Avoid crash due to excessive posted functions for AOF rewrite

Author: JohnSully

src/aof.cpp

@@ -165,10 +165,14 @@ void aofRewriteBufferAppend(unsigned char *s, unsigned long len) {
 
     /* Install a file event to send data to the rewrite child if there is
      * not one already. */
-    aePostFunction(g_pserver->rgthreadvar[IDX_EVENT_LOOP_MAIN].el, []{
-        if (g_pserver->aof_pipe_write_data_to_child >= 0)
-            aeCreateFileEvent(g_pserver->rgthreadvar[IDX_EVENT_LOOP_MAIN].el, g_pserver->aof_pipe_write_data_to_child, AE_WRITABLE, aofChildWriteDiffData, NULL);
-    });
+    if (!g_pserver->aof_rewrite_pending) {
+        g_pserver->aof_rewrite_pending = true;
+        aePostFunction(g_pserver->rgthreadvar[IDX_EVENT_LOOP_MAIN].el, [] {
+            g_pserver->aof_rewrite_pending = false;
+            if (g_pserver->aof_pipe_write_data_to_child >= 0)
+                aeCreateFileEvent(g_pserver->rgthreadvar[IDX_EVENT_LOOP_MAIN].el, g_pserver->aof_pipe_write_data_to_child, AE_WRITABLE, aofChildWriteDiffData, NULL);
+        });
+    }
 }
 
 /* Write the buffer (possibly composed of multiple blocks) into the specified

src/server.h

@@ -1733,6 +1733,7 @@ struct redisServer {
     int aof_stop_sending_diff;     /* If true stop sending accumulated diffs
                                       to child process. */
     sds aof_child_diff;             /* AOF diff accumulator child side. */
+    int aof_rewrite_pending = 0;    /* is a call to aofChildWriteDiffData already queued? */
     /* RDB persistence */
     long long dirty;                /* Changes to DB from the last save */
     long long dirty_before_bgsave;  /* Used to restore dirty on failed BGSAVE */