Mercurial > hg
view tests/test-absorb.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 | ab452995eaff |
children | 1be1689d9ce9 |
line wrap: on
line source
$ cat >> $HGRCPATH << EOF > [extensions] > absorb= > EOF $ sedi() { # workaround check-code > pattern="$1" > shift > for i in "$@"; do > sed "$pattern" "$i" > "$i".tmp > mv "$i".tmp "$i" > done > } $ hg init repo1 $ cd repo1 Do not crash with empty repo: $ hg absorb abort: no mutable changeset to change [255] Make some commits: $ for i in 1 2 3 4 5; do > echo $i >> a > hg commit -A a -m "commit $i" -q > done $ hg annotate a 0: 1 1: 2 2: 3 3: 4 4: 5 Change a few lines: $ cat > a <<EOF > 1a > 2b > 3 > 4d > 5e > EOF Preview absorb changes: $ hg absorb --print-changes --dry-run showing changes for a @@ -0,2 +0,2 @@ 4ec16f8 -1 5c5f952 -2 4ec16f8 +1a 5c5f952 +2b @@ -3,2 +3,2 @@ ad8b8b7 -4 4f55fa6 -5 ad8b8b7 +4d 4f55fa6 +5e Run absorb: $ hg absorb saved backup bundle to * (glob) 2 of 2 chunk(s) applied $ hg annotate a 0: 1a 1: 2b 2: 3 3: 4d 4: 5e Delete a few lines and related commits will be removed if they will be empty: $ cat > a <<EOF > 2b > 4d > EOF $ hg absorb saved backup bundle to * (glob) 3 of 3 chunk(s) applied $ hg annotate a 1: 2b 2: 4d $ hg log -T '{rev} {desc}\n' -Gp @ 2 commit 4 | diff -r 1cae118c7ed8 -r 58a62bade1c6 a | --- a/a Thu Jan 01 00:00:00 1970 +0000 | +++ b/a Thu Jan 01 00:00:00 1970 +0000 | @@ -1,1 +1,2 @@ | 2b | +4d | o 1 commit 2 | diff -r 84add69aeac0 -r 1cae118c7ed8 a | --- a/a Thu Jan 01 00:00:00 1970 +0000 | +++ b/a Thu Jan 01 00:00:00 1970 +0000 | @@ -0,0 +1,1 @@ | +2b | o 0 commit 1 Non 1:1 map changes will be ignored: $ echo 1 > a $ hg absorb nothing applied [1] Insertaions: $ cat > a << EOF > insert before 2b > 2b > 4d > insert aftert 4d > EOF $ hg absorb -q $ hg status $ hg annotate a 1: insert before 2b 1: 2b 2: 4d 2: insert aftert 4d Bookmarks are moved: $ hg bookmark -r 1 b1 $ hg bookmark -r 2 b2 $ hg bookmark ba $ hg bookmarks b1 1:b35060a57a50 b2 2:946e4bc87915 * ba 2:946e4bc87915 $ sedi 's/insert/INSERT/' a $ hg absorb -q $ hg status $ hg bookmarks b1 1:a4183e9b3d31 b2 2:c9b20c925790 * ba 2:c9b20c925790 Non-mofified files are ignored: $ touch b $ hg commit -A b -m b $ touch c $ hg add c $ hg rm b $ hg absorb nothing applied [1] $ sedi 's/INSERT/Insert/' a $ hg absorb saved backup bundle to * (glob) 2 of 2 chunk(s) applied $ hg status A c R b Public commits will not be changed: $ hg phase -p 1 $ sedi 's/Insert/insert/' a $ hg absorb -pn showing changes for a @@ -0,1 +0,1 @@ -Insert before 2b +insert before 2b @@ -3,1 +3,1 @@ 85b4e0e -Insert aftert 4d 85b4e0e +insert aftert 4d $ hg absorb saved backup bundle to * (glob) 1 of 2 chunk(s) applied $ hg diff -U 0 diff -r 1c8eadede62a a --- a/a Thu Jan 01 00:00:00 1970 +0000 +++ b/a * (glob) @@ -1,1 +1,1 @@ -Insert before 2b +insert before 2b $ hg annotate a 1: Insert before 2b 1: 2b 2: 4d 2: insert aftert 4d Make working copy clean: $ hg revert -q -C a b $ hg forget c $ rm c $ hg status Merge commit will not be changed: $ echo 1 > m1 $ hg commit -A m1 -m m1 $ hg bookmark -q -i m1 $ hg update -q '.^' $ echo 2 > m2 $ hg commit -q -A m2 -m m2 $ hg merge -q m1 $ hg commit -m merge $ hg bookmark -d m1 $ hg log -G -T '{rev} {desc} {phase}\n' @ 6 merge draft |\ | o 5 m2 draft | | o | 4 m1 draft |/ o 3 b draft | o 2 commit 4 draft | o 1 commit 2 public | o 0 commit 1 public $ echo 2 >> m1 $ echo 2 >> m2 $ hg absorb abort: no mutable changeset to change [255] $ hg revert -q -C m1 m2 Use a new repo: $ cd .. $ hg init repo2 $ cd repo2 Make some commits to multiple files: $ for f in a b; do > for i in 1 2; do > echo $f line $i >> $f > hg commit -A $f -m "commit $f $i" -q > done > done Use pattern to select files to be fixed up: $ sedi 's/line/Line/' a b $ hg status M a M b $ hg absorb a saved backup bundle to * (glob) 1 of 1 chunk(s) applied $ hg status M b $ hg absorb --exclude b nothing applied [1] $ hg absorb b saved backup bundle to * (glob) 1 of 1 chunk(s) applied $ hg status $ cat a b a Line 1 a Line 2 b Line 1 b Line 2 Test config option absorb.max-stack-size: $ sedi 's/Line/line/' a b $ hg log -T '{rev}:{node} {desc}\n' 3:712d16a8f445834e36145408eabc1d29df05ec09 commit b 2 2:74cfa6294160149d60adbf7582b99ce37a4597ec commit b 1 1:28f10dcf96158f84985358a2e5d5b3505ca69c22 commit a 2 0:f9a81da8dc53380ed91902e5b82c1b36255a4bd0 commit a 1 $ hg --config absorb.max-stack-size=1 absorb -pn absorb: only the recent 1 changesets will be analysed showing changes for a @@ -0,2 +0,2 @@ -a Line 1 -a Line 2 +a line 1 +a line 2 showing changes for b @@ -0,2 +0,2 @@ -b Line 1 712d16a -b Line 2 +b line 1 712d16a +b line 2 Test obsolete markers creation: $ cat >> $HGRCPATH << EOF > [experimental] > evolution=createmarkers > [absorb] > add-noise=1 > EOF $ hg --config absorb.max-stack-size=3 absorb absorb: only the recent 3 changesets will be analysed 2 of 2 chunk(s) applied $ hg log -T '{rev}:{node|short} {desc} {get(extras, "absorb_source")}\n' 6:3dfde4199b46 commit b 2 712d16a8f445834e36145408eabc1d29df05ec09 5:99cfab7da5ff commit b 1 74cfa6294160149d60adbf7582b99ce37a4597ec 4:fec2b3bd9e08 commit a 2 28f10dcf96158f84985358a2e5d5b3505ca69c22 0:f9a81da8dc53 commit a 1 $ hg absorb 1 of 1 chunk(s) applied $ hg log -T '{rev}:{node|short} {desc} {get(extras, "absorb_source")}\n' 10:e1c8c1e030a4 commit b 2 3dfde4199b4610ea6e3c6fa9f5bdad8939d69524 9:816c30955758 commit b 1 99cfab7da5ffdaf3b9fc6643b14333e194d87f46 8:5867d584106b commit a 2 fec2b3bd9e0834b7cb6a564348a0058171aed811 7:8c76602baf10 commit a 1 f9a81da8dc53380ed91902e5b82c1b36255a4bd0 Executable files: $ cat >> $HGRCPATH << EOF > [diff] > git=True > EOF $ cd .. $ hg init repo3 $ cd repo3 #if execbit $ echo > foo.py $ chmod +x foo.py $ hg add foo.py $ hg commit -mfoo #else $ hg import -q --bypass - <<EOF > # HG changeset patch > foo > > diff --git a/foo.py b/foo.py > new file mode 100755 > --- /dev/null > +++ b/foo.py > @@ -0,0 +1,1 @@ > + > EOF $ hg up -q #endif $ echo bla > foo.py $ hg absorb --dry-run --print-changes showing changes for foo.py @@ -0,1 +0,1 @@ 99b4ae7 - 99b4ae7 +bla $ hg absorb 1 of 1 chunk(s) applied $ hg diff -c . diff --git a/foo.py b/foo.py new file mode 100755 --- /dev/null +++ b/foo.py @@ -0,0 +1,1 @@ +bla $ hg diff Remove lines may delete changesets: $ cd .. $ hg init repo4 $ cd repo4 $ cat > a <<EOF > 1 > 2 > EOF $ hg commit -m a12 -A a $ cat > b <<EOF > 1 > 2 > EOF $ hg commit -m b12 -A b $ echo 3 >> b $ hg commit -m b3 $ echo 4 >> b $ hg commit -m b4 $ echo 1 > b $ echo 3 >> a $ hg absorb -pn showing changes for a @@ -2,0 +2,1 @@ bfafb49 +3 showing changes for b @@ -1,3 +1,0 @@ 1154859 -2 30970db -3 a393a58 -4 $ hg absorb -v | grep became bfafb49242db: 1 file(s) changed, became 1a2de97fc652 115485984805: 2 file(s) changed, became 0c930dfab74c 30970dbf7b40: became empty and was dropped a393a58b9a85: became empty and was dropped $ hg log -T '{rev} {desc}\n' -Gp @ 5 b12 | diff --git a/b b/b | new file mode 100644 | --- /dev/null | +++ b/b | @@ -0,0 +1,1 @@ | +1 | o 4 a12 diff --git a/a b/a new file mode 100644 --- /dev/null +++ b/a @@ -0,0 +1,3 @@ +1 +2 +3 Use revert to make the current change and its parent disappear. This should move us to the non-obsolete ancestor. $ cd .. $ hg init repo5 $ cd repo5 $ cat > a <<EOF > 1 > 2 > EOF $ hg commit -m a12 -A a $ hg id bfafb49242db tip $ echo 3 >> a $ hg commit -m a123 a $ echo 4 >> a $ hg commit -m a1234 a $ hg id 82dbe7fd19f0 tip $ hg revert -r 0 a $ hg absorb -pn showing changes for a @@ -2,2 +2,0 @@ f1c23dd -3 82dbe7f -4 $ hg absorb --verbose f1c23dd5d08d: became empty and was dropped 82dbe7fd19f0: became empty and was dropped a: 1 of 1 chunk(s) applied $ hg id bfafb49242db tip