Check other blocked clients when value could not be pushed

1 files changed, 41 insertions, 23 deletions

diff --git a/src/t_list.c b/src/t_list.c
index 3ce0f992f..866a6a3e2 100644
--- a/src/t_list.c
+++ b/src/t_list.c
@@ -780,35 +780,53 @@ void unblockClientWaitingData(redisClient *c) {
 int handleClientsWaitingListPush(redisClient *c, robj *key, robj *ele) {
     struct dictEntry *de;
     redisClient *receiver;
-    list *l;
+    int numclients;
+    list *clients;
     listNode *ln;
+    robj *dstkey, *dstobj;
 
     de = dictFind(c->db->blocking_keys,key);
     if (de == NULL) return 0;
-    l = dictGetEntryVal(de);
-    ln = listFirst(l);
-    redisAssert(ln != NULL);
-    receiver = ln->value;
-
-    robj *target = receiver->bpop.target;
-
-    unblockClientWaitingData(receiver);
-
-    if (target == NULL) {
-        /* BRPOP/BLPOP return a multi-bulk with the name
-         * of the popped list */
-        addReplyMultiBulkLen(receiver,2);
-        addReplyBulk(receiver,key);
-        addReplyBulk(receiver,ele);
-    } else {
-        /* BRPOPLPUSH */
-        robj *dobj = lookupKeyWrite(receiver->db,target);
-        if (dobj && checkType(receiver,dobj,REDIS_LIST)) return 0;
-        rpoplpushHandlePush(receiver,target,dobj,ele);
-        decrRefCount(target);
+    clients = dictGetEntryVal(de);
+    numclients = listLength(clients);
+
+    /* Try to handle the push as long as there are clients waiting for a push.
+     * Note that "numclients" is used because the list of clients waiting for a
+     * push on "key" is deleted by unblockClient() when empty.
+     *
+     * This loop will have more than 1 iteration when there is a BRPOPLPUSH
+     * that cannot push the target list because it does not contain a list. If
+     * this happens, it simply tries the next client waiting for a push. */
+    while (numclients--) {
+        ln = listFirst(clients);
+        redisAssert(ln != NULL);
+        receiver = ln->value;
+        dstkey = receiver->bpop.target;
+
+        /* This should remove the first element of the "clients" list. */
+        unblockClientWaitingData(receiver);
+        redisAssert(ln != listFirst(clients));
+
+        if (dstkey == NULL) {
+            /* BRPOP/BLPOP */
+            addReplyMultiBulkLen(receiver,2);
+            addReplyBulk(receiver,key);
+            addReplyBulk(receiver,ele);
+            return 1;
+        } else {
+            /* BRPOPLPUSH */
+            dstobj = lookupKeyWrite(receiver->db,dstkey);
+            if (dstobj && checkType(receiver,dstobj,REDIS_LIST)) {
+                decrRefCount(dstkey);
+            } else {
+                rpoplpushHandlePush(receiver,dstkey,dstobj,ele);
+                decrRefCount(dstkey);
+                return 1;
+            }
+        }
     }
 
-    return 1;
+    return 0;
 }
 
 int getTimeoutFromObjectOrReply(redisClient *c, robj *object, time_t *timeout) {