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From "Eduard Ordukhanov (Jira)" <j...@apache.org>
Subject [jira] [Issue Comment Deleted] (TINKERPOP-2288) Get ConnectionPoolBusyException and then ServerUnavailableExceptions
Date Tue, 03 Mar 2020 20:49:00 GMT

     [ https://issues.apache.org/jira/browse/TINKERPOP-2288?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Eduard Ordukhanov updated TINKERPOP-2288:
    Comment: was deleted

(was: Is it possible for a connection to close while there are still requests in flight?
 If thats a possibility then in the following code snippet it seems like "ReceiveMessagesAsync"
is never called, and therefore requests in flight are never decremented. (ReceiveMessagesAsync
has to be called for requests in flight to be removed, but the code execution will return
one line before hitting that function call)
private void BeginReceiving()
  var state = Volatile.Read(ref _connectionState);
  if (state == Closed) return;
If this can happen then it seems like in the following code snippet, the line

"if (connection.NrRequestsInFlight >= _maxInProcessPerConnection) continue;"

will always get executed, and the program will never reach the next line to remove the connection
from the pool in the following code block from the "TryGetAvailableConnection" function.


if (!connection.IsOpen)

I'm probably missing something, so I hope someone else can confirm whether or not this can


> 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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