67 lines
2.7 KiB
Markdown
67 lines
2.7 KiB
Markdown
# Overview
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This [Go](http://golang.org) package is an extraction of a piece of
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instrumentation code I whipped-up for a personal project that a friend of mine
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and I are working on. We were in need for some rudimentary statistics to
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observe behaviors of the server's various components, so this was written.
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The code here is not a verbatim copy thereof but rather a thoughtful
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re-implementation should other folks need to consume and analyze such telemetry.
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N.B. --- I have spent a bit of time working through the model in my head and
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probably haven't elucidated my ideas as clearly as I need to. If you examine
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src/main.go and src/export/registry.go, you'll find an example of what type of
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potential instrumentation use cases this package addresses. There are probably
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numerous Go language idiomatic changes that need to be made, but this task has
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been deferred for now.
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# Continuous Integration
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[](http://travis-ci.org/matttproud/golang_instrumentation)
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# Metrics
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A metric is a measurement mechanism.
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## Gauge
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A Gauge is a metric that exposes merely an instantaneous value or some snapshot
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thereof.
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## Histogram
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A Histogram is a metric that captures events or samples into buckets. It
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exposes its values via percentile estimations.
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### Buckets
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A Bucket is a generic container that collects samples and their values. It
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prescribes no behavior on its own aside from merely accepting a value,
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leaving it up to the concrete implementation to what to do with the injected
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values.
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#### Accumulating Bucket
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An Accumulating Bucket is a bucket that appends the new sample to a timestamped
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priority queue such that the eldest values are evicted according to a given
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policy.
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#### Eviction Policies
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Once an Accumulating Bucket reaches capacity, its eviction policy is invoked.
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This reaps the oldest N objects subject to certain behavior.
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##### Remove Oldest
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This merely removes the oldest N items without performing some aggregation
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replacement operation on them.
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##### Aggregate Oldest
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This removes the oldest N items while performing some summary aggregation
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operation thereupon, which is then appended to the list in the former values'
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place.
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#### Tallying Bucket
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A Tallying Bucket differs from an Accumulating Bucket in that it never stores
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any of the values emitted into it but rather exposes a simplied summary
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representation thereof. For instance, if a values therein is requested,
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it may situationally emit a minimum, maximum, an average, or any other
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reduction mechanism requested.
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# Testing
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This package employs [gocheck](http://labix.org/gocheck) for testing. Please
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ensure that all tests pass by running the following from the project root:
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$ go test ./...
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