Error message is the first step to troubleshoot Apache Cassandra issues. That can help us identify if the issue happens on client-side or server-side. Here are the 4 most common Cassandra issues below.
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Check Cassandra SyntaxError (client)
This and other QueryValidationException indicate that the client sent a malformed request. These are rarely server issues and usually indicate bad queries.
Check Cassandra UnavailableException (server) issue
This means that the Cassandra coordinator node has rejected the query as it believes that insufficent replica nodes are available. If many coordinators are throwing this error it likely means that there really are (typically) multiple nodes down in the cluster and you can identify them using nodetool status.
If only a single coordinator is throwing this error it may mean that node has been partitioned from the rest.
Check Cassandra OperationTimedOutException issue
This is the most frequent timeout message raised when clients set timeouts and means that the query took longer than the supplied timeout.
This is a client side timeout meaning that it took longer than the client specified timeout. The error message will include the coordinator node that was last tried which is usually a good starting point.
This error usually indicates either aggressive client timeout values or latent server coordinators/replicas.
Check Cassandra ReadTimeoutException issue
These are raised when clients do not specify lower timeouts and there is a coordinator timeouts based on the values supplied in the cassandra.yaml configuration file. They usually indicate a serious server side problem as the default values are usually multiple seconds.