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From "Florian Hockmann (Jira)" <j...@apache.org>
Subject [jira] [Commented] (TINKERPOP-2288) Get ConnectionPoolBusyException and then ServerUnavailableExceptions
Date Wed, 04 Mar 2020 16:22:00 GMT

    [ https://issues.apache.org/jira/browse/TINKERPOP-2288?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17051377#comment-17051377

Florian Hockmann commented on TINKERPOP-2288:

{quote} Is it possible for a connection to close while there are still requests in flight?

Sure, that can happen if either the user disposes the client completely although requests
are still in flight for example because the application gets shut down or because the connection
gets terminated, e.g., because it was closed by the server. I however don't think that the
conclusions you draw out of that are correct.

{{BeginReceiving}} is only called once during the initialization of a new connection that
is happening when {{ConnectAsync}} is called. The {{_connectionState}} is only set to {{Closed}}
when the {{Connection}} is closed completely which only happens when the whole client gets
disposed or if there is a connection problem. If that happens before {{BeginReceiving}} finishes
its execution, then there won't be any open requests on that {{Connection}} as the {{Connection}}
won't be used before {{ConnectAsync}} finishes which calls {{BeginReceiving}}.

> Get ConnectionPoolBusyException and then ServerUnavailableExceptions
> --------------------------------------------------------------------
>                 Key: TINKERPOP-2288
>                 URL: https://issues.apache.org/jira/browse/TINKERPOP-2288
>             Project: TinkerPop
>          Issue Type: Bug
>          Components: dotnet
>    Affects Versions: 3.4.1
>         Environment: Gremlin.Net 3.4.1
> Microsoft.NetCore.App 2.2
> Azure Cosmos DB
>            Reporter: patrice huot
>            Priority: Critical
> I am using .Net core Gremlin API  query Cosmos DB.
> From time to time we are getting an error saying that no connection is available and
then the server become unavailable. When this is occurring we need to restart the server.
It looks like the connections are not released properly and become unavailable forever.
> We have configured the pool size to 50 and the MaxInProcessPerConnection to 32 (Which
I guess should be sufficient).
> To diagnose the issue, Is there a way to access diagnostic information on the connection
pool in order to know how many connections are open and how many processes are running in
each connection?
> I would like to be able to monitor the connections usage to see if they are about to
be exhausted and to see if the number of used connections is always increasing or of the connection
lease is release when the queries completes?
> As a work around, Is there a way we can access this information from the code so that
I can catch those scenario and create logic that re-initiate the connection pool?

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