svn commit: r827834 - in /httpd/mod_fcgid/trunk: CHANGES-FCGID modules/fcgid/fcgid_proc_unix.c

[tr...@apache.org]

Author: trawick
Date: Tue Oct 20 23:19:56 2009
New Revision: 827834

URL: http://svn.apache.org/viewvc?rev=827834&view=rev
Log:
Recover from most "Resource temporarily unavailable" errors writing the
request to the FastCGI application.  These were common with large request
bodies on Mac OS X and intermittent on Solaris.

I couldn't reproduce the probem on FreeBSD or Linux.  A couple of old reports 
I found on the web were for Mac OS X.

Two different mechanisms are used to recover from EAGAIN:

  First, try writing progressively smaller buffers.  This was always
  sufficient to solve the issue for OS X in my testing.

  Last, try sleeping 250ms between attempts to write.  This was always
  required in my testing on Solaris, and 1 sleep was always enough.

PR: 48025

Modified:
    httpd/mod_fcgid/trunk/CHANGES-FCGID
    httpd/mod_fcgid/trunk/modules/fcgid/fcgid_proc_unix.c

Modified: httpd/mod_fcgid/trunk/CHANGES-FCGID
URL: http://svn.apache.org/viewvc/httpd/mod_fcgid/trunk/CHANGES-FCGID?rev=827834&r1=827833&r2=827834&view=diff
==============================================================================
--- httpd/mod_fcgid/trunk/CHANGES-FCGID [utf8] (original)
+++ httpd/mod_fcgid/trunk/CHANGES-FCGID [utf8] Tue Oct 20 23:19:56 2009
@@ -1,6 +1,10 @@
                                                          -*- coding: utf-8 -*-
 Changes with mod_fcgid 2.3.5
 
+  *) Recover from most "Resource temporarily unavailable" errors writing the
+     request to the FastCGI application.  These were common with large request
+     bodies on Mac OS X and intermittent on Solaris.  PR 48025.  [Jeff Trawick]
+
   *) Fix a bug in fixconf.sed that resulted in a prefix of "FcgidFcgid" on the
      updated directives.  [Dan Hulme <dhulme gmail.com>]
 

Modified: httpd/mod_fcgid/trunk/modules/fcgid/fcgid_proc_unix.c
URL: http://svn.apache.org/viewvc/httpd/mod_fcgid/trunk/modules/fcgid/fcgid_proc_unix.c?rev=827834&r1=827833&r2=827834&view=diff
==============================================================================
--- httpd/mod_fcgid/trunk/modules/fcgid/fcgid_proc_unix.c (original)
+++ httpd/mod_fcgid/trunk/modules/fcgid/fcgid_proc_unix.c Tue Oct 20 23:19:56 2009
@@ -699,6 +699,37 @@
         }
     }
 
+    if (APR_STATUS_IS_EAGAIN(rv)) {
+        /* socket is writable, but we can't write the entire buffer; try to write a
+         * smaller amount, and if even that fails then sleep
+         */
+        size_t to_write = vec[0].iov_len;
+        int slept = 0;
+        const apr_interval_time_t sleep_time = APR_USEC_PER_SEC / 4;
+        const int max_sleeps = 8;
+
+        do {
+            if ((retcode = write(unix_socket, vec[0].iov_base, to_write)) > 0) {
+                ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, ipc_handle->request,
+                              "wrote %d byte(s) and slept %d time(s) after EAGAIN",
+                              retcode, slept);
+                *writecnt = retcode;
+                return APR_SUCCESS;
+            }
+            if (APR_STATUS_IS_EAGAIN(errno)) {
+                if (to_write == 1) {
+                    apr_sleep(sleep_time);
+                    ++slept;
+                }
+                else {
+                    to_write /= 2;
+                }
+            }
+        } while ((APR_STATUS_IS_EINTR(errno) || APR_STATUS_IS_EAGAIN(errno))
+                 && slept < max_sleeps);
+        rv = errno;
+    }
+
     ap_log_rerror(APLOG_MARK, APLOG_INFO, rv,
                   ipc_handle->request,
                   "mod_fcgid: error writing data to FastCGI server");