Stream Introspection

The goal is to have an overview of the stream processing at the cluster level in order to:

• quickly understand where there is a bottleneck or problem without having to ssh
• take a decision on how to scale-out, scale-down, tune the existing configuration
• build a dedicated scaling metric that can be used by a horizontal auto scaler (HPA).

Because Nuxeo Stream is used at a low level it will cover all async processing: Async listeners, WorkManager, Bulk Service, and of course Nuxeo Stream (when using Kafka).

We want a representation at the cluster level that includes:

• all streams used with their number of partitions
• all Nuxeo nodes that participate in the async processing, with the number of threads for each computation
• the lag and latency for each consumer group
• computations failures
• eventually for each node: CPU usage, JVM memory pressure

The idea is to report all processor topologies on node start NXP-29934) and create a specific stream metrics reporter (NXP-29933) that informs about activities. A computation will aggregate both streams and build a representation that will be exposed as REST (NXP-29935).