exec plugin: Allow executed programs to close STDERR.

When an executed program is closing STDERR but continues running, the
daemon will wait for the child to exit and the child will eventually
block because the pipe is filled up, resulting in no statistics being
collected.

Thanks to Thorsten von Eicken for finding this problem :)

diff --git a/src/exec.c b/src/exec.c
index a78f902..afce839 100644 (file)
--- a/src/exec.c
+++ b/src/exec.c
@@ -585,7 +585,17 @@ static void *exec_read_one (void *arg) /* {{{ */
         if (errno == EAGAIN || errno == EINTR)  continue;
         break;
       }
-      else if (len == 0) break;  /* We've reached EOF */
+      else if (len == 0)
+      {
+       /* We've reached EOF */
+       NOTICE ("exec plugin: Program `%s' has closed STDERR.",
+           pl->exec);
+       close (fd_err);
+       FD_CLR (fd_err, &fdset);
+       highest_fd = fd;
+       fd_err = -1;
+       continue;
+      }
 
       pbuffer_err[len] = '\0';
 
@@ -615,6 +625,7 @@ static void *exec_read_one (void *arg) /* {{{ */
     copy = fdset;
   }
 
+  DEBUG ("exec plugin: exec_read_one: Waiting for `%s' to exit.", pl->exec);
   if (waitpid (pl->pid, &status, 0) > 0)
     pl->status = status;
 
@@ -628,7 +639,8 @@ static void *exec_read_one (void *arg) /* {{{ */
   pthread_mutex_unlock (&pl_lock);
 
   close (fd);
-  close (fd_err);
+  if (fd_err >= 0)
+    close (fd_err);
 
   pthread_exit ((void *) 0);
   return (NULL);