From ef0b15e0e641098ce59c1a15042894fd55c63f8a Mon Sep 17 00:00:00 2001
From: Mark Paluch <mpaluch@paluch.biz>
Date: Sat, 24 Nov 2018 13:59:56 +0100
Subject: [PATCH] Use Cluster write connections for read commands when using
 ReadFrom.MASTER #923

Lettuce now reuses master connections when ReadFrom is configured to MASTER (which is the default configuration). By reusing the master connection, we can reduce the number of used connections by up to 50% as we don't need an additional read connection while talking to the same node.
---
 .../cluster/PooledClusterConnectionProvider.java  |  3 ++-
 .../PooledClusterConnectionProviderUnitTests.java | 15 +++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/main/java/io/lettuce/core/cluster/PooledClusterConnectionProvider.java b/src/main/java/io/lettuce/core/cluster/PooledClusterConnectionProvider.java
index 96356f4643..96299c24ca 100644
--- a/src/main/java/io/lettuce/core/cluster/PooledClusterConnectionProvider.java
+++ b/src/main/java/io/lettuce/core/cluster/PooledClusterConnectionProvider.java
@@ -104,9 +104,10 @@ public CompletableFuture<StatefulRedisConnection<K, V>> getConnectionAsync(Inten
             logger.debug("getConnection(" + intent + ", " + slot + ")");
         }
 
-        if (intent == Intent.READ && readFrom != null) {
+        if (intent == Intent.READ && readFrom != null && readFrom != ReadFrom.MASTER) {
             return getReadConnection(slot);
         }
+
         return getWriteConnection(slot).toCompletableFuture();
     }
 
diff --git a/src/test/java/io/lettuce/core/cluster/PooledClusterConnectionProviderUnitTests.java b/src/test/java/io/lettuce/core/cluster/PooledClusterConnectionProviderUnitTests.java
index d3167bd331..0ed404f104 100644
--- a/src/test/java/io/lettuce/core/cluster/PooledClusterConnectionProviderUnitTests.java
+++ b/src/test/java/io/lettuce/core/cluster/PooledClusterConnectionProviderUnitTests.java
@@ -125,6 +125,21 @@ void shouldObtainConnection() {
         verifyNoMoreInteractions(connection);
     }
 
+    @Test
+    void shouldReuseMasterConnectionForReadFromMaster() {
+
+        when(clientMock.connectToNodeAsync(eq(CODEC), eq("localhost:1"), any(), any())).thenReturn(
+                ConnectionFuture.from(socketAddressMock, CompletableFuture.completedFuture(nodeConnectionMock)));
+
+        sut.setReadFrom(ReadFrom.MASTER);
+
+        StatefulRedisConnection<String, String> connection = sut.getConnection(Intent.READ, 1);
+
+        assertThat(connection).isSameAs(nodeConnectionMock);
+        verify(connection).setAutoFlushCommands(true);
+        verifyNoMoreInteractions(connection);
+    }
+
     @Test
     void shouldObtainConnectionReadFromSlave() {