Issue in Sharded cluster with replica set while data insertion

[dk9389]

We have deployed a replicated sharded cluster with 3 shards, each shard is a 3 member replica set(Primary,Secondary and Arbiter).

Also we are running 3 mongos and 3 config server instances. 

We are importing data in this cluster form SQL server using .net utility. While data insertion is in process and a step down of primary of replicaset of shard 1 happens and new primary is elected,then the insertion stops. Ideally it should not stop as shard 1 is a replica set and it is up and running,just a new primary is elected.

Can someone help me find out the reason for this.

Thnx

[darshana kedare]

Hi Folks,

I got the issue, actually .net application is using MongoDB driver which by default uses Acknowledge as a write concern. So when the primary steps down MongoDB driver is not getting the write response from that primary and hence this error occurs.

Is there any way to change the default write concerns in MongoDB driver, or just skip the error "write results unavailable"

PFA Screenshot of the error.

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Regards

Darshana Kedare

+91-9021330747

[Stephen Steneker]

On Thursday, 24 September 2015 00:39:15 UTC+10, dk9389 wrote:

I got the issue, actually .net application is using MongoDB driver which by default uses Acknowledge as a write concern. So when the primary steps down MongoDB driver is not getting the write response from that primary and hence this error occurs.

Is there any way to change the default write concerns in MongoDB driver, or just skip the error "write results unavailable"

Hi Darshana,

If there is no primary available to accept writes, it is expected that your application will get write exceptions until a new primary is elected. In this case your application can choose to retry the write (perhaps with a backoff strategy) or ignore the exception with Unacknowledged writes (if it is acceptable to potentially not write data for your use case).

The C# driver has a WriteConcern class:
 http://api.mongodb.org/csharp/2.0/html/T_MongoDB_Driver_WriteConcern.htm

.. which maps to the standard MongoDB write concerns:

 http://docs.mongodb.org/manual/core/write-concern/

As you have noted, the default write concern is to request acknowledgement by the mongod that receives the write.

Regards,

Stephen