From dd937030f02f4c3100b05fa0a9d40257b52f1eb0 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Fri, 24 May 2013 18:58:57 +0200
Subject: [PATCH] Replication: don't even queue replies to master commands.

When master send commands, there is no need for the slave to reply.
Redis used to queue the reply in the output buffer and discard the reply
later, this is a waste of work and it is not clear why it was this way
(I sincerely don't remember).

This commit changes it in order to don't queue the reply at all.

All tests passing.
---
 src/networking.c | 24 +++++++-----------------
 1 file changed, 7 insertions(+), 17 deletions(-)

diff --git a/src/networking.c b/src/networking.c
index 64298c4e..f269591c 100644
--- a/src/networking.c
+++ b/src/networking.c
@@ -116,15 +116,15 @@ redisClient *createClient(int fd) {
  * returns REDIS_OK, and make sure to install the write handler in our event
  * loop so that when the socket is writable new data gets written.
  *
- * If the client should not receive new data, because it is a fake client
- * or a slave not yet online, or because the setup of the write handler
+ * If the client should not receive new data, because it is a fake client,
+ * a master, a slave not yet online, or because the setup of the write handler
  * failed, the function returns REDIS_ERR.
  *
  * Typically gets called every time a reply is built, before adding more
  * data to the clients output buffers. If the function returns REDIS_ERR no
  * data should be appended to the output buffers. */
 int prepareClientToWrite(redisClient *c) {
-    if (c->flags & REDIS_LUA_CLIENT) return REDIS_OK;
+    if (c->flags & (REDIS_LUA_CLIENT|REDIS_MASTER)) return REDIS_OK;
     if (c->fd <= 0) return REDIS_ERR; /* Fake client */
     if (c->bufpos == 0 && listLength(c->reply) == 0 &&
         (c->replstate == REDIS_REPL_NONE ||
@@ -739,13 +739,8 @@ void sendReplyToClient(aeEventLoop *el, int fd, void *privdata, int mask) {
 
     while(c->bufpos > 0 || listLength(c->reply)) {
         if (c->bufpos > 0) {
-            if (c->flags & REDIS_MASTER) {
-                /* Don't reply to a master */
-                nwritten = c->bufpos - c->sentlen;
-            } else {
-                nwritten = write(fd,c->buf+c->sentlen,c->bufpos-c->sentlen);
-                if (nwritten <= 0) break;
-            }
+            nwritten = write(fd,c->buf+c->sentlen,c->bufpos-c->sentlen);
+            if (nwritten <= 0) break;
             c->sentlen += nwritten;
             totwritten += nwritten;
 
@@ -765,13 +760,8 @@ void sendReplyToClient(aeEventLoop *el, int fd, void *privdata, int mask) {
                 continue;
             }
 
-            if (c->flags & REDIS_MASTER) {
-                /* Don't reply to a master */
-                nwritten = objlen - c->sentlen;
-            } else {
-                nwritten = write(fd, ((char*)o->ptr)+c->sentlen,objlen-c->sentlen);
-                if (nwritten <= 0) break;
-            }
+            nwritten = write(fd, ((char*)o->ptr)+c->sentlen,objlen-c->sentlen);
+            if (nwritten <= 0) break;
             c->sentlen += nwritten;
             totwritten += nwritten;