glog

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 Go to latest Published: Jul 9, 2024 License: Apache-2.0 Imports: 22 Imported by: 100,001

README

glog

PkgGoDev

Leveled execution logs for Go.

This is an efficient pure Go implementation of leveled logs in the manner of the open source C++ package 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 the functions Info, Warning, Error, Fatal, plus formatting variants such as Infof. It also provides V-style loggingcontrolled 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 that have a name matched by regex: 

(Info|Warning|Error|Fatal)(Context)?(Depth)?(f)?

If Context is present, function takes context.Context argument. The context is used to pass through the Trace Context to log sinks that can make use of it. It is recommended to use the context variant of the functions over the non-context variants if a context is available to make sure the Trace Contexts are present in logs.

If Depth is present, this function calls log from a different depth in the call stack. This enables a callee to emit logs that use the callsite information of its caller or any other callers in the stack. When depth == 0, the original callee's line information is emitted. When depth > 0, depth frames are skipped in the call stack and the final frame is treated like the original callee to Info.

If 'f' is present, function formats according to a format specifier.

This package 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.
-log_dir=""
	Log files will be written to this directory instead of the
	default temporary directory.

Other flags provide aids to debugging. 

-log_backtrace_at=""
	A comma-separated list of file and line numbers 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 one of these statements. (Unlike with -vmodule, the ".go"
	must bepresent.)
-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 with "gopher",
	and
		-vmodule=/path/to/glog/glog_test=1
	sets the V level to 1 in the Go file /path/to/glog/glog_test.go.
	If a glob pattern contains a slash, it is matched against the full path,
	and the file name. Otherwise, the pattern is
	matched only against the file's basename.  When both -vmodule and -v
	are specified, the -vmodule values take precedence for the specified
	modules.

Index

Constants

This section is empty.

Variables

View Source 
var ErrNoLog = errors.New("log file not yet created")

ErrNoLog is the error we return if no log file has yet been created for the specified log type.

View Source 
var MaxSize uint64 = 1024 * 1024 * 1800

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

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 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 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 ErrorContext added in v1.2.0 

func ErrorContext(ctx context.Context, args ...any)

ErrorContext is like Error, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func ErrorContextDepth added in v1.2.0 

func ErrorContextDepth(ctx context.Context, depth int, args ...any)

ErrorContextDepth is like ErrorDepth, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func ErrorContextDepthf added in v1.2.0 

func ErrorContextDepthf(ctx context.Context, depth int, format string, args ...any)

ErrorContextDepthf is like ErrorDepthf, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func ErrorContextf added in v1.2.0 

func ErrorContextf(ctx context.Context, format string, args ...any)

ErrorContextf is like Errorf, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

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 ErrorDepthf added in v1.1.0 

func ErrorDepthf(depth int, format string, args ...any)

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

func Exit(args ...any)

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 ExitContext added in v1.2.0 

func ExitContext(ctx context.Context, args ...any)

ExitContext is like Exit, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func ExitContextDepth added in v1.2.0 

func ExitContextDepth(ctx context.Context, depth int, args ...any)

ExitContextDepth is like ExitDepth, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func ExitContextDepthf added in v1.2.0 

func ExitContextDepthf(ctx context.Context, depth int, format string, args ...any)

ExitContextDepthf is like ExitDepthf, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func ExitContextf added in v1.2.0 

func ExitContextf(ctx context.Context, format string, args ...any)

ExitContextf is like Exitf, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func ExitDepth 

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

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

func ExitDepthf added in v1.1.0 

func ExitDepthf(depth int, format string, args ...any)

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

func Exitf 

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

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 ...any)

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

func Fatal 

func Fatal(args ...any)

Fatal logs to the FATAL, ERROR, WARNING, and INFO logs, including a stack trace of all running goroutines, then calls os.Exit(2). Arguments are handled in the manner of fmt.Print; a newline is appended if missing.

func FatalContext added in v1.2.0 

func FatalContext(ctx context.Context, args ...any)

FatalContext is like Fatal, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func FatalContextDepth added in v1.2.0 

func FatalContextDepth(ctx context.Context, depth int, args ...any)

FatalContextDepth is like FatalDepth, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func FatalContextDepthf added in v1.2.0 

func FatalContextDepthf(ctx context.Context, depth int, format string, args ...any)

FatalContextDepthf is like FatalDepthf, but with an extra context.Context parameter.

func FatalContextf added in v1.2.0 

func FatalContextf(ctx context.Context, format string, args ...any)

FatalContextf is like Fatalf, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func FatalDepth 

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

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

func FatalDepthf added in v1.1.0 

func FatalDepthf(depth int, format string, args ...any)

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

func Fatalf 

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

Fatalf logs to the FATAL, ERROR, WARNING, and INFO logs, including a stack trace of all running goroutines, then calls os.Exit(2). Arguments are handled in the manner of fmt.Printf; a newline is appended if missing.

func Fatalln 

func Fatalln(args ...any)

Fatalln logs to the FATAL, ERROR, WARNING, and INFO logs, including a stack trace of all running goroutines, then calls os.Exit(2). 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 InfoContext added in v1.2.0 

func InfoContext(ctx context.Context, args ...any)

InfoContext is like Info, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func InfoContextDepth added in v1.2.0 

func InfoContextDepth(ctx context.Context, depth int, args ...any)

InfoContextDepth is like InfoDepth, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func InfoContextDepthf added in v1.2.0 

func InfoContextDepthf(ctx context.Context, depth int, format string, args ...any)

InfoContextDepthf is like InfoDepthf, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func InfoContextf added in v1.2.0 

func InfoContextf(ctx context.Context, format string, args ...any)

InfoContextf is like Infof, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func InfoDepth 

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

InfoDepth calls Info from a different depth in the call stack. This enables a callee to emit logs that use the callsite information of its caller or any other callers in the stack. When depth == 0, the original callee's line information is emitted. When depth > 0, depth frames are skipped in the call stack and the final frame is treated like the original callee to Info.

func InfoDepthf added in v1.1.0 

func InfoDepthf(depth int, format string, args ...any)

InfoDepthf acts as InfoDepth but with format 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 Names added in v1.1.0 

func Names(s string) ([]string, error)

Names returns the names of the log files holding the FATAL, ERROR, WARNING, or INFO logs. Returns ErrNoLog if the log for the given level doesn't exist (e.g. because no messages of that level have been written). This may return multiple names if the log type requested has rolled over.

func NewStandardLogger added in v1.1.0 

func NewStandardLogger(name string) *stdLog.Logger

NewStandardLogger returns a Logger that writes to the Google logs for the named and lower severities.

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

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 WarningContext added in v1.2.0 

func WarningContext(ctx context.Context, args ...any)

WarningContext is like Warning, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func WarningContextDepth added in v1.2.0 

func WarningContextDepth(ctx context.Context, depth int, args ...any)

WarningContextDepth is like WarningDepth, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func WarningContextDepthf added in v1.2.0 

func WarningContextDepthf(ctx context.Context, depth int, format string, args ...any)

WarningContextDepthf is like WarningDepthf, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

func WarningContextf added in v1.2.0 

func WarningContextf(ctx context.Context, format string, args ...any)

WarningContextf is like Warningf, but with an extra context.Context parameter. The context is used to pass the Trace Context to log sinks.

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 WarningDepthf added in v1.1.0 

func WarningDepthf(depth int, format string, args ...any)

WarningDepthf acts as Warningf but uses depth to determine which call frame to log. WarningDepthf(0, "msg") is the same as Warningf("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 specifies a level of verbosity for V logs. 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 (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 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 most the value of -v, or of -vmodule for the source file containing the call, the V call will log.

func VDepth added in v1.1.0 

func VDepth(depth int, level Level) Verbose

VDepth acts as V but uses depth to determine which call frame to check vmodule for. VDepth(0, level) is the same as V(level).

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) InfoContext added in v1.2.0 

func (v Verbose) InfoContext(ctx context.Context, args ...any)

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

func (Verbose) InfoContextDepth added in v1.2.0 

func (v Verbose) InfoContextDepth(ctx context.Context, depth int, args ...any)

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

func (Verbose) InfoContextDepthf added in v1.2.0 

func (v Verbose) InfoContextDepthf(ctx context.Context, depth int, format string, args ...any)

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

func (Verbose) InfoContextf added in v1.2.0 

func (v Verbose) InfoContextf(ctx context.Context, format string, args ...any)

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

func (Verbose) InfoDepth added in v1.1.0 

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

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

func (Verbose) InfoDepthf added in v1.1.0 

func (v Verbose) InfoDepthf(depth int, format string, args ...any)

InfoDepthf is equivalent to the global InfoDepthf 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.

Source Files

View all Source files

Directories

Path Synopsis
internal
logsink
stackdump
Package stackdump provides wrappers for runtime.Stack and runtime.Callers with uniform support for skipping caller frames.
 Package stackdump provides wrappers for runtime.Stack and runtime.Callers with uniform support for skipping caller frames.

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