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// Copyright 2020 New Relic Corporation. All rights reserved.
// SPDX-License-Identifier: Apache-2.0
package newrelic
import (
"bytes"
"path"
"runtime"
"strings"
)
// stackTrace is a stack trace.
type stackTrace []uintptr
// getStackTrace returns a new stackTrace.
func getStackTrace() stackTrace {
skip := 1 // skip runtime.Callers
callers := make([]uintptr, maxStackTraceFrames)
written := runtime.Callers(skip, callers)
return callers[:written]
}
type stacktraceFrame struct {
Name string
File string
Line int64
}
func (f stacktraceFrame) formattedName() string {
if strings.HasPrefix(f.Name, "go.") {
// This indicates an anonymous struct. eg.
// "go.(*struct { github.com/newrelic/go-agent.threadWithExtras }).NoticeError"
return f.Name
}
return path.Base(f.Name)
}
func (f stacktraceFrame) isAgent() bool {
// Note this is not a contains conditional rather than a prefix
// conditional to handle anonymous functions like:
// "go.(*struct { github.com/newrelic/go-agent.threadWithExtras }).NoticeError"
return strings.Contains(f.Name, "github.com/newrelic/go-agent/v3/internal.") ||
strings.Contains(f.Name, "github.com/newrelic/go-agent/v3/newrelic.")
}
func (f stacktraceFrame) WriteJSON(buf *bytes.Buffer) {
buf.WriteByte('{')
w := jsonFieldsWriter{buf: buf}
if f.Name != "" {
w.stringField("name", f.formattedName())
}
if f.File != "" {
w.stringField("filepath", f.File)
}
if f.Line != 0 {
w.intField("line", f.Line)
}
buf.WriteByte('}')
}
func writeFrames(buf *bytes.Buffer, frames []stacktraceFrame) {
// Remove top agent frames.
for len(frames) > 0 && frames[0].isAgent() {
frames = frames[1:]
}
// Truncate excessively long stack traces (they may be provided by the
// customer).
if len(frames) > maxStackTraceFrames {
frames = frames[0:maxStackTraceFrames]
}
buf.WriteByte('[')
for idx, frame := range frames {
if idx > 0 {
buf.WriteByte(',')
}
frame.WriteJSON(buf)
}
buf.WriteByte(']')
}
func (st stackTrace) frames() []stacktraceFrame {
if len(st) == 0 {
return nil
}
frames := runtime.CallersFrames(st) // CallersFrames is only available in Go 1.7+
fs := make([]stacktraceFrame, 0, maxStackTraceFrames)
var frame runtime.Frame
more := true
for more {
frame, more = frames.Next()
fs = append(fs, stacktraceFrame{
Name: frame.Function,
File: frame.File,
Line: int64(frame.Line),
})
}
return fs
}
// WriteJSON adds the stack trace to the buffer in the JSON form expected by the
// collector.
func (st stackTrace) WriteJSON(buf *bytes.Buffer) {
frames := st.frames()
writeFrames(buf, frames)
}
// MarshalJSON prepares JSON in the format expected by the collector.
func (st stackTrace) MarshalJSON() ([]byte, error) {
estimate := 256 * len(st)
buf := bytes.NewBuffer(make([]byte, 0, estimate))
st.WriteJSON(buf)
return buf.Bytes(), nil
}
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