[TINKERPOP-2531] Gremlin .NET driver ConnectionPool can remain without connections if server is down for 1-2 minutes

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.4.10
• Fix Version/s: 3.5.0, 3.4.11
• Assignee: Unassigned
• Reporter: Radu Iviniciu
• Created: 09/Mar/21 15:16
• Updated: 24/Mar/21 08:15
• Resolved: 24/Mar/21 08:15

Description

We are using Gremlin .NET client to connect to AWS Neptune.
If the server is down for even just 1 - 2 minutes (E,.g. Instance reboot) the connection pool can remain without any healthy connections permanently even after the server comes back up again.
Tracked this down to here:

https://github.com/apache/tinkerpop/blob/60bfc90ce43567d609b1165989c1c74ce825109b/gremlin-dotnet/src/Gremlin.Net/Driver/ConnectionPool.cs#L154

If the server was not ready yet and the connections were not restored as part of the previous TryGetAvailableConnection then the connection pool will remain empty indefinitely and all connections are dead even after the server is back up.

Is this longer-ish downtime a use case the client should handle ? Or is it expected behavior and we should let the caller handle the ServerUnavailableException, potentially recreate the GremClient altogether ?

What do you guys think ? If this is something the client should handle I can take a stab at it and put up a PR.
Thank you.