trace

Overview ¶

Package trace contains facilities for programs to generate trace for Go execution tracer.

The execution trace captures a wide range of execution events such as goroutine creation/blocking/unblocking, syscall enter/exit/block, GC-related events, changes of heap size, processor start/stop, etc. A precise nanosecond-precision timestamp and a stack trace is captured for most events. The generated trace can be interpreted using `go tool trace`.

Tracing a Go program ¶

Support for tracing tests and benchmarks built with the standard testing package is built into `go test`. For example, the following command runs the test in the current directory and writes the trace file (trace.out).

go test -trace=test.out

This runtime/trace package provides APIs to add equivalent tracing support to a standalone program. See the Example that demonstrates how to use this API to enable tracing.

There is also a standard HTTP interface to profiling data. Adding the following line will install handlers under the /debug/pprof/trace URL to download live profiles:

import _ "net/http/pprof"

See the net/http/pprof package for more details.

package main

import (
	"fmt"
	"log"
	"os"
	"runtime/trace"
)

// Example demonstrates the use of the trace package to trace
// the execution of a Go program. The trace output will be
// written to the file trace.out
func main() {
	f, err := os.Create("trace.out")
	if err != nil {
		log.Fatalf("failed to create trace output file: %v", err)
	}
	defer func() {
		if err := f.Close(); err != nil {
			log.Fatalf("failed to close trace file: %v", err)
		}
	}()

	if err := trace.Start(f); err != nil {
		log.Fatalf("failed to start trace: %v", err)
	}
	defer trace.Stop()

	// your program here
	RunMyProgram()
}

func RunMyProgram() {
	fmt.Printf("this function will be traced")
}