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Graphite-ng

Experimental version of a new generation Graphite API server in Golang, leveraging Go's efficient concurrency constructs. Goals are: speed, ease of deployment. elegant code.
Furthermore, this rewrite allows to fundamentally redesign some specific annoyances.

Limitations

  • Not all functions are supported yet
  • No reinventing whisper/ceres at this point. (I want to hook this up to a reliable timeseries store, maybe whisper, ceres, kairosdb, ...). (there's a carbon-es dir which is a carbon-cache that stores metrics in elasticsearch, but I'm still experimenting with it)
  • No wildcards yet

Omissions

  • only the json output, not the png renderer. (because client side rendering is best)
  • No web UI (because there are plenty of graphite dashboards out there)
  • No events system (anthracite is better than the very basic graphite events thing)

How it works

graphite-ng is a webserver that gives you a /render/ http endpoint where you can do queries like /render/sum(stats.web1,scale(stats.web2,5.2))from=123&until=456

graphite-ng converts all user input into a real, functioning Go program, compiles and runs it, and returns the output. It can do this because the graphite api notation can easily be converted to real program code. Great power, great responsability. The worker functions use goroutines and channels to stream data around and avoid blocking.

Installation & running

run this from the code checkout:

rm -f executor-*.go ; go install github.com/graphite-ng/graphite-ng && graphite-ng

then open something like this in your browser:

http://localhost:8080/render/?target=stats.web2&target=derivative(stats.web2)
http://localhost:8080/render/?target=sum(stats.web1,scale(stats.web2,5))&from=60&until=300

Which metrics and functions can I use?

Look at data.go and the functions directory. Since graphite-ng is not hooked up yet to a decent timeseries store, for now we'll have to do with the examples in data.go.

Function plugins

all functions come in plugin files. want to add a new function? just drop a .go file in the functions folder and restart. You can easily add your own functions that get data from external sources, manipulate data, or represent data in a different way; and then call those functions from your target string.

Metric store plugins

  • Graphite-ng can query metrics from different stores.
    At this point only the example text store works. I'm working on the elasticsearch one. A whisper plugin is on the roadmap.
  • Carbon-ng will be able to use plugins to store metrics. For now it can only store in the experimental elasticsearch store.

other interesting things & diff with real graphite:

  • every function can request a different timerange from the functions it depends on. E.g.:
    • derivative needs the datapoint from before the requested timerange
    • movingAverage(foo, X) needs x previous datapoints. Regular graphite doesn't support this so you end up with gaps in the beginning of the graph.
  • clever automatic rollups based on tags (TODO)
  • The pathExpression system in graphite is overly complicated and buggy.
    The keys in Graphite's json output are sometimes not exactly the requested target string (i.e. floats being rounded), it's not so easily fixed in Graphite which means client renderes have to implement ugly hacks to work around this. With graphite-ng we just use the exact same string.
  • avoid any results being dependent on any particular potentially unknown variable, aim for per second instead of per current-interval, etc. specifically:
    • derivative is a true derivative (ie (y2-y1)/(x2-x1)) unlike graphite's derivative where you depend on a factor that depends on whatever the resolution is at each point in time.
  • be mathematically/logically correct by default ("nil+123" should be "nil" not "123", though the functions could get a "sloppyness" argument)