• Kirill Smelkov's avatar
    Teach gitlab-workhorse to serve requests to get raw blobs · d763bd17
    Kirill Smelkov authored
    Currently GitLab serves requests to get raw blobs via Ruby-on-Rails code and
    Unicorn. Because RoR/Unicorn is relatively heavyweight, in environment where
    there are a lot of simultaneous requests to get raw blobs, this works very slow
    and server is constantly overloaded.
    
    On the other hand, to get raw blob content, we do not need anything from RoR
    framework - we only need to have access to project git repository on filesystem,
    and knowing whether access for getting data from there should be granted or
    not. That means it is possible to handle '.../raw/....' request directly
    in more lightweight and performant gitlab-workhorse.
    
    As gitlab-workhorse is written in Go, and Go has good concurrency/parallelism
    support and is generally much faster than Ruby, moving raw blob serving task to
    it makes sense and should be a net win.
    
    In this patch: we add infrastructure to process GET request for '/raw/...':
    
    - extract project / ref and path from URL
    - query auth backend for whether download access should be granted or not
    - emit blob content via spawning external `git cat-file`
    
    I've tried to mimic the output to be as close as the one emitted by RoR code,
    with the idea that for users the change should be transparent.
    
    As in this patch we do auth backend query for every request to get a blob, RoR
    code is still loaded very much, so essentially there is no speedup yet:
    
      (on a 8-CPU i7-3770S with 16GB of RAM, 2001:67c:1254:e:89::fa34 is on localhost)
    
      # without patch: request eventually goes to unicorn  (9 unicorn workers)
      $ ./wrk -c40 -d10 -t1 --latency http://[2001:67c:1254:e:89::fa34]:7777/root/slapos/raw/master/software/wendelin/software.cfg
      Running 10s test @ http://[2001:67c:1254:e:89::fa34]:7777/root/slapos/raw/master/software/wendelin/software.cfg
        1 threads and 40 connections
        Thread Stats   Avg      Stdev     Max   +/- Stdev
          Latency   609.34ms  156.92ms   1.18s    79.60%
          Req/Sec    64.22     19.90   120.00     67.00%
        Latency Distribution
           50%  596.50ms
           75%  678.23ms
           90%  805.72ms
           99%    1.04s
        642 requests in 10.01s, 1.24MB read
      Requests/sec:     64.16
      Transfer/sec:    127.00KB
    
      # with this patch: request handled by gitlab-workhorse
      $ ./wrk -c40 -d10 -t1 --latency http://[2001:67c:1254:e:89::fa34]:7777/root/slapos/raw/master/software/wendelin/software.cfg
      Running 10s test @ http://[2001:67c:1254:e:89::fa34]:7777/root/slapos/raw/master/software/wendelin/software.cfg
        1 threads and 40 connections
        Thread Stats   Avg      Stdev     Max   +/- Stdev
          Latency   622.99ms  200.08ms   1.40s    77.03%
          Req/Sec    62.65     22.37   120.00     55.00%
        Latency Distribution
           50%  589.51ms
           75%  726.88ms
           90%  896.09ms
           99%    1.18s
        626 requests in 10.01s, 1.11MB read
      Requests/sec:     62.55
      Transfer/sec:    113.73KB
    
    In the next patch we'll cache requests to auth backend and that will improve
    performance dramatically.
    d763bd17
auth.go 1.77 KB