Mercurial > hg
view tests/test-convert-bzr.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 | 5abc47d4ca6b |
children | 0c72eddb4be5 |
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#require bzr $ . "$TESTDIR/bzr-definitions" create and rename on the same file in the same step $ mkdir test-createandrename $ cd test-createandrename $ bzr init -q source test empty repo conversion (issue3233) $ hg convert source source-hg initializing destination source-hg repository scanning source... sorting... converting... back to the rename stuff $ cd source $ echo a > a $ echo c > c $ echo e > e $ bzr add -q a c e $ bzr commit -q -m 'Initial add: a, c, e' $ bzr mv a b a => b $ bzr mv c d c => d $ bzr mv e f e => f $ echo a2 >> a $ mkdir e $ bzr add -q a e $ bzr commit -q -m 'rename a into b, create a, rename c into d' $ cd .. $ hg convert source source-hg scanning source... sorting... converting... 1 Initial add: a, c, e 0 rename a into b, create a, rename c into d $ glog -R source-hg o 1@source "rename a into b, create a, rename c into d" files+: [b d f], files-: [c e], files: [a] | o 0@source "Initial add: a, c, e" files+: [a c e], files-: [], files: [] manifest $ hg manifest -R source-hg -r tip a b d f test --rev option $ hg convert -r 1 source source-1-hg initializing destination source-1-hg repository scanning source... sorting... converting... 0 Initial add: a, c, e $ glog -R source-1-hg o 0@source "Initial add: a, c, e" files+: [a c e], files-: [], files: [] test with filemap $ cat > filemap <<EOF > exclude a > EOF $ hg convert --filemap filemap source source-filemap-hg initializing destination source-filemap-hg repository scanning source... sorting... converting... 1 Initial add: a, c, e 0 rename a into b, create a, rename c into d $ hg -R source-filemap-hg manifest -r tip b d f convert from lightweight checkout $ bzr checkout --lightweight source source-light $ hg convert -s bzr source-light source-light-hg initializing destination source-light-hg repository warning: lightweight checkouts may cause conversion failures, try with a regular branch instead. $TESTTMP/test-createandrename/source-light does not look like a Bazaar repository abort: source-light: missing or unsupported repository [255] extract timestamps that look just like hg's {date|isodate}: yyyy-mm-dd HH:MM zzzz (no seconds!) compare timestamps $ cd source $ bzr log | \ > sed '/timestamp/!d;s/.\{15\}\([0-9: -]\{16\}\):.. \(.[0-9]\{4\}\)/\1 \2/' \ > > ../bzr-timestamps $ cd .. $ hg -R source-hg log --template "{date|isodate}\n" > hg-timestamps $ cmp bzr-timestamps hg-timestamps || diff -u bzr-timestamps hg-timestamps $ cd .. merge $ mkdir test-merge $ cd test-merge $ cat > helper.py <<EOF > import sys > from bzrlib import workingtree > wt = workingtree.WorkingTree.open('.') > > message, stamp = sys.argv[1:] > wt.commit(message, timestamp=int(stamp)) > EOF $ bzr init -q source $ cd source $ echo content > a $ echo content2 > b $ bzr add -q a b $ bzr commit -q -m 'Initial add' $ cd .. $ bzr branch -q source source-improve $ cd source $ echo more >> a $ "$PYTHON" ../helper.py 'Editing a' 100 $ cd ../source-improve $ echo content3 >> b $ "$PYTHON" ../helper.py 'Editing b' 200 $ cd ../source $ bzr merge -q ../source-improve $ bzr commit -q -m 'Merged improve branch' $ cd .. $ hg convert --datesort source source-hg initializing destination source-hg repository scanning source... sorting... converting... 3 Initial add 2 Editing a 1 Editing b 0 Merged improve branch $ glog -R source-hg o 3@source "Merged improve branch" files+: [], files-: [], files: [b] |\ | o 2@source-improve "Editing b" files+: [], files-: [], files: [b] | | o | 1@source "Editing a" files+: [], files-: [], files: [a] |/ o 0@source "Initial add" files+: [a b], files-: [], files: [] $ cd .. #if symlink execbit symlinks and executable files $ mkdir test-symlinks $ cd test-symlinks $ bzr init -q source $ cd source $ touch program $ chmod +x program $ ln -s program altname $ mkdir d $ echo a > d/a $ ln -s a syma $ bzr add -q altname program syma d/a $ bzr commit -q -m 'Initial setup' $ touch newprog $ chmod +x newprog $ rm altname $ ln -s newprog altname $ chmod -x program $ bzr add -q newprog $ bzr commit -q -m 'Symlink changed, x bits changed' $ cd .. $ hg convert source source-hg initializing destination source-hg repository scanning source... sorting... converting... 1 Initial setup 0 Symlink changed, x bits changed $ manifest source-hg 0 % manifest of 0 644 @ altname 644 d/a 755 * program 644 @ syma $ manifest source-hg tip % manifest of tip 644 @ altname 644 d/a 755 * newprog 644 program 644 @ syma test the symlinks can be recreated $ cd source-hg $ hg up 5 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg cat syma; echo a $ cd ../.. #endif Multiple branches $ bzr init-repo -q --no-trees repo $ bzr init -q repo/trunk $ bzr co repo/trunk repo-trunk $ cd repo-trunk $ echo a > a $ bzr add -q a $ bzr ci -qm adda $ bzr tag trunk-tag Created tag trunk-tag. $ bzr switch -b branch Tree is up to date at revision 1. Switched to branch: *repo/branch/ (glob) $ sleep 1 $ echo b > b $ bzr add -q b $ bzr ci -qm addb $ bzr tag branch-tag Created tag branch-tag. $ bzr switch --force ../repo/trunk Updated to revision 1. Switched to branch: */repo/trunk/ (glob) $ sleep 1 $ echo a >> a $ bzr ci -qm changea $ cd .. $ hg convert --datesort repo repo-bzr initializing destination repo-bzr repository scanning source... sorting... converting... 2 adda 1 addb 0 changea updating tags $ (cd repo-bzr; glog) o 3@default "update tags" files+: [.hgtags], files-: [], files: [] | o 2@default "changea" files+: [], files-: [], files: [a] | | o 1@branch "addb" files+: [b], files-: [], files: [] |/ o 0@default "adda" files+: [a], files-: [], files: [] Test tags (converted identifiers are not stable because bzr ones are not and get incorporated in extra fields). $ hg -R repo-bzr tags tip 3:* (glob) branch-tag 1:* (glob) trunk-tag 0:* (glob) Nested repositories (issue3254) $ bzr init-repo -q --no-trees repo/inner $ bzr init -q repo/inner/trunk $ bzr co repo/inner/trunk inner-trunk $ cd inner-trunk $ echo b > b $ bzr add -q b $ bzr ci -qm addb $ cd .. $ hg convert --datesort repo noinner-bzr initializing destination noinner-bzr repository scanning source... sorting... converting... 2 adda 1 addb 0 changea updating tags