From: John 'Warthog9' Hawley <warthog9@xxxxxxxxxx>
This changes slightly the behavior of gitweb, so that it verifies
that the box isn't inundated with before attempting to serve gitweb.
If the box is overloaded, it basically returns a 503 Server Unavailable
until the load falls below the defined threshold. This helps dramatically
if you have a box that's I/O bound, reaches a certain load and you
don't want gitweb, the I/O hog that it is, increasing the pain the
server is already undergoing.
This behavior is controlled by $maxload configuration variable.
Default is a load of 300, which for most cases should never be hit.
Unset it (set it to undefined value, i.e. undef) to turn off checking.
Currently it requires that '/proc/loadavg' file exists, otherwise the
load check is bypassed (load is taken to be 0). So platforms that do
not implement '/proc/loadavg' currently cannot use this feature.
Signed-off-by: John 'Warthog9' Hawley <warthog9@xxxxxxxxxx>
Signed-off-by: Jakub Narebski <jnareb@xxxxxxxxx>
---
This is my take on this patch, with all my concerns taken into
consideration... well, all except describing alterante approaches
to straight using /proc/loadavg.
Differences to original version by John 'Warthog9' Hawley (J.H.):
* Slightly improved wording in commit message and in comments
* $maxload described in gitweb/README, in "Gitweb config file variables"
section
* You can use '$maxload = undef;' to turn off load checking
* Error page for too high load is generated using die_error, which had
to be extended to handle 503 Service Unavailable HTTP error code
gitweb/README | 7 ++++++-
gitweb/gitweb.perl | 39 +++++++++++++++++++++++++++++++++++----
2 files changed, 41 insertions(+), 5 deletions(-)
diff --git a/gitweb/README b/gitweb/README
index e34ee79..6c2c8e1 100644
--- a/gitweb/README
+++ b/gitweb/README
@@ -174,7 +174,7 @@ not include variables usually directly set during build):
Base URL for relative URLs in pages generated by gitweb,
(e.g. $logo, $favicon, @stylesheets if they are relative URLs),
needed and used only for URLs with nonempty PATH_INFO via
- <base href="$base_url>. Usually gitweb sets its value correctly,
+ <base href="$base_url">. Usually gitweb sets its value correctly,
and there is no need to set this variable, e.g. to $my_uri or "/".
* $home_link
Target of the home link on top of all pages (the first part of view
@@ -228,6 +228,11 @@ not include variables usually directly set during build):
repositories from launching cross-site scripting (XSS) attacks. Set this
to true if you don't trust the content of your repositories. The default
is false.
+ * $maxload
+ Used to set the maximum load that we will still respond to gitweb queries.
+ If server load exceed this value then return "503 Service Unavaliable" error.
+ Server load is taken to be 0 if gitweb cannot determine its value. Set it to
+ undefined value to turn it off. The default is 300.
Projects list file format
diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index 7e477af..a0f0444 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -221,6 +221,12 @@ our %avatar_size = (
'double' => 32
);
+# Used to set the maximum load that we will still respond to gitweb queries.
+# If server load exceed this value then return "503 server busy" error.
+# If gitweb cannot determined server load, it is taken to be 0.
+# Leave it undefined (or set to 'undef') to turn off load checking.
+our $maxload = 300;
+
# You define site-wide feature defaults here; override them with
# $GITWEB_CONFIG as necessary.
our %feature = (
@@ -551,6 +557,26 @@ if (-e $GITWEB_CONFIG) {
do $GITWEB_CONFIG_SYSTEM if -e $GITWEB_CONFIG_SYSTEM;
}
+# Get loadavg of system, to compare against $maxload.
+# Currently it requires '/proc/loadavg' present to get loadavg;
+# if it is not present it returns 0, which means no load checking.
+sub get_loadavg {
+ open my $fd, '<', '/proc/loadavg'
+ or return 0;
+ my @load = split(/\s+/, scalar <$fd>);
+ close $fd;
+
+ # The first three columns measure CPU and IO utilization of the last one,
+ # five, and 10 minute periods. The fourth column shows the number of
+ # currently running processes and the total number of processes in the m/n
+ # format. The last column displays the last process ID used.
+ return $load[0] || 0;
+}
+
+if (defined $maxload && get_loadavg() > $maxload) {
+ die_error(503, "The load average on the server is too high");
+}
+
# version of the core git binary
our $git_version = qx("$GIT" --version) =~ m/git version (.*)$/ ? $1 : "unknown";
$number_of_git_cmds++;
@@ -3354,14 +3380,19 @@ sub git_footer_html {
# 500: The server isn't configured properly, or
# an internal error occurred (e.g. failed assertions caused by bugs), or
# an unknown error occurred (e.g. the git binary died unexpectedly).
+# 503: The server is currently unavailable (because it is overloaded,
+# or down for maintenance). Generally, this is a temporary state.
sub die_error {
my $status = shift || 500;
my $error = shift || "Internal server error";
- my %http_responses = (400 => '400 Bad Request',
- 403 => '403 Forbidden',
- 404 => '404 Not Found',
- 500 => '500 Internal Server Error');
+ my %http_responses = (
+ 400 => '400 Bad Request',
+ 403 => '403 Forbidden',
+ 404 => '404 Not Found',
+ 500 => '500 Internal Server Error',
+ 503 => '503 Service Unavailable',
+ );
git_header_html($http_responses{$status});
print <<EOF;
<div class="page_body">
--
1.6.5.3
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