Netty Metrics

[Florin Dragu]

I'm looking to see if there are any netty 4.0.x based metrics extensions/plugins that can capture metrics similar to what Netflix did in rxnetty  or even more basic stuff like metrics integration for tcp/http based on something like codahale metrics?

Thanks,

Florin

[Norman Maurer]

I don’t think anything exists… That said, contributions welcome :)

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Norman Maurer

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[Florin Dragu]

I started looking at what both rxnetty and vert.x are doing for capturing metrics. 

Is there any particular design you had in mind for a pure netty approach?

[Leonardo Gomes]

I could give a hand if you go for it. I would love to have those metrics directly into Netty as well.

Cheers,
Leo

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[Leonardo Gomes]

I had a quick look and it seems that this is an old topic going around since 2012:

https://developer.jboss.org/wiki/Netty4AndJMXIntegration

I've seen also a presentation from Norman mentioning that it would be the subject of a GSOC.

Any news/status?

There's a chance I could even work on it during my working-hours, so I'm really interested.

Peace,

Leo.

[Florin Dragu]

Not much progress yet - I hope to get to it starting on Mon. In the mean time I'll look at the post you sent bellow.

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[Leonardo Gomes]

Found this as well, which is introducing some metrics: https://github.com/netty/netty/pull/2788

[Florin Dragu]

After looking at previous posts/ideas and studying RxNetty and Vert.x I am thinking we could have metrics for the following groups (more or less):

• Server/Client Bootstrap
  
• Event Loop Group - Boss
  
• Event Loop Group - Workers
  
• Channel
  
• Channel Initializer
  
• Channel Pipeline
  
• Channel Inbound Handler
  
• Channel Outbound Handler
  
• TCP
  
• HTTP
  
• UDP
  

To capture the metrics and make them available we could have a MetricsPublisher or Collector that receives metric events (similar to RxNetty metrics) and distribute them to registered metrics listeners. The collector would have some config that allows different levels of instrumentation (low, mid, high).

There can be different metric listener implementation - one could be for codahale metrics, but it should be able to allow other implementations.

 

In terms of integrating into Netty there are 2 options:

1. Create the hooks directly in netty code for metrics collection/instrumentation (no bytecode manipulation) - this allows to collect everything we want, but every time we want to collect another thing it requires a change to netty code base
2. Create a netty extension for metrics collection (special handlers, etc) that collects metrics by using the official hooks and available listeners - this allows to keep the netty code clean, but may not have easy access to all events/metrics

Thoughts?

Florin

[Leonardo Gomes]

@Norman, Trustin: It would be nice to have your opinion here :)

Especially because https://github.com/netty/netty/pull/2788 has not been merged and it provides already some metrics, so I'm wondering that you probably already have an idea of what you'd like to see implemented.

Cheers,

Leo

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[Florin Dragu]

I have something working for what my team built on top on Netty4 to support mainly Restful endpoints - it can't be used in Netty as is, but I'll outline what I did:

I am using Codahale metrics (core, jvm and graphite jars) and a MetricsEvent extensible enum (that currently only has these 3 events REQUEST_RECEIVED, RESPONSE_SENT, RESPONSE_WRITE_FAILED).

I have a MetricsCollector that has this method void onEvent(MetricsEvent event, Object value)

and based on these 3 events and the object (in my case the object is a request state object I created and that I keep on the ChannelHandlerContext as an attribute to hold state all along the channel pipeline) I capture these metrics about the app and about the endpoints exposed: 

 - JVM metrics: gc, buffers, memory, threads 
 - App config properties; 
 - Counter inflightRequests; 
 - Counter processedRequests; 
 - Counter failedRequests; 
 - Counter responseWriteFailed; 
 - Histogram responseSizes; 
 - Histogram requestSizes; 
 - Timer getRequests; 
 - Timer postRequests; 
 - Timer putRequests; 
 - Timer deleteRequests; 
 - Timer otherRequests; 
 - Timer requests; 
 - Meter[] responses; // 1xx, 2xx, 3xx, 4xx, 5xx 
 - Map<String, Timer> restEndpointRequestsTimers; // API endpoints by matching path 
 - Map<String, Meter[]> restEndpointResponsesMeters; // API endpoints by matching path and 1xx, 2xx, 3xx, 4xx, 5xx for each endpoint

Cheers,

Florin