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https://issues.apache.org/jira/browse/TINKERPOP-2019?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17043525#comment-17043525
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Florian Hockmann commented on TINKERPOP-2019:
---------------------------------------------
{quote}Looks like receive error .NET Core bug. I have validated that it is kind
of impossible in Gremlin Driver.
{quote}
That's what I'm also wondering about here. Our code should make it impossible
for two read or two write operations to occur on the same connection at the
same time. It also looks like we can't really make any progress on this without
more information about the underlying {{System.Net.WebSockets}} implementation.
I think we should create an issue in the GitHub .NET repo for this. If you want
to do that as you already investigated that, then feel free to go ahead,
[~dzmitry.lahoda]. Otherwise, I will do it when I find some time to write it
together.
> Gremlin.Net.Driver.WebSocketConnection throws System.InvalidOperationException
> ------------------------------------------------------------------------------
>
> Key: TINKERPOP-2019
> URL: https://issues.apache.org/jira/browse/TINKERPOP-2019
> Project: TinkerPop
> Issue Type: Bug
> Components: dotnet
> Affects Versions: 3.3.3
> Environment: Azure App Service
> Reporter: Sami
> Priority: Critical
> Attachments: image-2020-02-21-05-32-58-730.png,
> image-2020-02-21-05-33-27-246.png, invalid.txt
>
>
> We're getting the following {{System.InvalidOperationException}} error
> message:
> {code:c#}
> "There is already one outstanding 'SendAsync' call for this WebSocket
> instance. ReceiveAsync and SendAsync can be called simultaneously, but at
> most one outstanding operation for each of them is allowed at the same time.
> Problem Id:
> System.InvalidOperationException at
> Gremlin.Net.Driver.WebSocketConnection+<SendMessageAsync>d__5.MoveNext"{code}
>
> We get this exception sporadically and only a few times out of thousands.
> Unfortunately we have not been able to reproduce it.
>
> I understand that when dealing with web sockets, it is allowed to have only
> a single pending "send" or a single pending "receive".
>
> After looking at GitHub's WebSocketConnection class, I don't see any
> orchestration between SendMessageAsync's {{_client.SendAsync}} (currently
> line 54) and ReceiveMessageAsync's {{_client.ReceiveAsync}} (currently line
> 66).
>
> Reference Link:
>
> [https://github.com/apache/tinkerpop/blob/master/gremlin-dotnet/src/Gremlin.Net/Driver/WebSocketConnection.cs]
>
> I'm wondering if not having orchestration in the WebSocketConnection class
> to keep the single pending "send" or a single pending "receive" rule may be
> the cause.
>
> In our .NET Core web api application, we create the GremlinConnection as a
> singleton in Startup.cs and then have one central call that makes Gremlin
> calls; i.e. it's a very straightforward implementation.
>
> Startup.cs:
> {code:c#}
> public void ConfigureServices(IServiceCollection services)
> {
> //...other stuff removed for brevity
> services.AddSingleton<IGremlinConnection, GremlinConnection>();
> }{code}
>
> Reader.cs:
> {code:c#}
> public async Task<IReadOnlyCollection<dynamic>> ExecuteGremlinQuery(string
> query)
> {
> try
> {
> return await _gremlinConnection.Client.SubmitAsync<dynamic>(query);
> }
> catch (Gremlin.Net.Driver.Exceptions.ResponseException responseException)
> {
> //our error handling removed for brevity!
> }
> }{code}
>
> We use the Gremlin.Net version 3.3.3 nuget package and the
> Microsoft.NETCore.App SDK
>
> Would it be possible to identify if this is indeed a bug on Gremlin.NET?
> And if it is, any thoughts on a best-practice (temporary) work-around that
> we can implement?
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