By default Redis refuses writes with an error if the latest BGSAVE failed (and at least one save point is configured). However people having good monitoring systems may prefer a server that continues to work, since they are notified that there are problems by their monitoring systems. This commit implements the ability to turn the feature on or off via redis.conf and CONFIG SET.

redis.conf

@@ -93,6 +93,21 @@ save 900 1
 save 300 10
 save 60 10000
 
+# By default Redis will stop accepting writes if RDB snapshots are enabled
+# (at least one save point) and the latest background save failed.
+# This will make the user aware (in an hard way) that data is not persisting
+# on disk properly, otherwise chances are that no one will notice and some
+# distater will happen.
+#
+# If the background saving process will start working again Redis will
+# automatically allow writes again.
+#
+# However if you have setup your proper monitoring of the Redis server
+# and persistence, you may want to disable this feature so that Redis will
+# continue to work as usually even if there are problems with disk,
+# permissions, and so forth.
+stop-writes-on-bgsave-error yes
+
 # Compress string objects using LZF when dump .rdb databases?
 # For default that's set to 'yes' as it's almost always a win.
 # If you want to save some CPU in the saving child set it to 'no' but

src/config.c

@@ -336,6 +336,11 @@ void loadServerConfigFromString(char *config) {
             server.client_obuf_limits[class].hard_limit_bytes = hard;
             server.client_obuf_limits[class].soft_limit_bytes = soft;
             server.client_obuf_limits[class].soft_limit_seconds = soft_seconds;
+        } else if (!strcasecmp(argv[0],"stop-writes-on-bgsave-error") &&
+                   argc == 2) {
+            if ((server.stop_writes_on_bgsave_err = yesnotoi(argv[1])) == -1) {
+                err = "argument must be 'yes' or 'no'"; goto loaderr;
+            }
         } else {
             err = "Bad directive or wrong number of arguments"; goto loaderr;
         }
@@ -604,7 +609,11 @@ void configSetCommand(redisClient *c) {
             server.client_obuf_limits[class].soft_limit_seconds = soft_seconds;
         }
         sdsfreesplitres(v,vlen);
+    } else if (!strcasecmp(c->argv[2]->ptr,"stop-writes-on-bgsave-error")) {
+        int yn = yesnotoi(o->ptr);
 
+        if (yn == -1) goto badfmt;
+        server.stop_writes_on_bgsave_err = yn;
     } else {
         addReplyErrorFormat(c,"Unsupported CONFIG parameter: %s",
             (char*)c->argv[2]->ptr);
@@ -822,6 +831,11 @@ void configGetCommand(redisClient *c) {
         sdsfree(buf);
         matches++;
     }
+    if (stringmatch(pattern,"stop-writes-on-bgsave-error",0)) {
+        addReplyBulkCString(c,"stop-writes-on-bgsave-error");
+        addReplyBulkCString(c,server.stop_writes_on_bgsave_err ? "yes" : "no");
+        matches++;
+    }
     setDeferredMultiBulkLength(c,replylen,matches*2);
 }
 

src/redis.c

@@ -1091,6 +1091,7 @@ void initServer() {
     server.stat_rejected_conn = 0;
     server.unixtime = time(NULL);
     server.lastbgsave_status = REDIS_OK;
+    server.stop_writes_on_bgsave_err = 1;
     aeCreateTimeEvent(server.el, 1, serverCron, NULL, NULL);
     if (server.ipfd > 0 && aeCreateFileEvent(server.el,server.ipfd,AE_READABLE,
         acceptTcpHandler,NULL) == AE_ERR) oom("creating file event");
@@ -1378,7 +1379,9 @@ int processCommand(redisClient *c) {
     }
 
     /* Don't accept write commands if there are problems persisting on disk. */
-    if (server.saveparamslen > 0 && server.lastbgsave_status == REDIS_ERR &&
+    if (server.stop_writes_on_bgsave_err &&
+        server.saveparamslen > 0
+        && server.lastbgsave_status == REDIS_ERR &&
         c->cmd->flags & REDIS_CMD_WRITE)
     {
         addReply(c, shared.bgsaveerr);

src/redis.h

@@ -637,6 +637,7 @@ struct redisServer {
     int rdb_compression;            /* Use compression in RDB? */
     time_t lastsave;                /* Unix time of last save succeeede */
     int lastbgsave_status;          /* REDIS_OK or REDIS_ERR */
+    int stop_writes_on_bgsave_err;  /* Don't allow writes if can't BGSAVE */
     /* Propagation of commands in AOF / replication */
     redisOpArray also_propagate;    /* Additional command to propagate. */
     /* Logging */