Hi,
We are trying to use ES as a system of record, so I trying to understand
its consistency and durability related guarantees and knobs.
For this scenario assume I will have a 2 copies ( 1 replica). From what I
have read and gleaned (
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/docs-index_.html#index-consistency)
=>
- write.consistency is a check to see if the operation can be executed.
It offers no guarantees in terms of data durability or operation guarantee - replication type => Is this for durability guarantees?
- sync all copies of the data are saved/indexed on nodes before it
returns. - async primary node will be synchronous the others will be async.
- sync all copies of the data are saved/indexed on nodes before it
Failure scenario question
Scenario is
=> PUT with write.consistency=quorum, but different replications =
sync/async.
=> What happens if there is a network glitch after the quorum check
succeeds, such that one of the non-primary shard machines is not reachable
or down?
- Put with write.consistency=quorum and replication=sync =>
- Would the operation fail from the callers perspective? Seems like
it would after some retries? - I have read that if the primary succeeds, and if it has problems
with replica then it will try to create a new shard, is that correct
understanding? I assume that should be preventable to handle network
failures/partitions?
- Would the operation fail from the callers perspective? Seems like
- Put with write.consistency=quorum and replication=async =>
- The operation succeeds, since primary shard is up.
- Now in sometime the unreachable node is back, how does it get that
copy of data that it did not get, is there some steps/process
that will do
that automatically?
If these have been asked/answered or documents, please point me to a source
and my apologies.
Thanks
Anand
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