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https://github.com/golang/go
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cb106d260e
This allows early exporters to adjust the event for later ones. This is used to lookup key values from the context if needed. Also add a Query type event which is intended to perform all event modifications but nothing else, and is used to lookup values from the context. This cleans up a weirdness where the current lookup presumes there will be an exporter with a matching mechanism. Change-Id: I835d1e0b2511553c30f94b7becfe7b7b5462c111 Reviewed-on: https://go-review.googlesource.com/c/tools/+/223657 Run-TryBot: Ian Cottrell <iancottrell@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
56 lines
1.5 KiB
Go
56 lines
1.5 KiB
Go
// Copyright 2019 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package event
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import (
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"context"
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"sync/atomic"
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"unsafe"
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)
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type Exporter interface {
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// ProcessEvent is a function that handles all events.
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// This is called with all events that should be delivered to the exporter
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// along with the context in which that event ocurred.
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// This method is called synchronously from the event call site, so it should
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// return quickly so as not to hold up user code.
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ProcessEvent(context.Context, Event) (context.Context, Event)
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Metric(context.Context, MetricData)
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}
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var (
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exporter unsafe.Pointer
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)
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func SetExporter(e Exporter) {
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p := unsafe.Pointer(&e)
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if e == nil {
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// &e is always valid, and so p is always valid, but for the early abort
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// of ProcessEvent to be efficient it needs to make the nil check on the
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// pointer without having to dereference it, so we make the nil interface
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// also a nil pointer
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p = nil
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}
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atomic.StorePointer(&exporter, p)
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}
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func ProcessEvent(ctx context.Context, ev Event) (context.Context, Event) {
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exporterPtr := (*Exporter)(atomic.LoadPointer(&exporter))
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if exporterPtr == nil {
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return ctx, ev
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}
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// and now also hand the event of to the current exporter
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return (*exporterPtr).ProcessEvent(ctx, ev)
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}
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func Metric(ctx context.Context, data MetricData) {
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exporterPtr := (*Exporter)(atomic.LoadPointer(&exporter))
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if exporterPtr == nil {
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return
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}
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(*exporterPtr).Metric(ctx, data)
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}
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