Mercurial > hg
view tests/test-fetch.t @ 40021:c537144fdbef
wireprotov2: support response caching
One of the things I've learned from managing VCS servers over the
years is that they are hard to scale. It is well known that some
companies have very beefy (read: very expensive) servers to power
their VCS needs. It is also known that specialized servers for
various VCS exist in order to facilitate scaling servers. (Mercurial
is in this boat.)
One of the aspects that make a VCS server hard to scale is the
high CPU load incurred by constant client clone/pull operations.
To alleviate the scaling pain associated with data retrieval
operations, I want to integrate caching into the Mercurial wire
protocol server as robustly as possible such that servers can
aggressively cache responses and defer as much server load as
possible.
This commit represents the initial implementation of a general
caching layer in wire protocol version 2.
We define a new interface and behavior for a wire protocol cacher
in repository.py. (This is probably where a reviewer should look
first to understand what is going on.)
The bulk of the added code is in wireprotov2server.py, where we
define how a command can opt in to being cached and integrate
caching into command dispatching.
From a very high-level:
* A command can declare itself as cacheable by providing a callable
that can be used to derive a cache key.
* At dispatch time, if a command is cacheable, we attempt to
construct a cacher and use it for serving the request and/or
caching the request.
* The dispatch layer handles the bulk of the business logic for
caching, making cachers mostly "dumb content stores."
* The mechanism for invalidating cached entries (one of the harder
parts about caching in general) is by varying the cache key when
state changes. As such, cachers don't need to be concerned with
cache invalidation.
Initially, we've hooked up support for caching "manifestdata" and
"filedata" commands. These are the simplest to cache, as they should
be immutable over time. Caching of commands related to changeset
data is a bit harder (because cache validation is impacted by
changes to bookmarks, phases, etc). This will be implemented later.
(Strictly speaking, censoring a file should invalidate caches. I've
added an inline TODO to track this edge case.)
To prove it works, this commit implements a test-only extension
providing in-memory caching backed by an lrucachedict. A new test
showing this extension behaving properly is added. FWIW, the
cacher is ~50 lines of code, demonstrating the relative ease with
which a cache can be added to a server.
While the test cacher is not suitable for production workloads, just
for kicks I performed a clone of just the changeset and manifest data
for the mozilla-unified repository. With a fully warmed cache (of just
the manifest data since changeset data is not cached), server-side
CPU usage dropped from ~73s to ~28s. That's pretty significant and
demonstrates the potential that response caching has on server
scalability!
Differential Revision: https://phab.mercurial-scm.org/D4773
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Wed, 26 Sep 2018 17:16:56 -0700 |
parents | eb586ed5d8ce |
children | 5c2a4f37eace |
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#require serve $ echo "[extensions]" >> $HGRCPATH $ echo "fetch=" >> $HGRCPATH test fetch with default branches only $ hg init a $ echo a > a/a $ hg --cwd a commit -Ama adding a $ hg clone a b updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg clone a c updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo b > a/b $ hg --cwd a commit -Amb adding b $ hg --cwd a parents -q 1:d2ae7f538514 should pull one change $ hg --cwd b fetch ../a pulling from ../a searching for changes adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files new changesets d2ae7f538514 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg --cwd b parents -q 1:d2ae7f538514 $ echo c > c/c $ hg --cwd c commit -Amc adding c $ hg clone c d updating to branch default 2 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg clone c e updating to branch default 2 files updated, 0 files merged, 0 files removed, 0 files unresolved We cannot use the default commit message if fetching from a local repo, because the path of the repo will be included in the commit message, making every commit appear different. should merge c into a $ hg --cwd c fetch -d '0 0' -m 'automated merge' ../a pulling from ../a searching for changes adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files (+1 heads) new changesets d2ae7f538514 updating to 2:d2ae7f538514 1 files updated, 0 files merged, 1 files removed, 0 files unresolved merging with 1:d36c0562f908 1 files updated, 0 files merged, 0 files removed, 0 files unresolved new changeset 3:a323a0c43ec4 merges remote changes with local $ ls c a b c $ hg serve --cwd a -a localhost -p $HGPORT -d --pid-file=hg.pid $ cat a/hg.pid >> "$DAEMON_PIDS" fetch over http, no auth (this also tests that editor is invoked if '--edit' is specified) $ HGEDITOR=cat hg --cwd d fetch --edit http://localhost:$HGPORT/ pulling from http://localhost:$HGPORT/ searching for changes adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files (+1 heads) new changesets d2ae7f538514 updating to 2:d2ae7f538514 1 files updated, 0 files merged, 1 files removed, 0 files unresolved merging with 1:d36c0562f908 1 files updated, 0 files merged, 0 files removed, 0 files unresolved Automated merge with http://localhost:$HGPORT/ HG: Enter commit message. Lines beginning with 'HG:' are removed. HG: Leave message empty to abort commit. HG: -- HG: user: test HG: branch merge HG: branch 'default' HG: changed c new changeset 3:* merges remote changes with local (glob) $ hg --cwd d tip --template '{desc}\n' Automated merge with http://localhost:$HGPORT/ $ hg --cwd d status --rev 'tip^1' --rev tip A c $ hg --cwd d status --rev 'tip^2' --rev tip A b fetch over http with auth (should be hidden in desc) (this also tests that editor is not invoked if '--edit' is not specified, even though commit message is not specified explicitly) $ HGEDITOR=cat hg --cwd e fetch http://user:password@localhost:$HGPORT/ pulling from http://user:***@localhost:$HGPORT/ searching for changes adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files (+1 heads) new changesets d2ae7f538514 updating to 2:d2ae7f538514 1 files updated, 0 files merged, 1 files removed, 0 files unresolved merging with 1:d36c0562f908 1 files updated, 0 files merged, 0 files removed, 0 files unresolved new changeset 3:* merges remote changes with local (glob) $ hg --cwd e tip --template '{desc}\n' Automated merge with http://localhost:$HGPORT/ $ hg clone a f updating to branch default 2 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg clone a g updating to branch default 2 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo f > f/f $ hg --cwd f ci -Amf adding f $ echo g > g/g $ hg --cwd g ci -Amg adding g $ hg clone -q f h $ hg clone -q g i should merge f into g $ hg --cwd g fetch -d '0 0' --switch -m 'automated merge' ../f pulling from ../f searching for changes adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files (+1 heads) new changesets 6343ca3eff20 0 files updated, 0 files merged, 0 files removed, 0 files unresolved merging with 3:6343ca3eff20 1 files updated, 0 files merged, 0 files removed, 0 files unresolved new changeset 4:f7faa0b7d3c6 merges remote changes with local $ rm i/g should abort, because i is modified $ hg --cwd i fetch ../h abort: uncommitted changes [255] test fetch with named branches $ hg init nbase $ echo base > nbase/a $ hg -R nbase ci -Am base adding a $ hg -R nbase branch a marked working directory as branch a (branches are permanent and global, did you want a bookmark?) $ echo a > nbase/a $ hg -R nbase ci -m a $ hg -R nbase up -C 0 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg -R nbase branch b marked working directory as branch b $ echo b > nbase/b $ hg -R nbase ci -Am b adding b pull in change on foreign branch $ hg clone nbase n1 updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg clone nbase n2 updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg -R n1 up -C a 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo aa > n1/a $ hg -R n1 ci -m a1 $ hg -R n2 up -C b 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg -R n2 fetch -m 'merge' n1 pulling from n1 searching for changes adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files new changesets 8fdc9284bbc5 parent should be 2 (no automatic update) $ hg -R n2 parents --template '{rev}\n' 2 $ rm -fr n1 n2 pull in changes on both foreign and local branches $ hg clone nbase n1 updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg clone nbase n2 updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg -R n1 up -C a 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo aa > n1/a $ hg -R n1 ci -m a1 $ hg -R n1 up -C b 2 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo bb > n1/b $ hg -R n1 ci -m b1 $ hg -R n2 up -C b 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg -R n2 fetch -m 'merge' n1 pulling from n1 searching for changes adding changesets adding manifests adding file changes added 2 changesets with 2 changes to 2 files new changesets 8fdc9284bbc5:3c4a837a864f 1 files updated, 0 files merged, 0 files removed, 0 files unresolved parent should be 4 (fast forward) $ hg -R n2 parents --template '{rev}\n' 4 $ rm -fr n1 n2 pull changes on foreign (2 new heads) and local (1 new head) branches with a local change $ hg clone nbase n1 updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg clone nbase n2 updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg -R n1 up -C a 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo a1 > n1/a $ hg -R n1 ci -m a1 $ hg -R n1 up -C b 2 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo bb > n1/b $ hg -R n1 ci -m b1 $ hg -R n1 up -C 1 1 files updated, 0 files merged, 1 files removed, 0 files unresolved $ echo a2 > n1/a $ hg -R n1 ci -m a2 created new head $ hg -R n2 up -C b 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo change >> n2/c $ hg -R n2 ci -A -m local adding c $ hg -R n2 fetch -d '0 0' -m 'merge' n1 pulling from n1 searching for changes adding changesets adding manifests adding file changes added 3 changesets with 3 changes to 2 files (+2 heads) new changesets d05ce59ff88d:a7954de24e4c updating to 5:3c4a837a864f 1 files updated, 0 files merged, 1 files removed, 0 files unresolved merging with 3:1267f84a9ea5 1 files updated, 0 files merged, 0 files removed, 0 files unresolved new changeset 7:2cf2a1261f21 merges remote changes with local parent should be 7 (new merge changeset) $ hg -R n2 parents --template '{rev}\n' 7 $ rm -fr n1 n2 pull in changes on foreign (merge of local branch) and local (2 new heads) with a local change $ hg clone nbase n1 updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg clone nbase n2 updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg -R n1 up -C a 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg -R n1 merge b 1 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ hg -R n1 ci -m merge $ hg -R n1 up -C 2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo c > n1/a $ hg -R n1 ci -m c $ hg -R n1 up -C 2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo cc > n1/a $ hg -R n1 ci -m cc created new head $ hg -R n2 up -C b 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo change >> n2/b $ hg -R n2 ci -A -m local $ hg -R n2 fetch -m 'merge' n1 pulling from n1 searching for changes adding changesets adding manifests adding file changes added 3 changesets with 2 changes to 1 files (+2 heads) new changesets b84e8d0f020f:3d3bf54f99c0 not merging with 1 other new branch heads (use "hg heads ." and "hg merge" to merge them) [1] parent should be 3 (fetch did not merge anything) $ hg -R n2 parents --template '{rev}\n' 3 $ rm -fr n1 n2 pull in change on different branch than dirstate $ hg init n1 $ echo a > n1/a $ hg -R n1 ci -Am initial adding a $ hg clone n1 n2 updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo b > n1/a $ hg -R n1 ci -m next $ hg -R n2 branch topic marked working directory as branch topic (branches are permanent and global, did you want a bookmark?) $ hg -R n2 fetch -m merge n1 abort: working directory not at branch tip (use 'hg update' to check out branch tip) [255] parent should be 0 (fetch did not update or merge anything) $ hg -R n2 parents --template '{rev}\n' 0 $ rm -fr n1 n2 test fetch with inactive branches $ hg init ib1 $ echo a > ib1/a $ hg --cwd ib1 ci -Am base adding a $ hg --cwd ib1 branch second marked working directory as branch second (branches are permanent and global, did you want a bookmark?) $ echo b > ib1/b $ hg --cwd ib1 ci -Am onsecond adding b $ hg --cwd ib1 branch -f default marked working directory as branch default $ echo c > ib1/c $ hg --cwd ib1 ci -Am newdefault adding c created new head $ hg clone ib1 ib2 updating to branch default 3 files updated, 0 files merged, 0 files removed, 0 files unresolved fetch should succeed $ hg --cwd ib2 fetch ../ib1 pulling from ../ib1 searching for changes no changes found $ rm -fr ib1 ib2 test issue1726 $ hg init i1726r1 $ echo a > i1726r1/a $ hg --cwd i1726r1 ci -Am base adding a $ hg clone i1726r1 i1726r2 updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo b > i1726r1/a $ hg --cwd i1726r1 ci -m second $ echo c > i1726r2/a $ hg --cwd i1726r2 ci -m third $ HGMERGE=true hg --cwd i1726r2 fetch ../i1726r1 pulling from ../i1726r1 searching for changes adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files (+1 heads) new changesets 7837755a2789 updating to 2:7837755a2789 1 files updated, 0 files merged, 0 files removed, 0 files unresolved merging with 1:d1f0c6c48ebd merging a 0 files updated, 1 files merged, 0 files removed, 0 files unresolved new changeset 3:* merges remote changes with local (glob) $ hg --cwd i1726r2 heads default --template '{rev}\n' 3 test issue2047 $ hg -q init i2047a $ cd i2047a $ echo a > a $ hg -q ci -Am a $ hg -q branch stable $ echo b > b $ hg -q ci -Am b $ cd .. $ hg -q clone -r 0 i2047a i2047b $ cd i2047b $ hg fetch ../i2047a pulling from ../i2047a searching for changes adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files new changesets c8735224de5c $ cd ..