Apache::SIG - Override apache signal handlers with Perl's
PerlFixupHandler Apache::SIG
When a client drops a connection and apache is in the middle of a
write, a timeout will occur and httpd sends a SIGPIPE. When
apache's SIGPIPE handler is used, Perl may be left in the middle of
it's eval context, causing bizarre errors during subsequent requests
are handled by that child. When Apache::SIG is used, it installs a
different SIGPIPE handler which rewinds the context to make sure Perl
is back to normal state, preventing these bizarre errors.
If you would like to log when a request was cancelled by a SIGPIPE in your
Apache access_log, you can declare Apache::SIG as a handler (any
Perl*Handler will do, as long as it is run before PerlHandler,
e.g. PerlFixupHandler), and you must also define a custom LogFormat in your
httpd.conf, like so:
PerlFixupHandler Apache::SIG
LogFormat ``%h %l %u %t \''%r\`` %s %b %{SIGPIPE}e''
If the server has noticed that the request was cancelled via a SIGPIPE,
then the log line will end with 1, otherwise it will just be a dash.
The signal handler in this package uses the subprocess_env table of the
main request object to supply the 'SIGPIPE' ``environment variable'' to
the log handler. If you already use the key 'SIGPIPE' in your
subprocess_env table, then you can redefine the key like this:
$Apache::SIG::PipeKey = 'my_SIGPIPE';
and log it like this:
LogFormat ``%h %l %u %t \''%r\`` %s %b %{my_SIGPIPE}e''
Doug MacEachern and Doug Bagley
perlvar(1)
