Mercurial > hg
view tests/test-qrecord.t @ 26623:5a95fe44121d
clonebundles: support for seeding clones from pre-generated bundles
Cloning can be an expensive operation for servers because the server
generates a bundle from existing repository data at request time. For
a large repository like mozilla-central, this consumes 4+ minutes
of CPU time on the server. It also results in significant network
utilization. Multiplied by hundreds or even thousands of clients and
the ensuing load can result in difficulties scaling the Mercurial server.
Despite generation of bundles being deterministic until the next
changeset is added, the generation of bundles to service a clone request
is not cached. Each clone thus performs redundant work. This is
wasteful.
This patch introduces the "clonebundles" extension and related
client-side functionality to help alleviate this deficiency. The
client-side feature is behind an experimental flag and is not enabled by
default.
It works as follows:
1) Server operator generates a bundle and makes it available on a
server (likely HTTP).
2) Server operator defines the URL of a bundle file in a
.hg/clonebundles.manifest file.
3) Client `hg clone`ing sees the server is advertising bundle URLs.
4) Client fetches and applies the advertised bundle.
5) Client performs equivalent of `hg pull` to fetch changes made since
the bundle was created.
Essentially, the server performs the expensive work of generating a
bundle once and all subsequent clones fetch a static file from
somewhere. Scaling static file serving is a much more manageable
problem than scaling a Python application like Mercurial. Assuming your
repository grows less than 1% per day, the end result is 99+% of CPU
and network load from clones is eliminated, allowing Mercurial servers
to scale more easily. Serving static files also means data can be
transferred to clients as fast as they can consume it, rather than as
fast as servers can generate it. This makes clones faster.
Mozilla has implemented similar functionality of this patch on
hg.mozilla.org using a custom extension. We are hosting bundle files in
Amazon S3 and CloudFront (a CDN) and have successfully offloaded
>1 TB/day in data transfer from hg.mozilla.org, freeing up significant
bandwidth and CPU resources. The positive impact has been stellar and
I believe it has proved its value to be included in Mercurial core. I
feel it is important for the client-side support to be enabled in core
by default because it means that clients will get faster, more reliable
clones and will enable server operators to reduce load without
requiring any client-side configuration changes (assuming clients are
up to date, of course).
The scope of this feature is narrowly and specifically tailored to
cloning, despite "serve pulls from pre-generated bundles" being a valid
and useful feature. I would eventually like for Mercurial servers to
support transferring *all* repository data via statically hosted files.
You could imagine a server that siphons all pushed data to bundle files
and instructs clients to apply a stream of bundles to reconstruct all
repository data. This feature, while useful and powerful, is
significantly more work to implement because it requires the server
component have awareness of discovery and a mapping of which changesets
are in which files. Full, clone bundles, by contrast, are much simpler.
The wire protocol command is named "clonebundles" instead of something
more generic like "staticbundles" to leave the door open for a new, more
powerful and more generic server-side component with minimal backwards
compatibility implications. The name "bundleclone" is used by Mozilla's
extension and would cause problems since there are subtle differences
in Mozilla's extension.
Mozilla's experience with this idea has taught us that some form of
"content negotiation" is required. Not all clients will support all
bundle formats or even URLs (advanced TLS requirements, etc). To ensure
the highest uptake possible, a server needs to advertise multiple
versions of bundles and clients need to be able to choose the most
appropriate from that list one. The "attributes" in each
server-advertised entry facilitate this filtering and sorting. Their
use will become apparent in subsequent patches.
Initial inspiration and credit for the idea of cloning from static files
belongs to Augie Fackler and his "lookaside clone" extension proof of
concept.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Fri, 09 Oct 2015 11:22:01 -0700 |
parents | 9bc11716bc86 |
children | 58f8b29c37ff |
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Create configuration $ echo "[ui]" >> $HGRCPATH $ echo "interactive=true" >> $HGRCPATH help record (no record) $ hg help record record extension - commands to interactively select changes for commit/qrefresh (use "hg help extensions" for information on enabling extensions) help qrecord (no record) $ hg help qrecord 'qrecord' is provided by the following extension: record commands to interactively select changes for commit/qrefresh (use "hg help extensions" for information on enabling extensions) $ echo "[extensions]" >> $HGRCPATH $ echo "record=" >> $HGRCPATH help record (record) $ hg help record hg record [OPTION]... [FILE]... interactively select changes to commit If a list of files is omitted, all changes reported by "hg status" will be candidates for recording. See "hg help dates" for a list of formats valid for -d/--date. You will be prompted for whether to record changes to each modified file, and for files with multiple changes, for each change to use. For each query, the following responses are possible: y - record this change n - skip this change e - edit this change manually s - skip remaining changes to this file f - record remaining changes to this file d - done, skip remaining changes and files a - record all changes to all remaining files q - quit, recording no changes ? - display help This command is not available when committing a merge. options ([+] can be repeated): -A --addremove mark new/missing files as added/removed before committing --close-branch mark a branch head as closed --amend amend the parent of the working directory -s --secret use the secret phase for committing -e --edit invoke editor on commit messages -I --include PATTERN [+] include names matching the given patterns -X --exclude PATTERN [+] exclude names matching the given patterns -m --message TEXT use text as commit message -l --logfile FILE read commit message from file -d --date DATE record the specified date as commit date -u --user USER record the specified user as committer -S --subrepos recurse into subrepositories -w --ignore-all-space ignore white space when comparing lines -b --ignore-space-change ignore changes in the amount of white space -B --ignore-blank-lines ignore changes whose lines are all blank (some details hidden, use --verbose to show complete help) help (no mq, so no qrecord) $ hg help qrecord hg qrecord [OPTION]... PATCH [FILE]... interactively record a new patch See "hg help qnew" & "hg help record" for more information and usage. (some details hidden, use --verbose to show complete help) $ hg init a qrecord (mq not present) $ hg -R a qrecord hg qrecord: invalid arguments hg qrecord [OPTION]... PATCH [FILE]... interactively record a new patch (use "hg qrecord -h" to show more help) [255] qrecord patch (mq not present) $ hg -R a qrecord patch abort: 'mq' extension not loaded [255] help (bad mq) $ echo "mq=nonexistent" >> $HGRCPATH $ hg help qrecord *** failed to import extension mq from nonexistent: [Errno *] * (glob) hg qrecord [OPTION]... PATCH [FILE]... interactively record a new patch See "hg help qnew" & "hg help record" for more information and usage. (some details hidden, use --verbose to show complete help) help (mq present) $ sed 's/mq=nonexistent/mq=/' $HGRCPATH > hgrc.tmp $ mv hgrc.tmp $HGRCPATH $ hg help qrecord hg qrecord [OPTION]... PATCH [FILE]... interactively record a new patch See "hg help qnew" & "hg help record" for more information and usage. options ([+] can be repeated): -e --edit invoke editor on commit messages -g --git use git extended diff format -U --currentuser add "From: <current user>" to patch -u --user USER add "From: <USER>" to patch -D --currentdate add "Date: <current date>" to patch -d --date DATE add "Date: <DATE>" to patch -I --include PATTERN [+] include names matching the given patterns -X --exclude PATTERN [+] exclude names matching the given patterns -m --message TEXT use text as commit message -l --logfile FILE read commit message from file -w --ignore-all-space ignore white space when comparing lines -b --ignore-space-change ignore changes in the amount of white space -B --ignore-blank-lines ignore changes whose lines are all blank --mq operate on patch repository (some details hidden, use --verbose to show complete help) $ cd a Base commit $ cat > 1.txt <<EOF > 1 > 2 > 3 > 4 > 5 > EOF $ cat > 2.txt <<EOF > a > b > c > d > e > f > EOF $ mkdir dir $ cat > dir/a.txt <<EOF > hello world > > someone > up > there > loves > me > EOF $ hg add 1.txt 2.txt dir/a.txt $ hg commit -m 'initial checkin' Changing files $ sed -e 's/2/2 2/;s/4/4 4/' 1.txt > 1.txt.new $ sed -e 's/b/b b/' 2.txt > 2.txt.new $ sed -e 's/hello world/hello world!/' dir/a.txt > dir/a.txt.new $ mv -f 1.txt.new 1.txt $ mv -f 2.txt.new 2.txt $ mv -f dir/a.txt.new dir/a.txt Whole diff $ hg diff --nodates diff -r 1057167b20ef 1.txt --- a/1.txt +++ b/1.txt @@ -1,5 +1,5 @@ 1 -2 +2 2 3 -4 +4 4 5 diff -r 1057167b20ef 2.txt --- a/2.txt +++ b/2.txt @@ -1,5 +1,5 @@ a -b +b b c d e diff -r 1057167b20ef dir/a.txt --- a/dir/a.txt +++ b/dir/a.txt @@ -1,4 +1,4 @@ -hello world +hello world! someone up qrecord with bad patch name, should abort before prompting $ hg qrecord .hg abort: patch name cannot begin with ".hg" [255] qrecord a.patch $ hg qrecord -d '0 0' -m aaa a.patch <<EOF > y > y > n > y > y > n > EOF diff --git a/1.txt b/1.txt 2 hunks, 2 lines changed examine changes to '1.txt'? [Ynesfdaq?] y @@ -1,3 +1,3 @@ 1 -2 +2 2 3 record change 1/4 to '1.txt'? [Ynesfdaq?] y @@ -3,3 +3,3 @@ 3 -4 +4 4 5 record change 2/4 to '1.txt'? [Ynesfdaq?] n diff --git a/2.txt b/2.txt 1 hunks, 1 lines changed examine changes to '2.txt'? [Ynesfdaq?] y @@ -1,5 +1,5 @@ a -b +b b c d e record change 3/4 to '2.txt'? [Ynesfdaq?] y diff --git a/dir/a.txt b/dir/a.txt 1 hunks, 1 lines changed examine changes to 'dir/a.txt'? [Ynesfdaq?] n After qrecord a.patch 'tip'" $ hg tip -p changeset: 1:5d1ca63427ee tag: a.patch tag: qbase tag: qtip tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: aaa diff -r 1057167b20ef -r 5d1ca63427ee 1.txt --- a/1.txt Thu Jan 01 00:00:00 1970 +0000 +++ b/1.txt Thu Jan 01 00:00:00 1970 +0000 @@ -1,5 +1,5 @@ 1 -2 +2 2 3 4 5 diff -r 1057167b20ef -r 5d1ca63427ee 2.txt --- a/2.txt Thu Jan 01 00:00:00 1970 +0000 +++ b/2.txt Thu Jan 01 00:00:00 1970 +0000 @@ -1,5 +1,5 @@ a -b +b b c d e After qrecord a.patch 'diff'" $ hg diff --nodates diff -r 5d1ca63427ee 1.txt --- a/1.txt +++ b/1.txt @@ -1,5 +1,5 @@ 1 2 2 3 -4 +4 4 5 diff -r 5d1ca63427ee dir/a.txt --- a/dir/a.txt +++ b/dir/a.txt @@ -1,4 +1,4 @@ -hello world +hello world! someone up qrecord b.patch $ hg qrecord -d '0 0' -m bbb b.patch <<EOF > y > y > y > y > EOF diff --git a/1.txt b/1.txt 1 hunks, 1 lines changed examine changes to '1.txt'? [Ynesfdaq?] y @@ -1,5 +1,5 @@ 1 2 2 3 -4 +4 4 5 record change 1/2 to '1.txt'? [Ynesfdaq?] y diff --git a/dir/a.txt b/dir/a.txt 1 hunks, 1 lines changed examine changes to 'dir/a.txt'? [Ynesfdaq?] y @@ -1,4 +1,4 @@ -hello world +hello world! someone up record change 2/2 to 'dir/a.txt'? [Ynesfdaq?] y After qrecord b.patch 'tip' $ hg tip -p changeset: 2:b056198bf878 tag: b.patch tag: qtip tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: bbb diff -r 5d1ca63427ee -r b056198bf878 1.txt --- a/1.txt Thu Jan 01 00:00:00 1970 +0000 +++ b/1.txt Thu Jan 01 00:00:00 1970 +0000 @@ -1,5 +1,5 @@ 1 2 2 3 -4 +4 4 5 diff -r 5d1ca63427ee -r b056198bf878 dir/a.txt --- a/dir/a.txt Thu Jan 01 00:00:00 1970 +0000 +++ b/dir/a.txt Thu Jan 01 00:00:00 1970 +0000 @@ -1,4 +1,4 @@ -hello world +hello world! someone up After qrecord b.patch 'diff' $ hg diff --nodates $ cd ..