glog

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Published: Apr 10, 2023 License: Apache-2.0, MIT Imports: 18 Imported by: 0

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
	https://github.com/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.

-logtostderr=false
	Logs are written to standard error instead of to files.
-alsologtostderr=false
	Logs are written to standard error as well as to files.
-stderrthreshold=ERROR
	Log events at or above this severity are logged to standard
	error as well as to files.

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

View Source
const (
	SmoduleTransport = iota
	SmoduleAIS
	SmoduleMemsys
	SmoduleCluster
	SmoduleFS
	SmoduleReb
	SmoduleEC
	SmoduleStats
	SmoduleIOS
	SmoduleXs
	SmoduleBackend
	SmoduleSpace
)

NOTE: for module names mapped to these constants, see cmn/debug/debug_on.go

Variables

View Source
var FileHeaderCB func() string
View Source
var MaxSize uint64 = 1024 * 1024 * 1800

MaxSize is the maximum size of a log file in bytes.

View Source
var (

	// Stats tracks the number of lines of output and number of bytes
	// per severity level. Values must be read with atomic.LoadInt64.
	Stats struct {
		Info, Warning, Error OutputStats
	}
)

Functions

func CopyStandardLogTo

func CopyStandardLogTo(name string)

CopyStandardLogTo arranges for messages written to the Go "log" package's default logs to also appear in the Google logs for the named and lower severities. Subsequent changes to the standard log's default output location or format may break this behavior.

Valid names are "INFO", "WARNING", "ERROR", and "FATAL". If the name is not recognized, CopyStandardLogTo panics.

func ErrLogName

func ErrLogName() string

func Error

func Error(args ...any)

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 ErrorDepth

func ErrorDepth(depth int, args ...any)

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

func Errorf

func Errorf(format string, args ...any)

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 Errorln

func Errorln(args ...any)

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 Flush

func Flush()

Flush flushes all pending log I/O.

func Info

func Info(args ...any)

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

func InfoDepth

func InfoDepth(depth int, args ...any)

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

func InfoLogName

func InfoLogName() string

func Infof

func Infof(format string, args ...any)

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

func Infoln

func Infoln(args ...any)

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

func SetLogDir

func SetLogDir(dir string)

func SetV

func SetV(smodule uint8, level Level)

SetV sets verbosity level for static module.

NOTE: SetV should be set in the init. Bugs are expected when SetV is called in-flight since no locks are taken.

func WarnLogName

func WarnLogName() string

func Warning

func Warning(args ...any)

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

func WarningDepth

func WarningDepth(depth int, args ...any)

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

func Warningf

func Warningf(format string, args ...any)

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

func Warningln

func Warningln(args ...any)

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

Types

type Level

type Level int32

Level is exported because it appears in the arguments to V and is the type of the v flag, which can be set programmatically. It's a distinct type because we want to discriminate it from logType. Variables of type level are only changed under logging.mu. The -v flag is read only with atomic ops, so the state of the logging module is consistent. Level is treated as a sync/atomic 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() any

Get is part of the flag.Value interface.

func (*Level) Set

func (*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 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 FastV

func FastV(level Level, smodule uint8) Verbose

FastV similarly to V checks if verbosity level is enough to print the log message. It is a fast inline function that doesn't take vmodule into account. As such, it is intended to be used for the datapath, primarily.

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 ...any)

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

func (Verbose) Infof

func (v Verbose) Infof(format string, args ...any)

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

func (Verbose) Infoln

func (v Verbose) Infoln(args ...any)

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

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