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checking the replication status of an object
Hi,
We have an application that stores content to a Centera cluster, content coming from another application. We send an ack to the other application for each "object", when the object is stored, that is when we have the clipid.
We would need to wait for the object to be replicated before sending back the ack (the other application needs to be 100% sure that the object is stored at both locations).
If I read correctly the API reference guide, I need to
- open a pool connection to the replica cluster (using appropriate IP addresses and PEA file)
- set FP_OPTION_MULTICLUSTER_EXISTS_STRATEGY to FP_NO_STRATEGY
- perform an FPClip_Exists()
My question is : is it necessary to check the existence of the blobs (FPTag_BlobExists()) associated to the clip or is the ClipExists() check enough ? In other words, are the blobs always replicated before the CDF ?
Each object contains between 2 to a few hundred blobs. Are these requests going to be expensive for the cluster ? (is it OK to check every 10 or 30 seconds or would it be better to wait a few minutes between checks ?)
Regards,
Didier
mckeown_paul
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October 3rd, 2012 04:00
Replication uses the same Centera API to replicate clips so if when the clip_write is done to persist the CDF all the blobs will have been written over. So you only need to perform a clip exists on the replica.
As for the timing, there will be a replication delay of 1 min before a clip is replicated (assuming no network delays as well) so you should wait at least 1 min for the first check then check maybe every 10 secs. If you could log some stats you might be able to see just how often it takes more than 1 min to replicate the clip.