wcfs: Provide isolation to clients
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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wcfs/client/.gitignore
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wcfs/client/__init__.py
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wcfs/client/_wcfs.pxd
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wcfs/client/_wcfs.pyx
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wcfs/client/wcfs.cpp
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wcfs/client/wcfs.h
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wcfs/client/wcfs_misc.cpp
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wcfs/client/wcfs_misc.h
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wcfs/client/wcfs_watchlink.h
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