Telemetry.Metrics
Defines data model and specifications for aggregating Telemetry events.
Telemetry.Metrics provides functions for building metric specifications - structs describing how values of particular events should be aggregated. Metric specifications can be provided to a reporter which knows how to translate the events into a metric in the system it reports to. This is the crucial part of this library design - it doesn't aggregate events itself in any way, it relies on 3rd party reporters to perform this work in a way that makes the most sense for a metrics system at hand.
To give a more concrete example, let's say that you want to count the number of database queries your application makes, and you want a separate counter for each query type and table. In this case, you would construct the following metric specification:
Telemetry.Metrics.counter(
"db.query",
name: "db.query.count",
tags: [:table, :query_type]
)This specification means that:
- metric should count the number of times a
[:db, :query]event has been emitted, regardless of event value - the name of the metric is
[:db, :query, :count] - the count should be broken down by each unique
:table/:query_typepair found in event metadata
Now when we provide such specification to the reporter and emit following events
:telemetry.execute([:db, :query], 32, %{table: "users", query_type: "select"})
:telemetry.execute([:db, :query], 67, %{table: "users", query_type: "insert"})
:telemetry.execute([:db, :query], 18, %{table: "users", query_type: "select"})
:telemetry.execute([:db, :query], 15, %{table: "users", query_type: "select"})we expect to find the following aggregations in the metric system we report to
| table | query_type | count |
|---|---|---|
users | select | 1 |
users | create | 1 |
products | select | 2 |
The way in which reporters aggregate or export this data is not in the scope of this project. Rather, a goal is to define a standardized set of aggregations that will be supported by reporters.
See the documentation for Telemetry.Metrics module for more details.
Copyright and License
Telemetry.Metrics is copyright (c) 2018 Chris McCord and Erlang Solutions.
Telemetry.Metrics source code is released under Apache License, Version 2.0.