package main // This file configures different log formatters via logrus. The // standard formatter uses a structured JSON format that is compatible // with Stackdriver Error Reporting. // // https://cloud.google.com/error-reporting/docs/formatting-error-messages import ( "bytes" "encoding/json" log "github.com/sirupsen/logrus" ) type stackdriverFormatter struct{} type serviceContext struct { Service string `json:"service"` Version string `json:"version"` } type reportLocation struct { FilePath string `json:"filePath"` LineNumber int `json:"lineNumber"` FunctionName string `json:"functionName"` } var nixeryContext = serviceContext{ Service: "nixery", } // isError determines whether an entry should be logged as an error // (i.e. with attached `context`). // // This requires the caller information to be present on the log // entry, as stacktraces are not available currently. func isError(e *log.Entry) bool { l := e.Level return (l == log.ErrorLevel || l == log.FatalLevel || l == log.PanicLevel) && e.HasCaller() } // logSeverity formats the entry's severity into a format compatible // with Stackdriver Logging. // // The two formats that are being mapped do not have an equivalent set // of severities/levels, so the mapping is somewhat arbitrary for a // handful of them. // // https://cloud.google.com/logging/docs/reference/v2/rest/v2/LogEntry#LogSeverity func logSeverity(l log.Level) string { switch l { case log.TraceLevel: return "DEBUG" case log.DebugLevel: return "DEBUG" case log.InfoLevel: return "INFO" case log.WarnLevel: return "WARNING" case log.ErrorLevel: return "ERROR" case log.FatalLevel: return "CRITICAL" case log.PanicLevel: return "EMERGENCY" default: return "DEFAULT" } } func (f stackdriverFormatter) Format(e *log.Entry) ([]byte, error) { msg := e.Data msg["serviceContext"] = &nixeryContext msg["message"] = &e.Message msg["eventTime"] = &e.Time msg["severity"] = logSeverity(e.Level) if e, ok := msg[log.ErrorKey]; ok { if err, isError := e.(error); isError { msg[log.ErrorKey] = err.Error() } else { delete(msg, log.ErrorKey) } } if isError(e) { loc := reportLocation{ FilePath: e.Caller.File, LineNumber: e.Caller.Line, FunctionName: e.Caller.Function, } msg["context"] = &loc } b := new(bytes.Buffer) err := json.NewEncoder(b).Encode(&msg) return b.Bytes(), err } func init() { nixeryContext.Version = version log.SetReportCaller(true) log.SetFormatter(stackdriverFormatter{}) }