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handler.go
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/
handler.go
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package ecslogs
import (
"fmt"
"io"
"reflect"
"runtime"
"strings"
"sync"
"syscall"
"time"
"unsafe"
"github.com/pkg/errors"
"github.com/segmentio/events"
"github.com/segmentio/objconv"
"github.com/segmentio/objconv/json"
)
// Handler is an event handler which formats events in a ecslogs-compatible
// format and writes them to its output.
//
// It is safe to use a handler concurrently from multiple goroutines.
type Handler struct {
Output io.Writer
Program string
Pid int
// synchronizes writes to the output
mutex sync.Mutex
}
// NewHandler creates a new handler which writes to output
func NewHandler(output io.Writer) *Handler {
return &Handler{
Output: output,
}
}
// HandleEvent satisfies the events.Handler interface.
func (h *Handler) HandleEvent(e *events.Event) {
f := fmtPool.Get().(*formatter)
f.buffer.Reset()
f.emitter.Reset(&f.buffer)
f.level = "INFO"
f.time = e.Time
f.message = e.Message
f.data.args = e.Args
f.info.Source = e.Source
f.info.Program = h.Program
f.info.Pid = h.Pid
if e.Debug {
f.level = "DEBUG"
}
for _, a := range e.Args {
if err, ok := a.Value.(error); ok {
f.level = "ERROR"
f.info.Errors = append(f.info.Errors, makeEventError(err))
}
}
(objconv.Encoder{Emitter: &f.emitter}).Encode(f.value)
f.buffer.WriteByte('\n')
h.mutex.Lock()
h.Output.Write(f.buffer.b)
h.mutex.Unlock()
f.info.Source = ""
f.info.Errors = f.info.Errors[:0]
fmtPool.Put(f)
}
type event struct {
Level *string `objconv:"level"`
Time *time.Time `objconv:"time"`
Info *eventInfo `objconv:"info"`
Data *eventData `objconv:"data"`
Message *string `objconv:"message"`
}
type eventInfo struct {
Program string `objconv:"program,omitempty"`
Source string `objconv:"source,omitempty"`
Pid int `objconv:"pid,omitempty"`
Errors []eventError `objconv:"errors,omitempty"`
}
type eventError struct {
Type string `objconv:"type,omitempty"`
Error string `objconv:"error,omitempty"`
Errno int `objconv:"errno,omitempty"`
Stack stackTrace `objconv:"stack,omitempty"`
}
func makeEventError(err error) eventError {
var cause = errors.Cause(err)
var etype = reflect.TypeOf(cause).String()
var error = err.Error()
var errno = 0
var stack stackTrace
if se, ok := cause.(syscall.Errno); ok {
errno = int(se)
}
if st, ok := err.(stackTracer); ok {
stack = stackTrace(st.StackTrace())
}
return eventError{
Type: etype,
Error: error,
Errno: errno,
Stack: stack,
}
}
type eventData struct {
args events.Args
}
func (data *eventData) EncodeValue(e objconv.Encoder) error {
n := len(data.args)
i := data.next(0)
return e.EncodeMap(-1, func(k objconv.Encoder, v objconv.Encoder) (err error) {
if i != n {
if err = k.Encode(&data.args[i].Name); err != nil {
return
}
if err = v.Encode(&data.args[i].Value); err != nil {
return
}
i = data.next(i + 1)
}
if i == n {
err = objconv.End
}
return
})
}
func (data *eventData) next(i int) int {
for _, a := range data.args[i:] {
if _, ok := a.Value.(error); !ok {
break
}
i++
}
return i
}
type stackTracer interface {
StackTrace() errors.StackTrace
}
type stackTrace []errors.Frame
func (st stackTrace) EncodeValue(e objconv.Encoder) error {
f := fmtPool.Get().(*formatter)
i := 0
err := e.EncodeArray(len(st), func(e objconv.Encoder) error {
f.buffer.Reset()
pc := uintptr(st[i])
file, line := events.SourceForPC(pc)
i++
fmt.Fprintf(&f.buffer, "%s:%d:%s", file, line, funcName(file, pc))
return e.Encode(stringNoCopy(f.buffer.b))
})
fmtPool.Put(f)
return err
}
func funcName(file string, pc uintptr) string {
callers := [1]uintptr{pc}
frames := runtime.CallersFrames(callers[:])
f, _ := frames.Next()
name := f.Function
if i := strings.LastIndexByte(name, '/'); i >= 0 {
name = name[i+1:]
}
return name
}
// The formatter type carries the state used during a single event formatting
// operation in HandlerEvent.
// The type is designed to allow complex memory optimizations when encoding the
// event, it actually prevents Go and especially the reflect package from doing
// any memory allocation.
type formatter struct {
value interface{}
level string
time time.Time
info eventInfo
data eventData
message string
buffer buffer
source buffer
emitter json.Emitter
}
var fmtPool = sync.Pool{
New: func() interface{} {
f := &formatter{
buffer: buffer{make([]byte, 0, 4096)},
source: buffer{make([]byte, 0, 256)},
emitter: *json.NewEmitter(nil),
}
f.value = &event{
Level: &f.level,
Time: &f.time,
Info: &f.info,
Data: &f.data,
Message: &f.message,
}
return f
},
}
// This buffer type is used as an optimization, it's faster than the standard
// bytes.Buffer because it doesn't expose such a rich API.
type buffer struct {
b []byte
}
func (buf *buffer) Reset() {
buf.b = buf.b[:0]
}
func (buf *buffer) Write(b []byte) (n int, err error) {
buf.b = append(buf.b, b...)
n = len(b)
return
}
func (buf *buffer) WriteByte(b byte) (err error) {
buf.b = append(buf.b, b)
return
}
func stringNoCopy(b []byte) string {
if len(b) == 0 {
return ""
}
return *(*string)(unsafe.Pointer(&reflect.StringHeader{
Data: uintptr(unsafe.Pointer(&b[0])),
Len: len(b),
}))
}