TimeoutExceptions from mongo c# driver with Async API

Question

We are using the latest beta driver from MongoDB (2.0.0-beta2) with all the async capabilities. But compared to the old implementation (1.10.0-rc0) we are getting some weird TimeoutExceptions. We have tried different server versions (among others, also 3.0.0-rc10), but that doesnot seem to influence this.

System.TimeoutException occurred
  HResult=-2146233083
  Message=Operation timed out after 00:00:30.
  Source=MongoDB.Driver
  StackTrace:
       at MongoDB.Driver.OperationExecutor.<ExecuteReadOperationAsync>d__0`1.MoveNext()
    --- End of stack trace from previous location where exception was thrown ---
       at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
       at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
       at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()
       at MongoDB.Driver.MongoCollectionImpl`1.<ExecuteReadOperation>d__5e`1.MoveNext()

We have a hard time reproducing this, firing a couple of thousands inserts, updates and finds does not trigger this bug. However, running our .NET web application does trigger this (after creating a couple of new entities).

The Exception location differs but one of the places is in our FindAll method. Our code does:

IMongoCollection<BsonDocument> col = _database.GetCollection<BsonDocument>(GetCollectionName(qmoType));
IFindFluent<BsonDocument, BsonDocument> findFluent = col.Find(MongoDBWhereBuilder.BuildWhere(where));

findFluent = findFluent.Sort(SortBy.Ascending(sort.Keys.ToArray());
findFluent = findFluent.Skip(skip);
findFluent = findFluent.Limit(take);

List<BsonDocument> list = await findFluent.ToListAsync();

The _database variable is shared between all requests (it is created once at startup).

How can we get a better grip on this problem? Or are there others that have this issue?

I've filed a ticket here: jira.mongodb.org/browse/CSHARP-1184. Probabably a better place to work through a bug than on StackOverflow. As mentioned in the ticket, you can increase the operation timeout value in MongoClientSettings. In addition, this setting didn't exist in the 1.x driver, so it could be that you are just seeing it now. Regardless, something taking longer than 30 seconds is extremely problematic. Thank you so much for testing. — Craig Wilson
– Craig Wilson, Commented Feb 25, 2015 at 17:33
@CraigWilson Thanks. I'm not sure if it is a bug or an error on our side. But I follow the ticket and add additional comments there. — Michiel Overeem
– Michiel Overeem, Commented Feb 26, 2015 at 7:07

Michiel Overeem · Accepted Answer · 2015-03-06 08:24:17Z

1

This is a bug in the beta2 driver. The fix is merged into master (and part of beta3): https://jira.mongodb.org/browse/CSHARP-1184

answered Mar 6, 2015 at 8:24

Michiel Overeem

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Carlos Torrecillas · Accepted Answer · 2015-11-18 11:45:36Z

0

I think that might still be present in versions 2.0.1/2.1.0. We had to downgrade to 1.10.0 which was the previous version we had and that made the number of connections going back to under 100 and the response times to less that 100ms (from 500-600 sometimes).

Maybe there is something in the legacy wrapper around the async code that is causing that delay.

answered Nov 18, 2015 at 11:45

Carlos Torrecillas

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2 Comments

Michiel Overeem Over a year ago

Did you file this bug with the mongodb team? We aren't seeing any regressions.

Carlos Torrecillas Over a year ago

I haven't raise that with them yet but I will do it

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