view tests/test-parseindex.t @ 39561:d06834e0f48e

wireprotov2peer: stream decoded responses

Previously, wire protocol version 2 would buffer all response data.
Only once all data was received did we CBOR decode it and resolve
the future associated with the command. This was obviously not
desirable. In future commits that introduce large response payloads,
this caused significant memory bloat and slowed down client
operations due to waiting on the server.

This commit refactors the response handling code so that response
data can be streamed.

Command response objects now contain a buffered CBOR decoder. As
new data arrives, it is fed into the decoder. Decoded objects are
made available to the generator as they are decoded.

Because there is a separate thread processing incoming frames and
feeding data into the response object, there is the potential for
race conditions when mutating response objects. So a lock has been
added to guard access to critical state variables.

Because the generator emitting decoded objects needs to wait on
those objects to become available, we've added an Event for the
generator to wait on so it doesn't busy loop. This does mean
there is the potential for deadlocks. And I'm pretty sure they can
occur in some scenarios. We already have a handful of TODOs around
this. But I've added some more. Fixing this will likely require
moving the background thread receiving frames into clienthandler.
We likely would have done this anyway when implementing the client
bits for the SSH transport.

Test output changes because the initial CBOR map holding the overall
response state is now always handled internally by the response
object.

Differential Revision: https://phab.mercurial-scm.org/D4474

revlog.parseindex must be able to parse the index file even if
an index entry is split between two 64k blocks.  The ideal test
would be to create an index file with inline data where
64k < size < 64k + 64 (64k is the size of the read buffer, 64 is
the size of an index entry) and with an index entry starting right
before the 64k block boundary, and try to read it.
We approximate that by reducing the read buffer to 1 byte.

  $ hg init a
  $ cd a
  $ echo abc > foo
  $ hg add foo
  $ hg commit -m 'add foo'
  $ echo >> foo
  $ hg commit -m 'change foo'
  $ hg log -r 0:
  changeset:   0:7c31755bf9b5
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add foo
  
  changeset:   1:26333235a41c
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     change foo
  
  $ cat >> test.py << EOF
  > from __future__ import print_function
  > from mercurial import changelog, vfs
  > from mercurial.node import *
  > 
  > class singlebyteread(object):
  >     def __init__(self, real):
  >         self.real = real
  > 
  >     def read(self, size=-1):
  >         if size == 65536:
  >             size = 1
  >         return self.real.read(size)
  > 
  >     def __getattr__(self, key):
  >         return getattr(self.real, key)
  > 
  >     def __enter__(self):
  >         self.real.__enter__()
  >         return self
  > 
  >     def __exit__(self, *args, **kwargs):
  >         return self.real.__exit__(*args, **kwargs)
  > 
  > def opener(*args):
  >     o = vfs.vfs(*args)
  >     def wrapper(*a, **kwargs):
  >         f = o(*a, **kwargs)
  >         return singlebyteread(f)
  >     return wrapper
  > 
  > cl = changelog.changelog(opener('.hg/store'))
  > print(len(cl), 'revisions:')
  > for r in cl:
  >     print(short(cl.node(r)))
  > EOF
  $ $PYTHON test.py
  2 revisions:
  7c31755bf9b5
  26333235a41c

  $ cd ..

#if no-pure

Test SEGV caused by bad revision passed to reachableroots() (issue4775):

  $ cd a

  $ $PYTHON <<EOF
  > from __future__ import print_function
  > from mercurial import changelog, vfs
  > cl = changelog.changelog(vfs.vfs('.hg/store'))
  > print('good heads:')
  > for head in [0, len(cl) - 1, -1]:
  >     print('%s: %r' % (head, cl.reachableroots(0, [head], [0])))
  > print('bad heads:')
  > for head in [len(cl), 10000, -2, -10000, None]:
  >     print('%s:' % head, end=' ')
  >     try:
  >         cl.reachableroots(0, [head], [0])
  >         print('uncaught buffer overflow?')
  >     except (IndexError, TypeError) as inst:
  >         print(inst)
  > print('good roots:')
  > for root in [0, len(cl) - 1, -1]:
  >     print('%s: %r' % (root, cl.reachableroots(root, [len(cl) - 1], [root])))
  > print('out-of-range roots are ignored:')
  > for root in [len(cl), 10000, -2, -10000]:
  >     print('%s: %r' % (root, cl.reachableroots(root, [len(cl) - 1], [root])))
  > print('bad roots:')
  > for root in [None]:
  >     print('%s:' % root, end=' ')
  >     try:
  >         cl.reachableroots(root, [len(cl) - 1], [root])
  >         print('uncaught error?')
  >     except TypeError as inst:
  >         print(inst)
  > EOF
  good heads:
  0: [0]
  1: [0]
  -1: []
  bad heads:
  2: head out of range
  10000: head out of range
  -2: head out of range
  -10000: head out of range
  None: an integer is required
  good roots:
  0: [0]
  1: [1]
  -1: [-1]
  out-of-range roots are ignored:
  2: []
  10000: []
  -2: []
  -10000: []
  bad roots:
  None: an integer is required

  $ cd ..

Test corrupted p1/p2 fields that could cause SEGV at parsers.c:

  $ mkdir invalidparent
  $ cd invalidparent

  $ hg clone --pull -q --config phases.publish=False ../a limit
  $ hg clone --pull -q --config phases.publish=False ../a segv
  $ rm -R limit/.hg/cache segv/.hg/cache

  $ $PYTHON <<EOF
  > data = open("limit/.hg/store/00changelog.i", "rb").read()
  > for n, p in [(b'limit', b'\0\0\0\x02'), (b'segv', b'\0\x01\0\0')]:
  >     # corrupt p1 at rev0 and p2 at rev1
  >     d = data[:24] + p + data[28:127 + 28] + p + data[127 + 32:]
  >     open(n + b"/.hg/store/00changelog.i", "wb").write(d)
  > EOF

  $ hg -R limit debugrevlogindex -f1 -c
     rev flag     size   link     p1     p2       nodeid
       0 0000       62      0      2     -1 7c31755bf9b5
       1 0000       65      1      0      2 26333235a41c

  $ hg -R limit debugdeltachain -c
      rev  chain# chainlen     prev   delta       size    rawsize  chainsize     ratio   lindist extradist extraratio
        0       1        1       -1    base         63         62         63   1.01613        63         0    0.00000
        1       2        1       -1    base         66         65         66   1.01538        66         0    0.00000

  $ hg -R segv debugrevlogindex -f1 -c
     rev flag     size   link     p1     p2       nodeid
       0 0000       62      0  65536     -1 7c31755bf9b5
       1 0000       65      1      0  65536 26333235a41c

  $ hg -R segv debugdeltachain -c
      rev  chain# chainlen     prev   delta       size    rawsize  chainsize     ratio   lindist extradist extraratio
        0       1        1       -1    base         63         62         63   1.01613        63         0    0.00000
        1       2        1       -1    base         66         65         66   1.01538        66         0    0.00000

  $ cat <<EOF > test.py
  > from __future__ import print_function
  > import sys
  > from mercurial import changelog, vfs
  > cl = changelog.changelog(vfs.vfs(sys.argv[1]))
  > n0, n1 = cl.node(0), cl.node(1)
  > ops = [
  >     ('reachableroots',
  >      lambda: cl.index.reachableroots2(0, [1], [0], False)),
  >     ('compute_phases_map_sets', lambda: cl.computephases([[0], []])),
  >     ('index_headrevs', lambda: cl.headrevs()),
  >     ('find_gca_candidates', lambda: cl.commonancestorsheads(n0, n1)),
  >     ('find_deepest', lambda: cl.ancestor(n0, n1)),
  >     ]
  > for l, f in ops:
  >     print(l + ':', end=' ')
  >     try:
  >         f()
  >         print('uncaught buffer overflow?')
  >     except ValueError as inst:
  >         print(inst)
  > EOF

  $ $PYTHON test.py limit/.hg/store
  reachableroots: parent out of range
  compute_phases_map_sets: parent out of range
  index_headrevs: parent out of range
  find_gca_candidates: parent out of range
  find_deepest: parent out of range
  $ $PYTHON test.py segv/.hg/store
  reachableroots: parent out of range
  compute_phases_map_sets: parent out of range
  index_headrevs: parent out of range
  find_gca_candidates: parent out of range
  find_deepest: parent out of range

  $ cd ..

#endif