From d4c1e981247cb8ac2c33d64dcef9937ee422f451 Mon Sep 17 00:00:00 2001
From: John Sully <john@csquare.ca>
Date: Tue, 11 Feb 2020 01:41:00 -0500
Subject: [PATCH] Implement an error handler so bug #125 can't happen

Former-commit-id: 16a019dba053fd0654116ff98a2ad0b66a9ed4e6
---
 src/aof.cpp        | 28 +++++++++++++++++++---------
 src/networking.cpp |  4 ++--
 src/server.cpp     |  1 +
 src/server.h       |  1 +
 4 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/src/aof.cpp b/src/aof.cpp
index 65647bbba..de8a8260e 100644
--- a/src/aof.cpp
+++ b/src/aof.cpp
@@ -124,6 +124,21 @@ void aofChildWriteDiffData(aeEventLoop *el, int fd, void *privdata, int mask) {
     }
 }
 
+void installAofRewriteEvent()
+{
+    serverTL->fRetrySetAofEvent = false;
+    if (!g_pserver->aof_rewrite_pending) {
+        g_pserver->aof_rewrite_pending = true;
+        int res = 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);
+        });
+        if (res != AE_OK)
+            serverTL->fRetrySetAofEvent = true;
+    }
+}
+
 /* Append data to the AOF rewrite buffer, allocating new blocks if needed. */
 void aofRewriteBufferAppend(unsigned char *s, unsigned long len) {
     listNode *ln = listLast(g_pserver->aof_rewrite_buf_blocks);
@@ -165,15 +180,7 @@ 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. */
-    if (!g_pserver->aof_rewrite_pending) {
-        g_pserver->aof_rewrite_pending = true;
-        int res = 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);
-        });
-        serverAssert(res == AE_OK); // we can't handle an error here
-    }
+    installAofRewriteEvent();
 }
 
 /* Write the buffer (possibly composed of multiple blocks) into the specified
@@ -349,6 +356,9 @@ void flushAppendOnlyFile(int force) {
     int sync_in_progress = 0;
     mstime_t latency;
 
+    if (serverTL->fRetrySetAofEvent)
+        installAofRewriteEvent();
+
     if (sdslen(g_pserver->aof_buf) == 0) {
         /* Check if we need to do fsync even the aof buffer is empty,
          * because previously in AOF_FSYNC_EVERYSEC mode, fsync is
diff --git a/src/networking.cpp b/src/networking.cpp
index 097df0f87..54e04406f 100644
--- a/src/networking.cpp
+++ b/src/networking.cpp
@@ -1003,7 +1003,7 @@ int clientHasPendingReplies(client *c) {
     return (c->bufpos || listLength(c->reply)) && !(c->flags & CLIENT_CLOSE_ASAP);
 }
 
-int chooseBestThreadForAccept(int ielCur)
+int chooseBestThreadForAccept()
 {
     listIter li;
     listNode *ln;
@@ -1133,7 +1133,7 @@ void acceptTcpHandler(aeEventLoop *el, int fd, void *privdata, int mask) {
         if (!g_fTestMode)
         {
             {
-            int ielTarget = chooseBestThreadForAccept(ielCur);
+            int ielTarget = chooseBestThreadForAccept();
             if (ielTarget != ielCur)
             {
                 char *szT = (char*)zmalloc(NET_IP_STR_LEN, MALLOC_LOCAL);
diff --git a/src/server.cpp b/src/server.cpp
index 2d6027348..15f52ab52 100644
--- a/src/server.cpp
+++ b/src/server.cpp
@@ -2884,6 +2884,7 @@ static void initServerThread(struct redisServerThreadVars *pvar, int fMain)
     pvar->el = aeCreateEventLoop(g_pserver->maxclients+CONFIG_FDSET_INCR);
     pvar->current_client = nullptr;
     pvar->clients_paused = 0;
+    pvar->fRetrySetAofEvent = false;
     if (pvar->el == NULL) {
         serverLog(LL_WARNING,
             "Failed creating the event loop. Error message: '%s'",
diff --git a/src/server.h b/src/server.h
index 3ff023677..3ec2e8948 100644
--- a/src/server.h
+++ b/src/server.h
@@ -1526,6 +1526,7 @@ struct redisServerThreadVars {
     struct fastlock lockPendingWrite { "thread pending write" };
     char neterr[ANET_ERR_LEN];   /* Error buffer for anet.c */
     long unsigned commandsExecuted = 0;
+    bool fRetrySetAofEvent = false;
 };
 
 struct redisMaster {