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https://issues.apache.org/jira/browse/TINKERPOP3-814?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14717138#comment-14717138
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stephen mallette commented on TINKERPOP3-814:
---------------------------------------------
Thanks for reporting this. Is there an "easy" way to get the driver into this
state? You mentioned the "gryo" serialization failure...anything I can
easily/readily reproduce?
> ConnectionPool can fill with dead Connections
> ---------------------------------------------
>
> Key: TINKERPOP3-814
> URL: https://issues.apache.org/jira/browse/TINKERPOP3-814
> Project: TinkerPop 3
> Issue Type: Bug
> Components: driver
> Affects Versions: 3.0.0-incubating
> Environment: "Cluster" of a single gremlin-server/Titan node. Single
> client. minConnectionPoolSize = 2; maxConnectionPoolSize = 10.
> Reporter: Kieran Sherlock
> Assignee: stephen mallette
>
> Client gets a GryoMessageSerializerV1d0 decoding error on a couple of
> requests (different unfiled issue). ConnectionPool gets into the situation
> where there are 2 dead connections being maintained in the pool, but no new
> connections are being issued.
> A sample of the log output...
> {noformat}
> 2015-08-27 09:57:18,122 [Grizzly-worker(15)] DEBUG
> org.apache.tinkerpop.gremlin.driver.ConnectionPool - Borrowing connection
> from pool on Host{address=localhost/127.0.0.1:18182,
> hostUri=ws://localhost:18182/gremlin} - timeout in 3000 MILLISECONDS
> 2015-08-27 09:57:18,122 [Grizzly-worker(15)] DEBUG
> org.apache.tinkerpop.gremlin.driver.ConnectionPool - Return least used
> Connection{host=Host{address=localhost/127.0.0.1:18182,
> hostUri=ws://localhost:18182/gremlin}, isDead=false, borrowed=1, pending=0}
> on Host{address=localhost/127.0.0.1:18182,
> hostUri=ws://localhost:18182/gremlin}
> 2015-08-27 09:57:18,122 [Grizzly-worker(15)] DEBUG
> org.apache.tinkerpop.gremlin.driver.Client - Submitted RequestMessage{,
> requestId=0349c1ce-19dc-4d54-9ca9-30965c9314ae, op='eval', processor='',
> args={<redacted>}} to -
> Connection{host=Host{address=localhost/127.0.0.1:18182,
> hostUri=ws://localhost:18182/gremlin}}
> 2015-08-27 09:57:18,125 [gremlin-driver-worker-6] DEBUG
> org.apache.tinkerpop.gremlin.driver.ConnectionPool - Attempting to return
> Connection{host=Host{address=localhost/127.0.0.1:18182,
> hostUri=ws://localhost:18182/gremlin}} on
> Host{address=localhost/127.0.0.1:18182, hostUri=ws://localhost:18182/gremlin}
> 2015-08-27 09:57:18,126 [gremlin-driver-worker-6] DEBUG
> org.apache.tinkerpop.gremlin.driver.ConnectionPool - On
> Host{address=localhost/127.0.0.1:18182, hostUri=ws://localhost:18182/gremlin}
> pool size of 3 > minPoolSize 2 and borrowed of 0 <=
> minSimultaneousUsagePerConnection 8 so destroy
> Connection{host=Host{address=localhost/127.0.0.1:18182,
> hostUri=ws://localhost:18182/gremlin}, isDead=false, borrowed=0, pending=0}
> 2015-08-27 09:57:18,126 [gremlin-driver-worker-6] DEBUG
> org.apache.tinkerpop.gremlin.driver.ConnectionPool -
> Connection{host=Host{address=localhost/127.0.0.1:18182,
> hostUri=ws://localhost:18182/gremlin}, isDead=false, borrowed=0, pending=0}
> destroyed
> 2015-08-27 09:57:18,126 [Grizzly-worker(15)] DEBUG
> org.apache.tinkerpop.gremlin.driver.ConnectionPool - Borrowing connection
> from pool on Host{address=localhost/127.0.0.1:18182,
> hostUri=ws://localhost:18182/gremlin} - timeout in 3000 MILLISECONDS
> 2015-08-27 09:57:18,126 [Grizzly-worker(15)] DEBUG
> org.apache.tinkerpop.gremlin.driver.ConnectionPool - Pool was initialized
> but a connection could not be selected earlier - waiting for connection on
> Host{address=localhost/127.0.0.1:18182, hostUri=ws://localhost:18182/gremlin}
> 2015-08-27 09:57:18,126 [Grizzly-worker(15)] DEBUG
> org.apache.tinkerpop.gremlin.driver.ConnectionPool - Wait 3000 MILLISECONDS
> for an available connection on Host{address=localhost/127.0.0.1:18182,
> hostUri=ws://localhost:18182/gremlin} with Thread[Grizzly-worker(15),5,main]
> 2015-08-27 09:57:21,127 [Grizzly-worker(15)] DEBUG
> org.apache.tinkerpop.gremlin.driver.ConnectionPool - Continue to wait for
> connection on -1 if {} > 0
> 2015-08-27 09:57:21,127 [Grizzly-worker(15)] DEBUG
> org.apache.tinkerpop.gremlin.driver.ConnectionPool - Timed-out waiting for
> connection on Host{address=localhost/127.0.0.1:18182,
> hostUri=ws://localhost:18182/gremlin} - possibly unavailable
> 2015-08-27 09:57:21,127 [gremlin-driver-worker-3] DEBUG
> org.apache.tinkerpop.gremlin.driver.Host - Trying to reconnect to dead host
> at Host{address=localhost/127.0.0.1:18182,
> hostUri=ws://localhost:18182/gremlin}
> 2015-08-27 09:57:21,128 [Grizzly-worker(15)] DEBUG
> org.apache.tinkerpop.gremlin.driver.Client - Submitted RequestMessage{,
> requestId=67761973-7ae7-4a6a-8e62-443fdb55142d, op='eval', processor='',
> args=<redacted>} to - connection not initialized
> 2015-08-27 09:57:21,128 [gremlin-driver-worker-3] DEBUG
> org.apache.tinkerpop.gremlin.driver.ConnectionPool - Trying to re-establish
> connection on Host{address=localhost/127.0.0.1:18182,
> hostUri=ws://localhost:18182/gremlin}
> 2015-08-27 09:57:21,128 [Grizzly-worker(15)] ERROR
> EdnaMetaDataServiceGremlinImpl - Failed man lookupMerchantAccountName
> java.lang.RuntimeException: java.lang.RuntimeException:
> java.util.concurrent.TimeoutException
> {noformat}
> This behavior continues with each subsequent request. The gremlin-server is
> available at all times.
> As a workaround I have applied the following patch, but I am pretty sure it
> is not the correct solution
> {noformat}
> diff --git
> a/gremlin-driver/src/main/java/org/apache/tinkerpop/gremlin/driver/ConnectionPool.java
>
> b/gremlin-driver/src/main/java/org/apache/tinkerpop/gremlin/driver/ConnectionPool.java
> index 30cd71f..cb8ebfa 100644
> ---
> a/gremlin-driver/src/main/java/org/apache/tinkerpop/gremlin/driver/ConnectionPool.java
> +++
> b/gremlin-driver/src/main/java/org/apache/tinkerpop/gremlin/driver/ConnectionPool.java
> @@ -352,7 +352,7 @@ final class ConnectionPool {
> }
> remaining = to - TimeUtil.timeSince(start, unit);
> - logger.debug("Continue to wait for connection on {} if {} > 0",
> remaining);
> + logger.debug("Continue to wait for connection on {} if {} > 0",
> host, remaining);
> } while (remaining > 0);
> logger.debug("Timed-out waiting for connection on {} - possibly
> unavailable", host);
> @@ -371,13 +371,16 @@ final class ConnectionPool {
> // let the load-balancer know that the host is acting poorly
> this.cluster.loadBalancingStrategy().onUnavailable(host);
> -
> }
> private boolean tryReconnect(final Host h) {
> logger.debug("Trying to re-establish connection on {}", host);
> try {
> + // remove dead connections
> + for (Connection c : connections)
> + if (c.isDead())
> + definitelyDestroyConnection(c);
> connections.add(new Connection(host.getHostUri(), this, cluster,
> settings().maxInProcessPerConnection));
> this.open.set(connections.size());
> {noformat}
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