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https://issues.apache.org/jira/browse/CASSANDRA-15860?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17136328#comment-17136328
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Jeremy Hanna commented on CASSANDRA-15860:
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You cannot change the num_tokens on a running cluster, you have to either
# add another logical datacenter with a different num_tokens value (normal add
datacenter procedure, add nodes without replication and then do a nodetool
rebuild on each node after adding replication) or
# create a new cluster with a different num_tokens value and sstable load data
from the original cluster
I would go with option 1 if you can.
The reason why you can't change after data has been written is because data is
already stored on the node for the 512 token ranges it has already claimed.
You can't change that without rewriting the data around the cluster. So it's
simplest to add a new DC where that data can be written again. See this [blog
post|https://thelastpickle.com/blog/2019/02/21/set-up-a-cluster-with-even-token-distribution.html]
for setting up token allocation optimally.
> Cannot change the number of tokens from 512 to 256 Fatal configuration error;
> unable to start server.
> -----------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-15860
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15860
> Project: Cassandra
> Issue Type: Bug
> Reporter: Krishnakumar Jinka
> Priority: Normal
>
> Hello, I was following this issue from jira:
> https://issues.apache.org/jira/browse/CASSANDRA-11811?jql=text%20~%20%22CassandraDaemon.java%20Cannot%20change%22
> . We are using 3.11.2 and i see this error in the log while starting the
> cassandra, and it fails. I read the jira and understood that mutation
> happens, thereby doubling the number of tokens, and hence due to mismatch
> INFO [main] [2020-05-28 11:05:14] OutboundTcpConnection.java:108 -
> OutboundTcpConnection using coalescing strategy DISABLED
> INFO [HANDSHAKE-/192.168.5.53] [2020-05-28 11:05:14]
> OutboundTcpConnection.java:560 - Handshaking version with /192.168.5.53
> INFO [main] [2020-05-28 11:05:15] StorageService.java:707 - Loading persisted
> ring state
> INFO [main] [2020-05-28 11:05:15] StorageService.java:825 - Starting up
> server gossip
> INFO [main] [2020-05-28 11:05:15] TokenMetadata.java:479 - Updating topology
> for /192.168.5.52
> INFO [main] [2020-05-28 11:05:15] TokenMetadata.java:479 - Updating topology
> for /192.168.5.52
> Cannot change the number of tokens from 512 to 256
> Fatal configuration error; unable to start server. See log for stacktrace.
> ERROR [main] [2020-05-28 11:05:15] CassandraDaemon.java:708 - Fatal
> configuration error
> org.apache.cassandra.exceptions.ConfigurationException: Cannot change the
> number of tokens from 512 to 256
> at
> org.apache.cassandra.service.StorageService.joinTokenRing(StorageService.java:989)
> ~[apache-cassandra-3.11.2.jar:3.11.2]
> at
> org.apache.cassandra.service.StorageService.initServer(StorageService.java:682)
> ~[apache-cassandra-3.11.2.jar:3.11.2]
> at
> org.apache.cassandra.service.StorageService.initServer(StorageService.java:613)
> ~[apache-cassandra-3.11.2.jar:3.11.2]
> at
> org.apache.cassandra.service.CassandraDaemon.setup(CassandraDaemon.java:379)
> [apache-cassandra-3.11.2.jar:3.11.2]
> at
> org.apache.cassandra.service.CassandraDaemon.activate(CassandraDaemon.java:602)
> [apache-cassandra-3.11.2.jar:3.11.2]
> at
> org.apache.cassandra.service.CassandraDaemon.main(CassandraDaemon.java:691)
> [apache-cassandra-3.11.2.jar:3.11.2]
> INFO [StorageServiceShutdownHook] [2020-05-28 11:05:15] HintsService.java:220
> - Paused hints dispatch
> INFO [StorageServiceShutdownHook] [2020-05-28 11:05:15] Gossiper.java:1540 -
> Announcing shutdown
> INFO [StorageServiceShutdownHook] [2020-05-28 11:05:15]
> StorageService.java:2292 - Node /192.168.5.52 state jump to shutdown
> INFO [HANDSHAKE-/192.168.5.53] [2020-05-28 11:05:15]
> OutboundTcpConnection.java:560 - Handshaking version with /192.168.5.53
> I would like to know
> # what would be the root cause of this error
> # How to recover from this error. Because everytime i start the Cassandra,
> it is blocked due to this.
> /etc/cassandra/conf/cassandra.yaml
> contains num_tokens as 256 , auto_bootstrap is not provided, i guess by
> default it will be true.
> INFO [main] [2020-05-28 11:05:13] StorageService.java:618 - Cassandra
> version: 3.11.2
> INFO [main] [2020-05-28 11:05:13] StorageService.java:619 - Thrift API
> version: 20.1.0
> INFO [main] [2020-05-28 11:05:13] StorageService.java:620 - CQL supported
> versions: 3.4.4 (default: 3.4.4)
> INFO [main] [2020-05-28 11:05:13] StorageService.java:622 - Native protocol
> supported versions: 3/v3, 4/v4, 5/v5-beta (default: 4/v4)
>
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