Provide APIs to monitor pipeline

[suyograo]

Today, most Logstash monitoring functions are accomplished by tailing logs or outputting debug messages. Users typically send specially tagged tracer events to check the health of the system. These special events are also used to measure the latency of the pipeline. This is definitely not straightforward and it becomes hard to administer a large-scale Logstash cluster.

We plan to introduce a Logstash monitoring API endpoint, which will provide visibility into the pipeline. Some important metrics are:

• health
• number of events processed
• latency metrics (average, percentile, etc)
• size of the persistent queues (Provide option to have variable size internal queues which are persisted #2606)
• number of errors/success

Medium term, we should provide plugin level granularity. For example, it would be great to know how long (on average) an event spends on grok filters, geo ip filters etc. This would help users drill in to the expensive parts of the pipeline.

Care should be taken to make sure metrics collection do not add additional stress on the pipeline and affect the latency and throughput of the events.

[ph]

This is certainly something I would like to improve, I was bite to debug an issue on a cluster and the tools aren't that great. I am pretty sure @abonuccelli-es would give us some awesome input :)

[nellicus]

@suyograo @ph sorry a bit late here
not sure if these were mentioned somewhere else however, couple of ideas:

• have logstash to produce internal events providing metrics (e.g. regularly print every T seconds even if no actual events coming in SLC events sent/received, SLC events filtered,queue sizes etc. also some one off ones e.g Instance started/stopped, queue full, destination down).
• having an array where each logstash instance appends its own ID (if anything like will exist?). imagine one event going through multi-logstash layer, this would help understanding through which logstash instances the event has gone through
• for events coming via tcp/udp add a @source field where we stamp the sourceIP of the sender. a bit like 'path' when we read files

any other info at runtime via API of course great to have

[KlavsKlavsen]

I would definetely prefer to have logstash have the same kind of API that mysql, varnish and many more have.. where you connect to a management port - and get numbers out.
It's pretty cheap for logstash to just keep a memory segment for performance stats and update that, and then i can poll the counters at the interval I want to (every minute f.ex.) and input into my favourite monitoring stack (I use graphite) - to get graphs and to be able to do alerting based on a time-perspective.

An ability to have logstash simply just send performance counters to api's such as graphite etc. - would also be super cool.

[simmel]

To expose those numbers via JMX would be perfect!
Then we could just use jmxtrans-agent to output it to a console, file, graphite or statsd.