Thanks for clarification and I think I did make it clear.
At 2013-04-16 01:59:59,"Shawn Heisey" <s...@elyograg.org> wrote: >On 4/15/2013 9:58 AM, SuoNayi wrote: >> 1. What's the model between the master and replicas in one shard? >> If the replicas are able to catch up with the master when the master >> receives a update request it will scatter the request to all the active >> replicas and expect responses before the request get executed >> by itself.This is called push model,right? >> When a new replica is present it will download the whole index from >> the master can this be called pull model?but when the master pushes >> updates to it how the replica behaves,continuing to download the whole >> index while keeping a track of the updates in a log(tlog) ? > >There is no master. SolrCloud is fully distributed. One replica on >each shard is elected leader, but that is not a permanent designation. > >> 2.What's the main use of the transaction log? >> Is it only used to serve the NRT get requests and not related with data sync >> between the master and replica? > >The transaction log is used to replay transactions when a node starts >up. If the differences between the leader replica and a replica that >just started are small enough, the transaction log will be used to bring >them back into sync. If they are too different, the one that just >started will replicate the full index from the leader. I am pretty sure >that the _version_ field present on every document is used to determine >whether replicas are in sync, not the index version. > >> 3.Will the leader election be related with index version? >> If a shard has 3 replicas and when the master goes down how to choose the >> master, >> do they compare the lastest index version for each one or only consider the >> earliest presence time? > >Here is my understanding about leader elections, I hope it's right! >Leader elections only take place when the leader goes down. Once a >replica is elected leader, it will remain leader unless it goes down. >The other replicas can go up and down and the leader will retain that >role. I do not think the index version is used at all, the _version_ >field in the index is probably used instead. > >Thanks, >Shawn >
