Hey there, thanks for reaching out. I could use some help from someone with more Prometheus experience. I hope you don't mind I've included the Heka list since I think we might find some good help there too.
I'll start by explaining what caused me to set out on this plugin. I want Prometheus to be able to scrape a growing list of prescribed Influxdb queries. The original thought was to code up a simple proxy that could translate a Prometheus scrape request into an Influxdb query. I quickly realized how capturing all the query types ahead of time would be hard and that I'd probably have to recompile often. Since data massaging is all I need, I realized I wanted a scripting engine that could run inside the proxy. I've only dabbled in cgo and don't have time to dive in deeper to learn how to build a Lua sandbox in a go program, but Heka's got this fully baked and I've hacked on Heka enough to be productive more quickly. With Heka, it's easy to compose an input spec for an output plugin which can then drive that output plugin's logic. The best way to massage messages in Heka are in sandbox decoders or, if any aggregation is needed, in filters. The phase doesn't matter to the output plugin so long as the Heka message includes the necessary field to drive the output plugin properly. For us at imgix, this means we can route a lot of data to Prometheus, not just Influxdb queries. We aggregate many log types into counters and histograms in Heka currently. With a small amount of additional Lua and a sensible input message spec, these metrics can now be made available to Prometheus. I set out to provide both Counters and Gauges originally, but found that only Gauges made sense to me--at least for now. Both Influxdb and Heka filters are better suited to perform aggregations than a Heka output plugin--we only need Prometheus to see the snaphot. A Heka filter or an Influxdb query can emit the values we want Prometheus to see at any given time interval (often 15s I think?) Sending raw values to an output plugin to perform increments or histogram calculations in Heka is sort of an anti-pattern IMO. I'm not opposed to including support for Counters if I'm wrong about this; but I did cut them for the time being while I wrap my head around the Prometheus client library and various object's thread safety. One of the goals I've formulated is to not require the known set of metric_names (tag=value) sets upon initialization, but to dynamically add new metrics as Heka routes messages into the output plugin. The current state of my repo doesn't achieve this. Does Describe only get called once on the prometheus client? Is there a way to trigger Describe to get called periodically or on demand? If not, I'll probably find a StoppableListener implementation, instantiate a new prometheus client, and create a new http server as new metrics are discovered. Think there's a better way? On Tue, Jun 2, 2015 at 10:29 AM, Johannes Ziemke <johannes.zie...@docker.com > wrote: > Hi, > > just read your code and it seems like it supports only gauges. Do you plan > to add support for counters as well? I'm actually most interested about > counters since the most common thing I'll need to do is count various kind > of log lines. > And how do you plan to get data for your gauges? Do you have some custom > input provinding messages with full labels and everything or do you do some > mapping in between? > > On Tue, Jun 2, 2015 at 5:45 PM, Johannes Ziemke < > johannes.zie...@docker.com> wrote: > >> Hi David, >> >> I just saw that you're working on a prometheus plugin for heka as well. >> Here is my first take: https://github.com/docker-infra/heka-prometheus >> >> Maybe we should join efforts and work on this together or at least chat >> about it. Looks like it's not trivial to get this right and I have not much >> experience with heka but lots with prometheus, so might be helpful :) >> >> I saw you in #heka and I'm there as well (nick: fish). Or come by at >> #prometheus on freenode. >> > >
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