After running tpstats on all nodes. I see a lot of nodes having high number of ALL TIME BLOCKED NTR. We have a 4 node cluster and the values for NTR ALL TIME BLOCKED are :
NODE 1: 23953 NODE 2: 2935 NODE 3: 15229 NODE 4: 5951
I know ALL TIME BLOCKED is bad and hence worried as to what I am doing wrong.
This pool handles cql requests, so it is the number of active CQL requests allowed. Its limited to prevent too many active ones from OOMing your system (ie each returning large blobs). This effectively applies backpressure to your client application to slow down. Unfortunately if you have small requests this isnt ideal and hurts your throughput so in CASSANDRA-11363 they added a setting to make the space tradeoff for small bursty workloads.
If you upgrade to 2.2.8+ you can set the max queue size of that threadpool with -Dcassandra.max_queued_native_transport_requests=4096
来源：https://stackoverflow.com/questions/41376735/high-native-transport-requests-all-time-blocked