RM_GetContextFlags provides indication that we're in a fork child (#7783)

src/aof.c

@@ -1603,7 +1603,7 @@ int rewriteAppendOnlyFileBackground(void) {
     if (hasActiveChildProcess()) return C_ERR;
     if (aofCreatePipes() != C_OK) return C_ERR;
     openChildInfoPipe();
-    if ((childpid = redisFork()) == 0) {
+    if ((childpid = redisFork(CHILD_TYPE_AOF)) == 0) {
         char tmpfile[256];
 
         /* Child */
@@ -1611,7 +1611,7 @@ int rewriteAppendOnlyFileBackground(void) {
         redisSetCpuAffinity(server.aof_rewrite_cpulist);
         snprintf(tmpfile,256,"temp-rewriteaof-bg-%d.aof", (int) getpid());
         if (rewriteAppendOnlyFile(tmpfile) == C_OK) {
-            sendChildCOWInfo(CHILD_INFO_TYPE_AOF, "AOF rewrite");
+            sendChildCOWInfo(CHILD_TYPE_AOF, "AOF rewrite");
             exitFromChild(0);
         } else {
             exitFromChild(1);

src/childinfo.c

@@ -76,11 +76,11 @@ void receiveChildInfo(void) {
     if (read(server.child_info_pipe[0],&server.child_info_data,wlen) == wlen &&
         server.child_info_data.magic == CHILD_INFO_MAGIC)
     {
-        if (server.child_info_data.process_type == CHILD_INFO_TYPE_RDB) {
+        if (server.child_info_data.process_type == CHILD_TYPE_RDB) {
             server.stat_rdb_cow_bytes = server.child_info_data.cow_size;
-        } else if (server.child_info_data.process_type == CHILD_INFO_TYPE_AOF) {
+        } else if (server.child_info_data.process_type == CHILD_TYPE_AOF) {
             server.stat_aof_cow_bytes = server.child_info_data.cow_size;
-        } else if (server.child_info_data.process_type == CHILD_INFO_TYPE_MODULE) {
+        } else if (server.child_info_data.process_type == CHILD_TYPE_MODULE) {
             server.stat_module_cow_bytes = server.child_info_data.cow_size;
         }
     }

src/module.c

@@ -1991,6 +1991,7 @@ int RM_GetContextFlags(RedisModuleCtx *ctx) {
 
     /* Presence of children processes. */
     if (hasActiveChildProcess()) flags |= REDISMODULE_CTX_FLAGS_ACTIVE_CHILD;
+    if (server.in_fork_child) flags |= REDISMODULE_CTX_FLAGS_IS_CHILD;
 
     return flags;
 }
@@ -6899,7 +6900,7 @@ int RM_Fork(RedisModuleForkDoneHandler cb, void *user_data) {
     }
 
     openChildInfoPipe();
-    if ((childpid = redisFork()) == 0) {
+    if ((childpid = redisFork(CHILD_TYPE_MODULE)) == 0) {
         /* Child */
         redisSetProcTitle("redis-module-fork");
     } else if (childpid == -1) {
@@ -6919,7 +6920,7 @@ int RM_Fork(RedisModuleForkDoneHandler cb, void *user_data) {
  * retcode will be provided to the done handler executed on the parent process.
  */
 int RM_ExitFromChild(int retcode) {
-    sendChildCOWInfo(CHILD_INFO_TYPE_MODULE, "Module fork");
+    sendChildCOWInfo(CHILD_TYPE_MODULE, "Module fork");
     exitFromChild(retcode);
     return REDISMODULE_OK;
 }

src/rdb.c

@@ -1385,7 +1385,7 @@ int rdbSaveBackground(char *filename, rdbSaveInfo *rsi) {
     server.lastbgsave_try = time(NULL);
     openChildInfoPipe();
 
-    if ((childpid = redisFork()) == 0) {
+    if ((childpid = redisFork(CHILD_TYPE_RDB)) == 0) {
         int retval;
 
         /* Child */
@@ -1393,7 +1393,7 @@ int rdbSaveBackground(char *filename, rdbSaveInfo *rsi) {
         redisSetCpuAffinity(server.bgsave_cpulist);
         retval = rdbSave(filename,rsi);
         if (retval == C_OK) {
-            sendChildCOWInfo(CHILD_INFO_TYPE_RDB, "RDB");
+            sendChildCOWInfo(CHILD_TYPE_RDB, "RDB");
         }
         exitFromChild((retval == C_OK) ? 0 : 1);
     } else {
@@ -2561,7 +2561,7 @@ int rdbSaveToSlavesSockets(rdbSaveInfo *rsi) {
 
     /* Create the child process. */
     openChildInfoPipe();
-    if ((childpid = redisFork()) == 0) {
+    if ((childpid = redisFork(CHILD_TYPE_RDB)) == 0) {
         /* Child */
         int retval, dummy;
         rio rdb;
@@ -2576,7 +2576,7 @@ int rdbSaveToSlavesSockets(rdbSaveInfo *rsi) {
             retval = C_ERR;
 
         if (retval == C_OK) {
-            sendChildCOWInfo(CHILD_INFO_TYPE_RDB, "RDB");
+            sendChildCOWInfo(CHILD_TYPE_RDB, "RDB");
         }
 
         rioFreeFd(&rdb);

src/redismodule.h

@@ -112,6 +112,8 @@
 #define REDISMODULE_CTX_FLAGS_ACTIVE_CHILD (1<<18)
 /* The next EXEC will fail due to dirty CAS (touched keys). */
 #define REDISMODULE_CTX_FLAGS_MULTI_DIRTY (1<<19)
+/* Redis is currently running inside background child process. */
+#define REDISMODULE_CTX_FLAGS_IS_CHILD (1<<20)
 
 /* Keyspace changes notification classes. Every class is associated with a
  * character for configuration purposes.

src/scripting.c

@@ -1858,7 +1858,7 @@ void ldbSendLogs(void) {
 int ldbStartSession(client *c) {
     ldb.forked = (c->flags & CLIENT_LUA_DEBUG_SYNC) == 0;
     if (ldb.forked) {
-        pid_t cp = redisFork();
+        pid_t cp = redisFork(CHILD_TYPE_LDB);
         if (cp == -1) {
             addReplyError(c,"Fork() failed: can't run EVAL in debugging mode.");
             return 0;

src/server.c

@@ -2886,6 +2886,7 @@ void initServer(void) {
     server.aof_state = server.aof_enabled ? AOF_ON : AOF_OFF;
     server.hz = server.config_hz;
     server.pid = getpid();
+    server.in_fork_child = CHILD_TYPE_NONE;
     server.main_thread_id = pthread_self();
     server.current_client = NULL;
     server.fixed_time_expire = 0;
@@ -4989,7 +4990,8 @@ void removeSignalHandlers(void) {
  * accepting writes because of a write error condition. */
 static void sigKillChildHandler(int sig) {
     UNUSED(sig);
-    serverLogFromHandler(LL_WARNING, "Received SIGUSR1 in child, exiting now.");
+    int level = server.in_fork_child == CHILD_TYPE_MODULE? LL_VERBOSE: LL_WARNING;
+    serverLogFromHandler(level, "Received SIGUSR1 in child, exiting now.");
     exitFromChild(SERVER_CHILD_NOERROR_RETVAL);
 }
 
@@ -5015,11 +5017,13 @@ void closeClildUnusedResourceAfterFork() {
         close(server.cluster_config_file_lock_fd);  /* don't care if this fails */
 }
 
-int redisFork() {
+/* purpose is one of CHILD_TYPE_ types */
+int redisFork(int purpose) {
     int childpid;
     long long start = ustime();
     if ((childpid = fork()) == 0) {
         /* Child */
+        server.in_fork_child = purpose;
         setOOMScoreAdj(CONFIG_OOM_BGCHILD);
         setupChildSignalHandlers();
         closeClildUnusedResourceAfterFork();

src/server.h

@@ -1046,9 +1046,11 @@ struct clusterState;
 #endif
 
 #define CHILD_INFO_MAGIC 0xC17DDA7A12345678LL
-#define CHILD_INFO_TYPE_RDB 0
+#define CHILD_TYPE_NONE 0
-#define CHILD_INFO_TYPE_AOF 1
+#define CHILD_TYPE_RDB 1
-#define CHILD_INFO_TYPE_MODULE 3
+#define CHILD_TYPE_AOF 2
+#define CHILD_TYPE_LDB 3
+#define CHILD_TYPE_MODULE 4
 
 struct redisServer {
     /* General */
@@ -1062,6 +1064,7 @@ struct redisServer {
                                    the actual 'hz' field value if dynamic-hz
                                    is enabled. */
     int hz;                     /* serverCron() calls frequency in hertz */
+    int in_fork_child;          /* indication that this is a fork child */
     redisDb *db;
     dict *commands;             /* Command table */
     dict *orig_commands;        /* Command table before command renaming. */
@@ -1904,7 +1907,7 @@ void sendChildInfo(int process_type);
 void receiveChildInfo(void);
 
 /* Fork helpers */
-int redisFork();
+int redisFork(int type);
 int hasActiveChildProcess();
 void sendChildCOWInfo(int ptype, char *pname);