Core: master_process_auto_reload directive.

When a child process exits on an abnormal signal, such as SIGKILL
or SIGSEGV, master process will perform reconfiguration.

src/core/nginx.c

@@ -55,6 +55,13 @@ static ngx_command_t  ngx_core_commands[] = {
       offsetof(ngx_core_conf_t, master),
       NULL },
 
+    { ngx_string("master_process_auto_reload"),
+      NGX_MAIN_CONF|NGX_DIRECT_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      0,
+      offsetof(ngx_core_conf_t, auto_reload),
+      NULL },
+
     { ngx_string("timer_resolution"),
       NGX_MAIN_CONF|NGX_DIRECT_CONF|NGX_CONF_TAKE1,
       ngx_conf_set_msec_slot,
@@ -1113,6 +1120,7 @@ ngx_core_module_create_conf(ngx_cycle_t *cycle)
 
     ccf->daemon = NGX_CONF_UNSET;
     ccf->master = NGX_CONF_UNSET;
+    ccf->auto_reload = NGX_CONF_UNSET;
     ccf->timer_resolution = NGX_CONF_UNSET_MSEC;
     ccf->shutdown_timeout = NGX_CONF_UNSET_MSEC;
 
@@ -1142,6 +1150,7 @@ ngx_core_module_init_conf(ngx_cycle_t *cycle, void *conf)
 
     ngx_conf_init_value(ccf->daemon, 1);
     ngx_conf_init_value(ccf->master, 1);
+    ngx_conf_init_value(ccf->auto_reload, 0);
     ngx_conf_init_msec_value(ccf->timer_resolution, 0);
     ngx_conf_init_msec_value(ccf->shutdown_timeout, 0);
 

src/core/ngx_cycle.c

@@ -434,6 +434,7 @@ ngx_init_cycle(ngx_cycle_t *old_cycle)
         }
 
         shm_zone[i].shm.log = cycle->log;
+        shm_zone[i].skip_inherit = 0;
 
         opart = &old_cycle->shared_memory.part;
         oshm_zone = opart->elts;
@@ -463,6 +464,10 @@ ngx_init_cycle(ngx_cycle_t *old_cycle)
                 continue;
             }
 
+            if (shm_zone[i].tag == oshm_zone[n].tag && oshm_zone[i].skip_inherit) {
+                break;
+            }
+
             if (shm_zone[i].tag == oshm_zone[n].tag && shm_zone[i].noreuse) {
                 data = oshm_zone[n].data;
                 break;
@@ -1363,6 +1368,7 @@ ngx_shared_memory_add(ngx_conf_t *cf, ngx_str_t *name, size_t size, void *tag)
     shm_zone->init = NULL;
     shm_zone->tag = tag;
     shm_zone->noreuse = 0;
+    shm_zone->skip_inherit = 0;
 
     return shm_zone;
 }

src/core/ngx_cycle.h

@@ -32,7 +32,8 @@ struct ngx_shm_zone_s {
     ngx_shm_zone_init_pt      init;
     void                     *tag;
     void                     *sync;
-    ngx_uint_t                noreuse;  /* unsigned  noreuse:1; */
+    ngx_uint_t                noreuse:1;
+    ngx_uint_t                skip_inherit:1;
 };
 
 
@@ -89,6 +90,7 @@ struct ngx_cycle_s {
 typedef struct {
     ngx_flag_t                daemon;
     ngx_flag_t                master;
+    ngx_flag_t                auto_reload;
 
     ngx_msec_t                timer_resolution;
     ngx_msec_t                shutdown_timeout;

src/os/unix/ngx_process.c

@@ -23,7 +23,7 @@ typedef struct {
 static void ngx_execute_proc(ngx_cycle_t *cycle, void *data);
 static void ngx_signal_handler(int signo, siginfo_t *siginfo, void *ucontext);
 static void ngx_process_get_status(void);
-static void ngx_unlock_mutexes(ngx_pid_t pid);
+static void ngx_unlock_mutexes(ngx_pid_t pid, ngx_int_t skip_inherit);
 
 
 int              ngx_argc;
@@ -470,15 +470,20 @@ ngx_signal_handler(int signo, siginfo_t *siginfo, void *ucontext)
 static void
 ngx_process_get_status(void)
 {
-    int              status;
+    int               status;
-    char            *process;
+    char             *process;
-    ngx_pid_t        pid;
+    ngx_pid_t         pid;
-    ngx_err_t        err;
+    ngx_err_t         err;
-    ngx_int_t        i;
+    ngx_int_t         i, skip_inherit;
-    ngx_uint_t       one;
+    ngx_uint_t        one;
+    ngx_core_conf_t  *ccf;
 
+    skip_inherit = 0;
     one = 0;
 
+    ccf = (ngx_core_conf_t *) ngx_get_conf(ngx_cycle->conf_ctx,
+                                           ngx_core_module);
+
     for ( ;; ) {
         pid = waitpid(-1, &status, WNOHANG);
 
@@ -541,6 +546,15 @@ ngx_process_get_status(void)
                           "%s %P exited on signal %d",
                           process, pid, WTERMSIG(status));
 #endif
+            if (ccf->auto_reload) {
+                ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, 0,
+                              "reconfiguring due to child exiting from "
+                              "abnormal signal %d", WTERMSIG(status));
+
+                ngx_processes[i].respawn = 0;
+                ngx_reconfigure = 1;
+                skip_inherit = 1;
+            }
 
         } else {
             ngx_log_error(NGX_LOG_NOTICE, ngx_cycle->log, 0,
@@ -556,13 +570,13 @@ ngx_process_get_status(void)
             ngx_processes[i].respawn = 0;
         }
 
-        ngx_unlock_mutexes(pid);
+        ngx_unlock_mutexes(pid, skip_inherit);
     }
 }
 
 
 static void
-ngx_unlock_mutexes(ngx_pid_t pid)
+ngx_unlock_mutexes(ngx_pid_t pid, ngx_int_t skip_inherit)
 {
     ngx_uint_t        i;
     ngx_shm_zone_t   *shm_zone;
@@ -604,6 +618,10 @@ ngx_unlock_mutexes(ngx_pid_t pid)
                           "shared memory zone \"%V\" was locked by %P",
                           &shm_zone[i].shm.name, pid);
         }
+
+        if (skip_inherit) {
+            shm_zone[i].skip_inherit = 1;
+        }
     }
 }