Mercurial > hg
view tests/test-newbranch.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 | 1c7167009936 |
children | 8197b395710e |
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$ branchcache=.hg/cache/branch2 $ listbranchcaches() { > for f in .hg/cache/branch2*; > do echo === $f ===; > cat $f; > done; > } $ purgebranchcaches() { > rm .hg/cache/branch2* > } $ hg init t $ cd t $ hg branches $ echo foo > a $ hg add a $ hg ci -m "initial" $ hg branch foo marked working directory as branch foo (branches are permanent and global, did you want a bookmark?) $ hg branch foo $ hg ci -m "add branch name" $ hg branch bar marked working directory as branch bar $ hg ci -m "change branch name" Branch shadowing: $ hg branch default abort: a branch of the same name already exists (use 'hg update' to switch to it) [255] $ hg branch -f default marked working directory as branch default $ hg ci -m "clear branch name" created new head There should be only one default branch head $ hg heads . changeset: 3:1c28f494dae6 tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: clear branch name Merging and branches $ hg co foo 0 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg branch foo set existing branch name fails unless force - setting existing parent branch works without force: $ hg branch bar abort: a branch of the same name already exists (use 'hg update' to switch to it) [255] $ hg branch -f bar marked working directory as branch bar $ hg branch foo marked working directory as branch foo $ echo bleah > a $ hg ci -m "modify a branch" $ hg merge default 0 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ hg branch foo set existing branch name where branch head is ancestor: $ hg branch bar abort: a branch of the same name already exists (use 'hg update' to switch to it) [255] set (other) parent branch as branch name $ hg branch default marked working directory as branch default set (first) parent branch as branch name $ hg branch foo marked working directory as branch foo $ hg ci -m "merge" $ hg log -G -T '{rev}:{node|short} {branch} {desc}\n' @ 5:530046499edf foo merge |\ | o 4:adf1a74a7f7b foo modify a branch | | o | 3:1c28f494dae6 default clear branch name | | o | 2:c21617b13b22 bar change branch name |/ o 1:6c0e42da283a foo add branch name | o 0:db01e8ea3388 default initial $ hg branches foo 5:530046499edf default 3:1c28f494dae6 (inactive) bar 2:c21617b13b22 (inactive) $ hg branches -q foo default bar Test for invalid branch cache: $ hg rollback repository tip rolled back to revision 4 (undo commit) working directory now based on revisions 4 and 3 $ cp ${branchcache}-served .hg/bc-invalid $ hg log -r foo changeset: 4:adf1a74a7f7b branch: foo tag: tip parent: 1:6c0e42da283a user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: modify a branch $ cp .hg/bc-invalid $branchcache $ hg --debug log -r foo changeset: 4:adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6 branch: foo tag: tip phase: draft parent: 1:6c0e42da283a56b5edc5b4fadb491365ec7f5fa8 parent: -1:0000000000000000000000000000000000000000 manifest: 1:8c342a37dfba0b3d3ce073562a00d8a813c54ffe user: test date: Thu Jan 01 00:00:00 1970 +0000 files: a extra: branch=foo description: modify a branch $ purgebranchcaches $ echo corrupted > $branchcache $ hg log -qr foo 4:adf1a74a7f7b $ listbranchcaches === .hg/cache/branch2 === corrupted === .hg/cache/branch2-served === adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6 4 c21617b13b220988e7a2e26290fbe4325ffa7139 o bar 1c28f494dae69a2f8fc815059d257eccf3fcfe75 o default adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6 o foo Push should update the branch cache: $ hg init ../target Pushing just rev 0: $ hg push -qr 0 ../target $ (cd ../target/; listbranchcaches) === .hg/cache/branch2-base === db01e8ea3388fd3c7c94e1436ea2bd6a53d581c5 0 db01e8ea3388fd3c7c94e1436ea2bd6a53d581c5 o default Pushing everything: $ hg push -qf ../target $ (cd ../target/; listbranchcaches) === .hg/cache/branch2-base === adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6 4 c21617b13b220988e7a2e26290fbe4325ffa7139 o bar 1c28f494dae69a2f8fc815059d257eccf3fcfe75 o default adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6 o foo Update with no arguments: tipmost revision of the current branch: $ hg up -q -C 0 $ hg up -q $ hg id 1c28f494dae6 $ hg up -q 1 $ hg up -q $ hg id adf1a74a7f7b (foo) tip $ hg branch foobar marked working directory as branch foobar $ hg up 0 files updated, 0 files merged, 0 files removed, 0 files unresolved Fast-forward merge: $ hg branch ff marked working directory as branch ff $ echo ff > ff $ hg ci -Am'fast forward' adding ff $ hg up foo 0 files updated, 0 files merged, 1 files removed, 0 files unresolved $ hg merge ff 1 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ hg branch foo $ hg commit -m'Merge ff into foo' $ hg parents changeset: 6:185ffbfefa30 branch: foo tag: tip parent: 4:adf1a74a7f7b parent: 5:1a3c27dc5e11 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: Merge ff into foo $ hg manifest a ff Test merging, add 3 default heads and one test head: $ cd .. $ hg init merges $ cd merges $ echo a > a $ hg ci -Ama adding a $ echo b > b $ hg ci -Amb adding b $ hg up 0 0 files updated, 0 files merged, 1 files removed, 0 files unresolved $ echo c > c $ hg ci -Amc adding c created new head $ hg up 0 0 files updated, 0 files merged, 1 files removed, 0 files unresolved $ echo d > d $ hg ci -Amd adding d created new head $ hg up 0 0 files updated, 0 files merged, 1 files removed, 0 files unresolved $ hg branch test marked working directory as branch test (branches are permanent and global, did you want a bookmark?) $ echo e >> e $ hg ci -Ame adding e $ hg log changeset: 4:3a1e01ed1df4 branch: test tag: tip parent: 0:cb9a9f314b8b user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: e changeset: 3:980f7dc84c29 parent: 0:cb9a9f314b8b user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: d changeset: 2:d36c0562f908 parent: 0:cb9a9f314b8b user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: c changeset: 1:d2ae7f538514 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: b changeset: 0:cb9a9f314b8b user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: a Implicit merge with test branch as parent: $ hg merge abort: branch 'test' has one head - please merge with an explicit rev (run 'hg heads' to see all heads) [255] $ hg up -C default 1 files updated, 0 files merged, 1 files removed, 0 files unresolved Implicit merge with default branch as parent: $ hg merge abort: branch 'default' has 3 heads - please merge with an explicit rev (run 'hg heads .' to see heads) [255] 3 branch heads, explicit merge required: $ hg merge 2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ hg ci -m merge 2 branch heads, implicit merge works: $ hg merge 1 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ cd .. We expect that bare update on new branch, updates to parent $ hg init bareupdateonnewbranch $ cd bareupdateonnewbranch $ hg update 0 files updated, 0 files merged, 0 files removed, 0 files unresolved $ touch a $ hg commit -A -m "a" adding a $ touch b $ hg commit -A -m "b" adding b $ touch c $ hg commit -A -m "c" adding c $ hg update -r 1 0 files updated, 0 files merged, 1 files removed, 0 files unresolved $ hg log -G o changeset: 2:991a3460af53 | tag: tip | user: test | date: Thu Jan 01 00:00:00 1970 +0000 | summary: c | @ changeset: 1:0e067c57feba | user: test | date: Thu Jan 01 00:00:00 1970 +0000 | summary: b | o changeset: 0:3903775176ed user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: a $ hg branch dev marked working directory as branch dev (branches are permanent and global, did you want a bookmark?) $ hg update 0 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg summary parent: 1:0e067c57feba b branch: dev commit: (new branch) update: (current) phases: 3 draft $ cd .. We need special handling for repositories with no "default" branch because "null" revision belongs to non-existent "default" branch. $ hg init nodefault $ cd nodefault $ hg branch -q foo $ touch 0 $ hg ci -Aqm0 $ touch 1 $ hg ci -Aqm1 $ hg update -qr0 $ hg branch -q bar $ touch 2 $ hg ci -Aqm2 $ hg update -qr0 $ hg branch -q baz $ touch 3 $ hg ci -Aqm3 $ hg ci --close-branch -m 'close baz' $ hg update -q null $ hg log -GT'{rev} {branch}\n' _ 4 baz | o 3 baz | | o 2 bar |/ | o 1 foo |/ o 0 foo a) updating from "null" should bring us to the tip-most branch head as there is no "default" branch: $ hg update -q null $ hg id -bn -1 default $ hg update 2 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg id -bn 2 bar b) but if we are at uncommitted "default" branch, we should stick to the current revision: $ hg update -q 0 $ hg branch default marked working directory as branch default $ hg id -bn 0 default $ hg update 0 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg id -bn 0 default c) also, if we have uncommitted branch at "null", we should stick to it: $ hg update -q null $ hg branch new marked working directory as branch new $ hg id -bn -1 new $ hg update 0 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg id -bn -1 new $ cd .. We expect that update --clean discard changes in working directory, and updates to the head of parent branch. $ hg init updatebareclean $ cd updatebareclean $ hg update --clean 0 files updated, 0 files merged, 0 files removed, 0 files unresolved $ touch a $ hg commit -A -m "a" adding a $ touch b $ hg commit -A -m "b" adding b $ touch c $ hg commit -A -m "c" adding c $ hg log changeset: 2:991a3460af53 tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: c changeset: 1:0e067c57feba user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: b changeset: 0:3903775176ed user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: a $ hg update -r 1 0 files updated, 0 files merged, 1 files removed, 0 files unresolved $ hg branch new-branch marked working directory as branch new-branch (branches are permanent and global, did you want a bookmark?) $ echo "aa" >> a $ hg update --clean 2 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg status $ hg branch default $ hg parent changeset: 2:991a3460af53 tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: c We expect that update --clean on non existing parent discards a new branch and updates to the tipmost non-closed branch head $ hg update null 0 files updated, 0 files merged, 3 files removed, 0 files unresolved $ hg branch newbranch marked working directory as branch newbranch (branches are permanent and global, did you want a bookmark?) $ hg update -C 3 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg summary parent: 2:991a3460af53 tip c branch: default commit: (clean) update: (current) phases: 3 draft