blob: 5bad139e758e4b399cbc33a5694281ed234e0abb [file] [log] [blame]
// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package log supports structured and unstructured logging with levels.
package log
import (
"context"
"errors"
"fmt"
"log"
"os"
"strings"
"sync"
"cloud.google.com/go/logging"
"golang.org/x/pkgsite/internal/derrors"
"golang.org/x/pkgsite/internal/experiment"
)
var (
mu sync.Mutex
logger interface {
log(context.Context, logging.Severity, interface{})
} = stdlibLogger{}
// currentLevel holds current log level.
// No logs will be printed below currentLevel.
currentLevel = logging.Default
)
type (
// traceIDKey is the type of the context key for trace IDs.
traceIDKey struct{}
// labelsKey is the type of the context key for labels.
labelsKey struct{}
)
// Set the log level
func SetLevel(v string) {
mu.Lock()
defer mu.Unlock()
currentLevel = toLevel(v)
}
func getLevel() logging.Severity {
mu.Lock()
defer mu.Unlock()
return currentLevel
}
// NewContextWithTraceID creates a new context from ctx that adds the trace ID.
func NewContextWithTraceID(ctx context.Context, traceID string) context.Context {
return context.WithValue(ctx, traceIDKey{}, traceID)
}
// NewContextWithLabel creates anew context from ctx that adds a label that will
// appear in the log entry.
func NewContextWithLabel(ctx context.Context, key, value string) context.Context {
oldLabels, _ := ctx.Value(labelsKey{}).(map[string]string)
// Copy the labels, to preserve immutability of contexts.
newLabels := map[string]string{}
for k, v := range oldLabels {
newLabels[k] = v
}
newLabels[key] = value
return context.WithValue(ctx, labelsKey{}, newLabels)
}
// stackdriverLogger logs to GCP Stackdriver.
type stackdriverLogger struct {
sdlogger *logging.Logger
}
func (l *stackdriverLogger) log(ctx context.Context, s logging.Severity, payload interface{}) {
// Convert errors to strings, or they may serialize as the empty JSON object.
if err, ok := payload.(error); ok {
payload = err.Error()
}
traceID, _ := ctx.Value(traceIDKey{}).(string) // if not present, traceID is "", which is fine
labels, _ := ctx.Value(labelsKey{}).(map[string]string)
es := experimentString(ctx)
if len(es) > 0 {
nl := map[string]string{}
for k, v := range labels {
nl[k] = v
}
nl["experiments"] = es
labels = nl
}
l.sdlogger.Log(logging.Entry{
Severity: s,
Labels: labels,
Payload: payload,
Trace: traceID,
})
}
// stdlibLogger uses the Go standard library logger.
type stdlibLogger struct{}
func init() {
// Log to stdout on GKE so the log messages are severity Info, rather than Error.
if os.Getenv("GO_DISCOVERY_ON_GKE") != "" {
log.SetOutput(os.Stdout)
}
}
func (stdlibLogger) log(ctx context.Context, s logging.Severity, payload interface{}) {
var extras []string
traceID, _ := ctx.Value(traceIDKey{}).(string) // if not present, traceID is ""
if traceID != "" {
extras = append(extras, fmt.Sprintf("traceID %s", traceID))
}
if labels, ok := ctx.Value(labelsKey{}).(map[string]string); ok {
extras = append(extras, fmt.Sprint(labels))
}
es := experimentString(ctx)
if len(es) > 0 {
extras = append(extras, fmt.Sprintf("experiments %s", es))
}
var extra string
if len(extras) > 0 {
extra = " (" + strings.Join(extras, ", ") + ")"
}
log.Printf("%s%s: %+v", s, extra, payload)
}
func experimentString(ctx context.Context) string {
return strings.Join(experiment.FromContext(ctx).Active(), ", ")
}
// UseStackdriver switches from the default stdlib logger to a Stackdriver
// logger. It assumes config.Init has been called. UseStackdriver returns a
// "parent" *logging.Logger that should be used to log the start and end of a
// request. It also creates and remembers internally a "child" logger that will
// be used to log within a request. The two loggers are necessary to get request-scoped
// logs in Stackdriver.
// See https://cloud.google.com/appengine/docs/standard/go/writing-application-logs.
//
// UseStackdriver can only be called once. If it is called a second time, it returns an error.
func UseStackdriver(ctx context.Context, logName, projectID string, opts []logging.LoggerOption) (_ *logging.Logger, err error) {
defer derrors.Wrap(&err, "UseStackdriver(ctx, %q)", logName)
client, err := logging.NewClient(ctx, projectID)
if err != nil {
return nil, err
}
parent := client.Logger(logName, opts...)
child := client.Logger(logName+"-child", opts...)
mu.Lock()
defer mu.Unlock()
if _, ok := logger.(*stackdriverLogger); ok {
return nil, errors.New("already called once")
}
logger = &stackdriverLogger{child}
return parent, nil
}
// Infof logs a formatted string at the Info level.
func Infof(ctx context.Context, format string, args ...interface{}) {
logf(ctx, logging.Info, format, args)
}
// Warningf logs a formatted string at the Warning level.
func Warningf(ctx context.Context, format string, args ...interface{}) {
logf(ctx, logging.Warning, format, args)
}
// Errorf logs a formatted string at the Error level.
func Errorf(ctx context.Context, format string, args ...interface{}) {
logf(ctx, logging.Error, format, args)
}
// Debugf logs a formatted string at the Debug level.
func Debugf(ctx context.Context, format string, args ...interface{}) {
logf(ctx, logging.Debug, format, args)
}
// Fatalf logs formatted string at the Critical level followed by exiting the program.
func Fatalf(ctx context.Context, format string, args ...interface{}) {
logf(ctx, logging.Critical, format, args)
die()
}
func logf(ctx context.Context, s logging.Severity, format string, args []interface{}) {
doLog(ctx, s, fmt.Sprintf(format, args...))
}
// Info logs arg, which can be a string or a struct, at the Info level.
func Info(ctx context.Context, arg interface{}) { doLog(ctx, logging.Info, arg) }
// Warning logs arg, which can be a string or a struct, at the Warning level.
func Warning(ctx context.Context, arg interface{}) { doLog(ctx, logging.Warning, arg) }
// Error logs arg, which can be a string or a struct, at the Error level.
func Error(ctx context.Context, arg interface{}) { doLog(ctx, logging.Error, arg) }
// Debug logs arg, which can be a string or a struct, at the Debug level.
func Debug(ctx context.Context, arg interface{}) { doLog(ctx, logging.Debug, arg) }
// Fatal logs arg, which can be a string or a struct, at the Critical level followed by exiting the program.
func Fatal(ctx context.Context, arg interface{}) {
doLog(ctx, logging.Critical, arg)
die()
}
func doLog(ctx context.Context, s logging.Severity, payload interface{}) {
if getLevel() > s {
return
}
mu.Lock()
l := logger
mu.Unlock()
l.log(ctx, s, payload)
}
func die() {
mu.Lock()
if sl, ok := logger.(*stackdriverLogger); ok {
sl.sdlogger.Flush()
}
mu.Unlock()
os.Exit(1)
}
// toLevel returns the logging.Severity for a given string.
// Possible input values are "", "debug", "info", "warning", "error", "fatal".
// In case of invalid string input, it maps to DefaultLevel.
func toLevel(v string) logging.Severity {
v = strings.ToLower(v)
switch v {
case "":
// default log level will print everything.
return logging.Default
case "debug":
return logging.Debug
case "info":
return logging.Info
case "warning":
return logging.Warning
case "error":
return logging.Error
case "fatal":
return logging.Critical
}
// Default log level in case of invalid input.
log.Printf("Error: %s is invalid LogLevel. Possible values are [debug, info, warning, error, fatal]", v)
return logging.Default
}