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https://issues.apache.org/jira/browse/TINKERPOP-2019?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17036355#comment-17036355
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Dzmitry L commented on TINKERPOP-2019:
--------------------------------------

Yes, I'm using CosmosDb. Reproduction steps are not clear. The bug appeared 
twice on simple query like `g.V('123-123-123')`.

> 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
>
> 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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