github.com/decred/politeia@v1.4.0/politeiawww/logger/logger.go (about)

     1  // Copyright (c) 2017-2021 The Decred developers
     2  // Use of this source code is governed by an ISC
     3  // license that can be found in the LICENSE file.
     4  
     5  package logger
     6  
     7  import (
     8  	"fmt"
     9  	"os"
    10  	"path/filepath"
    11  	"sort"
    12  
    13  	"github.com/decred/slog"
    14  	"github.com/jrick/logrotate/rotator"
    15  )
    16  
    17  // logWriter implements an io.Writer that outputs to both standard output and
    18  // the write-end pipe of an initialized log rotator.
    19  type logWriter struct{}
    20  
    21  func (logWriter) Write(p []byte) (n int, err error) {
    22  	os.Stdout.Write(p)
    23  	if logRotator == nil {
    24  		return 0, nil
    25  	}
    26  	return logRotator.Write(p)
    27  }
    28  
    29  // Loggers per subsystem.  A single backend logger is created and all subsytem
    30  // loggers created from it will write to the backend.  When adding new
    31  // subsystems, add the subsystem logger variable here and to the
    32  // subsystemLoggers map.
    33  //
    34  // Loggers can not be used before the log rotator has been initialized with a
    35  // log file.  This must be performed early during application startup by calling
    36  // initLogRotator.
    37  var (
    38  	// backendLog is the logging backend used to create all subsystem loggers.
    39  	// The backend must not be used before the log rotator has been initialized,
    40  	// or data races and/or nil pointer dereferences will occur.
    41  	backendLog = slog.NewBackend(logWriter{})
    42  
    43  	// logRotator is one of the logging outputs.  It should be closed on
    44  	// application shutdown.
    45  	logRotator *rotator.Rotator
    46  
    47  	// subsystemsLoggers contains all of the subsystem loggers. A new subsystem
    48  	// logger is registered using Register().
    49  	subsystemLoggers = map[string]slog.Logger{}
    50  )
    51  
    52  // InitLogRotator initializes the logging rotater to write logs to logFile and
    53  // create roll files in the same directory.  It must be called before the
    54  // package-global log rotater variables are used.
    55  func InitLogRotator(logFile string) {
    56  	logDir, _ := filepath.Split(logFile)
    57  	err := os.MkdirAll(logDir, 0700)
    58  	if err != nil {
    59  		fmt.Fprintf(os.Stderr, "failed to create log directory: %v\n", err)
    60  		os.Exit(1)
    61  	}
    62  	r, err := rotator.New(logFile, 10*1024, false, 3)
    63  	if err != nil {
    64  		fmt.Fprintf(os.Stderr, "failed to create file rotator: %v\n", err)
    65  		os.Exit(1)
    66  	}
    67  
    68  	logRotator = r
    69  }
    70  
    71  // CloseLogRotator closes the log rotator.
    72  func CloseLogRotator() {
    73  	if logRotator != nil {
    74  		logRotator.Close()
    75  	}
    76  }
    77  
    78  // NewSubsystem registers and returns a new subsystem logger.
    79  func NewSubsystem(subsystemTag string) slog.Logger {
    80  	l := backendLog.Logger(subsystemTag)
    81  	subsystemLoggers[subsystemTag] = l
    82  	return l
    83  }
    84  
    85  // SupportedSubsystems returns a sorted slice of the supported subsystems for
    86  // logging purposes.
    87  func SupportedSubsystems() []string {
    88  	// Convert the subsystemLoggers map keys to a slice.
    89  	subsystems := make([]string, 0, len(subsystemLoggers))
    90  	for subsysID := range subsystemLoggers {
    91  		subsystems = append(subsystems, subsysID)
    92  	}
    93  
    94  	// Sort the subsytems for stable display.
    95  	sort.Strings(subsystems)
    96  	return subsystems
    97  }
    98  
    99  // SetLogLevel sets the logging level for provided subsystem.  Invalid
   100  // subsystems are ignored.  Uninitialized subsystems are dynamically created as
   101  // needed.
   102  func SetLogLevel(subsystemID string, logLevel string) {
   103  	// Ignore invalid subsystems.
   104  	logger, ok := subsystemLoggers[subsystemID]
   105  	if !ok {
   106  		return
   107  	}
   108  
   109  	// Defaults to info if the log level is invalid.
   110  	level, _ := slog.LevelFromString(logLevel)
   111  	logger.SetLevel(level)
   112  }
   113  
   114  // SetLogLevels sets the log level for all subsystem loggers to the passed
   115  // level.  It also dynamically creates the subsystem loggers as needed, so it
   116  // can be used to initialize the logging system.
   117  func SetLogLevels(logLevel string) {
   118  	// Configure all sub-systems with the new logging level.  Dynamically
   119  	// create loggers as needed.
   120  	for subsystemID := range subsystemLoggers {
   121  		SetLogLevel(subsystemID, logLevel)
   122  	}
   123  }
   124  
   125  // LogClosure is a closure that can be printed with %v to be used to
   126  // generate expensive-to-create data for a detailed log level and avoid doing
   127  // the work if the data isn't printed.
   128  type LogClosure func() string
   129  
   130  func (c LogClosure) String() string {
   131  	return c()
   132  }
   133  
   134  // NewLogClosure returns a new LogClosure.
   135  func NewLogClosure(c func() string) LogClosure {
   136  	return LogClosure(c)
   137  }