Close Connection on SessionClient - AWS Neptune - gremlin

Question

I use aws-neptune.
And I try to implement my queries as transactional(with sessionClient like: https://docs.aws.amazon.com/neptune/latest/userguide/access-graph-gremlin-sessions.html). But when I try to implement it, closing client throws exception. There is similar issue like my case: https://groups.google.com/g/janusgraph-users/c/N1TPbUU7Szw
My code looks like:
#Bean
public Cluster gremlinCluster()
{
return Cluster.build()
.addContactPoint(GREMLIN_ENDPOINT)
.port(GREMLIN_PORT)
.enableSsl(GREMLIN_SSL_ENABLED)
.keyCertChainFile("classpath:SFSRootCAG2.pem")
.create();
}
private void runInTransaction()
{
String sessionId = UUID.randomUUID().toString();
Client.SessionedClient client = cluster.connect(sessionId);
try
{
client.submit("query...");
}
finally
{
if (client != null)
{
client.close();
}
}
}
And exception is:
INFO (ConnectionPool.java:225) - Signalled closing of connection pool on Host{address=...} with core size of 1
WARN (Connection.java:322) - Timeout while trying to close connection on ... - force closing - server will close session on shutdown or expiration.
java.util.concurrent.TimeoutException
at java.util.concurrent.CompletableFuture.timedGet(CompletableFuture.java:1771)
Is there any suggestion?

Answer 1

This might be a connectivity problem with the server which you are not able to observe while sending the query because you are not waiting for the future to complete.
When you do a client.submit("query...");, you receive a future. You need to wait for that future to complete to observe any exceptions (or success).
I would suggest the following:
Try hitting the server with a health status call using curl to verify connectivity with the server.
Replace the client.submit("query..."); with client.submit("query...").all().join(); to get the error during connection with the server.