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* Update License header for all source files - Add Apache 2.0 header to source files that did not have one. - Update all existing headers dated to 2019 to be 2020 - Remove comma from License header to comply with the Apache 2.0 guidelines. * Update Copyright notice Use the standard Copyright notices outlined by the [CNCF](https://github.com/cncf/foundation/blob/master/copyright-notices.md#copyright-notices)
74 lines
3.5 KiB
Go
74 lines
3.5 KiB
Go
// Copyright The OpenTelemetry Authors
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//
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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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// metric package provides an API for reporting diagnostic
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// measurements using four basic kinds of instruments.
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//
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// The three basic kinds are:
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//
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// - counters
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// - measures
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// - observers
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//
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// All instruments report either float64 or int64 values.
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//
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// The primary object that handles metrics is Meter. Meter can be
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// obtained from Provider. The implementations of the Meter and
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// Provider are provided by SDK. Normally, the Meter is used directly
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// only for the instrument creation, LabelSet generation and batch
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// recording.
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//
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// LabelSet is a set of keys and values that are in a suitable,
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// optimized form to be used by Meter.
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//
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// Counters are instruments that are reporting a quantity or a sum. An
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// example could be bank account balance or bytes downloaded. Counters
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// can be created with either NewFloat64Counter or
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// NewInt64Counter. Counters expect non-negative values by default to
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// be reported. This can be changed with the WithMonotonic option
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// (passing false as a parameter) passed to the Meter.New*Counter
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// function - this allows reporting negative values. To report the new
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// value, use an Add function.
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//
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// Measures are instruments that are reporting values that are
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// recorded separately to figure out some statistical properties from
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// those values (like average). An example could be temperature over
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// time or lines of code in the project over time. Measures can be
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// created with either NewFloat64Measure or NewInt64Measure. Measures
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// by default take only non-negative values. This can be changed with
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// the WithAbsolute option (passing false as a parameter) passed to
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// the New*Measure function - this allows reporting negative values
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// too. To report a new value, use the Record function.
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//
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// Observers are instruments that are reporting a current state of a
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// set of values. An example could be voltage or
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// temperature. Observers can be created with either
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// RegisterFloat64Observer or RegisterInt64Observer. Observers by
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// default have no limitations about reported values - they can be
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// less or greater than the last reported value. This can be changed
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// with the WithMonotonic option passed to the Register*Observer
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// function - this permits the reported values only to go
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// up. Reporting of the new values happens asynchronously, with the
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// use of a callback passed to the Register*Observer function. The
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// callback can report multiple values. There is no unregister function.
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//
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// Counters and measures support creating bound instruments for a
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// potentially more efficient reporting. The bound instruments have
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// the same function names as the instruments (so a Counter bound
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// instrument has Add, and a Measure bound instrument has Record).
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// Bound Instruments can be created with the Bind function of the
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// respective instrument. When done with the bound instrument, call
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// Unbind on it.
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package metric // import "go.opentelemetry.io/otel/api/metric"
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