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go/internal/telemetry/export/log.go
Ian Cottrell cb106d260e internal/telemetry: allow ProcessEvent to modify the event
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>
2020-03-18 13:22:01 +00:00

56 lines
1.4 KiB
Go

// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package export
import (
"context"
"fmt"
"io"
"os"
"golang.org/x/tools/internal/telemetry/event"
)
func init() {
event.SetExporter(LogWriter(os.Stderr, true))
}
// LogWriter returns an Exporter that logs events to the supplied writer.
// If onlyErrors is true it does not log any event that did not have an
// associated error.
// It ignores all telemetry other than log events.
func LogWriter(w io.Writer, onlyErrors bool) event.Exporter {
return &logWriter{writer: w, onlyErrors: onlyErrors}
}
type logWriter struct {
writer io.Writer
onlyErrors bool
}
func (w *logWriter) ProcessEvent(ctx context.Context, ev event.Event) (context.Context, event.Event) {
switch {
case ev.IsLog():
if w.onlyErrors && ev.Error == nil {
return ctx, ev
}
fmt.Fprintf(w.writer, "%v\n", ev)
case ev.IsStartSpan():
if span := GetSpan(ctx); span != nil {
fmt.Fprintf(w.writer, "start: %v %v", span.Name, span.ID)
if span.ParentID.IsValid() {
fmt.Fprintf(w.writer, "[%v]", span.ParentID)
}
}
case ev.IsEndSpan():
if span := GetSpan(ctx); span != nil {
fmt.Fprintf(w.writer, "finish: %v %v", span.Name, span.ID)
}
}
return ctx, ev
}
func (w *logWriter) Metric(context.Context, event.MetricData) {}