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From traw...@apache.org
Subject svn commit: r1363557 - in /httpd/httpd/trunk: CHANGES docs/log-message-tags/next-number server/mpm/event/event.c server/mpm/worker/worker.c
Date Thu, 19 Jul 2012 21:31:52 GMT
Author: trawick
Date: Thu Jul 19 21:31:52 2012
New Revision: 1363557

URL: http://svn.apache.org/viewvc?rev=1363557&view=rev
Log:
mpm_event, mpm_worker: Remain active amidst prevalent child process
resource shortages.

This is a somewhat different direction than r168182 ("transient thread
creation errors shouldn't take down the whole server").

r168182: If APEXIT_CHILDSICK is received and there aren't any
         active children at the time, exit.

Now:     If APEXIT_CHILDSICK is received and we never successfully
         initialized a child, exit.

The issue seen with the r168182 handling is that it is rather easy
to be left with no active child processes (which causes the server
to exit completely) during a resource shortage that lasts for some
measurable period of time, as contrasted with a resource shortage 
that results in only a handful of allocation failures.

Now the server will remain active, though as long as the resource
shortage exists children may continually fail and the parent will
try once per second to create a replacement.  The existing logic
to reduce the spawn rate after such errors will prevent the 
parent from trying to create children more rapidly.

Modified:
    httpd/httpd/trunk/CHANGES
    httpd/httpd/trunk/docs/log-message-tags/next-number
    httpd/httpd/trunk/server/mpm/event/event.c
    httpd/httpd/trunk/server/mpm/worker/worker.c

Modified: httpd/httpd/trunk/CHANGES
URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/CHANGES?rev=1363557&r1=1363556&r2=1363557&view=diff
==============================================================================
--- httpd/httpd/trunk/CHANGES [utf-8] (original)
+++ httpd/httpd/trunk/CHANGES [utf-8] Thu Jul 19 21:31:52 2012
@@ -1,6 +1,9 @@
                                                          -*- coding: utf-8 -*-
 Changes with Apache 2.5.0
 
+  *) mpm_event, mpm_worker: Remain active amidst prevalent child process
+     resource shortages.  [Jeff Trawick]
+
   *) mpm_event, mpm_worker: Fix cases where the spawn rate wasn't reduced
      after child process resource shortages.  [Jeff Trawick]
 

Modified: httpd/httpd/trunk/docs/log-message-tags/next-number
URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/docs/log-message-tags/next-number?rev=1363557&r1=1363556&r2=1363557&view=diff
==============================================================================
--- httpd/httpd/trunk/docs/log-message-tags/next-number (original)
+++ httpd/httpd/trunk/docs/log-message-tags/next-number Thu Jul 19 21:31:52 2012
@@ -1 +1 @@
-2324
+2326

Modified: httpd/httpd/trunk/server/mpm/event/event.c
URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/server/mpm/event/event.c?rev=1363557&r1=1363556&r2=1363557&view=diff
==============================================================================
--- httpd/httpd/trunk/server/mpm/event/event.c (original)
+++ httpd/httpd/trunk/server/mpm/event/event.c Thu Jul 19 21:31:52 2012
@@ -183,6 +183,7 @@ static apr_uint32_t lingering_count = 0;
 static apr_uint32_t suspended_count = 0;    /* Number of suspended connections */
 static apr_uint32_t clogged_count = 0;      /* Number of threads processing ssl conns */
 static int resource_shortage = 0;
+static int had_healthy_child = 0;
 static fd_queue_t *worker_queue;
 static fd_queue_info_t *worker_queue_info;
 static int mpm_state = AP_MPMQ_STARTING;
@@ -2403,6 +2404,7 @@ static void perform_idle_server_maintena
         int any_dying_threads = 0;
         int any_dead_threads = 0;
         int all_dead_threads = 1;
+        int child_threads_active = 0;
 
         if (i >= retained->max_daemons_limit
             && totally_free_length == retained->idle_spawn_rate)
@@ -2438,6 +2440,7 @@ static void perform_idle_server_maintena
                 }
                 if (status >= SERVER_READY && status < SERVER_GRACEFUL) {
                     ++active_thread_count;
+                    ++child_threads_active;
                 }
             }
         }
@@ -2464,6 +2467,9 @@ static void perform_idle_server_maintena
             }
             ++free_length;
         }
+        else if (child_threads_active == threads_per_child) {
+            had_healthy_child = 1;
+        }
         /* XXX if (!ps->quiescing)     is probably more reliable  GLA */
         if (!any_dying_threads) {
             last_non_dead = i;
@@ -2472,21 +2478,23 @@ static void perform_idle_server_maintena
     }
 
     if (retained->sick_child_detected) {
-        if (active_thread_count > 0) {
-            /* some child processes appear to be working.  don't kill the
-             * whole server.
+        if (had_healthy_child) {
+            /* Assume this is a transient error, even though it may not be.  Leave
+             * the server up in case it is able to serve some requests or the
+             * problem will be resolved.
              */
             retained->sick_child_detected = 0;
         }
         else {
-            /* looks like a basket case.  give up.
+            /* looks like a basket case, as no child ever fully initialized; give up.
              */
             shutdown_pending = 1;
             child_fatal = 1;
             ap_log_error(APLOG_MARK, APLOG_ALERT, 0,
-                         ap_server_conf, APLOGNO(00483)
-                         "No active workers found..."
-                         " Apache is exiting!");
+                         ap_server_conf, APLOGNO(02324)
+                         "A resource shortage or other unrecoverable failure "
+                         "was encountered before any child process initialized "
+                         "successfully... httpd is exiting!");
             /* the child already logged the failure details */
             return;
         }

Modified: httpd/httpd/trunk/server/mpm/worker/worker.c
URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/server/mpm/worker/worker.c?rev=1363557&r1=1363556&r2=1363557&view=diff
==============================================================================
--- httpd/httpd/trunk/server/mpm/worker/worker.c (original)
+++ httpd/httpd/trunk/server/mpm/worker/worker.c Thu Jul 19 21:31:52 2012
@@ -129,6 +129,7 @@ static int listener_may_exit = 0;
 static int requests_this_child;
 static int num_listensocks = 0;
 static int resource_shortage = 0;
+static int had_healthy_child = 0;
 static fd_queue_t *worker_queue;
 static fd_queue_info_t *worker_queue_info;
 static int mpm_state = AP_MPMQ_STARTING;
@@ -1473,6 +1474,7 @@ static void perform_idle_server_maintena
         int any_dying_threads = 0;
         int any_dead_threads = 0;
         int all_dead_threads = 1;
+        int child_threads_active = 0;
 
         if (i >= retained->max_daemons_limit && totally_free_length == retained->idle_spawn_rate)
             /* short cut if all active processes have been examined and
@@ -1507,6 +1509,7 @@ static void perform_idle_server_maintena
                 }
                 if (status >= SERVER_READY && status < SERVER_GRACEFUL) {
                     ++active_thread_count;
+                    ++child_threads_active;
                 }
             }
         }
@@ -1532,6 +1535,9 @@ static void perform_idle_server_maintena
             }
             ++free_length;
         }
+        else if (child_threads_active == threads_per_child) {
+            had_healthy_child = 1;
+        }
         /* XXX if (!ps->quiescing)     is probably more reliable  GLA */
         if (!any_dying_threads) {
             last_non_dead = i;
@@ -1540,21 +1546,23 @@ static void perform_idle_server_maintena
     }
 
     if (retained->sick_child_detected) {
-        if (active_thread_count > 0) {
-            /* some child processes appear to be working.  don't kill the
-             * whole server.
+        if (had_healthy_child) {
+            /* Assume this is a transient error, even though it may not be.  Leave
+             * the server up in case it is able to serve some requests or the
+             * problem will be resolved.
              */
             retained->sick_child_detected = 0;
         }
         else {
-            /* looks like a basket case.  give up.
+            /* looks like a basket case, as no child ever fully initialized; give up.
              */
             shutdown_pending = 1;
             child_fatal = 1;
             ap_log_error(APLOG_MARK, APLOG_ALERT, 0,
-                         ap_server_conf, APLOGNO(00285)
-                         "No active workers found..."
-                         " Apache is exiting!");
+                         ap_server_conf, APLOGNO(02325)
+                         "A resource shortage or other unrecoverable failure "
+                         "was encountered before any child process initialized "
+                         "successfully... httpd is exiting!");
             /* the child already logged the failure details */
             return;
         }



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