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https://issues.apache.org/jira/browse/CASSANDRA-12683?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16143219#comment-16143219
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Jeff Jirsa commented on CASSANDRA-12683:
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Hi Andy,
What's the replication strategy configured on your keyspace?
> Batch statement fails with consistency ONE when only 1 node up in DC
> --------------------------------------------------------------------
>
> Key: CASSANDRA-12683
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12683
> Project: Cassandra
> Issue Type: Bug
> Components: Coordination
> Environment: 3 Cassandra nodes (N1, N2, N3)
> 2 Data Centers (DC1, DC2)
> N1 and N2 members of DC1
> N3 a member of DC2
> 1 keyspace using SimpleReplicationStrategy with RF=3 (can also be 2):
> CREATE KEYSPACE ks WITH
> REPLICATION={'class':'SimpleStrategy','replication_factor':3};
> 1 column family in the keyspace. For simplicity, a partition key of bigint
> and one other field of any type. No cluster key needed:
> CREATE TABLE ks.test (
> id bigint,
> flag boolean,
> PRIMARY KEY(id)
> );
> Reporter: Andy Klages
> Priority: Minor
>
> If Cassandra node N2 is stopped, that only leaves one node (N1) in DC1
> running. Output from "nodetool status" is:
> Datacenter: DC1
> =========================
> Status=Up/Down
> |/ State=Normal/Leaving/Joining/Moving
> -- Address Load Tokens Owns Host ID
> Rack
> DN N2 ...
> UN N1 ...
> Datacenter: DC2
> ======================
> Status=Up/Down
> |/ State=Normal/Leaving/Joining/Moving
> -- Address Load Tokens Owns Host ID
> Rack
> UN N3 ...
> The following batch statement will fail when executed on N1 with consistency
> level of ONE using cqlsh (also fails with Java using Datastax driver):
> CONSISTENCY ONE
> BEGIN BATCH
> UPDATE ks.test SET flag=true where id=1;
> UPDATE ks.test SET flag=true where id=2;
> APPLY BATCH;
> The failure is:
> File
> "apache-cassandra-2.1.15/bin/../lib/cassandra-driver-internal-only-2.7.2.zip/cassandra-driver-2.7.2/cassandra/cluster.py",
> line 3347, in result
> raise self._final_exception
> Unavailable: code=1000 [Unavailable exception] message="Cannot achieve
> consistency level ONE" info={'required_replicas': 1, 'alive_replicas': 0,
> 'consistency': 'ONE'}
> There are 2 replicas alive but for some reason, Cassandra thinks there are
> none.
> If each statement is executed individually (i.e. no batch), each one succeeds.
> This same batch query succeeds on N3, which is the other node in the cluster
> that is running. My analysis shows this happens when the query is executed on
> a node in a DC where all other nodes in that DC is down. The batch statement
> has 2 or more queries with different partition keys. If all of the partition
> keys are the same value, it succeeds. As the replication factor is set to the
> number of nodes in the cluster (full replication) and the consistency level
> is ONE, the batch statement should succeed.
> 2 workarounds for this are:
> 1. Set the consistency level to ANY.
> 2. Use an unlogged batch.
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