lucene-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Shalin Shekhar Mangar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-9835) Create another replication mode for SolrCloud
Date Mon, 27 Feb 2017 11:06:45 GMT

    [ https://issues.apache.org/jira/browse/SOLR-9835?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15885586#comment-15885586
] 

Shalin Shekhar Mangar commented on SOLR-9835:
---------------------------------------------

# Dat, can you please add javadocs for all the new methods in UpdateLog?
# I was looking into SOLR-9706 and it applies to this patch too. However, the fix is easy
because most of the corruption checks added by SOLR-6640 aren't necessary in this new replication
mode so we can safely skip them.

> Create another replication mode for SolrCloud
> ---------------------------------------------
>
>                 Key: SOLR-9835
>                 URL: https://issues.apache.org/jira/browse/SOLR-9835
>             Project: Solr
>          Issue Type: Bug
>      Security Level: Public(Default Security Level. Issues are Public) 
>            Reporter: Cao Manh Dat
>            Assignee: Shalin Shekhar Mangar
>         Attachments: SOLR-9835.patch, SOLR-9835.patch, SOLR-9835.patch, SOLR-9835.patch,
SOLR-9835.patch, SOLR-9835.patch, SOLR-9835.patch, SOLR-9835.patch, SOLR-9835.patch, SOLR-9835.patch,
SOLR-9835.patch, SOLR-9835.patch
>
>
> The current replication mechanism of SolrCloud is called state machine, which replicas
start in same initial state and for each input, the input is distributed across replicas so
all replicas will end up with same next state. 
> But this type of replication have some drawbacks
> - The commit (which costly) have to run on all replicas
> - Slow recovery, because if replica miss more than N updates on its down time, the replica
have to download entire index from its leader.
> So we create create another replication mode for SolrCloud called state transfer, which
acts like master/slave replication. In basically
> - Leader distribute the update to other replicas, but the leader only apply the update
to IW, other replicas just store the update to UpdateLog (act like replication).
> - Replicas frequently polling the latest segments from leader.
> Pros:
> - Lightweight for indexing, because only leader are running the commit, updates.
> - Very fast recovery, replicas just have to download the missing segments.
> On CAP point of view, this ticket will trying to promise to end users a distributed systems
:
> - Partition tolerance
> - Weak Consistency for normal query : clusters can serve stale data. This happen when
leader finish a commit and slave is fetching for latest segment. This period can at most {{pollInterval
+ time to fetch latest segment}}.
> - Consistency for RTG : if we *do not use DQBs*, replicas will consistence with master
just like original SolrCloud mode
> - Weak Availability : just like original SolrCloud mode. If a leader down, client must
wait until new leader being elected.
> To use this new replication mode, a new collection must be created with an additional
parameter {{liveReplicas=1}}
> {code}
> http://localhost:8983/solr/admin/collections?action=CREATE&name=newCollection&numShards=2&replicationFactor=1&liveReplicas=1
> {code}



--
This message was sent by Atlassian JIRA
(v6.3.15#6346)

---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: dev-help@lucene.apache.org


Mime
View raw message