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Install a SIGTERM handler in ssh-connect

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Summary:
Ref T10547. This has been around for a while but I was never able to reproduce it. I caught a repro case in the cluster recently and I think this is the right fix.

We tell Subversion to run `ssh-connect` instead of `ssh` so we can provide options and credentials, by using `SVN_SSH` in the environment. Subversion will sometimes kill the SSH tunnel subprocess aggressively with SIGTERM -- as of writing, you can search for `SIGTERM` in `make_tunnel()` here:

http://svn.apache.org/repos/asf/subversion/trunk/subversion/libsvn_ra_svn/client.c

By default, when a PHP process gets SIGTERM it just exits immediately, without running destructors or shutdown functions. Since destructors/shutdown functions don't run, `TempFile` doesn't get a chance to remove the file.

I don't have a clear picture of //when// Subversion sends SIGTERM to the child process. I can't really get this to trigger locally via `svn`, although I was able to get it to trigger explicitly. So I'm only about 95% sure this fixes it, but it seems likely.

Test Plan:
Locally, I couldn't get this to reproduce "normally" even knowing the cause (maybe Subversion doesn't do the SIGTERM stuff on OSX?) but I was able to get it to reproduce reliabily by adding `posix_kill(getmypid(), SIGTERM);` to the body of the script.

With that added, running the script with `PHABRICATOR_CREDENTIAL=PHID-CDTL-...` in the environment reliably left straggler temporary files.

Adding `declare()` and a signal handler fixed this: the script now runs the `TempFile` destructor and longer leaves the stragglers around.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10547

Differential Revision: https://secure.phabricator.com/D16102
This commit is contained in:
epriestley 2016-06-13 09:15:20 -07:00
parent bba53205de
commit f56f1b05c0
1 changed files with 15 additions and 0 deletions
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15
scripts/ssh/ssh-connect.php
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@ -4,6 +4,11 @@
// This is a wrapper script for Git, Mercurial, and Subversion. It primarily
// serves to inject "-o StrictHostKeyChecking=no" into the SSH arguments.
// In some cases, Subversion sends us SIGTERM. If we don't catch the signal and
// react to it, we won't run object destructors by default and thus won't clean
// up temporary files. Declare ticks so we can install a signal handler.
declare(ticks=1);
$root = dirname(dirname(dirname(__FILE__)));
require_once $root.'/scripts/__init_script__.php';
@ -21,6 +26,16 @@ $args->parsePartial(
));
$unconsumed_argv = $args->getUnconsumedArgumentVector();
if (function_exists('pcntl_signal')) {
pcntl_signal(SIGTERM, 'ssh_connect_signal');
}
function ssh_connect_signal($signo) {
// This is just letting destructors fire. In particular, we want to clean
// up any temporary files we wrote. See T10547.
exit(128 + $signo);
}
$pattern = array();
$arguments = array();