glog

package module
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 Go to latest Published: Mar 4, 2025 License: Apache-2.0 Imports: 16 Imported by: 24

README 

glog
====

Leveled execution logs for Go.

This is an efficient pure Go implementation of leveled logs in the
manner of the open source C++ package
	http://code.google.com/p/google-glog

By binding methods to booleans it is possible to use the log package
without paying the expense of evaluating the arguments to the log.
Through the -vmodule flag, the package also provides fine-grained
control over logging at the file level.

The comment from glog.go introduces the ideas:

	Package glog implements logging analogous to the Google-internal
	C++ INFO/ERROR/V setup.  It provides functions Info, Warning,
	Error, Fatal, plus formatting variants such as Infof. It
	also provides V-style logging controlled by the -v and
	-vmodule=file=2 flags.
	
	Basic examples:
	
		glog.Info("Prepare to repel boarders")
	
		glog.Fatalf("Initialization failed: %s", err)
	
	See the documentation for the V function for an explanation
	of these examples:
	
		if glog.V(2) {
			glog.Info("Starting transaction...")
		}
	
		glog.V(2).Infoln("Processed", nItems, "elements")


The repository contains an open source version of the log package
used inside Google. The master copy of the source lives inside
Google, not here. The code in this repo is for export only and is not itself
under development. Feature requests will be ignored.

Send bug reports to golang-nuts@googlegroups.com.

Documentation

Overview

Package glog implements logging analogous to the Google-internal C++ INFO/ERROR/V setup. It provides functions Info, Warning, Error, Fatal, plus formatting variants such as Infof. It also provides V-style logging controlled by the -v and -vmodule=file=2 flags.

Basic examples: 

glog.Info("Prepare to repel boarders")

glog.Fatalf("Initialization failed: %s", err)

See the documentation for the V function for an explanation of these examples: 

if glog.V(2) {
	glog.Info("Starting transaction...")
}

glog.V(2).Infoln("Processed", nItems, "elements")

Log output is buffered and written periodically using Flush. Programs should call Flush before exiting to guarantee all log output is written.

By default, all log statements write to files in a temporary directory. This package provides several flags that modify this behavior. As a result, flag.Parse must be called before any logging is done. 

Other flags provide aids to debugging.

-log_backtrace_at=""
	When set to a file and line number holding a logging statement,
	such as
		-log_backtrace_at=gopherflakes.go:234
	a stack trace will be written to the Info log whenever execution
	hits that statement. (Unlike with -vmodule, the ".go" must be
	present.)
-v=0
	Enable V-leveled logging at the specified level.
-vmodule=""
	The syntax of the argument is a comma-separated list of pattern=N,
	where pattern is a literal file name (minus the ".go" suffix) or
	"glob" pattern and N is a V level. For instance,
		-vmodule=gopher*=3
	sets the V level to 3 in all Go files whose names begin "gopher".

Index

Constants

This section is empty.

Variables

View Source 
var ExternalOutput externalWriter

This ExternalOutput is to be used only for external logs

View Source 
var Stats struct {
	Info, Warning, Error OutputStats
}

Stats tracks the number of lines of output and number of bytes per severity level. Values must be read with atomic.LoadInt64.

Functions

func ContextWithData 

func ContextWithData(ctx context.Context, args ...interface{}) context.Context

ContextWithData creates a context as extension of the parent context, with the provided data stored as a value. Any existing data on the parent context will be replaced.

func ContextWithPrefix 

func ContextWithPrefix(ctx context.Context, prefix string) context.Context

ContextWithPrefix creates a context as extension of the parent context, with the provided prefix stored as a value. Any existing prefix on the parent context will be replaced.

func Data 

func Data(arg interface{}) interface{}

Data tags an item to be ignored by glog when logging but to pass it to any registered backends. An example would be: 

var req *http.Request
...
glog.Error("failed to complete process", glog.Data(req))

func Error 

func Error(args ...interface{})

Error logs to the ERROR, WARNING, and INFO logs. Arguments are handled in the manner of fmt.Print; a newline is appended if missing.

func ErrorIf 

func ErrorIf(err error, args ...interface{})

ErrorIf logs to the ERROR, WARNING, and INFO logs. Arguments are handled in the manner of fmt.Print; a newline is appended if missing.

func ErrorWithDepth 

func ErrorWithDepth(extraDepth int, args ...interface{})

ErrorWithDepth is equivalent to Error but with a specified extra depth (on the call stack). Arguments are handled in the manner of fmt.Print; a newline is appended if missing.

func Errorf 

func Errorf(format string, args ...interface{})

Errorf logs to the ERROR, WARNING, and INFO logs. Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.

func ErrorfIf 

func ErrorfIf(err error, format string, args ...interface{})

ErrorfIf logs to the ERROR, WARNING, and INFO logs. Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.

func ErrorfWithDepth 

func ErrorfWithDepth(extraDepth int, format string, args ...interface{})

ErrorfWithDepth is equivalent to Errorf but with a specified extra depth (on the call stack). Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.

func Errorln 

func Errorln(args ...interface{})

Errorln logs to the ERROR, WARNING, and INFO logs. Arguments are handled in the manner of fmt.Println; a newline is appended if missing.

func ErrorlnWithDepth 

func ErrorlnWithDepth(extraDepth int, args ...interface{})

ErrorlnWithDepth is equivalent to Errorln but with a specified extra depth (on the call stack). Arguments are handled in the manner of fmt.Println; a newline is appended if missing.

func Exit 

func Exit(args ...interface{})

Exit logs to the FATAL, ERROR, WARNING, and INFO logs, then calls os.Exit(1). Arguments are handled in the manner of fmt.Print; a newline is appended if missing.

func ExitWithDepth 

func ExitWithDepth(depth int, args ...interface{})

ExitWithDepth acts as Exit but uses depth to determine which call frame to log. ExitWithDepth(0, "msg") is the same as Exit("msg").

func Exitf 

func Exitf(format string, args ...interface{})

Exitf logs to the FATAL, ERROR, WARNING, and INFO logs, then calls os.Exit(1). Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.

func Exitln 

func Exitln(args ...interface{})

Exitln logs to the FATAL, ERROR, WARNING, and INFO logs, then calls os.Exit(1).

func Fatal 

func Fatal(args ...interface{})

Fatal logs to the FATAL, ERROR, WARNING, and INFO logs, including a stack trace of all running goroutines, then calls os.Exit(255). Arguments are handled in the manner of fmt.Print; a newline is appended if missing.

func FatalIf 

func FatalIf(err error, args ...interface{})

FatalIf logs to the FATAL, ERROR, WARNING, and INFO, including a stack trace of all running goroutines, then calls os.Exit(255). Arguments are handled in the manner of fmt.Print; a newline is appended if missing.

func FatalWithDepth 

func FatalWithDepth(extraDepth int, args ...interface{})

FatalWithDepth is equivalent to Fatal but with a specified extra depth (on the call stack). Arguments are handled in the manner of fmt.Print; a newline is appended if missing.

func Fatalf 

func Fatalf(format string, args ...interface{})

Fatalf logs to the FATAL, ERROR, WARNING, and INFO logs, including a stack trace of all running goroutines, then calls os.Exit(255). Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.

func FatalfWithDepth 

func FatalfWithDepth(extraDepth int, format string, args ...interface{})

FatalfWithDepth is equivalent to Fatalf but with a specified extra depth (on the call stack). Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.

func Fatalln 

func Fatalln(args ...interface{})

Fatalln logs to the FATAL, ERROR, WARNING, and INFO logs, including a stack trace of all running goroutines, then calls os.Exit(255). Arguments are handled in the manner of fmt.Println; a newline is appended if missing.

func FatallnWithDepth 

func FatallnWithDepth(extraDepth int, args ...interface{})

FatallnWithDepth is equivalent to Fatalln but with a specified extra depth (on the call stack). Arguments are handled in the manner of fmt.Println; a newline is appended if missing.

func Flush 

func Flush()

Flush flushes all pending log I/O.

func Info 

func Info(args ...interface{})

Info logs to the INFO log. Arguments are handled in the manner of fmt.Print; a newline is appended if missing.

func InfoWithDepth 

func InfoWithDepth(extraDepth int, args ...interface{})

InfoWithDepth is equivalent to Info but with a specified extra depth (on the call stack). Arguments are handled in the manner of fmt.Print; a newline is appended if missing.

func Infof 

func Infof(format string, args ...interface{})

Infof logs to the INFO log. Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.

func InfofWithDepth 

func InfofWithDepth(extraDepth int, format string, args ...interface{})

InfofWithDepth is equivalent to Infof but with a specified extra depth (on the call stack). Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.

func Infoln 

func Infoln(args ...interface{})

Infoln logs to the INFO log. Arguments are handled in the manner of fmt.Println; a newline is appended if missing.

func InfolnWithDepth 

func InfolnWithDepth(extraDepth int, args ...interface{})

InfolnWithDepth is equivalent to Infoln but with a specified extra depth (on the call stack). Arguments are handled in the manner of fmt.Println; a newline is appended if missing.

func RegisterBackend 

func RegisterBackend() <-chan Event

RegisterBackend returns a channel on which Event's will be passed when they are logged.

The caller is responsible for any necessary synchronization such that the call to this function "happens before" any events to be logged to this channel or other calls to RegisterBackend().

func SetOutput 

func SetOutput(w io.Writer)

SetOutput overrides the logging output writer.

If the provided writer is an *os.File, or otherwise has a 'Sync() error' method, it is called periodically (and by Flush) to commit pending data.

func Warning 

func Warning(args ...interface{})

Warning logs to the WARNING and INFO logs. Arguments are handled in the manner of fmt.Print; a newline is appended if missing.

func WarningIf 

func WarningIf(err error, args ...interface{})

WarningIf logs to the WARNING, and INFO logs. Arguments are handled in the manner of fmt.Print; a newline is appended if missing.

func WarningWithDepth 

func WarningWithDepth(extraDepth int, args ...interface{})

WarningWithDepth is equivalent to Warning but with a specified extra depth (on the call stack). Arguments are handled in the manner of fmt.Print; a newline is appended if missing.

func Warningf 

func Warningf(format string, args ...interface{})

Warningf logs to the WARNING and INFO logs. Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.

func WarningfIf 

func WarningfIf(err error, format string, args ...interface{})

WarningfIf logs to the WARNING, and INFO logs. Arguments are handled in the manner of fmt.Print; a newline is appended if missing.

func WarningfWithDepth 

func WarningfWithDepth(extraDepth int, format string, args ...interface{})

WarningfWithDepth is equivalent to Warningf but with a specified extra depth (on the call stack). Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.

func Warningln 

func Warningln(args ...interface{})

Warningln logs to the WARNING and INFO logs. Arguments are handled in the manner of fmt.Println; a newline is appended if missing.

func WarninglnWithDepth 

func WarninglnWithDepth(extraDepth int, args ...interface{})

WarninglnWithDepth is equivalent to Warningln but with a specified extra depth (on the call stack). Arguments are handled in the manner of fmt.Println; a newline is appended if missing.

Types

type ErrorArg 

type ErrorArg struct {
	Error error
}

ErrorArg captures information about an error passed as an argument. It is passed to backends as a data arg.

func (ErrorArg) RootCause 

func (xe ErrorArg) RootCause() error

RootCause returns the innermost error.

type Event 

type Event struct {
	Severity   string
	Message    []byte
	Data       []interface{}
	StackTrace []uintptr // inner to outer
}

An Event contains a logged event's severity (INFO, WARN, ERROR, FATAL), a format string (if Infof, Warnf, Errorf or Fatalf were used) and a slice of everything else passed to the log call.

func GetErrorEvent 

func GetErrorEvent(args ...interface{}) Event

GetErrorEvent returns an ERROR level Event of args

func NewEvent 

func NewEvent(s severity, message []byte, dataArgs []interface{}, extraDepth int) Event

NewEvent creates a glog.Event from the logged event's severity, format string (if Infof, Warnf, Errorf or Fatalf were called) and any other arguments passed to the log call. NewEvent separates out any items tagged by Data() and stores them in Event.Data.

type FormatStringArg 

type FormatStringArg struct {
	Format string
}

FormatStringArg is used to capture the raw format string passed to glog, which often contains an error message without identifying details that can be used to help group the message.

type Level 

type Level int32

Level specifies a level of verbosity for V logs. *Level implements flag.Value; the -v flag is of type Level and should be modified only through the flag.Value interface.

func (*Level) Get 

func (l *Level) Get() interface{}

Get is part of the flag.Value interface.

func (*Level) Set 

func (l *Level) Set(value string) error

Set is part of the flag.Value interface.

func (*Level) String 

func (l *Level) String() string

String is part of the flag.Value interface.

type Logger 

type Logger struct {
	// contains filtered or unexported fields
}

Logger provides logging functionality with additional data and prefixing.

func NewLogger 

func NewLogger() *Logger

NewLogger creates a Logger instance with no additional data.

func WithContext 

func WithContext(ctx context.Context) *Logger

WithContext creates a logger from a context.Context

func WithData 

func WithData(args ...interface{}) *Logger

WithData creates a Logger with a given set of backend data. All args provided will be wrapped with glog.Data prior to being sent.

func WithPrefix 

func WithPrefix(prefix string) *Logger

WithPrefix creates a Logger with a given prefix.

func (*Logger) AppendData 

func (l *Logger) AppendData(vars ...interface{}) *Logger

AppendData creates a Logger from an existing logger, appending the provided data to the data in the existing logger.

func (*Logger) Error 

func (l *Logger) Error(args ...interface{})

Error is equivalent to the global Error function, with the addition of prefix and data content from this Logger.

func (*Logger) ErrorIf 

func (l *Logger) ErrorIf(err error, args ...interface{})

ErrorIf is equivalent to the global ErrorIf function, with the addition of prefix and data content from this Logger.

func (*Logger) Errorf 

func (l *Logger) Errorf(format string, args ...interface{})

Errorf is equivalent to the global Errorf function, with the addition of prefix and data content from this Logger.

func (*Logger) ErrorfIf 

func (l *Logger) ErrorfIf(err error, format string, args ...interface{})

ErrorfIf is equivalent to the global ErrorfIf function, with the addition of prefix and data content from this Logger.

func (*Logger) Errorln 

func (l *Logger) Errorln(args ...interface{})

Errorln is equivalent to the global Errorln function, with the addition of prefix and data content from this Logger.

func (*Logger) Fatal 

func (l *Logger) Fatal(args ...interface{})

Fatal is equivalent to the global Fatal function, with the addition of prefix and data content from this Logger.

func (*Logger) FatalIf 

func (l *Logger) FatalIf(err error, args ...interface{})

FatalIf is equivalent to the global FatalIf function, with the addition of prefix and data content from this Logger.

func (*Logger) Fatalf 

func (l *Logger) Fatalf(format string, args ...interface{})

Fatalf is equivalent to the global Fatalf function, with the addition of prefix and data content from this Logger.

func (*Logger) Fatalln 

func (l *Logger) Fatalln(args ...interface{})

Fatalln is equivalent to the global Fatalln function, with the addition of prefix and data content from this Logger.

func (*Logger) GetErrorEvent 

func (l *Logger) GetErrorEvent(args ...interface{}) Event

GetErrorEvent is equivalent to the global GetErrorEvent function, with the addition of prefix and data content from this Logger.

func (*Logger) Info 

func (l *Logger) Info(args ...interface{})

Info is equivalent to the global Info function, with the addition of prefix and data content from this Logger.

func (*Logger) Infof 

func (l *Logger) Infof(format string, args ...interface{})

Infof is equivalent to the global Infof function, with the addition of prefix and data content from this Logger.

func (*Logger) Infoln 

func (l *Logger) Infoln(args ...interface{})

Infoln is equivalent to the global Infoln function, with the addition of prefix and data content from this Logger.

func (*Logger) Warning 

func (l *Logger) Warning(args ...interface{})

Warning is equivalent to the global Warning function, with the addition of prefix and data content from this Logger.

func (*Logger) Warningf 

func (l *Logger) Warningf(format string, args ...interface{})

Warningf is equivalent to the global Warningf function, with the addition of prefix and data content from this Logger.

func (*Logger) Warningln 

func (l *Logger) Warningln(args ...interface{})

Warningln is equivalent to the global Warningln function, with the addition of prefix and data content from this Logger.

func (*Logger) WithData 

func (l *Logger) WithData(vars ...interface{}) *Logger

WithData creates a Logger from an existing logger, using the specifed data. Any existing data on the input Logger will be replaced.

func (*Logger) WithPrefix 

func (l *Logger) WithPrefix(prefix string) *Logger

WithPrefix creates a Logger from an existing logger with a specified prefix. Any prefix on the input Logger will be replaced.

type OutputStats 

type OutputStats struct {
	// contains filtered or unexported fields
}

OutputStats tracks the number of output lines and bytes written.

func (*OutputStats) Bytes 

func (s *OutputStats) Bytes() int64

Bytes returns the number of bytes written.

func (*OutputStats) Lines 

func (s *OutputStats) Lines() int64

Lines returns the number of lines written.

type Verbose 

type Verbose bool

Verbose is a boolean type that implements Infof (like Printf) etc. See the documentation of V for more information.

func V 

func V(level Level) Verbose

V reports whether verbosity at the call site is at least the requested level. The returned value is a boolean of type Verbose, which implements Info, Infoln and Infof. These methods will write to the Info log if called. Thus, one may write either 

if glog.V(2) { glog.Info("log this") }

or 

glog.V(2).Info("log this")

The second form is shorter but the first is cheaper if logging is off because it does not evaluate its arguments.

Whether an individual call to V generates a log record depends on the setting of the -v and --vmodule flags; both are off by default. If the level in the call to V is at least the value of -v, or of -vmodule for the source file containing the call, the V call will log.

func (Verbose) Info 

func (v Verbose) Info(args ...interface{})

Info is equivalent to the global Info function, guarded by the value of v. See the documentation of V for usage.

func (Verbose) InfoWithDepth 

func (v Verbose) InfoWithDepth(extraDepth int, args ...interface{})

InfoWithDepth is equivalent to Info but with a specified extra depth (on the call stack). See the documentation of V for usage.

func (Verbose) Infof 

func (v Verbose) Infof(format string, args ...interface{})

Infof is equivalent to the global Infof function, guarded by the value of v. See the documentation of V for usage.

func (Verbose) InfofWithDepth 

func (v Verbose) InfofWithDepth(extraDepth int, format string, args ...interface{})

InfofWithDepth is equivalent to Infof but with a specified extra depth (on the call stack). See the documentation of V for usage.

func (Verbose) Infoln 

func (v Verbose) Infoln(args ...interface{})

Infoln is equivalent to the global Infoln function, guarded by the value of v. See the documentation of V for usage.

func (Verbose) InfolnWithDepth 

func (v Verbose) InfolnWithDepth(extraDepth int, args ...interface{})

InfolnWithDepth is equivalent to Infoln but with a specified extra depth (on the call stack). See the documentation of V for usage.

Source Files

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