git-cache-proxy: Abandon fetch attempt if client disconnects

The git client sends the command and then waits for our response.  We
can tell if it has disconnected, because our stdin (the socket) will
be readable.

This is a good idea because otherwise if we have clients with their
own (formal or informal) timeouts, we can build up a backlog of
queued useless fetch attempts.

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

diff --git a/scripts/git-cache-proxy b/scripts/git-cache-proxy
index 518ca9a8fe8c34b816b34e1a0dd3b176e703bbbc..636ebfecb2adb51e0f0296ccd7a334c3e51ea89e 100755 (executable)
--- a/scripts/git-cache-proxy
+++ b/scripts/git-cache-proxy
@@ -321,6 +321,19 @@ sub clonefetch () {
 
     if ($fetch) {
 
+       my $rbits = '';
+       vec($rbits,0,1) = 1;
+       my $ebits = $rbits;
+       my $r=select $rbits,undef,$ebits,0;
+       $r>=0 or fail "select recheck STDOUT failed: $!";
+       if ($r) {
+           servinfo 'client disconnected (stdin unexpectedly'.
+               (vec($rbits,0,1) ? ' readable' : '').
+               (vec($ebits,0,1) ? ' exception' : '').
+               ')';
+           exit 0;
+       }
+
        our @cmd;
 
        if (!$exists) {