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  1. Cassandra
  2. CASSANDRA-14957

Rolling Restart Of Nodes Causes Dataloss Due To Schema Collision


    • Type: Bug
    • Status: Resolved
    • Priority: Normal
    • Resolution: Duplicate
    • Fix Version/s: 4.0
    • Component/s: Cluster/Schema
    • Labels:
    • Severity:


      We were issuing a rolling restart on a mission-critical five node C* cluster.
      The first node which was restarted got the following messages in its system.log:

      January 2nd 2019, 12:06:37.310 - INFO 12:06:35 Initializing tasks_scheduler_external.tasks
      WARN 12:06:39 UnknownColumnFamilyException reading from socket; closing
      org.apache.cassandra.db.UnknownColumnFamilyException: Couldn't find table for cfId bd7200a0-1567-11e8-8974-855d74ee356f. If a table was just created, this is likely due to the schema not being fully propagated. Please wait for schema agreement on table creation.
      at org.apache.cassandra.config.CFMetaData$Serializer.deserialize(CFMetaData.java:1336) ~[apache-cassandra-3.0.10.jar:3.0.10]
      at org.apache.cassandra.db.partitions.PartitionUpdate$PartitionUpdateSerializer.deserialize30(PartitionUpdate.java:660) ~[apache-cassandra-3.0.10.jar:3.0.10]
      at org.apache.cassandra.db.partitions.PartitionUpdate$PartitionUpdateSerializer.deserialize(PartitionUpdate.java:635) ~[apache-cassandra-3.0.10.jar:3.0.10]
      at org.apache.cassandra.db.Mutation$MutationSerializer.deserialize(Mutation.java:330) ~[apache-cassandra-3.0.10.jar:3.0.10]
      at org.apache.cassandra.db.Mutation$MutationSerializer.deserialize(Mutation.java:349) ~[apache-cassandra-3.0.10.jar:3.0.10]
      at org.apache.cassandra.db.Mutation$MutationSerializer.deserialize(Mutation.java:286) ~[apache-cassandra-3.0.10.jar:3.0.10]
      at org.apache.cassandra.net.MessageIn.read(MessageIn.java:98) ~[apache-cassandra-3.0.10.jar:3.0.10]
      at org.apache.cassandra.net.IncomingTcpConnection.receiveMessage(IncomingTcpConnection.java:201) ~[apache-cassandra-3.0.10.jar:3.0.10]
      at org.apache.cassandra.net.IncomingTcpConnection.receiveMessages(IncomingTcpConnection.java:178) ~[apache-cassandra-3.0.10.jar:3.0.10]
      at org.apache.cassandra.net.IncomingTcpConnection.run(IncomingTcpConnection.java:92) ~[apache-cassandra-3.0.10.jar:3.0.10]


      The latter was then repeated several times across the cluster.
      It was then found out that the table in question `tasks_scheduler_external.tasks` was created with a new schema version sometime along the entire cluster consecutive restart and became available once the schema agreement settled, which started taking requests leaving the previous version of the schema unavailable for any request, thus generating a data loss to our online system.

      Data loss was recovered by manually copying SSTables from the previous version directory of the schema to the new one followed by `nodetool refresh` to the relevant table.

      The above has repeated itself for several tables across various keyspaces.

      One other thing to mention is that a repair was in place for the first node to be restarted, which was obviously stopped as the daemon was shut down, but this doesn't seem to do with the above at first glance.

      Seems somewhat related to:


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              • Assignee:
                via.vokal Avraham Kalvo
                Vincent White
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                • Created: