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https://github.com/golang/go
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903869a827
Makes Event implement TagMap directly, instead of having to build an entirely new object. Change-Id: I0c1e8638de3dc3347f60fd93af3df6b7f8387751 Reviewed-on: https://go-review.googlesource.com/c/tools/+/227300 Run-TryBot: Ian Cottrell <iancottrell@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
69 lines
2.2 KiB
Go
69 lines
2.2 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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"time"
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"unsafe"
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)
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// Exporter is a function that handles events.
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// It may return a modified context and event.
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type Exporter func(context.Context, Event, TagMap) context.Context
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var (
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exporter unsafe.Pointer
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)
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// SetExporter sets the global exporter function that handles all events.
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// The exporter 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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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 function
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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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// deliver is called to deliver an event to the supplied exporter.
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// it will fill in the time and generate the basic tag source.
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func deliver(ctx context.Context, exporter Exporter, ev Event) context.Context {
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// add the current time to the event
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ev.At = time.Now()
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// hand the event off to the current exporter
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return exporter(ctx, ev, ev)
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}
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// dispatch is called to deliver an event to the global exporter if set.
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func dispatch(ctx context.Context, ev Event) context.Context {
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// get the global exporter and abort early if there is not one
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exporterPtr := (*Exporter)(atomic.LoadPointer(&exporter))
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if exporterPtr == nil {
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return ctx
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}
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return deliver(ctx, *exporterPtr, ev)
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}
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// dispatchPair is called to deliver a start event to the supplied exporter.
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// It also returns a function that will deliver the end event to the same
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// exporter.
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// it will fill in the time and generate the basic tag source.
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func dispatchPair(ctx context.Context, begin, end Event) (context.Context, func()) {
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// get the global exporter and abort early if there is not one
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exporterPtr := (*Exporter)(atomic.LoadPointer(&exporter))
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if exporterPtr == nil {
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return ctx, func() {}
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}
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ctx = deliver(ctx, *exporterPtr, begin)
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return ctx, func() { deliver(ctx, *exporterPtr, end) }
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}
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