I'm moving nodes around on a Cassandra cluster, and seeing Back pressure disabled! in the log. I'm also seeing (around a minute earlier) Back pressure enabled with average index queue size: 1106.

What do these mean? Are they bad?



This is a safety mechanism in DataStax Enterprise Search to avoid overloading the system. When you have very fast producers that push data in for indexing, indexing may get backed up. The system will detect that at flush time and block new requests until the system has caught up.

So basically unless you see problems, this is part of normal operations. It might indicate temporary stress on the system, like when adding or removing nodes (as that will potentially cause reindexing of larger portions of the data), but unless you constantly see this and it won't go away the system will be reaching steady state again.

Hope this helps.


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