view tests/test-bugzilla.t @ 33207:895ecec31c70

revlog: add an experimental option to mitigated delta issues (issue5480)

The general delta heuristic to select a delta do not scale with the number of
branch. The delta base is frequently too far away to be able to reuse a chain
according to the "distance" criteria. This leads to insertion of larger delta (or
even full text) that themselves push the bases for the next delta further away
leading to more large deltas and full texts. This full text and frequent
recomputation throw Mercurial performance in disarray.

For example of a slightly large repository

  280 000 files (2 150 000 versions)
  430 000 changesets (10 000 topological heads)

Number below compares repository with and without the distance criteria:

manifest size:
    with:    21.4 GB
    without:  0.3 GB

store size:
    with:    28.7 GB
    without   7.4 GB

bundle last 15 00 revisions:
    with:    800 seconds
             971 MB
    without:  50 seconds
              73 MB

unbundle time (of the last 15K revisions):
    with:    1150 seconds (~19 minutes)
    without:   35 seconds

Similar issues has been observed in other repositories.


Adding a new option or "feature" on stable is uncommon. However, given that this
issues is making Mercurial practically unusable, I'm exceptionally targeting
this patch for stable.

What is actually needed is a full rework of the delta building and reading
logic. However, that will be a longer process and churn not suitable for stable.

In the meantime, we introduces a quick and dirty mitigation of this in the
'experimental' config space. The new option introduces a way to set the maximum
amount of memory usable to store a diff in memory. This extend the ability for
Mercurial to create chains without removing all safe guard regarding memory
access. The option should be phased out when core has a more proper solution
available.

Setting the limit to '0' remove all limits, setting it to '-1' use the default
limit (textsize x 4).

mock bugzilla driver for testing template output:

  $ cat <<EOF > bzmock.py
  > from __future__ import absolute_import
  > from mercurial import extensions
  > 
  > def extsetup(ui):
  >     bugzilla = extensions.find('bugzilla')
  >     class bzmock(bugzilla.bzaccess):
  >         def __init__(self, ui):
  >             super(bzmock, self).__init__(ui)
  >             self._logfile = ui.config('bugzilla', 'mocklog')
  >         def updatebug(self, bugid, newstate, text, committer):
  >             with open(self._logfile, 'a') as f:
  >                 f.write('update bugid=%r, newstate=%r, committer=%r\n'
  >                         % (bugid, newstate, committer))
  >                 f.write('----\n' + text + '\n----\n')
  >         def notify(self, bugs, committer):
  >             with open(self._logfile, 'a') as f:
  >                 f.write('notify bugs=%r, committer=%r\n'
  >                         % (bugs, committer))
  >     bugzilla.bugzilla._versions['mock'] = bzmock
  > EOF

set up mock repository:

  $ hg init mockremote
  $ cat <<EOF > mockremote/.hg/hgrc
  > [extensions]
  > bugzilla =
  > bzmock = $TESTTMP/bzmock.py
  > 
  > [bugzilla]
  > version = mock
  > mocklog = $TESTTMP/bzmock.log
  > 
  > [hooks]
  > incoming.bugzilla = python:hgext.bugzilla.hook
  > 
  > [web]
  > baseurl=http://example.org/hg
  > 
  > %include $TESTTMP/bzstyle.hgrc
  > EOF

  $ hg clone -q mockremote mocklocal

push with default template:

  $ echo '[bugzilla]' > bzstyle.hgrc
  $ echo foo > mocklocal/foo
  $ hg ci -R mocklocal -Aqm 'Fixes bug 123'
  $ hg -R mocklocal push -q
  $ cat bzmock.log && rm bzmock.log
  update bugid=123, newstate={}, committer='test'
  ----
  changeset 7875a8342c6f in repo $TESTTMP/mockremote refers to bug 123. (glob)
  details:
  	Fixes bug 123
  ----
  notify bugs={123: {}}, committer='test'

push with style:

  $ cat <<EOF > bzstyle.map
  > changeset = "{node|short} refers to bug {bug}."
  > EOF
  $ echo "style = $TESTTMP/bzstyle.map" >> bzstyle.hgrc
  $ echo foo >> mocklocal/foo
  $ hg ci -R mocklocal -qm 'Fixes bug 456'
  $ hg -R mocklocal push -q
  $ cat bzmock.log && rm bzmock.log
  update bugid=456, newstate={}, committer='test'
  ----
  2808b172464b refers to bug 456.
  ----
  notify bugs={456: {}}, committer='test'

push with template (overrides style):

  $ cat <<EOF >> bzstyle.hgrc
  > template = Changeset {node|short} in {root|basename}.
  >            {hgweb}/rev/{node|short}\n
  >            {desc}
  > EOF
  $ echo foo >> mocklocal/foo
  $ hg ci -R mocklocal -qm 'Fixes bug 789'
  $ hg -R mocklocal push -q
  $ cat bzmock.log && rm bzmock.log
  update bugid=789, newstate={}, committer='test'
  ----
  Changeset a770f3e409f2 in mockremote.
  http://example.org/hg/rev/a770f3e409f2
  
  Fixes bug 789
  ----
  notify bugs={789: {}}, committer='test'