1 // Copyright 2015 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // Package trace contains facilities for programs to generate trace 6 // for Go execution tracer. 7 // 8 // The execution trace captures a wide range of execution events such as 9 // goroutine creation/blocking/unblocking, syscall enter/exit/block, 10 // GC-related events, changes of heap size, processor start/stop, etc. 11 // A precise nanosecond-precision timestamp and a stack trace is 12 // captured for most events. The generated trace can be interpreted 13 // using `go tool trace`. 14 // 15 // Tracing a Go program 16 // 17 // Support for tracing tests and benchmarks built with the standard 18 // testing package is built into `go test`. For example, the following 19 // command runs the test in the current directory and writes the trace 20 // file (trace.out). 21 // 22 // go test -trace=test.out 23 // 24 // This runtime/trace package provides APIs to add equivalent tracing 25 // support to a standalone program. See the Example that demonstrates 26 // how to use this API to enable tracing. 27 // 28 // There is also a standard HTTP interface to profiling data. Adding the 29 // following line will install handlers under the /debug/pprof/trace URL 30 // to download live profiles: 31 // 32 // import _ "net/http/pprof" 33 // 34 // See the net/http/pprof package for more details. 35 package trace 36 37 import ( 38 "io" 39 "runtime" 40 ) 41 42 // Start enables tracing for the current program. 43 // While tracing, the trace will be buffered and written to w. 44 // Start returns an error if tracing is already enabled. 45 func Start(w io.Writer) error { 46 if err := runtime.StartTrace(); err != nil { 47 return err 48 } 49 go func() { 50 for { 51 data := runtime.ReadTrace() 52 if data == nil { 53 break 54 } 55 w.Write(data) 56 } 57 }() 58 return nil 59 } 60 61 // Stop stops the current tracing, if any. 62 // Stop only returns after all the writes for the trace have completed. 63 func Stop() { 64 runtime.StopTrace() 65 } 66
