diff --git a/src/ae.cpp b/src/ae.cpp
index e6177c46c..490826b8e 100644
--- a/src/ae.cpp
+++ b/src/ae.cpp
@@ -144,8 +144,17 @@ void aeProcessCmd(aeEventLoop *eventLoop, int fd, void *, int )
 
         case AE_ASYNC_OP::PostCppFunction:
         {
+            if (cmd.pctl != nullptr)
+                cmd.pctl->mutexcv.lock();
+            
             std::unique_lock<decltype(g_lock)> ulock(g_lock);
             (*cmd.pfn)();
+            
+            if (cmd.pctl != nullptr)
+            {
+                cmd.pctl->cv.notify_all();
+                cmd.pctl->mutexcv.unlock();
+            }
             delete cmd.pfn;
         }
             break;
@@ -186,6 +195,11 @@ int aeCreateRemoteFileEvent(aeEventLoop *eventLoop, int fd, int mask,
 
 int aePostFunction(aeEventLoop *eventLoop, aePostFunctionProc *proc, void *arg)
 {
+    if (eventLoop == g_eventLoopThisThread)
+    {
+        proc(arg);
+        return AE_OK;
+    }
     aeCommand cmd;
     cmd.op = AE_ASYNC_OP::PostFunction;
     cmd.proc = proc;
@@ -195,14 +209,33 @@ int aePostFunction(aeEventLoop *eventLoop, aePostFunctionProc *proc, void *arg)
     return AE_OK;
 }
 
-int aePostFunction(aeEventLoop *eventLoop, std::function<void()> fn)
+int aePostFunction(aeEventLoop *eventLoop, std::function<void()> fn, bool fSynchronous)
 {
+    if (eventLoop == g_eventLoopThisThread)
+    {
+        fn();
+        return AE_OK;
+    }
+
     aeCommand cmd;
     cmd.op = AE_ASYNC_OP::PostCppFunction;
     cmd.pfn = new std::function<void()>(fn);
+    cmd.pctl = nullptr;
+    if (fSynchronous)
+        cmd.pctl = new aeCommandControl();
+    std::unique_lock<std::mutex> ulock(cmd.pctl->mutexcv, std::defer_lock);
+    if (fSynchronous)
+        cmd.pctl->mutexcv.lock();
     auto size = write(eventLoop->fdCmdWrite, &cmd, sizeof(cmd));
     AE_ASSERT(size == sizeof(cmd));
-    return AE_OK;
+    int ret = AE_OK;
+    if (fSynchronous)
+    {
+        cmd.pctl->cv.wait(ulock);
+        ret = cmd.pctl->rval;
+        delete cmd.pctl;
+    }
+    return ret;
 }
 
 aeEventLoop *aeCreateEventLoop(int setsize) {
@@ -232,7 +265,8 @@ aeEventLoop *aeCreateEventLoop(int setsize) {
     if (pipe(rgfd) < 0)
         goto err;
     eventLoop->fdCmdRead = rgfd[0];
-    eventLoop->fdCmdWrite = rgfd[1];
+    eventLoop->fdCmdWrite = rgfd[1];;
+    fcntl(eventLoop->fdCmdWrite, F_SETFL, O_NONBLOCK);
     fcntl(eventLoop->fdCmdRead, F_SETFL, O_NONBLOCK);
     eventLoop->cevents = 0;
     aeCreateFileEvent(eventLoop, eventLoop->fdCmdRead, AE_READABLE|AE_READ_THREADSAFE, aeProcessCmd, NULL);
@@ -325,8 +359,7 @@ void aeDeleteFileEventAsync(aeEventLoop *eventLoop, int fd, int mask)
     cmd.fd = fd;
     cmd.mask = mask;
     auto cb = write(eventLoop->fdCmdWrite, &cmd, sizeof(cmd));
-    if (cb != sizeof(cmd))
-        fprintf(stderr, "Failed to write to pipe.\n");
+    AE_ASSERT(cb == sizeof(cmd));
 }
 
 extern "C" void aeDeleteFileEvent(aeEventLoop *eventLoop, int fd, int mask)
diff --git a/src/ae.h b/src/ae.h
index affe5363f..f1aa0380c 100644
--- a/src/ae.h
+++ b/src/ae.h
@@ -131,7 +131,7 @@ aeEventLoop *aeCreateEventLoop(int setsize);
 int aePostFunction(aeEventLoop *eventLoop, aePostFunctionProc *proc, void *arg);
 #ifdef __cplusplus
 }   // EXTERN C
-int aePostFunction(aeEventLoop *eventLoop, std::function<void()> fn);
+int aePostFunction(aeEventLoop *eventLoop, std::function<void()> fn, bool fSynchronous = false);
 extern "C" {
 #endif
 void aeDeleteEventLoop(aeEventLoop *eventLoop);
diff --git a/src/networking.cpp b/src/networking.cpp
index 226751571..659fb65ba 100644
--- a/src/networking.cpp
+++ b/src/networking.cpp
@@ -1154,6 +1154,7 @@ void disconnectSlaves(void) {
  * This is used by freeClient() and replicationCacheMaster(). */
 void unlinkClient(client *c) {
     listNode *ln;
+    AssertCorrectThread(c);
 
     /* If this is marked as current client unset it. */
     if (server.current_client == c) server.current_client = NULL;
@@ -1196,6 +1197,13 @@ void unlinkClient(client *c) {
         listDelNode(server.rgthreadvar[c->iel].unblocked_clients,ln);
         c->flags &= ~CLIENT_UNBLOCKED;
     }
+
+    if (c->flags & CLIENT_PENDING_ASYNCWRITE) {
+        ln = listSearchKey(server.rgthreadvar[c->iel].clients_pending_asyncwrite,c);
+        serverAssert(ln != NULL);
+        listDelNode(server.rgthreadvar[c->iel].clients_pending_asyncwrite,ln);
+        c->flags &= ~CLIENT_PENDING_ASYNCWRITE;
+    }
 }
 
 void freeClient(client *c) {
diff --git a/src/replication.cpp b/src/replication.cpp
index 33b15d8d1..179a48028 100644
--- a/src/replication.cpp
+++ b/src/replication.cpp
@@ -298,6 +298,9 @@ void replicationFeedSlavesFromMasterStream(list *slaves, char *buf, size_t bufle
         if (slave->replstate == SLAVE_STATE_WAIT_BGSAVE_START) continue;
         addReplyProtoAsync(slave,buf,buflen);
     }
+    
+    if (listLength(slaves))
+        ProcessPendingAsyncWrites();    // flush them to their respective threads
 }
 
 void replicationFeedMonitors(client *c, list *monitors, int dictid, robj **argv, int argc) {
@@ -2039,7 +2042,10 @@ void replicationHandleMasterDisconnection(void) {
      * the slaves only if we'll have to do a full resync with our master. */
 }
 
+void replicaofCommandCore(client *c);
 void replicaofCommand(client *c) {
+    // Changing the master needs to be done on the main thread.
+
     /* SLAVEOF is not allowed in cluster mode as replication is automatically
      * configured using the current address of the master node. */
     if (server.cluster_enabled) {
@@ -2047,6 +2053,23 @@ void replicaofCommand(client *c) {
         return;
     }
 
+    if ((serverTL - server.rgthreadvar) == IDX_EVENT_LOOP_MAIN)
+    {
+        replicaofCommandCore(c);
+    }
+    else
+    {
+        aeReleaseLock();
+        aePostFunction(server.rgthreadvar[IDX_EVENT_LOOP_MAIN].el, [=]{
+            replicaofCommandCore(c);
+        }, true /*fSync*/);
+        aeAcquireLock();
+    }
+}
+
+void replicaofCommandCore(client *c) {
+    
+
     /* The special host/port combination "NO" "ONE" turns the instance
      * into a master. Otherwise the new master address is set. */
     if (!strcasecmp((const char*)ptrFromObj(c->argv[1]),"no") &&
@@ -2068,7 +2091,7 @@ void replicaofCommand(client *c) {
         if (server.masterhost && !strcasecmp(server.masterhost,(const char*)ptrFromObj(c->argv[1]))
             && server.masterport == port) {
             serverLog(LL_NOTICE,"REPLICAOF would result into synchronization with the master we are already connected with. No operation performed.");
-            addReplySds(c,sdsnew("+OK Already connected to specified master\r\n"));
+            addReplySdsAsync(c,sdsnew("+OK Already connected to specified master\r\n"));
             return;
         }
         /* There was no previous master or the user specified a different one,
@@ -2079,7 +2102,7 @@ void replicaofCommand(client *c) {
             server.masterhost, server.masterport, client);
         sdsfree(client);
     }
-    addReply(c,shared.ok);
+    addReplyAsync(c,shared.ok);
 }
 
 /* ROLE command: provide information about the role of the instance
diff --git a/src/server.c b/src/server.c
index 21d295a42..a2fd4b337 100644
--- a/src/server.c
+++ b/src/server.c
@@ -3181,7 +3181,7 @@ void preventCommandReplication(client *c) {
     c->flags |= CLIENT_PREVENT_REPL_PROP;
 }
 
-static void ProcessPendingAsyncWrites()
+void ProcessPendingAsyncWrites()
 {
     while(listLength(serverTL->clients_pending_asyncwrite)) {
         client *c = (client*)listNodeValue(listFirst(serverTL->clients_pending_asyncwrite));
@@ -5046,8 +5046,9 @@ int main(int argc, char **argv) {
 
     initServer();
 
-    server.cthreads = 2; //testing
+    server.cthreads = 1; //testing
     initNetworking(1 /* fReusePort */);
+    serverTL = &server.rgthreadvar[IDX_EVENT_LOOP_MAIN];
 
     if (background || server.pidfile) createPidFile();
     redisSetProcTitle(argv[0]);
diff --git a/src/server.h b/src/server.h
index 2613bcbe1..10fa38c55 100644
--- a/src/server.h
+++ b/src/server.h
@@ -1641,6 +1641,8 @@ void addReplySdsAsync(client *c, sds s);
 void addReplyBulkSdsAsync(client *c, sds s);
 void addReplyPushLenAsync(client *c, long length);
 
+void ProcessPendingAsyncWrites(void);
+
 #ifdef __GNUC__
 void addReplyErrorFormat(client *c, const char *fmt, ...)
     __attribute__((format(printf, 2, 3)));