wireproto: compress data from a generator
Currently, the "getbundle" wire protocol command obtains a generator of
data, converts it to a util.chunkbuffer, then converts it back to a
generator via the protocol's groupchunks() implementation. For the SSH
protocol, groupchunks() simply reads 4kb chunks then write()s the
data to a file descriptor. For the HTTP protocol, groupchunks() reads
32kb chunks, feeds those into a zlib compressor, emits compressed data
as it is available, and that is sent to the WSGI layer, where it is
likely turned into HTTP chunked transfer chunks as is or further
buffered and turned into a larger chunk.
For both the SSH and HTTP protocols, there is inefficiency from using
util.chunkbuffer.
For SSH, emitting consistent 4kb chunks sounds nice. However, the file
descriptor it is writing to is almost certainly buffered. That means
that a Python .write() probably doesn't translate into exactly what is
written to the I/O layer.
For HTTP, we're going through an intermediate layer to zlib compress
data. So all util.chunkbuffer is doing is ensuring that the chunks we
feed into the zlib compressor are of uniform size. This means more CPU
time in Python buffering and emitting chunks in util.chunkbuffer but
fewer function calls to zlib.
This patch introduces and implements a new wire protocol abstract
method: compresschunks(). It is like groupchunks() except it operates
on a generator instead of something with a .read(). The SSH
implementation simply proxies chunks. The HTTP implementation uses
zlib compression.
To avoid duplicate code, the HTTP groupchunks() has been reimplemented
in terms of compresschunks().
To prove this all works, the "getbundle" wire protocol command has been
switched to compresschunks(). This removes the util.chunkbuffer from
that command. Now, data essentially streams straight from the
changegroup emitter to the wire, possibly through a zlib compressor.
Generators all the way, baby.
There were slim to no performance changes on the server as measured
with the mozilla-central repository. This is likely because CPU
time is dominated by reading revlogs, producing the changegroup, and
zlib compressing the output stream. Still, this brings us a little
closer to our ideal of using generators everywhere.
#require serve
Some tests for hgweb in an empty repository
$ hg init test
$ cd test
$ hg serve -n test -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log
$ cat hg.pid >> $DAEMON_PIDS
$ (get-with-headers.py localhost:$HGPORT 'shortlog')
200 Script output follows
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-US">
<head>
<link rel="icon" href="/static/hgicon.png" type="image/png" />
<meta name="robots" content="index, nofollow" />
<link rel="stylesheet" href="/static/style-paper.css" type="text/css" />
<script type="text/javascript" src="/static/mercurial.js"></script>
<title>test: log</title>
<link rel="alternate" type="application/atom+xml"
href="/atom-log" title="Atom feed for test" />
<link rel="alternate" type="application/rss+xml"
href="/rss-log" title="RSS feed for test" />
</head>
<body>
<div class="container">
<div class="menu">
<div class="logo">
<a href="https://mercurial-scm.org/">
<img src="/static/hglogo.png" alt="mercurial" /></a>
</div>
<ul>
<li class="active">log</li>
<li><a href="/graph/tip">graph</a></li>
<li><a href="/tags">tags</a></li>
<li><a href="/bookmarks">bookmarks</a></li>
<li><a href="/branches">branches</a></li>
</ul>
<ul>
<li><a href="/rev/tip">changeset</a></li>
<li><a href="/file/tip">browse</a></li>
</ul>
<ul>
</ul>
<ul>
<li><a href="/help">help</a></li>
</ul>
<div class="atom-logo">
<a href="/atom-log" title="subscribe to atom feed">
<img class="atom-logo" src="/static/feed-icon-14x14.png" alt="atom feed" />
</a>
</div>
</div>
<div class="main">
<h2 class="breadcrumb"><a href="/">Mercurial</a> </h2>
<h3>log</h3>
<form class="search" action="/log">
<p><input name="rev" id="search1" type="text" size="30" value="" /></p>
<div id="hint">Find changesets by keywords (author, files, the commit message), revision
number or hash, or <a href="/help/revsets">revset expression</a>.</div>
</form>
<div class="navigate">
<a href="/shortlog/tip?revcount=30">less</a>
<a href="/shortlog/tip?revcount=120">more</a>
| rev -1:
</div>
<table class="bigtable">
<thead>
<tr>
<th class="age">age</th>
<th class="author">author</th>
<th class="description">description</th>
</tr>
</thead>
<tbody class="stripes2">
</tbody>
</table>
<div class="navigate">
<a href="/shortlog/tip?revcount=30">less</a>
<a href="/shortlog/tip?revcount=120">more</a>
| rev -1:
</div>
<script type="text/javascript">
ajaxScrollInit(
'/shortlog/%next%',
'', <!-- NEXTHASH
function (htmlText, previousVal) {
var m = htmlText.match(/'(\w+)', <!-- NEXTHASH/);
return m ? m[1] : null;
},
'.bigtable > tbody',
'<tr class="%class%">\
<td colspan="3" style="text-align: center;">%text%</td>\
</tr>'
);
</script>
</div>
</div>
<script type="text/javascript">process_dates()</script>
</body>
</html>
$ echo babar
babar
$ (get-with-headers.py localhost:$HGPORT 'log')
200 Script output follows
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-US">
<head>
<link rel="icon" href="/static/hgicon.png" type="image/png" />
<meta name="robots" content="index, nofollow" />
<link rel="stylesheet" href="/static/style-paper.css" type="text/css" />
<script type="text/javascript" src="/static/mercurial.js"></script>
<title>test: log</title>
<link rel="alternate" type="application/atom+xml"
href="/atom-log" title="Atom feed for test" />
<link rel="alternate" type="application/rss+xml"
href="/rss-log" title="RSS feed for test" />
</head>
<body>
<div class="container">
<div class="menu">
<div class="logo">
<a href="https://mercurial-scm.org/">
<img src="/static/hglogo.png" alt="mercurial" /></a>
</div>
<ul>
<li class="active">log</li>
<li><a href="/graph/tip">graph</a></li>
<li><a href="/tags">tags</a></li>
<li><a href="/bookmarks">bookmarks</a></li>
<li><a href="/branches">branches</a></li>
</ul>
<ul>
<li><a href="/rev/tip">changeset</a></li>
<li><a href="/file/tip">browse</a></li>
</ul>
<ul>
</ul>
<ul>
<li><a href="/help">help</a></li>
</ul>
<div class="atom-logo">
<a href="/atom-log" title="subscribe to atom feed">
<img class="atom-logo" src="/static/feed-icon-14x14.png" alt="atom feed" />
</a>
</div>
</div>
<div class="main">
<h2 class="breadcrumb"><a href="/">Mercurial</a> </h2>
<h3>log</h3>
<form class="search" action="/log">
<p><input name="rev" id="search1" type="text" size="30" value="" /></p>
<div id="hint">Find changesets by keywords (author, files, the commit message), revision
number or hash, or <a href="/help/revsets">revset expression</a>.</div>
</form>
<div class="navigate">
<a href="/shortlog/tip?revcount=5">less</a>
<a href="/shortlog/tip?revcount=20">more</a>
| rev -1:
</div>
<table class="bigtable">
<thead>
<tr>
<th class="age">age</th>
<th class="author">author</th>
<th class="description">description</th>
</tr>
</thead>
<tbody class="stripes2">
</tbody>
</table>
<div class="navigate">
<a href="/shortlog/tip?revcount=5">less</a>
<a href="/shortlog/tip?revcount=20">more</a>
| rev -1:
</div>
<script type="text/javascript">
ajaxScrollInit(
'/shortlog/%next%',
'', <!-- NEXTHASH
function (htmlText, previousVal) {
var m = htmlText.match(/'(\w+)', <!-- NEXTHASH/);
return m ? m[1] : null;
},
'.bigtable > tbody',
'<tr class="%class%">\
<td colspan="3" style="text-align: center;">%text%</td>\
</tr>'
);
</script>
</div>
</div>
<script type="text/javascript">process_dates()</script>
</body>
</html>
$ (get-with-headers.py localhost:$HGPORT 'graph')
200 Script output follows
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-US">
<head>
<link rel="icon" href="/static/hgicon.png" type="image/png" />
<meta name="robots" content="index, nofollow" />
<link rel="stylesheet" href="/static/style-paper.css" type="text/css" />
<script type="text/javascript" src="/static/mercurial.js"></script>
<title>test: revision graph</title>
<link rel="alternate" type="application/atom+xml"
href="/atom-log" title="Atom feed for test: log" />
<link rel="alternate" type="application/rss+xml"
href="/rss-log" title="RSS feed for test: log" />
<!--[if IE]><script type="text/javascript" src="/static/excanvas.js"></script><![endif]-->
</head>
<body>
<div class="container">
<div class="menu">
<div class="logo">
<a href="https://mercurial-scm.org/">
<img src="/static/hglogo.png" alt="mercurial" /></a>
</div>
<ul>
<li><a href="/shortlog/tip">log</a></li>
<li class="active">graph</li>
<li><a href="/tags">tags</a></li>
<li><a href="/bookmarks">bookmarks</a></li>
<li><a href="/branches">branches</a></li>
</ul>
<ul>
<li><a href="/rev/tip">changeset</a></li>
<li><a href="/file/tip">browse</a></li>
</ul>
<ul>
<li><a href="/help">help</a></li>
</ul>
<div class="atom-logo">
<a href="/atom-log" title="subscribe to atom feed">
<img class="atom-logo" src="/static/feed-icon-14x14.png" alt="atom feed" />
</a>
</div>
</div>
<div class="main">
<h2 class="breadcrumb"><a href="/">Mercurial</a> </h2>
<h3>graph</h3>
<form class="search" action="/log">
<p><input name="rev" id="search1" type="text" size="30" /></p>
<div id="hint">Find changesets by keywords (author, files, the commit message), revision
number or hash, or <a href="/help/revsets">revset expression</a>.</div>
</form>
<div class="navigate">
<a href="/graph/tip?revcount=30">less</a>
<a href="/graph/tip?revcount=120">more</a>
| rev -1:
</div>
<noscript><p>The revision graph only works with JavaScript-enabled browsers.</p></noscript>
<div id="wrapper">
<ul id="nodebgs" class="stripes2"></ul>
<canvas id="graph" width="39" height="12"></canvas>
<ul id="graphnodes"></ul>
</div>
<script type="text/javascript">
<!-- hide script content
var data = [];
var graph = new Graph();
graph.scale(39);
graph.vertex = function(x, y, color, parity, cur) {
this.ctx.beginPath();
color = this.setColor(color, 0.25, 0.75);
this.ctx.arc(x, y, radius, 0, Math.PI * 2, true);
this.ctx.fill();
var bg = '<li class="bg"></li>';
var left = (this.bg_height - this.box_size) + (this.columns + 1) * this.box_size;
var nstyle = 'padding-left: ' + left + 'px;';
var tagspan = '';
if (cur[7].length || cur[8].length || (cur[6][0] != 'default' || cur[6][1])) {
tagspan = '<span class="logtags">';
if (cur[6][1]) {
tagspan += '<span class="branchhead" title="' + cur[6][0] + '">';
tagspan += cur[6][0] + '</span> ';
} else if (!cur[6][1] && cur[6][0] != 'default') {
tagspan += '<span class="branchname" title="' + cur[6][0] + '">';
tagspan += cur[6][0] + '</span> ';
}
if (cur[7].length) {
for (var t in cur[7]) {
var tag = cur[7][t];
tagspan += '<span class="tag">' + tag + '</span> ';
}
}
if (cur[8].length) {
for (var b in cur[8]) {
var bookmark = cur[8][b];
tagspan += '<span class="tag">' + bookmark + '</span> ';
}
}
tagspan += '</span>';
}
var item = '<li style="' + nstyle + '"><span class="desc">';
item += '<a href="/rev/' + cur[0] + '" title="' + cur[0] + '">' + cur[3] + '</a>';
item += '</span>' + tagspan + '<span class="info">' + cur[5] + ', by ' + cur[4] + '</span></li>';
return [bg, item];
}
graph.render(data);
// stop hiding script -->
</script>
<div class="navigate">
<a href="/graph/tip?revcount=30">less</a>
<a href="/graph/tip?revcount=120">more</a>
| rev -1:
</div>
<script type="text/javascript">
ajaxScrollInit(
'/graph/-1?revcount=%next%&style=paper',
60+60,
function (htmlText, previousVal) { return previousVal + 60; },
'#wrapper',
'<div class="%class%" style="text-align: center;">%text%</div>',
'graph'
);
</script>
</div>
</div>
<script type="text/javascript">process_dates()</script>
</body>
</html>
$ (get-with-headers.py localhost:$HGPORT 'file')
200 Script output follows
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-US">
<head>
<link rel="icon" href="/static/hgicon.png" type="image/png" />
<meta name="robots" content="index, nofollow" />
<link rel="stylesheet" href="/static/style-paper.css" type="text/css" />
<script type="text/javascript" src="/static/mercurial.js"></script>
<title>test: 000000000000 /</title>
</head>
<body>
<div class="container">
<div class="menu">
<div class="logo">
<a href="https://mercurial-scm.org/">
<img src="/static/hglogo.png" alt="mercurial" /></a>
</div>
<ul>
<li><a href="/shortlog/tip">log</a></li>
<li><a href="/graph/tip">graph</a></li>
<li><a href="/tags">tags</a></li>
<li><a href="/bookmarks">bookmarks</a></li>
<li><a href="/branches">branches</a></li>
</ul>
<ul>
<li><a href="/rev/tip">changeset</a></li>
<li class="active">browse</li>
</ul>
<ul>
</ul>
<ul>
<li><a href="/help">help</a></li>
</ul>
</div>
<div class="main">
<h2 class="breadcrumb"><a href="/">Mercurial</a> </h2>
<h3>
directory / @ -1:<a href="/rev/000000000000">000000000000</a>
<span class="tag">tip</span>
</h3>
<form class="search" action="/log">
<p><input name="rev" id="search1" type="text" size="30" /></p>
<div id="hint">Find changesets by keywords (author, files, the commit message), revision
number or hash, or <a href="/help/revsets">revset expression</a>.</div>
</form>
<table class="bigtable">
<thead>
<tr>
<th class="name">name</th>
<th class="size">size</th>
<th class="permissions">permissions</th>
</tr>
</thead>
<tbody class="stripes2">
<tr class="fileline">
<td class="name"><a href="/file/tip/">[up]</a></td>
<td class="size"></td>
<td class="permissions">drwxr-xr-x</td>
</tr>
</tbody>
</table>
</div>
</div>
<script type="text/javascript">process_dates()</script>
</body>
</html>
$ (get-with-headers.py localhost:$HGPORT 'atom-bookmarks')
200 Script output follows
<?xml version="1.0" encoding="ascii"?>
<feed xmlns="http://www.w3.org/2005/Atom">
<id>http://*:$HGPORT/</id> (glob)
<link rel="self" href="http://*:$HGPORT/atom-bookmarks"/> (glob)
<link rel="alternate" href="http://*:$HGPORT/bookmarks"/> (glob)
<title>test: bookmarks</title>
<summary>test bookmark history</summary>
<author><name>Mercurial SCM</name></author>
<updated>1970-01-01T00:00:00+00:00</updated>
</feed>
$ cd ..