From 967f2c0d7f56702059f433c248c1d2640dc26fde Mon Sep 17 00:00:00 2001
From: David Steele <david@pgmasters.net>
Date: Wed, 1 Apr 2020 16:56:15 -0400
Subject: [PATCH] Enable TCP_NODELAY.

PostgreSQL enables this option when available which seems like a good idea since we also buffer transmissions.

Note that as in PostgreSQL there is no way to disable this option.
---
 src/common/io/socket/common.c      |  9 +++++++++
 test/src/module/common/ioTlsTest.c | 10 +++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/common/io/socket/common.c b/src/common/io/socket/common.c
index 47579db07..ee563adf6 100644
--- a/src/common/io/socket/common.c
+++ b/src/common/io/socket/common.c
@@ -63,6 +63,15 @@ sckOptionSet(int fd)
 
     ASSERT(socketLocal.init);
 
+    // Disable the Nagle algorithm. This means that segments are always sent as soon as possible, even if there is only a small
+    // amount of data. Our internal buffering minimizes the benefit of this optimization so lower latency is preferred.
+#ifdef TCP_NODELAY
+    int socketValue = 1;
+
+    THROW_ON_SYS_ERROR(
+        setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &socketValue, sizeof(int)) == -1, ProtocolError, "unable set TCP_NODELAY");
+#endif
+
     // Enable TCP keepalives
     if (socketLocal.keepAlive)
     {
diff --git a/test/src/module/common/ioTlsTest.c b/test/src/module/common/ioTlsTest.c
index 8aa501b08..534bfc2ae 100644
--- a/test/src/module/common/ioTlsTest.c
+++ b/test/src/module/common/ioTlsTest.c
@@ -125,12 +125,20 @@ testRun(void)
             THROW_ON_SYS_ERROR(fd == -1, HostConnectError, "unable to create socket");
 
             // ---------------------------------------------------------------------------------------------------------------------
-            TEST_TITLE("enable keep-alive and options");
+            TEST_TITLE("enable options");
 
             sckInit(true, 32, 3113, 818);
             sckOptionSet(fd);
 
             socklen_t socketValueSize = sizeof(int);
+            int noDelayValue = 0;
+
+            THROW_ON_SYS_ERROR(
+                getsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &noDelayValue, &socketValueSize) == -1, ProtocolError,
+                "unable get TCP_NO_DELAY");
+
+            TEST_RESULT_INT(noDelayValue, 1, "check TCP_NODELAY");
+
             int keepAliveValue = 0;
 
             THROW_ON_SYS_ERROR(