zmq: enable tcp keepalive

mruddy · mruddy · commit c276df775914 · 2018-11-15T08:16:25.000-05:00
diff --git a/doc/zmq.md b/doc/zmq.md
@@ -98,6 +98,20 @@ ZMQ_SUBSCRIBE option set to one or either of these prefixes (for
 instance, just `hash`); without doing so will result in no messages
 arriving. Please see `contrib/zmq/zmq_sub.py` for a working example.
 
+The ZMQ_PUB socket's ZMQ_TCP_KEEPALIVE option is enabled. This means that
+the underlying SO_KEEPALIVE option is enabled when using a TCP transport.
+The effective TCP keepalive values are managed through the underlying
+operating system configuration and must be configured prior to connection establishment.
+
+For example, when running on GNU/Linux, one might use the following
+to lower the keepalive setting to 10 minutes:
+
+sudo sysctl -w net.ipv4.tcp_keepalive_time=600
+
+Setting the keepalive values appropriately for your operating environment may
+improve connectivity in situations where long-lived connections are silently
+dropped by network middle boxes.
+
 ## Remarks
 
 From the perspective of bitcoind, the ZeroMQ socket is write-only; PUB
diff --git a/src/zmq/zmqpublishnotifier.cpp b/src/zmq/zmqpublishnotifier.cpp
@@ -86,6 +86,14 @@ bool CZMQAbstractPublishNotifier::Initialize(void *pcontext)
             return false;
         }
 
+        const int so_keepalive_option {1};
+        rc = zmq_setsockopt(psocket, ZMQ_TCP_KEEPALIVE, &so_keepalive_option, sizeof(so_keepalive_option));
+        if (rc != 0) {
+            zmqError("Failed to set SO_KEEPALIVE");
+            zmq_close(psocket);
+            return false;
+        }
+
         rc = zmq_bind(psocket, address.c_str());
         if (rc != 0)
         {

Original file line number	Diff line number	Diff line change
`@@ -86,6 +86,14 @@ bool CZMQAbstractPublishNotifier::Initialize(void *pcontext)`
`86`	`86`	`return false;`
`87`	`87`	`}`
`88`	`88`
	`89`	`+ const int so_keepalive_option {1};`
	`90`	`+ rc = zmq_setsockopt(psocket, ZMQ_TCP_KEEPALIVE, &so_keepalive_option, sizeof(so_keepalive_option));`
	`91`	`+ if (rc != 0) {`
	`92`	`+ zmqError("Failed to set SO_KEEPALIVE");`
	`93`	`+ zmq_close(psocket);`
	`94`	`+ return false;`
	`95`	`+ }`
	`96`	`+`
`89`	`97`	`rc = zmq_bind(psocket, address.c_str());`
`90`	`98`	`if (rc != 0)`
`91`	`99`	`{`