mpm_event, mpm_worker: Remain active amidst prevalent child process

resource shortages.

Submitted by: trawick
Reviewed by: wrowe, rjung

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1374330 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/CHANGES b/CHANGES
index eafa09bbcfc79fbf3befd5ee94a8764f30798105..6941b58c14f7e595e5b481c814f1e553e25924c2 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -5,6 +5,9 @@ Changes with Apache 2.2.23
      envvars: Fix insecure handling of LD_LIBRARY_PATH that could lead to the
      current working directory to be searched for DSOs. [Stefan Fritsch]
 
+  *) mpm_event, mpm_worker: Remain active amidst prevalent child process
+     resource shortages.  [Jeff Trawick]
+
   *) mod_proxy_balancer: Restore balancing after a failed worker has
      recovered when using lbmethod_bybusyness.  PR 48735.  [Jeff Trawick]
 

diff --git a/STATUS b/STATUS
index 00d5eea4cd1ae67a8f9d89fb2b1a7b846d7a2b63..7801ecb384c0174b6fe961de12fe08fe33f82585 100644 (file)
--- a/STATUS
+++ b/STATUS
@@ -112,14 +112,6 @@ PATCHES ACCEPTED TO BACKPORT FROM TRUNK:
     2.2.x patch: http://people.apache.org/~jim/patches/mod_proxy_ajp-erroroverride.patch
     +1: igalic, jim, rpluem
 
-   * mpm_event, mpm_worker: Remain active amidst prevalent child process
-     resource shortages.
-     trunk patch: http://svn.apache.org/viewvc?rev=1363557&view=rev
-     trunk patch: http://svn.apache.org/viewvc?rev=1364601&view=rev
-     2.4.x patch: trunk patch works
-     2.2.x patch: http://people.apache.org/~trawick/r1363557_1364601_to_2.2.x.txt
-     +1: trawick, wrowe, rjung
-
 PATCHES PROPOSED TO BACKPORT FROM TRUNK:
   [ New proposals should be added at the end of the list ]
 

diff --git a/server/mpm/experimental/event/event.c b/server/mpm/experimental/event/event.c
index bbee899ea11e66161d0a776a6f9a43611dc8024f..82efd0cd651942787db9522aba3574784918d9d9 100644 (file)
--- a/server/mpm/experimental/event/event.c
+++ b/server/mpm/experimental/event/event.c
@@ -148,6 +148,7 @@ static int ap_daemons_limit = 0;
 static int server_limit = DEFAULT_SERVER_LIMIT;
 static int first_server_limit = 0;
 static int thread_limit = DEFAULT_THREAD_LIMIT;
+static int had_healthy_child = 0;
 static int first_thread_limit = 0;
 static int changed_limit_at_restart;
 static int dying = 0;
@@ -1657,6 +1658,7 @@ static void perform_idle_server_maintenance(void)
         int any_dying_threads = 0;
         int any_dead_threads = 0;
         int all_dead_threads = 1;
+        int child_threads_active = 0;
 
         if (i >= ap_max_daemons_limit
             && totally_free_length == idle_spawn_rate)
@@ -1686,10 +1688,11 @@ static void perform_idle_server_maintenance(void)
                     ++idle_thread_count;
                 }
                 if (status >= SERVER_READY && status < SERVER_GRACEFUL) {
-                    ++active_thread_count;
+                    ++child_threads_active;
                 }
             }
         }
+        active_thread_count += child_threads_active;
         if (any_dead_threads
             && totally_free_length < idle_spawn_rate
             && free_length < MAX_SPAWN_RATE
@@ -1713,6 +1716,9 @@ static void perform_idle_server_maintenance(void)
             }
             ++free_length;
         }
+        else if (child_threads_active == ap_threads_per_child) {
+            had_healthy_child = 1;
+        }
         /* XXX if (!ps->quiescing)     is probably more reliable  GLA */
         if (!any_dying_threads) {
             last_non_dead = i;
@@ -1721,21 +1727,23 @@ static void perform_idle_server_maintenance(void)
     }
 
     if (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.
              */
             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,
-                         "No active workers found..."
-                         " Apache is exiting!");
+                         "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;
         }
@@ -2198,6 +2206,7 @@ static int worker_pre_config(apr_pool_t * pconf, apr_pool_t * plog,
     ap_pid_fname = DEFAULT_PIDLOG;
     ap_lock_fname = DEFAULT_LOCKFILE;
     ap_max_requests_per_child = DEFAULT_MAX_REQUESTS_PER_CHILD;
+    had_healthy_child = 0;
     ap_extended_status = 0;
 #ifdef AP_MPM_WANT_SET_MAX_MEM_FREE
     ap_max_mem_free = APR_ALLOCATOR_MAX_FREE_UNLIMITED;

diff --git a/server/mpm/worker/worker.c b/server/mpm/worker/worker.c
index f13f639426fc19fee91d0fac86366807a97f3333..edf33fc5c4576e3bf3dedc400f5b326ee677f6cf 100644 (file)
--- a/server/mpm/worker/worker.c
+++ b/server/mpm/worker/worker.c
@@ -124,6 +124,7 @@ static int first_server_limit = 0;
 static int thread_limit = DEFAULT_THREAD_LIMIT;
 static int first_thread_limit = 0;
 static int changed_limit_at_restart;
+static int had_healthy_child = 0;
 static int dying = 0;
 static int workers_may_exit = 0;
 static int start_thread_may_exit = 0;
@@ -1419,6 +1420,7 @@ static void perform_idle_server_maintenance(void)
         int any_dying_threads = 0;
         int any_dead_threads = 0;
         int all_dead_threads = 1;
+        int child_threads_active = 0;
 
         if (i >= ap_max_daemons_limit && totally_free_length == idle_spawn_rate)
             break;
@@ -1449,10 +1451,11 @@ static void perform_idle_server_maintenance(void)
                     ++idle_thread_count;
                 }
                 if (status >= SERVER_READY && status < SERVER_GRACEFUL) {
-                    ++active_thread_count;
+                    ++child_threads_active;
                 }
             }
         }
+        active_thread_count += child_threads_active;
         if (any_dead_threads && totally_free_length < idle_spawn_rate
                 && free_length < MAX_SPAWN_RATE
                 && (!ps->pid               /* no process in the slot */
@@ -1475,6 +1478,9 @@ static void perform_idle_server_maintenance(void)
             }
             ++free_length;
         }
+        else if (child_threads_active == ap_threads_per_child) {
+            had_healthy_child = 1;
+        }
         /* XXX if (!ps->quiescing)     is probably more reliable  GLA */
         if (!any_dying_threads) {
             last_non_dead = i;
@@ -1483,21 +1489,23 @@ static void perform_idle_server_maintenance(void)
     }
 
     if (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.
              */
             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,
-                         "No active workers found..."
-                         " Apache is exiting!");
+                         "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;
         }
@@ -2011,6 +2019,7 @@ static int worker_pre_config(apr_pool_t *pconf, apr_pool_t *plog,
     ap_pid_fname = DEFAULT_PIDLOG;
     ap_lock_fname = DEFAULT_LOCKFILE;
     ap_max_requests_per_child = DEFAULT_MAX_REQUESTS_PER_CHILD;
+    had_healthy_child = 0;
     ap_extended_status = 0;
 #ifdef AP_MPM_WANT_SET_MAX_MEM_FREE
         ap_max_mem_free = APR_ALLOCATOR_MAX_FREE_UNLIMITED;