Query regarding Replica set failover and high availability

[Ratish Puduppully]

Hi,

In case of a write-intensive application, I had some concerns regarding the time taken for a failover.

Going through the FAQ below and a similar post before, any writes which happen during the time the failover is in progress will be lost? This will cost writes of 10s to 1min.

Please confirm.

http://docs.mongodb.org/manual/faq/replica-sets/#how-long-does-replica-set-failover-take 

https://groups.google.com/d/msg/mongodb-user/lH3W5FtvMlw/iudHJh-P09EJ

What are the options available in such a scenario. One is to build backup options for the same in the application code.

Regards,

Ratish

[Scott Hernandez]

Yes, you application will need to handle failures during writes (which would imply that you are doing safe writes -- WriteConcern.SAFE -- since you need to check if the write is not successful). If these writes fail because of a replica set fai-over that is just one common way, as well as temporary network issues but they all come down to something went wrong and you have to reconcile possibly incomplete writes.

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[Ratish Puduppully]

Thanks for the reply, Scott.

Yes, I am doing safe write-- WriteConcern.SAFE. 

So, in case of MongoException, I need to catch the server exception and handle it in the application.

Regards,

Ratish

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[Scott Hernandez]

Yes, you need to handle any exception during writes.

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