Hi Anand, I would love to know as well, and asked in this thread today: "quorum write + sync replication: guarantees".
It is pretty important information given ElasticSearch is being touted as a reliable data store... which the presence of a "write consistency level" setting would tempt one to believe, but there doesn't seem to be evidence to support the guarantees that implies. Cheers, Shikhar On Sat, Apr 5, 2014 at 12:06 AM, Anand Somani <[email protected]> wrote: > 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. > > 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? > > > 1. Put with write.consistency=quorum and replication=sync => > 1. Would the operation fail from the callers perspective? Seems > like it would after some retries? > 2. 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? > 2. Put with write.consistency=quorum and replication=async => > 1. The operation succeeds, since primary shard is up. > 2. 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 > > -- > You received this message because you are subscribed to the Google Groups > "elasticsearch" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/elasticsearch/CANN9sNpFY39T2t2uy51Zh0m1p%3DBpqtqb7f9ho1iWTV%3DeUab23Q%40mail.gmail.com > <https://groups.google.com/d/msgid/elasticsearch/CANN9sNpFY39T2t2uy51Zh0m1p%3DBpqtqb7f9ho1iWTV%3DeUab23Q%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/elasticsearch/CAHWG4DPhhY20_PPDOC%2BDTCsDv%2BddhkNDd-Q5pejeAS-SK3qREg%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
