client_golang/metrics/timer.go

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// Copyright (c) 2012, Matt T. Proud
// All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
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package metrics
import (
"time"
)
// This callback is called upon the completion of the timer—i.e., when it stops.
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type CompletionCallback func(duration time.Duration)
// This is meant to capture a function that a StopWatch can call for purposes
// of instrumentation.
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type InstrumentableCall func()
// StopWatch is the structure that captures instrumentation for durations.
// N.B.(mtp): A major limitation hereof is that the StopWatch protocol cannot
// retain instrumentation if a panic percolates within the context that is
// being measured.
type StopWatch interface {
Stop() time.Duration
}
type stopWatch struct {
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endTime time.Time
onCompletion CompletionCallback
startTime time.Time
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}
// Return a new StopWatch that is ready for instrumentation.
func Start(onCompletion CompletionCallback) StopWatch {
return &stopWatch{
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onCompletion: onCompletion,
startTime: time.Now(),
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}
}
// Stop the StopWatch returning the elapsed duration of its lifetime while
// firing an optional CompletionCallback in the background.
func (s *stopWatch) Stop() time.Duration {
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s.endTime = time.Now()
duration := s.endTime.Sub(s.startTime)
if s.onCompletion != nil {
go s.onCompletion(duration)
}
return duration
}
// Provide a quick way of instrumenting a InstrumentableCall and emitting its
// duration.
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func InstrumentCall(instrumentable InstrumentableCall, onCompletion CompletionCallback) time.Duration {
s := Start(onCompletion)
instrumentable()
return s.Stop()
}