log.go

// Copyright (c) 2016 The Decred developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.

package main

import (
	"fmt"
	"os"
	"path/filepath"

	"github.com/decred/dcrstakepool/controllers"
	"github.com/decred/dcrstakepool/models"
	"github.com/decred/dcrstakepool/signal"
	"github.com/decred/dcrstakepool/stakepooldclient"
	"github.com/decred/dcrstakepool/system"
	"github.com/decred/slog"
	"github.com/jrick/logrotate/rotator"
)

// logWriter implements an io.Writer that outputs to both standard output and
// the write-end pipe of an initialized log rotator.
type logWriter struct{}

func (logWriter) Write(p []byte) (n int, err error) {
	os.Stdout.Write(p)
	if logRotator != nil {
		return logRotator.Write(p)
	}
	return 0, nil
}

// Loggers per subsystem.  A single backend logger is created and all subsytem
// loggers created from it will write to the backend.  When adding new
// subsystems, add the subsystem logger variable here and to the
// subsystemLoggers map.
//
// Loggers can not be used before the log rotator has been initialized with a
// log file.  This must be performed early during application startup by calling
// initLogRotator.
var (

	// backendLog is the logging backend used to create all subsystem loggers.
	// The backend must not be used before the log rotator has been initialized,
	// or data races and/or nil pointer dereferences will occur.
	backendLog = slog.NewBackend(logWriter{})

	// logRotator is one of the logging outputs.  It should be closed on
	// application shutdown.
	logRotator *rotator.Rotator

	controllersLog      = backendLog.Logger("CNTL")
	log                 = backendLog.Logger("DCRS")
	modelsLog           = backendLog.Logger("MODL")
	stakepooldclientLog = backendLog.Logger("GRPC")
	systemLog           = backendLog.Logger("SYTM")
)

// Initialize package-global logger variables.
func init() {
	controllers.UseLogger(controllersLog)
	models.UseLogger(modelsLog)
	stakepooldclient.UseLogger(stakepooldclientLog)
	system.UseLogger(systemLog)
	signal.UseLogger(systemLog)
}

// subsystemLoggers maps each subsystem identifier to its associated logger.
var subsystemLoggers = map[string]slog.Logger{
	"DCRS": log,
	"CNTL": controllersLog,
	"GRPC": stakepooldclientLog,
	"MODL": modelsLog,
	"SYTM": systemLog,
}

// initLogRotator initializes the logging rotater to write logs to logFile and
// create roll files in the same directory.  It must be called before the
// package-global log rotater variables are used.
func initLogRotator(logFile string) {
	logDir, _ := filepath.Split(logFile)
	err := os.MkdirAll(logDir, 0700)
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create log directory: %v\n", err)
		os.Exit(1)
	}
	r, err := rotator.New(logFile, 10*1024, false, 3)
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create file rotator: %v\n", err)
		os.Exit(1)
	}

	logRotator = r
}

// setLogLevel sets the logging level for provided subsystem.  Invalid
// subsystems are ignored.  Uninitialized subsystems are dynamically created as
// needed.
func setLogLevel(subsystemID string, logLevel string) {
	// Ignore invalid subsystems.
	logger, ok := subsystemLoggers[subsystemID]
	if !ok {
		return
	}

	// Defaults to info if the log level is invalid.
	level, _ := slog.LevelFromString(logLevel)
	logger.SetLevel(level)
}

// setLogLevels sets the log level for all subsystem loggers to the passed
// level.  It also dynamically creates the subsystem loggers as needed, so it
// can be used to initialize the logging system.
func setLogLevels(logLevel string) {
	// Configure all sub-systems with the new logging level.  Dynamically
	// create loggers as needed.
	for subsystemID := range subsystemLoggers {
		setLogLevel(subsystemID, logLevel)
	}
}