Changeset 17284

Timestamp:

2008-09-15T12:26:54+12:00 (16 years ago)

Author:

ak19

Message:

The PerlDoc seems to indicate that it is necessary to call waitpid after launching a childprocess with open2(), in that otherwise we might be stuck with zombie child processes. In any case, this was necessary in a standalone wget script that used open2(), and the addition of new code to do this in Z3940Download.pm seems to make the code work as before.

File:

• gsdl/trunk/perllib/downloaders/Z3950Download.pm (modified) (3 diffs)

gsdl/trunk/perllib/downloaders/Z3950Download.pm

@@ -36 +36 @@
 use BaseDownload;
 use IPC::Open2;
+use POSIX ":sys_wait_h"; # for waitpid, http://perldoc.perl.org/functions/waitpid.html
 
 sub BEGIN {
@@ -149 +150 @@
     my $childpid = open2(*YAZOUT, *YAZIN, $yaz)
     or (print STDERR "<<Finished>>\n" and die "can't open pipe to yaz-client: $!");
+    $self->{'pid'} = $childpid;
     $self->{'YAZOUT'} = *YAZOUT;
     $self->{'YAZIN'} = *YAZIN;
@@ -187 +189 @@
 
     close($self->{'YAZOUT'});
+
+    # Is the following necessary? The PerlDoc on open2 (http://perldoc.perl.org/IPC/Open2.html)
+    # says that waitpid must be called to "reap the child process", or otherwise it will hang
+    # around like a zombie process in the background. Adding it here makes the code work as 
+    # before, but it is certainly necessary to call waitpid on wget (see WgetDownload.pm).
+    # http://perldoc.perl.org/functions/waitpid.html
+    my $kidpid;
+    do {
+    $kidpid = waitpid($self->{'pid'}, WNOHANG);
+    } while $kidpid > 0; # waiting for pid to become -1
 }