wireproto: add config knob for http header length limit
Well-behaved Mercurial clients will respect the httpheader capability by not
sending http headers longer than the given limit in bytes. The limit is
currently hard-coded at 1024 bytes, a safe value for any web server.
Since parsing headers is a notable factor in web server performance, tuning
header size can nontrivially improve performance for request-heavy operations
(eg. obsolete marker negotiation). Exposing the maximum header length limit
as a configuration setting is a simple way to enable such tuning.
--- a/mercurial/help/config.txt Wed Jul 01 15:12:45 2015 -0500
+++ b/mercurial/help/config.txt Mon Jun 29 12:35:31 2015 -0400
@@ -1291,6 +1291,10 @@
checking that all new file revisions specified in manifests are
present. Default is False.
+``maxhttpheaderlen``
+ Instruct HTTP clients not to send request headers longer than this
+ many bytes. Default is 1024.
+
``smtp``
--------
--- a/mercurial/wireproto.py Wed Jul 01 15:12:45 2015 -0500
+++ b/mercurial/wireproto.py Mon Jun 29 12:35:31 2015 -0400
@@ -624,7 +624,8 @@
capsblob = bundle2.encodecaps(bundle2.getrepocaps(repo))
caps.append('bundle2=' + urllib.quote(capsblob))
caps.append('unbundle=%s' % ','.join(changegroupmod.bundlepriority))
- caps.append('httpheader=1024')
+ caps.append(
+ 'httpheader=%d' % repo.ui.configint('server', 'maxhttpheaderlen', 1024))
return caps
# If you are writing an extension and consider wrapping this function. Wrap