The project's documentation is not up-to-date due to rapidly-changing requirements that have quieted down in the interim, but the overall API should be stable for several months even if things change under the hood.
An update to reflect the current state is pending. Key changes for current users:
- The code has been qualified in production environments.
- Label-oriented metric exposition and registration, including docstrings.
- Deprecation of gocheck in favor of native table-driven tests.
- The best way to get a handle on this is to look at the examples.
Barring that, the antique documentation is below:
This Go package is an extraction of a piece of instrumentation code I whipped-up for a personal project that a friend of mine and I are working on. We were in need for some rudimentary statistics to observe behaviors of the server's various components, so this was written.
The code here is not a verbatim copy thereof but rather a thoughtful re-implementation should other folks need to consume and analyze such telemetry.
N.B. --- I have spent a bit of time working through the model in my head and probably haven't elucidated my ideas as clearly as I need to. If you examine examples/{simple,uniform_random}/main.go and registry.go, you'll find several examples of what types of potential instrumentation use cases this package addresses. There are probably numerous Go language idiomatic changes that need to be made, but this task has been deferred for now.
Please read the generated documentation for the project's documentation from source code.
A metric is a measurement mechanism.
A Gauge is a metric that exposes merely an instantaneous value or some snapshot thereof.
A Histogram is a metric that captures events or samples into buckets. It exposes its values via percentile estimations.
A Bucket is a generic container that collects samples and their values. It prescribes no behavior on its own aside from merely accepting a value, leaving it up to the concrete implementation to what to do with the injected values.
An Accumulating Bucket is a bucket that appends the new sample to a timestamped priority queue such that the eldest values are evicted according to a given policy.
Once an Accumulating Bucket reaches capacity, its eviction policy is invoked. This reaps the oldest N objects subject to certain behavior.
This merely removes the oldest N items without performing some aggregation replacement operation on them.
This removes the oldest N items while performing some summary aggregation operation thereupon, which is then appended to the list in the former values' place.
A Tallying Bucket differs from an Accumulating Bucket in that it never stores any of the values emitted into it but rather exposes a simplied summary representation thereof. For instance, if a values therein is requested, it may situationally emit a minimum, maximum, an average, or any other reduction mechanism requested.
This package employs gocheck for testing. Please ensure that all tests pass by running the following from the project root:
$ go test ./...