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package skynet
import (
// "strings"
// LogPayload stores detailed logging information, including all
// fields used by Clarity Service's semantic_logger (see
// See the
// LogPayload struct's inline comments for instructions as to which
// fields should be populated by whom or what (e.g., the user
// (manually), helper functions, or methods on the various loggers in
// this package.)
// Valid log levels -- a list of which is stored in the `LogLevels`
// slice -- include TRACE, DEBUG, INFO, WARN, ERROR, and FATAL.
type LogPayload struct {
// Set by user by passing values to NewLogPayload()
Level LogLevel `json:"level" bson:"level"`
Message string `json:"message" bson:"message"`
// Set automatically within NewLogPayload()
LevelIndex int `json:"level_index" bson:"level_index"`
Name string `json:"name" bson:"name"` // Name of calling function
// Set by .setKnownFields()
PID int `json:"pid" bson:"pid"`
Time time.Time `json:"time" bson:"time"`
HostName string `json:"host_name" bson:"host_name"`
// Set by .SetTags() convenience method
Tags []string `json:"tags" bson:"tags"`
// Should be set by .Log()
UUID string `json:"uuid" bson:"uuid"` // Logger's UUID
// Should be set by BenchmarkInfo() if called
Duration time.Duration `json:"duration" bson:"duration"`
// Optionally set by user manually
ThreadName string `json:"thread_name" bson:"thread_name"`
Application string `json:"application" bson:"application"`
Payload interface{} `json:"payload" bson:"payload"` // Arbitrary data
Exception *Exception `json:"exception" bson:"exception"`
type Exception struct {
Name string `json:"name" bson:"name"`
Message string `json:"message" bson:"message"`
// Set by Fatal() method if need be
StackTrace []string `json:"stack_trace" bson:"stack_trace"`
// SetException sets the given payload's `Exception` field. The
// payload's "exception" data is generated from a panic's stacktrace
// using the `genStacktrace` helper function.
func (payload *LogPayload) SetException() {
// TODO: If the following logging format is still used in by
//, use it here:
// message << " -- " << "#{exception.class}: #{exception.message}\n
// #{(exception.backtrace || []).join("\n")}"
// ...then use this code to fill .Message with the above-formatted
// logging information:
// formatStr := "%s -- %s: %s\n%s"
// stacktrace := strings.Join(payload.Exception.StackTrace, "\n")
// payload.Exception.Message = fmt.Sprintf(formatStr, payload.Message, "panic",
// payload.Message, stacktrace)
payload.Exception = &Exception{
// TODO: Decide what `Name` should be. Go doesn't have
// exceptions, and therefore has no exceptions whose names we
// can put here.
Name: "",
Message: payload.Message,
StackTrace: genStacktrace(),
// setKnownFields sets the `Application`, `PID`, `Time`, and
// `HostName` fields of the given payload. See the documentation on
// the LogPayload type for which fields should be set where, and by
// whom (the user) or what (a function or method).
func (payload *LogPayload) setKnownFields() {
payload.PID = os.Getpid()
payload.Time = time.Now()
hostname, err := os.Hostname()
if err != nil {
log.Printf("Error getting hostname: %v\n", err)
payload.HostName = hostname
// SetTags is a convenience method for adding tags to *LogPayload's,
// since `payload.SetTags("tag1", "tag2")` is cleaner than
// `payload.Tags = []string{"tag1", "tag2"}`
func (payload *LogPayload) SetTags(tags ...string) {
payload.Tags = tags
// NewLogPayload is a convenience function for creating *LogPayload's
func NewLogPayload(level LogLevel, formatStr string, vars ...interface{}) *LogPayload {
payload := &LogPayload{
Level: level,
LevelIndex: levelIndex(level),
Message: fmt.Sprintf(formatStr, vars...),
// 1 == skynet.NewLogPayload
// 2 == skynet.(*MongoSemanticLogger).Fatal
// 3 == What we want
// 4 (or shortly thereafter) == main.main
Name: getCallerName(3),
// payload.setKnownFields() called in .Log() method; not calling here
// TODO: Come up with a way to intelligently auto-fill ThreadName,
// if possible
return payload
func getCallerName(skip int) string {
pc, _, _, _ := runtime.Caller(skip)
f := runtime.FuncForPC(pc)
return f.Name()
type LogLevel string
const (
TRACE LogLevel = "trace"
DEBUG LogLevel = "debug"
INFO LogLevel = "info"
WARN LogLevel = "warn"
ERROR LogLevel = "error"
FATAL LogLevel = "fatal"
// LogLevel stores the valid log levels as specified by
// Its index corresponds
// to the log level it represents. (LogLevels[0] == "trace", ...,
// LogLevels[5] == "fatal")
var LogLevels = []LogLevel{
// levelIndex turns the given level into its corresponding integer
// value. "trace" == 0, "debug" == 1, ... "fatal" == 5
func levelIndex(level LogLevel) int {
switch level {
case TRACE:
return 0
case DEBUG:
return 1
case INFO:
return 2
case WARN:
return 3
case ERROR:
return 4
case FATAL:
return 5
return -1
// LessSevereThan tells you whether or not `level` is a less severe
// LogLevel than `level2`. This is useful for determining which logs
// to view.
func (level LogLevel) LessSevereThan(level2 LogLevel) bool {
return levelIndex(level) < levelIndex(level2)
// NOTE: The data type names are what they are (and rather verbose) in
// part so that "SemanticLogger" can be replaced with "Logger" in this
// file once the contents of logger.go is no longer needed.
// SemanticLogger is meant to match the format and functionality of
type SemanticLogger interface {
Log(payload *LogPayload)
Trace(msg string)
Debug(msg string)
Info(msg string)
Warn(msg string)
Error(msg string)
Fatal(msg string)
BenchmarkInfo(level LogLevel, msg string, f func(logger SemanticLogger))
// genStacktrace is a helper function for generating stacktrace
// data. Used to populate (*LogPayload).StackTrace
func genStacktrace() (stacktrace []string) {
// TODO: Make sure that `skip` should begin at 1, not 2
for skip := 1; ; skip++ {
pc, file, line, ok := runtime.Caller(skip)
if !ok {
f := runtime.FuncForPC(pc)
traceLine := fmt.Sprintf("%s:%d %s()\n", file, line, f.Name())
stacktrace = append(stacktrace, traceLine)