dotcloud/docker

package stack // import "github.com/docker/docker/pkg/stack"

import (
    "fmt"
    "os"
    "path/filepath"
    "runtime"
    "strings"
    "time"

    "github.com/pkg/errors"
)

const stacksLogNameTemplate = "goroutine-stacks-%s.log"

// Dump outputs the runtime stack to os.StdErr.
func Dump() {
    _ = dump(os.Stderr)
}

// DumpToFile appends the runtime stack into a file named "goroutine-stacks-<timestamp>.log"
// in dir and returns the full path to that file. If no directory name is
// provided, it outputs to os.Stderr.
func DumpToFile(dir string) (string, error) {
    var f *os.File
    if dir != "" {
        path := filepath.Join(dir, fmt.Sprintf(stacksLogNameTemplate, strings.ReplaceAll(time.Now().Format(time.RFC3339), ":", "")))
        var err error
        f, err = os.OpenFile(path, os.O_CREATE|os.O_WRONLY, 0o666)
        if err != nil {
            return "", errors.Wrap(err, "failed to open file to write the goroutine stacks")
        }
        defer f.Close()
        defer f.Sync()
    } else {
        f = os.Stderr
    }
    return f.Name(), dump(f)
}

func dump(f *os.File) error {
    var (
        buf       []byte
        stackSize int
    )
    bufferLen := 16384
    for stackSize == len(buf) {
        buf = make([]byte, bufferLen)
        stackSize = runtime.Stack(buf, true)
        bufferLen *= 2
    }
    buf = buf[:stackSize]
    if _, err := f.Write(buf); err != nil {
        return errors.Wrap(err, "failed to write goroutine stacks")
    }
    return nil
}