55 lines
2.8 KiB
Go
55 lines
2.8 KiB
Go
// Copyright 2015 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package metric
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// Collector is the interface implemented by anything that can be used by
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// Prometheus to collect metrics. A Collector has to be registered for
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// collection.
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//
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// The stock metrics provided in their respective packages (like Gauge, Counter,
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// Summary, Histogram) are also Collectors (which only ever collect one metric,
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// namely itself). An implementer of Collector may, however, collect multiple
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// metrics in a coordinated fashion and/or create metrics on the fly. Examples
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// for collectors already implemented in this library are the metric vectors
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// (i.e. collection of multiple instances of the same Metric but with different
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// label values) like gauge.Vec or summary.Vec, and the ExpvarCollector.
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//
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// Two Collectors are considered equal if their Describe methods yield the same
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// set of descriptors.
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type Collector interface {
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// Describe sends all descriptors required to describe the metrics
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// collected by this Collector to the provided channel and returns once
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// the last descriptor has been sent. The sent descriptors fulfill the
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// consistency and uniqueness requirements described in the Desc
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// documentation. This method idempotently sends the same descriptors
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// throughout the lifetime of the Collector. If a Collector encounters
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// an error while executing this method, it must send an invalid
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// descriptor (created with NewInvalidDesc) to signal the error to the
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// registry.
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Describe(chan<- Desc)
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// Collect is called by Prometheus when collecting metrics. The
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// implementation sends each collected metric via the provided channel
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// and returns once the last metric has been sent. Each sent metric must
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// be consistent with one of the descriptors returned by
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// Describe. Returned metrics that are described by the same descriptor
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// must differ in their variable label values. This method may be called
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// concurrently and must therefore be implemented in a concurrency safe
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// way. Blocking occurs at the expense of total performance of rendering
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// all registered metrics. Ideally, Collector implementations support
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// concurrent readers. If a Collector finds itself unable to collect a
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// metric, it can signal the error to the registry by sending a Metric
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// that will return the error in its Write method..
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Collect(chan<- Metric)
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}
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