[TINKERPOP-2268] Prevent Connection Failure from Hanging

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Incomplete
• Component/s: dotnet
• Environment: .Net Core
• Flags: Patch
• Assignee: Unassigned
• Reporter: MichaelZ
• Created: 23/Jul/19 11:51
• Updated: 14/Dec/20 09:18
• Resolved: 11/Nov/20 15:26

Description

When a consumer of the Gremlin.Net client calls to execute a Gremlin query, i.e. "SubmitAsync," and there is no valid connection, there will be a costly timeout error. I have experienced 30 to 90 second timeouts.

I was on vacation, so I didn't do this earlier, but I have written a little patch that will refresh the connection pool when there is no valid connection, and it works flawlessly.  This is quick code, and there is a more elegant solution, but what I did is to check IsOpen on the first connection snapshot, and create a new pool if it was stale.  Here is is the code on the GremlinClient object:

private ConnectionPool _connectionPool; //{color:#ff0000}used to be readonly{color}

// member variables
 private readonly GremlinServer _gremlinServer = null;
 private readonly GraphSONReader _graphSONReader = null;
 private readonly GraphSONWriter _graphSONWriter = null;
 private readonly string _mimeType = null;

private readonly ConnectionPoolSettings _connectionPoolSettings = null;

private readonly Action<ClientWebSocketOptions> _webSocketConfiguration = null;
 //

public GremlinClient(GremlinServer gremlinServer, GraphSONReader graphSONReader = null,
 GraphSONWriter graphSONWriter = null, string mimeType = null,
 ConnectionPoolSettings connectionPoolSettings = null,
 Action<ClientWebSocketOptions> webSocketConfiguration = null)
 {
 //
 _gremlinServer = gremlinServer;
 _graphSONReader = graphSONReader;
 _graphSONWriter = graphSONWriter;
 _mimeType = mimeType;
 _connectionPoolSettings = connectionPoolSettings;
 _webSocketConfiguration = webSocketConfiguration;
 //
 {color:#ff0000}NewConnectionPool(){color};
 }

private void NewConnectionPool()

{

var reader = _graphSONReader ?? new GraphSON3Reader();

var writer = _graphSONWriter ?? new GraphSON3Writer();

var connectionFactory = new ConnectionFactory(_gremlinServer, reader, writer, _mimeType ?? DefaultMimeType, _webSocketConfiguration);

_connectionPool = new ConnectionPool(connectionFactory, _connectionPoolSettings ?? new ConnectionPoolSettings());

}

/// <summary>
 /// Provides whether the first available connection snapshot in pool is still open.
 /// </summary>
 {color:#ff0000}private{color} bool HasOpenConnection => (bool)_connectionPool?.FirstConnectionSnapshot?.IsOpen;

/// <inheritdoc />
 public async Task<ResultSet<T>> SubmitAsync<T>(RequestMessage requestMessage)
 {
 if (!HasOpenConnection)
 {
 Debug.WriteLine("=====================================");
 Debug.WriteLine("new connection pool");

{color:#ff0000}NewConnectionPool(){color};
 }

using (var connection = await _connectionPool.GetAvailableConnectionAsync().ConfigureAwait(false))

{ return await connection.SubmitAsync<T>(requestMessage).ConfigureAwait(false); }

}