JAVA-2057: Do not create pool when SUGGEST_UP topology event received (apache#1149)

tolbertam · web-flow · commit 6794c38674aa · 2018-12-13T13:47:25.000-06:00
Motivation:

There is a small window where a NEW_NODE event may be sent over the
control connection while a pool is initializing. This is more likely to
happen in testing, where a cluster is brought up and the driver connects
to it immediately.

In this case, the driver would erroneously create another pool, which
would create additional connections. The first pool created between
the currently initializing one and the new one being created would be
untracked with its connections remanining open even after the Session is
closed.

Modifications:

Change onTopologyEvent to no longer call createOrReconnectPool, instead
only call reconnectNow() if there is an already established pool.
initializing pool future present in the pending map.

Result:

SUGGEST_UP events now only trigger reconnect on existing pool, and will
no longer create a new pool.
diff --git a/changelog/README.md b/changelog/README.md
@@ -4,6 +4,7 @@
 
 ### 4.0.0-beta3 (in progress)
 
+- [bug] JAVA-2057: Do not create pool when SUGGEST\_UP topology event received
 - [improvement] JAVA-2049: Add shorthand method to SessionBuilder to specify local DC
 - [bug] JAVA-2037: Fix NPE when preparing statement with no bound variables
 - [improvement] JAVA-2014: Schedule timeouts on a separate Timer
diff --git a/core/src/main/java/com/datastax/oss/driver/internal/core/session/PoolManager.java b/core/src/main/java/com/datastax/oss/driver/internal/core/session/PoolManager.java
@@ -340,7 +340,10 @@ private void onTopologyEvent(TopologyEvent event) {
         if (node.getDistance() != NodeDistance.IGNORED) {
           LOG.debug(
               "[{}] Received a SUGGEST_UP event for {}, reconnecting pool now", logPrefix, node);
-          createOrReconnectPool(node);
+          ChannelPool pool = pools.get(node);
+          if (pool != null) {
+            pool.reconnectNow();
+          }
         }
       }
     }

Original file line number	Diff line number	Diff line change
`@@ -340,7 +340,10 @@ private void onTopologyEvent(TopologyEvent event) {`
`340`	`340`	`if (node.getDistance() != NodeDistance.IGNORED) {`
`341`	`341`	`LOG.debug(`
`342`	`342`	`"[{}] Received a SUGGEST_UP event for {}, reconnecting pool now", logPrefix, node);`
`343`		`- createOrReconnectPool(node);`
	`343`	`+ ChannelPool pool = pools.get(node);`
	`344`	`+ if (pool != null) {`
	`345`	`+ pool.reconnectNow();`
	`346`	`+ }`
`344`	`347`	`}`
`345`	`348`	`}`
`346`	`349`	`}`