Mercurial > hg
view tests/test-setdiscovery.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 | 1de3364320af |
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Function to test discovery between two repos in both directions, using both the local shortcut (which is currently not activated by default) and the full remotable protocol: $ testdesc() { # revs_a, revs_b, dagdesc > if [ -d foo ]; then rm -rf foo; fi > hg init foo > cd foo > hg debugbuilddag "$3" > hg clone . a $1 --quiet > hg clone . b $2 --quiet > echo > echo "% -- a -> b tree" > hg -R a debugdiscovery b --verbose --old > echo > echo "% -- a -> b set" > hg -R a debugdiscovery b --verbose --debug --config progress.debug=true > echo > echo "% -- a -> b set (tip only)" > hg -R a debugdiscovery b --verbose --debug --config progress.debug=true --rev tip > echo > echo "% -- b -> a tree" > hg -R b debugdiscovery a --verbose --old > echo > echo "% -- b -> a set" > hg -R b debugdiscovery a --verbose --debug --config progress.debug=true > echo > echo "% -- b -> a set (tip only)" > hg -R b debugdiscovery a --verbose --debug --config progress.debug=true --rev tip > cd .. > } Small superset: $ testdesc '-ra1 -ra2' '-rb1 -rb2 -rb3' ' > +2:f +1:a1:b1 > <f +4 :a2 > +5 :b2 > <f +3 :b3' % -- a -> b tree comparing with b searching for changes unpruned common: 01241442b3c2 66f7d451a68b b5714e113bc0 common heads: 01241442b3c2 b5714e113bc0 local is subset % -- a -> b set comparing with b query 1; heads searching for changes all local heads known remotely common heads: 01241442b3c2 b5714e113bc0 local is subset % -- a -> b set (tip only) comparing with b query 1; heads searching for changes all local heads known remotely common heads: b5714e113bc0 % -- b -> a tree comparing with a searching for changes unpruned common: 01241442b3c2 b5714e113bc0 common heads: 01241442b3c2 b5714e113bc0 remote is subset % -- b -> a set comparing with a query 1; heads searching for changes all remote heads known locally common heads: 01241442b3c2 b5714e113bc0 remote is subset % -- b -> a set (tip only) comparing with a query 1; heads searching for changes all remote heads known locally common heads: 01241442b3c2 b5714e113bc0 remote is subset Many new: $ testdesc '-ra1 -ra2' '-rb' ' > +2:f +3:a1 +3:b > <f +30 :a2' % -- a -> b tree comparing with b searching for changes unpruned common: bebd167eb94d common heads: bebd167eb94d % -- a -> b set comparing with b query 1; heads searching for changes taking initial sample searching: 2 queries query 2; still undecided: 29, sample size is: 29 2 total queries in *.????s (glob) common heads: bebd167eb94d % -- a -> b set (tip only) comparing with b query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 31, sample size is: 31 2 total queries in *.????s (glob) common heads: 66f7d451a68b % -- b -> a tree comparing with a searching for changes unpruned common: 66f7d451a68b bebd167eb94d common heads: bebd167eb94d % -- b -> a set comparing with a query 1; heads searching for changes taking initial sample searching: 2 queries query 2; still undecided: 2, sample size is: 2 2 total queries in *.????s (glob) common heads: bebd167eb94d % -- b -> a set (tip only) comparing with a query 1; heads searching for changes taking initial sample searching: 2 queries query 2; still undecided: 2, sample size is: 2 2 total queries in *.????s (glob) common heads: bebd167eb94d Both sides many new with stub: $ testdesc '-ra1 -ra2' '-rb' ' > +2:f +2:a1 +30 :b > <f +30 :a2' % -- a -> b tree comparing with b searching for changes unpruned common: 2dc09a01254d common heads: 2dc09a01254d % -- a -> b set comparing with b query 1; heads searching for changes taking initial sample searching: 2 queries query 2; still undecided: 29, sample size is: 29 2 total queries in *.????s (glob) common heads: 2dc09a01254d % -- a -> b set (tip only) comparing with b query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 31, sample size is: 31 2 total queries in *.????s (glob) common heads: 66f7d451a68b % -- b -> a tree comparing with a searching for changes unpruned common: 2dc09a01254d 66f7d451a68b common heads: 2dc09a01254d % -- b -> a set comparing with a query 1; heads searching for changes taking initial sample searching: 2 queries query 2; still undecided: 29, sample size is: 29 2 total queries in *.????s (glob) common heads: 2dc09a01254d % -- b -> a set (tip only) comparing with a query 1; heads searching for changes taking initial sample searching: 2 queries query 2; still undecided: 29, sample size is: 29 2 total queries in *.????s (glob) common heads: 2dc09a01254d Both many new: $ testdesc '-ra' '-rb' ' > +2:f +30 :b > <f +30 :a' % -- a -> b tree comparing with b searching for changes unpruned common: 66f7d451a68b common heads: 66f7d451a68b % -- a -> b set comparing with b query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 31, sample size is: 31 2 total queries in *.????s (glob) common heads: 66f7d451a68b % -- a -> b set (tip only) comparing with b query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 31, sample size is: 31 2 total queries in *.????s (glob) common heads: 66f7d451a68b % -- b -> a tree comparing with a searching for changes unpruned common: 66f7d451a68b common heads: 66f7d451a68b % -- b -> a set comparing with a query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 31, sample size is: 31 2 total queries in *.????s (glob) common heads: 66f7d451a68b % -- b -> a set (tip only) comparing with a query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 31, sample size is: 31 2 total queries in *.????s (glob) common heads: 66f7d451a68b Both many new skewed: $ testdesc '-ra' '-rb' ' > +2:f +30 :b > <f +50 :a' % -- a -> b tree comparing with b searching for changes unpruned common: 66f7d451a68b common heads: 66f7d451a68b % -- a -> b set comparing with b query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 51, sample size is: 51 2 total queries in *.????s (glob) common heads: 66f7d451a68b % -- a -> b set (tip only) comparing with b query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 51, sample size is: 51 2 total queries in *.????s (glob) common heads: 66f7d451a68b % -- b -> a tree comparing with a searching for changes unpruned common: 66f7d451a68b common heads: 66f7d451a68b % -- b -> a set comparing with a query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 31, sample size is: 31 2 total queries in *.????s (glob) common heads: 66f7d451a68b % -- b -> a set (tip only) comparing with a query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 31, sample size is: 31 2 total queries in *.????s (glob) common heads: 66f7d451a68b Both many new on top of long history: $ testdesc '-ra' '-rb' ' > +1000:f +30 :b > <f +50 :a' % -- a -> b tree comparing with b searching for changes unpruned common: 7ead0cba2838 common heads: 7ead0cba2838 % -- a -> b set comparing with b query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 1049, sample size is: 11 sampling from both directions searching: 3 queries query 3; still undecided: 31, sample size is: 31 3 total queries in *.????s (glob) common heads: 7ead0cba2838 % -- a -> b set (tip only) comparing with b query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 1049, sample size is: 11 sampling from both directions searching: 3 queries query 3; still undecided: 31, sample size is: 31 3 total queries in *.????s (glob) common heads: 7ead0cba2838 % -- b -> a tree comparing with a searching for changes unpruned common: 7ead0cba2838 common heads: 7ead0cba2838 % -- b -> a set comparing with a query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 1029, sample size is: 11 sampling from both directions searching: 3 queries query 3; still undecided: 15, sample size is: 15 3 total queries in *.????s (glob) common heads: 7ead0cba2838 % -- b -> a set (tip only) comparing with a query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 1029, sample size is: 11 sampling from both directions searching: 3 queries query 3; still undecided: 15, sample size is: 15 3 total queries in *.????s (glob) common heads: 7ead0cba2838 One with >200 heads, which used to use up all of the sample: $ hg init manyheads $ cd manyheads $ echo "+300:r @a" >dagdesc $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads $ echo "@b *r+3" >>dagdesc # one more head $ hg debugbuilddag <dagdesc reading DAG from stdin $ hg heads -t --template . | wc -c \s*261 (re) $ hg clone -b a . a adding changesets adding manifests adding file changes added 1340 changesets with 0 changes to 0 files (+259 heads) new changesets 1ea73414a91b:1c51e2c80832 updating to branch a 0 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg clone -b b . b adding changesets adding manifests adding file changes added 304 changesets with 0 changes to 0 files new changesets 1ea73414a91b:513314ca8b3a updating to branch b 0 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg -R a debugdiscovery b --debug --verbose --config progress.debug=true comparing with b query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 1240, sample size is: 100 sampling from both directions searching: 3 queries query 3; still undecided: 1140, sample size is: 200 sampling from both directions searching: 4 queries query 4; still undecided: \d+, sample size is: 200 (re) sampling from both directions searching: 5 queries query 5; still undecided: \d+, sample size is: 200 (re) sampling from both directions searching: 6 queries query 6; still undecided: \d+, sample size is: \d+ (re) 6 total queries in *.????s (glob) common heads: 3ee37d65064a $ hg -R a debugdiscovery b --debug --verbose --config progress.debug=true --rev tip comparing with b query 1; heads searching for changes taking quick initial sample searching: 2 queries query 2; still undecided: 303, sample size is: 9 sampling from both directions searching: 3 queries query 3; still undecided: 3, sample size is: 3 3 total queries in *.????s (glob) common heads: 3ee37d65064a Test actual protocol when pulling one new head in addition to common heads $ hg clone -U b c $ hg -R c id -ir tip 513314ca8b3a $ hg -R c up -qr default $ touch c/f $ hg -R c ci -Aqm "extra head" $ hg -R c id -i e64a39e7da8b $ hg serve -R c -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log $ cat hg.pid >> $DAEMON_PIDS $ hg -R b incoming http://localhost:$HGPORT/ -T '{node|short}\n' comparing with http://localhost:$HGPORT/ searching for changes e64a39e7da8b $ killdaemons.py $ cut -d' ' -f6- access.log | grep -v cmd=known # cmd=known uses random sampling "GET /?cmd=capabilities HTTP/1.1" 200 - "GET /?cmd=batch HTTP/1.1" 200 - x-hgarg-1:cmds=heads+%3Bknown+nodes%3D513314ca8b3ae4dac8eec56966265b00fcf866db x-hgproto-1:0.1 0.2 comp=$USUAL_COMPRESSIONS$ partial-pull "GET /?cmd=getbundle HTTP/1.1" 200 - x-hgarg-1:$USUAL_BUNDLE_CAPS$&cg=1&common=513314ca8b3ae4dac8eec56966265b00fcf866db&heads=e64a39e7da8b0d54bc63e81169aff001c13b3477 x-hgproto-1:0.1 0.2 comp=$USUAL_COMPRESSIONS$ partial-pull "GET /?cmd=listkeys HTTP/1.1" 200 - x-hgarg-1:namespace=phases x-hgproto-1:0.1 0.2 comp=$USUAL_COMPRESSIONS$ partial-pull $ cat errors.log $ cd .. Issue 4438 - test coverage for 3ef893520a85 issues. $ mkdir issue4438 $ cd issue4438 #if false generate new bundles: $ hg init r1 $ for i in `"$PYTHON" $TESTDIR/seq.py 101`; do hg -R r1 up -qr null && hg -R r1 branch -q b$i && hg -R r1 ci -qmb$i; done $ hg clone -q r1 r2 $ for i in `"$PYTHON" $TESTDIR/seq.py 10`; do hg -R r1 up -qr null && hg -R r1 branch -q c$i && hg -R r1 ci -qmc$i; done $ hg -R r2 branch -q r2change && hg -R r2 ci -qmr2change $ hg -R r1 bundle -qa $TESTDIR/bundles/issue4438-r1.hg $ hg -R r2 bundle -qa $TESTDIR/bundles/issue4438-r2.hg #else use existing bundles: $ hg init r1 $ hg -R r1 -q unbundle $TESTDIR/bundles/issue4438-r1.hg $ hg -R r1 -q up $ hg init r2 $ hg -R r2 -q unbundle $TESTDIR/bundles/issue4438-r2.hg $ hg -R r2 -q up #endif Set iteration order could cause wrong and unstable results - fixed in 73cfaa348650: $ hg -R r1 outgoing r2 -T'{rev} ' comparing with r2 searching for changes 101 102 103 104 105 106 107 108 109 110 (no-eol) The case where all the 'initialsamplesize' samples already were common would give 'all remote heads known locally' without checking the remaining heads - fixed in 86c35b7ae300: $ cat >> $TESTTMP/unrandomsample.py << EOF > import random > def sample(population, k): > return sorted(population)[:k] > random.sample = sample > EOF $ cat >> r1/.hg/hgrc << EOF > [extensions] > unrandomsample = $TESTTMP/unrandomsample.py > EOF $ hg -R r1 outgoing r2 -T'{rev} ' --config extensions.blackbox= comparing with r2 searching for changes 101 102 103 104 105 106 107 108 109 110 (no-eol) $ hg -R r1 --config extensions.blackbox= blackbox * @5d0b986a083e0d91f116de4691e2aaa54d5bbec0 (*)> serve --cmdserver chgunix * (glob) (chg !) * @5d0b986a083e0d91f116de4691e2aaa54d5bbec0 (*)> -R r1 outgoing r2 *-T{rev} * --config *extensions.blackbox=* (glob) * @5d0b986a083e0d91f116de4691e2aaa54d5bbec0 (*)> found 101 common and 1 unknown server heads, 2 roundtrips in *.????s (glob) * @5d0b986a083e0d91f116de4691e2aaa54d5bbec0 (*)> -R r1 outgoing r2 *-T{rev} * --config *extensions.blackbox=* exited 0 after *.?? seconds (glob) * @5d0b986a083e0d91f116de4691e2aaa54d5bbec0 (*)> -R r1 --config *extensions.blackbox=* blackbox (glob) $ cd ..