracked set T₁ and vδT computed for tracked set T₂ ) and that trackSet | (δPP₁|δPP₂) = (trackSet|δPP₁) | (trackSet|δPP₂) ( i.e. tracking set updated for union of δPP₁ and δPP₂ is the same as union of tracking set updated with δPP₁ and tracking set updated with δPP₂ ) these merge properties allow to run computation for δ(vδT) and δ(trackSet) independently and with ΔBtail unlocked, which in turn enables running several Track/queries in parallel. 4. while vδT rebuild is being run, krebuildJobs keeps corresponding keycov entry to indicate in-progress rebuild. Should a query need vδT for keys from that job, it first waits for corresponding job(s) to complete. Explained rebuild organization allows non-overlapping queries/track-requests to run simultaneously. (This property is essential to WCFS because otherwise WCFS would not be able to serve several non-overlapping READ requests to one file in parallel.) -------- (*) implemented in treediff.go (+) full database scan ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Some preliminary history: kirr/wendelin.core@877e64a9 X wcfs: Fix tests to pass again kirr/wendelin.core@c32055fc X wcfs/xbtree: ΔBtail tests += ø -> Tree; Tree -> ø kirr/wendelin.core@78f2f88b X wcfs/xbtree: Fix treediff(a, ø) kirr/wendelin.core@5324547c X wcfs/xbtree: root(a) must stay in trackSet even after treediff(a,ø) kirr/wendelin.core@f65f775b X wcfs/xbtree: treediff(ø, b) kirr/wendelin.core@c75b1c6f X wcfs/xbtree: Start killing holeIdx kirr/wendelin.core@0fa06cbd X kadj must be taken into account as kadj^δZ kirr/wendelin.core@ef5e5183 X treediff ret += δtkeycov kirr/wendelin.core@f30826a6 X another bug in δtkeyconv computation kirr/wendelin.core@0917380e X wcfs: assert that keycov only grow kirr/wendelin.core@502e05c2 X found why TestΔBTailAllStructs was not effective to find δtkeycov bugs kirr/wendelin.core@450ba707 X Fix rebuild with ø @at2 kirr/wendelin.core@f60528c9 X ΔBtail.Clone had bug that it was aliasing klon and orig data kirr/wendelin.core@9d20f8e8 X treediff: Fix BUG while computing AB coverage kirr/wendelin.core@ddb28043 X rebuild: Don't return nil for empty ΔPPTreeSubSet - that leads to SIGSEGV kirr/wendelin.core@324241eb X rebuild: tests: Don't reflect.DeepEqual in inner loop kirr/wendelin.core@8f6e2b1e X rebuild: tests: Don't access ZODB in XGetδKV kirr/wendelin.core@2c0b4793 X rebuild: tests: Don't access ZODB in xtrackKeys kirr/wendelin.core@8f0e37f2 X rebuild: tests: Precompute kadj10·kadj21 kirr/wendelin.core@271d953d X rebuild: tests: Move ΔBtail.Clone test out of hot inner loop into separate test kirr/wendelin.core@a87cc6de X rebuild: tests: Don't recompute trackSet(keys1R2) several times kirr/wendelin.core@01433e96 X rebuild: tests: Don't compute keyCover in trackSet kirr/wendelin.core@7371f9c5 X rebuild: tests: Inline _assertTrack kirr/wendelin.core@3e9164b3 X rebuild: tests: Don't exercise keys from keys2 that already became tracked after Track(keys1) + Update kirr/wendelin.core@e9c4b619 X rebuild: tests: Random testing kirr/wendelin.core@d0fe680a X δbtail += ForgetPast kirr/wendelin.core@210e9b07 X Fix ΔBtail.SliceByRootRev (lo,hi] handling kirr/wendelin.core@855ab4b8 X ΔBtail: Goodbye .KVAtTail kirr/wendelin.core@2f5582e6 X ΔBtail: Tweak tests to run faster in normal mode kirr/wendelin.core@cf352737 X random testing found another failing test for rebuild... kirr/wendelin.core@7f7e34e0 X wcfs/xbtree: Fix update not to add duplicate extra point if rebuild - called by Update - already added it kirr/wendelin.core@6ad0052c X ΔBtail.Track: No need to return error kirr/wendelin.core@aafcacdf X xbtree: GetAt test kirr/wendelin.core@784a6761 X xbtree: Fix KAdj definition after treediff was reworked this summer to base decisions on node keycoverage instead of particular node keys kirr/wendelin.core@0bb1c22e X xbtree: Verify that ForgetPast clones vδT on trim kirr/wendelin.core@a8945cbf X Start reworking rebuild routines not to modify data inplace kirr/wendelin.core@b74dda09 X Start switching Track from Track(key) to Track(keycov) kirr/wendelin.core@dea85e87 X Switch GetAt to vδTSnapForTrackedKey kirr/wendelin.core@aa0288ce X Switch SliceByRootRev to vδTSnapForTracked kirr/wendelin.core@c4366b14 X xbtree: tests: Also verify state of ΔTtail.ktrackNew kirr/wendelin.core@b98706ad X Track should be nop if keycov/path is already in krebuildJobs kirr/wendelin.core@e141848a X test.go ↑ timeout 10m -> 20m kirr/wendelin.core@423f77be X wcfs: Goodby holeIdx kirr/wendelin.core@37c2e806 X wcfs: Teach treediff to compute not only δtrack (set of nodes), but also δ for track-key coverage kirr/wendelin.core@52c72dbb X ΔBtail.rebuild started to work draftly kirr/wendelin.core@c9f13fc7 X Get rebuild tests to run in a sane time; Add proper random-based testing for rebuild kirr/wendelin.core@c7f1e3c9 X xbtree: Factor testing infrastructure bits into xbtree/xbtreetest kirr/wendelin.core@7602c1f4 ΔBtail concurrency
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Kirill Smelkov authored
This algorithm will be internally used by ΔBtail in the next patch. The algorithm would be simple, if we would need to diff two trees completely. However in ΔBtail only subpart of BTree nodes are tracked(*) and the diff has to work modulo that tracking set. No tests now because ΔBtail tests will cover treediff functionality as well. Some preliminary history: kirr/wendelin.core@78f2f88b X wcfs/xbtree: Fix treediff(a, ø) kirr/wendelin.core@5324547c X wcfs/xbtree: root(a) must stay in trackSet even after treediff(a,ø) kirr/wendelin.core@f65f775b X wcfs/xbtree: treediff(ø, b) kirr/wendelin.core@c75b1c6f X wcfs/xbtree: Start killing holeIdx kirr/wendelin.core@ef5e5183 X treediff ret += δtkeycov kirr/wendelin.core@9d20f8e8 X treediff: Fix BUG while computing AB coverage kirr/wendelin.core@ddb28043 X rebuild: Don't return nil for empty ΔPPTreeSubSet - that leads to SIGSEGV kirr/wendelin.core@f68398c9 X wcfs: Move treediff into its own file (*) because full BTree scan is needed to discover all of its nodes. Quoting treediff documentation: ---- 8< ---- treediff provides diff for BTrees Use δZConnectTracked + treediff to compute BTree-diff caused by δZ: δZConnectTracked(δZ, trackSet) -> δZTC, δtopsByRoot treediff(root, δtops, δZTC, trackSet, zconn{Old,New}) -> δT, δtrack, δtkeycov δZConnectTracked computes BTree-connected closure of δZ modulo tracked set and also returns δtopsByRoot to indicate which tree objects were changed and in which subtree parts. With that information one can call treediff for each changed root to compute BTree-diff and δ for trackSet itself. BTree diff algorithm diffT, diffB and δMerge constitute the diff algorithm implementation. diff(A,B) works on pair of A and B whole key ranges splitted into regions covered by tree nodes. The splitting represents current state of recursion into corresponding tree. If a node in particular key range is Bucket, that bucket contributes to δ- in case of A, and to δ+ in case of B. If a node in particular key range is Tree, the algorithm may want to expand that tree node into its children and to recourse into some of the children. There are two phases: - Phase 1 expands A top->down driven by δZTC, adds reached buckets to δ-, and queues key regions of those buckets to be processed on B. - Phase 2 starts processing from queued key regions, expands them on B and adds reached buckets to δ+. Then it iterates to reach consistency in between A and B because processing buckets on B side may increase δ key coverage, and so corresponding key ranges has to be again processed on A. Which in turn may increase δ key coverage again, and needs to be processed on B side, etc... The final δ is merge of δ- and δ+. diffT has more detailed explanation of phase 1 and phase 2 logic.
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Kirill Smelkov authored
This data structures will be used in ΔBtail to maintain sef of tracked BTree nodes, and to represent δ to such set. Some preliminary history: kirr/wendelin.core@78f2f88b X wcfs/xbtree: Fix treediff(a, ø) kirr/wendelin.core@5324547c X wcfs/xbtree: root(a) must stay in trackSet even after treediff(a,ø) kirr/wendelin.core@f65f775b X wcfs/xbtree: treediff(ø, b) kirr/wendelin.core@66bc41ce X Fix bug in PPTreeSubSet.Difference - it was always leaving root node alive kirr/wendelin.core@ddb28043 X rebuild: Don't return nil for empty ΔPPTreeSubSet - that leads to SIGSEGV kirr/wendelin.core@a87cc6de X rebuild: tests: Don't recompute trackSet(keys1R2) several times Quoting PPTreeSubSet and ΔPPTreeSubSet documentation: ---- 8< ---- PPTreeSubSet represents PP-connected subset of tree node objects. It is PP(xleafs) where PP(node) maps node to {node, node.parent, node.parent,parent, ...} up to top root from where the node is reached. The nodes in the set are represented by their Oid. Usually PPTreeSubSet is built as PP(some-leafs), but in general the starting nodes are arbitrary. PPTreeSubSet can also have many root nodes, thus not necessarily representing a subset of a single tree. Usual set operations are provided: Union, Difference and Intersection. Nodes can be added into the set via AddPath. Path is reverse operation - it returns path to tree node given its oid. Every node in the set comes with .parent pointer. ~~~~ ΔPPTreeSubSet represents a change to PPTreeSubSet. It can be applied via PPTreeSubSet.ApplyΔ . The result B of applying δ to A is: B = A.xDifference(δ.Del).xUnion(δ.Add) (*) (*) NOTE δ.Del and δ.Add might have their leafs starting from non-leaf nodes in A/B. This situation arises when δ represents a change in path to particular node, but that node itself does not change, for example: c* c / \ / 41* 42 41 | | | \ 22 43 46 43 | | | 44 22 44 Here nodes {c, 41} are changed, node 42 is unlinked, and node 46 is added. Nodes 43 and 44 stay unchanged. δ.Del = c-42-43 | c-41-22 δ.Add = c-41-43 | c-41-46-22 The second component with "-22" builds from leaf, but the first component with "-43" builds from non-leaf node. ΔnchildNonLeafs = {43: +1} Only complete result of applying all - xfixup(-1, ΔnchildNonLeafs) - δ.Del, - δ.Add, and - xfixup(+1, ΔnchildNonLeafs) produces correctly PP-connected set.
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Kirill Smelkov authored
RangedMap is Key->VALUE map with adjacent keys mapped to the same value coalesced into Ranges. RangedKeySet is set of Keys with adjacent keys coalesced into Ranges. This data structures will be needed for ΔBtail. For now the implementation is simple since it keeps whole map in a linear slice because both RangedMap and RangedKeySet will be used in ΔBtail to keep something proportional to δ of a change, which is assumed to be small or medium most of the time. Some preliminary history: kirr/wendelin.core@6ea5920a X xbtree: Less copy/garbage in RangedKeySet ops kirr/wendelin.core@3ecacd99 X need to keep Value first so that sizeof(set-entry) = sizeof(KeyRange) kirr/wendelin.core@a5b9b19b X SetRange draftly works kirr/wendelin.core@ed2de0de X Tests for Get kirr/wendelin.core@3b7b69e6 X fixes for empty set/range kirr/wendelin.core@6972f999 X xbtree/blib: RangedMap, RangedSet += IntersectsRange, Intersection kirr/wendelin.core@57be0126 X RangedMap - like RangedSet but for dict
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Kirill Smelkov authored
Add treeenv.go that combines Treegen and client side access to ZODB with committed trees as extension to testing.T . The environment allows to easily see which tree update was committed, what is the difference in terms of KV, what is the state of updated tree and state of pointed-to ZBlk objects. This will be used to test upcoming ΔBtail and ΔFtail. Main functionality is in treeenv.go; the other added files are to support that. Some preliminary history: kirr/wendelin.core@f07502fc X xbtreetest: Teach T & Commit to automatically provide At in symbolic form kirr/wendelin.core@0d62b05e X Adjust to btree.VGet & friends signature change to include keycov in visit callback kirr/wendelin.core@588a512a X zdata: Switch SliceByFileRev not to clone Zinblk kirr/wendelin.core@e9c4b619 X rebuild: tests: Random testing kirr/wendelin.core@43090ac7 X tests: Factor-out tree-test-env into tTreeEnv kirr/wendelin.core@d4a523b2 X δbtail: tests: Run much faster with live ZODB cache kirr/wendelin.core@271d953d X rebuild: tests: Move ΔBtail.Clone test out of hot inner loop into separate test kirr/wendelin.core@c32055fc X wcfs/xbtree: ΔBtail tests += ø -> Tree; Tree -> ø kirr/wendelin.core@5324547c X wcfs/xbtree: root(a) must stay in trackSet even after treediff(a,ø) kirr/wendelin.core@8f6e2b1e X rebuild: tests: Don't access ZODB in XGetδKV
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Kirill Smelkov authored
Lacking generics we have set.go.in and instantiation for Set[int64], set[string], Set[Oid] and Set[Tid] - that will be used in follow-up patches. The set.go.in itself is mostly a generalized copy from git-backup: https://lab.nexedi.com/kirr/git-backup/blob/c9db60e8/set.go
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Kirill Smelkov authored
treegen.go and treegen.py together provide a way - to commit a particular BTree topology into ZODB, and - to generate set of random tree topologies that all correspond to particular {k->v} dict. this will be used in upcoming ΔBtail and ΔFtail tests. See treegen.py documentation for details. Some preliminary history: kirr/wendelin.core@9eca74ec X Teach AllStructs to emit topologies with values kirr/wendelin.core@1b962f03 X Restructure: found bug that it was not marking objects as modified kirr/wendelin.core@2139af2c X treegen: Verify that tree actually saved to storage is what was requested kirr/wendelin.core@b5e39d4a X wcfs/treegen: allstructs: Do not keep all tree structures in memory kirr/wendelin.core@e9c4b619 X rebuild: tests: Random testing kirr/wendelin.core@c32055fc X wcfs/xbtree: ΔBtail tests += ø -> Tree; Tree -> ø kirr/wendelin.core@4300d88a X wcfs/xbtreetest/treegen.py: Fix it on ZODB4
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Kirill Smelkov authored
This will be the place to keep BTree-related utilities. For now it provides only type aliases since Go lacks generics.
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Kirill Smelkov authored
To handle invalidations, WCFS will need to detect changes to both ZBlk objects and to ZBigFile.blktab BTree that is mapping file blocks to ZBlk objects. And with BTree detecting changes is much more complex, because when a BTree changes, it might be rebalanced, or keys migrated from one tree/bucket node to another tree/bucket node. In other words a BTree change might be not only a change to a {}key->value dictionary, but also a change to BTree topology. Because there are many BTree topologies that correspond to the same {}key->value state, a change from kv₁ to kv₂, even if kv₁ and kv₂ are close to each other, might be accompanied by a dramatic change to topology of the tree. This creates a need for thoroughly testing the BTree difference algorithm because many of BTree topologies changes are tricky, and if a simple algorithm works on relatively stable topology updates, it does not necessarily mean that that same algorithm will continue to work correctly in the general case. So, as a preparatory step, here comes xbtree.py package, that can be used to inspect tree topologies, to create trees with specified topology and to manipulate topology of an existing tree. This package will be used in tests for upcoming ΔBtail. For debugging, and also since those tests will involve both Go and Python parts, it creates the need to be able to specify and exchange topology of a tree via compact string. This package also defines so called "topology encoding" to do so. Some preliminar history: kirr/wendelin.core@fb56193f X fix metric to keep Z <- N order stable over key^ kirr/wendelin.core@809304d1 X "B:" indicates ø bucket with k&b, "B" - ø bucket with only keys kirr/wendelin.core@9eca74ec X Teach AllStructs to emit topologies with values kirr/wendelin.core@1b962f03 X Restructure: found bug that it was not marking objects as modified kirr/wendelin.core@9181c5d9 X Restructure; verify that it marks as changed only modifed nodes kirr/wendelin.core@e9902c4a X improve `xbtree topoview` For the reference xbtree.py package documentation is quoted below. ---- 8< ---- Package xbtree provides utilities for inspecting/manipulating internal structure of integer-keyed BTrees. It will be primarily used to help verify ΔBTail in WCFS. - `Tree` represents a tree node. - `Bucket` represents a bucket node. - `StructureOf` returns internal structure of ZODB BTree represented as Tree and Bucket nodes. - `Restructure` reorganizes ZODB BTree instance according to specified topology structure. - `AllStructs` generates all possible BTree topology structures with given keys. Topology encoding ----------------- Topology encoding provides way to represent structure of a Tree as path-like string. TopoEncode converts Tree into its topology-encoded representation, while TopoDecode decodes topology-encoded string back into Tree. The following example illustrates topology encoding represented by string "T3/T-T/B1-T5/B-B7,8,9": [ 3 ] T3/ represents Tree([3]) / \ [ ] [ ] T-T/ represents two empty Tree([]) ↓ ↓ |1|[ 5 ] B1-T5/ represent Bucket([1]) and Tree([5]) / \ || |7|8|9| B-B7,8,9 represents empty Bucket([]) and Bucket([7,8,9]) Topology encoding specification: A Tree is encoded by level-order traversal, delimiting layers with "/". Inside a layer Tree and Bucket nodes are signalled as "T<keys>" ; Tree "B<keys>" ; Bucket with only keys "B<keys+values>" ; Bucket with keys and values Keys are represented as ","-delimited list of integers. For example Tree or Bucket with [1,3,5] keys are represented as "T1,3,5" ; Tree([1,3,5]) "B1,3,5" ; Bucket([1,3,5]) Keys+values are represented as ","-delimited list of "<key>:<value>" pairs. For example Bucket corresponding to {1:1, 2:4, 3:9} is represented as "B1:1,2:4,3:9" ; Bucket([1,2,3], [1,4,9]) Empty keys+values are represented as ":" - an empty Bucket for key->value mapping is represented as "B:" ; Bucket([], []) Nodes inside one layer are delimited with "-". For example a layer consisting of an empty Tree, a Tree with [1,3] keys, and Bucket with [4,5] keys is represented as "T-T1,3-B4,5" ; layer with Tree([]), Tree([1,3]) and Bucket([4,5]) A layer consists of nodes that are followed by node-node links from upper layer in left-to-right order. Visualization ------------- The following visualization utilities are provided to help understand BTrees better: - `topoview` displays BTree structure given its topology-encoded representation. - `Tree.graphviz` returns Tree graph representation in dot language.
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Kirill Smelkov authored
For WCFS to be efficient it will have to carefully preserve OS cache on file invalidations. As preparatory step establish infrastructure for verifying state of OS file cache and start asserting on OS cache state in a couple of places. See comments added to tFile constructor that describe how OS cache state verification is setup. Some preliminary history: kirr/wendelin.core@8293025b X Thoughts on how to avoid readahead touching pages of neighbour block kirr/wendelin.core@3054e4a3 X not touching neighbour block works via setting MADV_RANDOM in last 1/4 of every block kirr/wendelin.core@18362227 X #5 access still triggers read to #4 ? kirr/wendelin.core@17dbf94e X Provide mlock2 fallback for Ubuntu kirr/wendelin.core@d134c0b9 X wcfs: test: try to live with only hard memlock limit adjusted kirr/wendelin.core@c2423296 X Fix mlock2 build on Debian 8
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Kirill Smelkov authored
Provide filesystem view of in-ZODB ZBigFiles, but do not implement support for invalidations nor isolation protocol yet. In particular, because ZODB invalidations are not yet handled, the filesystem does not update its data in accordance with ZODB updates, and instead provides stale data view that corresponds to the state of ZODB at the time when wcfs was mounted. The main parts of this patch are: - wcfs/wcfs.go is filesystem implementation itself together with overview. - wcfs/__init__.py is python wrapper to spawn and interoperate with that filesystem. - wcfs/wcfs_test.py is tests. Some preliminary history: kirr/wendelin.core@fe7efb94 X start of wcfs kirr/wendelin.core@878b2787 X draft loading kirr/wendelin.core@d58c71e8 X don't overalign end by 1 blksize if end is already aligned kirr/wendelin.core@29c9f13d X readBlk: Fix thinko in already case kirr/wendelin.core@59552328 X wcfs: Care to disable OS polling on us kirr/wendelin.core@c00d94c7 X workaround lack of exception chaining on Python2 with xdefer kirr/wendelin.core@0398e23d X bytearray turned out to be copying data kirr/wendelin.core@7a837040 X print wcfs.py py-level traceback on SIGBUS (e.g. wcfs.go aborting due to bug/panic) kirr/wendelin.core@661b871f X make sure tests don't get stuck even if wcfs gets killed -9 ... kirr/wendelin.core@2c043d29 X More effort to unmount failed wcfs.go kirr/wendelin.core@1ccc4478 X Use `with gil` + regular py code instead of PyGILState_Ensure/PyGILState_Release/PyRun_SimpleString kirr/wendelin.core@5dc9c791 X wcfs: Kill xdefer kirr/wendelin.core@91e9eba8 X wcfs: test: Register tFile to tDB early kirr/wendelin.core@a7138fef X wcfs: mkdir /tmp/wcfs with sticky bit kirr/wendelin.core@1eec76d0 X wcfs: try to set sticky for /tmp/wcfs even if the directory already exists kirr/wendelin.core@c2c35851 X wcfs: tests: Factor-out waiting for a general condition to become true into waitfor kirr/wendelin.core@78f36993 X wcfs: test: Fix thinko in getting /sys/fs/fuse/connection/<X> for wcfs kirr/wendelin.core@bc9eb16f X wcfs: tests: Don't use testmntpt everywhere kirr/wendelin.core@6dec74e7 X wcfs: tests: Split tDB into -> tDB + tWCFS kirr/wendelin.core@3a6bd764 X wcfs: tests: Run `fusermount -u` the second time if we had to kill wcfs kirr/wendelin.core@112720f3 X wcfs: tests: Print which files are still opened on wcfs if `fusermount -u` fails kirr/wendelin.core@bb40185b X wcfs: Take $WENDELIN_CORE_WCFS_OPTIONS into account not only from under join kirr/wendelin.core@03a9ef33 X wcfs: Remove credentials from zurl when computing wcfs mountpoint kirr/wendelin.core@68ee5bdc X wcfs: lsof tweaks kirr/wendelin.core@21671879 X wcfs: Teach entrypoint frontend to handle subcommands: serve, status, stop kirr/wendelin.core@b0642b80 X wcfs: Switch mountpoints from /tmp/wcfs/* to /dev/shm/* kirr/wendelin.core@b0ca031f X wcfs: Teach join/serve to start successfully even after unclean wcfs shutdown kirr/wendelin.core@5bfa8cf8 X wcfs: Add start to spawn a Server that can be later stopped (draft) kirr/wendelin.core@5fcec261 X wcfs: Run fusermount and friends with /bin:/usr/bin always on path kirr/wendelin.core@669d7a20 fixup! X wcfs: Run fusermount and friends with /bin:/usr/bin always on path kirr/wendelin.core@6b22f8c4 X wcfs: Teach start to start successfully even after unclean wcfs shutdown kirr/wendelin.core@15389db0 X wcfs: Tune _fuse_unmount to include `fusermount -u` error message into raised exception kirr/wendelin.core@153c002a X wcfs: _fuse_unmount: Try first `kill -TERM` before `kill -QUIT` wcfs kirr/wendelin.core@3244f3a6 X wcfs: lsof +D misbehaves - don't use it kirr/wendelin.core@a126e709 X wcfs: Put client log into its own logger kirr/wendelin.core@ac303d1e X wcfs: tests: -v -> show only wcfs.py logs verbosely kirr/wendelin.core@d671a9e9 X wcfs: Give more time to stop wcfs server
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Kirill Smelkov authored
Add functionality to load objects from ZODB as saved by py wendelin.core. Mostly straightforward code. The main part is in zblk.go . Contrary to python implementation, go can load ZBlk1's subobjects in parallel, which, given scalable ZODB storage, can be significantly faster compared to serially loading all ZData subobjects as py code does. TODO test wrt data saved by Python3. Some preliminary history: kirr/wendelin.core@878b2787 X draft loading kirr/wendelin.core@bf9a7405 X No longer rely on ZODB cache invariant for invalidations kirr/wendelin.core@0d62b05e X Adjust to btree.VGet & friends signature change to include keycov in visit callback kirr/wendelin.core@b74dda09 X Start switching Track from Track(key) to Track(keycov)
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Kirill Smelkov authored
Add initial stub for WCFS program and tests. WCFS functionality will be added step-by-step in follow-up commits. Some preliminary history: 0ae88a32 X .nxdtest: Verify Go bits with GOMAXPROCS=1,2,`nproc` 23528eb4 X wcfs: make it to use go modules for dependencies
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Kirill Smelkov authored
In 6637d216 (lib/zodb: Add zstor_2zurl - way to convert a ZODB storage into URL to access it) we added zstor_2zurl function to convert a ZODB storage client object into an URL to access the storage. At that time the function knew how to understand FileStorage only. Let's add support for other storages that WCFS will need to support now. NEO URI scheme matches the one currently used on ZODB/go side. It semantically needs nexedi/neoppod!18 to be also applied to NEO/py side, but we do not care for now that that patch is not merged (yet, or forever) because extracted ZURL is used only with WCFS which uses NEO/go. NEO support also depends on custom patch to remember SSL credentials on NEO Client: kirr/neo@a2f192cb Some preliminary history: kirr/wendelin.core@5cb39463 fixup! X wcfs/zeo started to work locally kirr/wendelin.core@1cf3b228 X zstor_2zurl += NEO kirr/wendelin.core@7f8fa32a X lib/zodb: zstor_2zurl += NEO/SSL support kirr/wendelin.core@e26524df X wcfs, lib/zodb: DemoStorage support
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- 25 Oct, 2021 8 commits
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Kirill Smelkov authored
Upcoming libwcfs (C++ part of WCFS client) will need to use virtmem code and link to libvirtmem.
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Kirill Smelkov authored
Manaully, because there is no automatic dependency tracking in setuptools... Dependency tracking is needed to avoid miscompilation after incremental update under SlapOS/buildout/testnode/... when e.g. only .h was changed.
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Kirill Smelkov authored
This is similar to e870781d (Top-level in-tree import redirector) but for upcoming pyx modules.
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Kirill Smelkov authored
Soon we are going to split virtmem code into its own DSO to which bigfile extension will link. As plain setuptools does not support such dynamic linking, we are going to use setuptools_dso instead. But more: some of our upcoming extensions and DSOs will need to use Cython and C++ parts of Pygolang. Prepare that and use Extensions and DSO from golang.pyx.build to support that right from the start.
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Kirill Smelkov authored
Currently we have only one extension wendelin.bigfile._bigfile, but we are going to add more both python extensions and non-python DSOs. Start preparing to that by factoring-out common code.
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Kirill Smelkov authored
lib/tests/testprog/zloadrace.py:90:1 'ZODB.FileStorage.FileStorage' imported but unused This amends commit c37a989d.
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Kirill Smelkov authored
Do what we can do without gdb and then tail to regular segmentation fault. With core file gdb can still be used, but it is handy if we already can get traceback of the crash into the log automatically. TODO better use https://github.com/ianlancetaylor/libbacktrace because backtrace_symbols often does not provide symbolic information. We do not do this now because libbacktrace is not always automatically installed.
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Kirill Smelkov authored
This makes sure that those programs are always built afresh instead being stuck at outdated build. This is needed because corresponding test .c file includes many other .c files and we don't implement dependency tracking.
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- 01 Apr, 2021 3 commits
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Kirill Smelkov authored
Else, e.g. after a failing test, that closed its storage and DB, but not all Connections, another test, just by starting new transaction, would invoke synchronization on that unclosed connection, which will try to access closed storage and likely fail. Fixes e.g. https://nexedijs.erp5.net/#/test_result_module/20210401-31B27B3D/5 Crash scenariou is the same as described in 5a5ed2c7 (tests: Force-close ZODB connections in teardown, that testing code forgot to explicitly close). Only now we try to isolate tests from each other not only for different modules, but also for tests inside the same module.
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Kirill Smelkov authored
The tests verify that there is no concurrency bugs around load, Connection.open and invalidations. See e.g. https://github.com/zopefoundation/ZODB/issues/290 https://github.com/zopefoundation/ZEO/issues/155 By including the tests into wendelin.core, we will have CI coverage for all supported storages (FileStorage, ZEO, NEO), and for all supported ZODB (currently ZODB4, ZODB4-wc2 and ZODB5). ZEO5 is know to currently fail zloadrace. However, even though ZODB#290 was fixed, ZEO5 turned out to also fail on zopenrace: def test_zodb_zopenrace(): # exercises ZODB.Connection + particular storage implementation > zopenrace.main() lib/tests/test_zodb.py:382: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ <decorator-gen-1>:2: in main ??? ../../tools/go/pygolang/golang/__init__.py:103: in _ return f(*argv, **kw) lib/tests/testprog/zopenrace.py:115: in main test(zstor) <decorator-gen-2>:2: in test ??? ../../tools/go/pygolang/golang/__init__.py:103: in _ return f(*argv, **kw) lib/tests/testprog/zopenrace.py:201: in test wg.wait() golang/_sync.pyx:246: in golang._sync.PyWorkGroup.wait ??? golang/_sync.pyx:226: in golang._sync.PyWorkGroup.go.pyrunf ??? lib/tests/testprog/zopenrace.py:165: in T1 t1() _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ def t1(): transaction.begin() zconn = db.open() root = zconn.root() obj1 = root['obj1'] obj2 = root['obj2'] # obj1 - reload it from zstor # obj2 - get it from zconn cache obj1._p_invalidate() # both objects must have the same values i1 = obj1.i i2 = obj2.i if i1 != i2: > raise AssertionError("T1: obj1.i (%d) != obj2.i (%d)" % (i1, i2)) E AssertionError: T1: obj1.i (3) != obj2.i (2) lib/tests/testprog/zopenrace.py:156: AssertionError
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Kirill Smelkov authored
Previously if an assert or something failed in spawned thread, the main thread was usually spinning indefinitely = tests hang. -> Switch all threading places to use sync.WorkGroup and this way if a thread fails, all other threads are canceled and the exception is reported back to wg.wait in main thread. Since we start to go this route, NotifyChannel is reworked to fully use channels instead of busy-waiting.
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- 26 Mar, 2021 1 commit
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Kirill Smelkov authored
setuptools_dso 2 started to emit those autogenerated files. See https://github.com/mdavidsaver/setuptools_dso/pull/15 for details.
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- 08 Mar, 2021 3 commits
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Kirill Smelkov authored
NEO 1.9 was released in 2018 and is outdated by now. NEO 1.12 is currently the latest NEO release.
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Kirill Smelkov authored
After switching to ZODB >= 4 in the previous commit, we can safely require zodbtools, because there is now no conflict in between ZODB3/ZODB eggs.
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Kirill Smelkov authored
It's been a while since last ZODB3 3.10.7 release in 2016 and the last commit in upstream ZODB3 repository (3.10 branch) is from 2017. The world switched since then to ZODB4 and to ZODB5 after that. We were still requiring ZODB3, because ZODB3 3.11 egg was just a dependency on newer ZODB, ZEO, BTrees and persistent; and this way we could be supporting all ZODB3.10.x and ZODB4 and ZODB5 via ZODB3.11. However upcoming Wendelin.core 2, for its proper working, needs MVCC semantic as implemented in ZODB5. This forces us, even for ZODB4, to backport non-trivial bits from ZODB5 (see [1]). Maintaining ZODB3 support at this point becomes non-practical, because, to our knowledge, there is no wendelin.core user that plans to continue using ZODB3 without switching to at least ZODB4 in the near future. So goodbye ZODB3. Even though ZODB still stays with us, it gives a feeling similar to [2], because in 2014, when I was myself learning ZODB, it was through ZODB3 - still at the time when all ZODB bits were living together in one place. [1] nexedi/ZODB!1 [2] https://lists.osuosl.org/pipermail/darcs-users/2008-September/014095.html
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- 11 Dec, 2020 1 commit
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Kirill Smelkov authored
DB.close() does `del self.storage`. https://github.com/zopefoundation/ZODB/blob/5.6.0-14-g0eae10cd0/src/ZODB/DB.py#L646 This way if DB was closed, but some conn(s) were not, it will crash in teardown as e.g. below: _____________ ERROR at teardown of test_bigfile_zblk1_zdata_reuse ______________ def teardown_module(): > testdb.teardown() bigfile/tests/test_filezodb.py:58: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ self = <wendelin.lib.testing.TestDB_ZEO object at 0x7fb9c0216350> def teardown(self): # close connections that test code forgot to close for connref, tb in self.connv: conn = connref() if conn is None: continue if not conn.opened: continue # still alive, but closed print("W: testdb: teardown: %s left not closed by test code" "; opened by:\n%s" % (conn, tb), file=sys.stderr) db = conn.db() > stor = db.storage E AttributeError: 'DB' object has no attribute 'storage' lib/testing.py:217: AttributeError The fix is simple - don't use db.storage at all, because it is not actually used in that code.
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- 17 Nov, 2020 2 commits
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Kirill Smelkov authored
Since ZBigFile keeps references to fileh objects that are created through it it forms a file <=> fileh cycle that is not collected without cyclic GC: https://lab.nexedi.com/nexedi/wendelin.core/blob/v0.13-52-ga702d41/bigfile/file_zodb.py#L497 https://lab.nexedi.com/nexedi/wendelin.core/blob/v0.13-52-ga702d41/bigfile/file_zodb.py#L566-571 We did not noticed this leak until now because it is small, but with upcoming wendelin.core 2 it is important to release a fileh, because there is WCFS connection associated with fileh, and if fileh is not released, that connection also stays alive, keeping on-WCFS resources still being used, and preventing WCFS from being unmounted cleanly. -> Add cyclic GC support to PyBigFile / PyBigFileH NOTE: we still don't allow PyVMA <=> PyBigFileH cycles to be collected, because fileh_close called from fileh.__del__ asserts that there are no live mappings left. See added comments for details. There is no known practical need to use such cycles, so this should be ok. See also other patches on cyclic GC topic: - 450ad804 (bigarray: ArrayRef support for BigArray) // adds cyclic GC support for PyVMA - d97641d2 (bigfile/py: Properly untrack PyVMA from GC before dealloc) /proposed-for-review-on nexedi/wendelin.core!12
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Kirill Smelkov authored
The logic in pyvma_traverse and pyvma_clear needs to be synchronized with PyVMA deallocation. In the next patche we'll be amending this logic, and it will help a reader to keep all those functions together. For the reference: PyVMA support for cyclic GC was introduced in 450ad804 (bigarray: ArrayRef support for BigArray). See also d97641d2 (bigfile/py: Properly untrack PyVMA from GC before dealloc). /proposed-for-review-on nexedi/wendelin.core!12
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