From f0728a7ead982eb819fd65d4a47a76608f1fb661 Mon Sep 17 00:00:00 2001
From: VivekSainiEQ <vivek@eqalpha.com>
Date: Thu, 29 Apr 2021 18:51:30 +0000
Subject: [PATCH] Performance optimizations

Former-commit-id: 7fd83d467784d293f7da78b74f9b9763ce387238
---
 src/replication.cpp | 71 ++-------------------------------------------
 1 file changed, 3 insertions(+), 68 deletions(-)

diff --git a/src/replication.cpp b/src/replication.cpp
index ef33fbfd9..1bae2773a 100644
--- a/src/replication.cpp
+++ b/src/replication.cpp
@@ -47,8 +47,7 @@
 #include <unordered_map>
 #include <string>
 
-// #define BYPASS_BUFFER
-// #define RESIZE_BACKLOG
+#define BYPASS_BUFFER
 
 void replicationDiscardCachedMaster(redisMaster *mi);
 void replicationResurrectCachedMaster(redisMaster *mi, connection *conn);
@@ -89,10 +88,10 @@ int RDBGeneratedByReplication = 0;
 void resizeReplicationBacklogForClients(long long newsize);
 
 void setReplIdx(client *c, long long idx, long long off){
-    if (prepareClientToWrite(c) != C_OK) return;
     // serverLog(LL_NOTICE, "calling this garbage function w/ idx and off: %lld, %lld, %lld", idx, off, off-idx);
     // serverLog(LL_NOTICE, "Repl Index started at: %lld", c->repl_curr_idx);
     if (c->repl_curr_idx == -1){
+        if (prepareClientToWrite(c) != C_OK) return;
         c->repl_curr_idx = idx;
         c->repl_curr_off = off;
     }
@@ -432,17 +431,6 @@ void feedReplicationBacklog(const void *ptr, size_t len) {
                 resizeReplicationBacklogForClients(newsize);
             }
         }
-#ifdef RESIZE_BACKLOG
-        long long lowest_replica_offset = getLowestOffsetAmongReplicas();
-        minimumsize = g_pserver->master_repl_offset + len - lowest_replica_offset;
-        if (lowest_replica_offset != -1 && minimumsize > g_pserver->repl_backlog_size){
-            serverLog(LL_WARNING, "THE REPLICATION BACKLOG SIZE IS TOO SMALL, THIS IS A PROBLEM");
-            long long oldsize = g_pserver->repl_backlog_size;
-            resizeReplicationBacklogForClients(std::max(g_pserver->repl_backlog_size * 2, minimumsize));
-            serverLog(LL_WARNING, "changed size from %lld to %lld", oldsize, g_pserver->repl_backlog_size);
-            flushReplBacklogToClients();
-        }
-#endif
     }
 
     // serverLog(LL_NOTICE, "Pt2 start with: master_repl_offset: %lld, repl_batch_offStart: %lld, " 
@@ -4635,30 +4623,11 @@ void replicateSubkeyExpire(redisDb *db, robj_roptr key, robj_roptr subkey, long
 
 void _clientAsyncReplyBufferReserve(client *c, size_t len);
 
-/* Has the end of the replication backlog overflowed past the beginning? */
-bool replOverflowHasOccured(){
-    
-    if (g_pserver->repl_backlog_idx > g_pserver->repl_batch_idxStart){
-        long long repl_idx_difference = g_pserver->repl_backlog_idx > g_pserver->repl_batch_idxStart ? 
-                g_pserver->repl_backlog_idx - g_pserver->repl_batch_idxStart :
-                (g_pserver->repl_backlog_size + g_pserver->repl_backlog_idx) - g_pserver->repl_batch_idxStart;
-
-        return g_pserver->master_repl_offset - g_pserver->repl_batch_offStart > repl_idx_difference;
-    }
-    return false;
-}
-
-thread_local int transmittedCount = 0;
-
 void flushReplBacklogToClients()
 {
     serverAssert(GlobalLocksAcquired());
-    if (g_pserver->repl_batch_offStart < 0){
-        if (getLowestOffsetAmongReplicas() == -1){
-            serverLog(LL_NOTICE, "this is a case i probably have to handle");
-        }
+    if (g_pserver->repl_batch_offStart < 0)
         return;
-    }
 
     
     if (g_pserver->repl_batch_offStart != g_pserver->master_repl_offset) {
@@ -4668,39 +4637,9 @@ void flushReplBacklogToClients()
         serverAssert(g_pserver->master_repl_offset - g_pserver->repl_batch_offStart <= g_pserver->repl_backlog_size);
         serverAssert(g_pserver->repl_batch_idxStart != g_pserver->repl_backlog_idx);
 
-        // serverAssert(!replOverflowHasOccured());
         listIter li;
         listNode *ln;
         listRewind(g_pserver->slaves, &li);
-
-#if 0
-        // check for potential overflow first
-        while ((ln = listNext(&li))) {
-            client *replica = (client*)listNodeValue(ln);
-            // serverLog(LL_NOTICE, "replica state: %d", replica->replstate);
-
-            if (replica->replstate == SLAVE_STATE_WAIT_BGSAVE_START) continue;
-            if (replica->flags & CLIENT_CLOSE_ASAP) continue;
-            if (replica->repl_curr_idx == -1) continue;
-
-            std::unique_lock<fastlock> ul(replica->lock, std::defer_lock);
-            if (FCorrectThread(replica))
-                ul.lock();
-            else
-                fAsyncWrite = true;
-
-            if (g_pserver->master_repl_offset - replica->repl_curr_off > g_pserver->repl_backlog_size){
-                serverLog(LL_WARNING, "THE REPLICATION BACKLOG SIZE IS TOO SMALL, THIS IS A PROBLEM");
-                long long oldsize = g_pserver->repl_backlog_size;
-                resizeReplicationBacklogForClients(std::max(g_pserver->repl_backlog_size * 2, g_pserver->master_repl_offset - replica->repl_curr_off));
-                serverLog(LL_WARNING, "changing size from %lld to %lld", oldsize, g_pserver->repl_backlog_size);
-            }
-
-        }
-
-        listRewind(g_pserver->slaves, &li);
-#endif
-
         while ((ln = listNext(&li))) {
             client *replica = (client*)listNodeValue(ln);
 
@@ -4721,10 +4660,6 @@ void flushReplBacklogToClients()
                 setReplIdx(replica, g_pserver->repl_batch_idxStart, g_pserver->repl_batch_offStart);
                 continue;
             }
-#else
-            if (replica->replstate == SLAVE_STATE_ONLINE){
-                // serverLog(LL_NOTICE, "would be calling this garbage function w/ offset: %lld", g_pserver->repl_batch_idxStart);
-            }
 #endif
             if (g_pserver->repl_backlog_idx >= g_pserver->repl_batch_idxStart) {
                 long long cbCopy = g_pserver->repl_backlog_idx - g_pserver->repl_batch_idxStart;