We have good timing metrics for many of the primary actions in the event loop:
I've noticed a few things while analyzing job performance at LinkedIn:
1. We can usually identify problems in Choose using the sub metrics for Deserialization and Poll. I don't think any work needs to be done here.
2. Slowness in Process or Window is usually caused by business logic (e.g. side calls to remote DBs), but it can also be caused by slowness (e.g. "stalls" in the case of RocksDB) in the KV Store.
3. Slowness in Commit can be caused by slowness flushing the stores or producers. It can also come from checkpointing.
#2 would be better if we had timers around all the main KV Store operations, including get, put, delete, and the batch operations. Then we can isolate KV Store performance from business logic performance.
#3 would be improved if we had timers around all the flushes. Specifically, I think we should add a "flush-ns" metric to the KeyValueStoreMetrics and update it from each of the stores. I noticed that KafkaSystemProducerMetrics has a "flush-ns" metric, so the kafka producer is covered.
To summarize, this ticket is to add metrics around all KV Store operations, not just for user operations like get/put, but flush as well.
Related work: SAMZA-449