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Published: Feb 10, 2021 License: BSD-3-Clause Imports: 19 Imported by: 0


Goka web interface

Observing the progress of recovery and execution of a goka processor is often vital for basic debugging purposes or performance analyses.

Goka provides a very simple web interface that allows to show statistics about individual partitions including state, offsets and lag as well as input- and output rate.

For low level inspection of table data, it provides a simple interface to query values from views or processor tables.


First, to get a web interface we need a router. If the program using Goka already uses a router, Goka's web interface can easily be attached to it instead.

So first, initialize the monitoring server using a router with

root := mux.NewRouter()
monitorServer := monitor.NewServer("/monitor", root)

Suppose we have a processor proc, then we can simply attach it to the monitor

proc := goka.NewProcessor(...)

Ok, then let's start the processor and the server with

go proc.Run(context.Background())
http.ListenAndServe(":9095", root)

Opening the browser on localhost:9095/monitor/ will then show us a list of all attached processors and views and by selecting one of them we'll get statistics of the processor, similar like this

Processor View


Ok nice, but if you don't have another router with an index and links to the monitor, it's really annoying to add monitor/ to your browser url every time you want to open the monitor. That's why Goka provides a small convenience index server, that the Monitoring and the Query servers can be attached to.

idxServer := index.NewServer("/", root)
idxServer.AddComponent(monitorServer, "Monitor")

So next time we open the page at localhost:9095, we'll get some nice links to the monitor.



As mentioned earlier, we can also add a query server that allows us to request a value by key from a View or a Processor table, simply by attaching it to a Query server. Also let's add the new server to the index as well to avoid repeated typing of query/ in the url.

queryServer := query.NewServer("/query", root)
idxServer.AddComponent(queryServer, "Query")
queryServer.AttachSource("user-clicks", p.Get)

Opening a query page gives us a page like this:




The example in main.go demonstrates the concepts and typical applications of the web interface by creating an Emitter, multiple Processors and a web interface.

Be sure to have Apache Kafka and Zookeeper running by starting it in the examples-folder.

examples$ make start

Then run the monitoring example with:

examples$ go run 8-monitoring/main.go


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