What's not clear is how does elasticsearch identify what pieces of data is missing between the primary and the replica?
On Wed, Apr 30, 2014 at 3:27 AM, Radu Gheorghe <[email protected]>wrote: > Hi Mohit, > > I'll answer inline. > > On Mon, Apr 28, 2014 at 4:57 PM, Mohit Anchlia <[email protected]>wrote: >> >>> Trying to understand the following scenarios of consistency in >>> elasticsearch: >>> >>> 1) sync replication - How does elasticsearch deals with consistency >>> issue that may arise from 1 node momentarily going down and missing writes >>> to it? >>> >> > This depends on the write consistency setting. By default, the operation > only succeeds if a quorum of replicas can index the document: > > http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/docs-index_.html#index-consistency > > >> When the node comes backup and the reads going to the non-primary shards >>> could get inconsistent data? >>> >> > No, when the node comes back up it will sync the stuff it missed with the > other nodes. > > >> 2) async replication - What happens if replication is slow for some >>> reason, could users see inconsistent data? >>> >> > Yes, if you hit a shard that didn't get the latest operation, it could see > an "old" version of the data. You can use "preference" to try and hit the > primary shard all the time, but then your replicas will just be sitting > there for redundancy: > > http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-request-preference.html > > >> 3) sync/async replication - how does elasticsearch keep data in sync for >>> those writes that never happened on the non-primary shard because of >>> network/node failures? >>> >> > It either uses the transaction log or it transfers the whole shard to that > node. > > Best regards, > Radu > -- > Performance Monitoring * Log Analytics * Search Analytics > Solr & Elasticsearch Support * http://sematext.com/ > > -- > 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/CAHXA0_3aJ4qZt47uyjqs0gd6L1Fz0EhLrV_L7jzSFAYOEvz1Nw%40mail.gmail.com<https://groups.google.com/d/msgid/elasticsearch/CAHXA0_3aJ4qZt47uyjqs0gd6L1Fz0EhLrV_L7jzSFAYOEvz1Nw%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/CAOT3TWpdBxiXZgDw5HXdeRPr5oJtnwHTwHNFr2_UoJYobPqzxw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
