[jira] [Assigned] (TINKERPOP-2135) Gremlin.Net ConnectionPool doesn't handle closed idle connections properly

["Florian Hockmann (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TINKERPOP-2135?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Florian Hockmann reassigned TINKERPOP-2135:
-------------------------------------------

    Assignee: Florian Hockmann

> Gremlin.Net ConnectionPool doesn't handle closed idle connections properly
> --------------------------------------------------------------------------
>
>                 Key: TINKERPOP-2135
>                 URL: https://issues.apache.org/jira/browse/TINKERPOP-2135
>             Project: TinkerPop
>          Issue Type: Bug
>          Components: dotnet
>    Affects Versions: 3.4.0
>            Reporter: Florian Hockmann
>            Assignee: Florian Hockmann
>            Priority: Major
>
> The {{ConnectionPool}} of Gremlin.Net checks whether a connection is actually still open before it returns that connection to execute a request ([in {{SelectLeastUsedConnection}}|https://github.com/apache/tinkerpop/blob/67764ba23d67d9f62048c22e8bbcefb87463584e/gremlin-dotnet/src/Gremlin.Net/Driver/ConnectionPool.cs#L124]):
> {code:java}
> if (connection.IsOpen) return true;
> DefinitelyDestroyConnection(connection);
> {code}
> However, the connection stays in the pool as {{DefinitelyDestroyConnection}} only disposes the connection:
> {code:java}
> private void DefinitelyDestroyConnection(Connection connection)
> {
>     connection.Dispose();
>     Interlocked.Decrement(ref _nrConnections);
> }
> {code}
> This is problematic as it can potentially fill the pool with unusable connections. Even worse, {{SelectLeastUsedConnection}} will likely return such an unusable connection since it only checks for the number of in-flight requests and a disposed connection won't have any in-flight requests. This means that {{GetConnectionFromPool}} will try to get a connection until another still valid connection also has no in-flight requests.
> Note: This all can only happen when a connection was closed while sitting idle in the pool which shouldn't usually happen due to the heartbeat. If a connection problem occurs during the execution of a request, then all connections will be closed and new ones will be created.



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