This workload needs more threads refers to the kernel threads dedicated to MemSQL, specifically the value of max_connection_threads. If you see this error frequently, you may need to increase the value of max_connection_threads.
Elements refers to the the number of queued queries (queries which are waiting for execution threads).
Pops refers to the cumulative number of queries that have been scheduled. The significance of the pops value is that if it stays at the same value it means the scheduler isn't making progress because queries currently executing in the system are still running.
The root cause of this warning depends on where you are seeing the message:
- If you are seeing this warning message in the logs of aggregator nodes the source of this warning message is long-running, concurrent queries.
- If you are seeing this warning message in the logs of leaf nodes the source of this warning message is a query involving a distributed join.
Note: It is possible for a BACKUP to indirectly cause this warning. If a BACKUP is executed when there are long-running queries executing in the cluster the BACKUP will have to wait for the long-running queries to complete. During this time new queries entering the cluster will also have to wait for the long-running query to finish. If you are seeing this error in close proximity to BACKUPS in the Master Aggregator tracelog check to make sure BACKUPS are not being executed when long-running queries are present in the cluster.