capnslog

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 Go to latest Published: Feb 25, 2021 License: MIT Imports: 20 Imported by: 0

README

capnslog, the CoreOS logging package

There are far too many logging packages out there, with varying degrees of licenses, far too many features (colorization, all sorts of log frameworks) or are just a pain to use (lack of Fatalln()?). capnslog provides a simple but consistent logging interface suitable for all kinds of projects.

Design Principles
package main is the place where logging gets turned on and routed

A library should not touch log options, only generate log entries. Libraries are silent until main lets them speak.

All log options are runtime-configurable.

Still the job of main to expose these configurations. main may delegate this to, say, a configuration webhook, but does so explicitly.

There is one log object per package. It is registered under its repository and package name.

main activates logging for its repository and any dependency repositories it would also like to have output in its logstream. main also dictates at which level each subpackage logs.

There is one output stream, and it is an io.Writer composed with a formatter.

Splitting streams is probably not the job of your program, but rather, your log aggregation framework. If you must split output streams, again, main configures this and you can write a very simple two-output struct that satisfies io.Writer.

Fancy colorful formatting and JSON output are beyond the scope of a basic logging framework -- they're application/log-collector dependent. These are, at best, provided as options, but more likely, provided by your application.

Log objects are an interface

An object knows best how to print itself. Log objects can collect more interesting metadata if they wish, however, because text isn't going away anytime soon, they must all be marshalable to text. The simplest log object is a string, which returns itself. If you wish to do more fancy tricks for printing your log objects, see also JSON output -- introspect and write a formatter which can handle your advanced log interface. Making strings is the only thing guaranteed.

Log levels have specific meanings:
  • Critical: Unrecoverable. Must fail.
  • Error: Data has been lost, a request has failed for a bad reason, or a required resource has been lost
  • Warning: (Hopefully) Temporary conditions that may cause errors, but may work fine. A replica disappearing (that may reconnect) is a warning.
  • Notice: Normal, but important (uncommon) log information.
  • Info: Normal, working log information, everything is fine, but helpful notices for auditing or common operations.
  • Debug: Everything is still fine, but even common operations may be logged, and less helpful but more quantity of notices.
  • Trace: Anything goes, from logging every function call as part of a common operation, to tracing execution of a query.

Documentation

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func Enabled 

func Enabled() bool

Enabled checks whether the local systemd journal is available for logging.

func GlogHeader 

func GlogHeader(level LogLevel, depth int) []byte

func Print 

func Print(priority Priority, format string, a ...interface{}) error

Print prints a message to the local systemd journal using Send().

func Send 

func Send(message string, priority Priority, vars map[string]string) error

Send a message to the local systemd journal. vars is a map of journald fields to values. Fields must be composed of uppercase letters, numbers, and underscores, but must not start with an underscore. Within these restrictions, any arbitrary field name may be used. Some names have special significance: see the journalctl documentation (http://www.freedesktop.org/software/systemd/man/systemd.journal-fields.html) for more details. vars may be nil.

func SetFormatter 

func SetFormatter(f Formatter)

SetFormatter sets the formatting function for all logs.

func SetGlobalLogLevel 

func SetGlobalLogLevel(l LogLevel)

SetGlobalLogLevel sets the log level for all packages in all repositories registered with capnslog.

Types

type Formatter 

type Formatter interface {
	Format(pkg string, level LogLevel, depth int, entries ...interface{})
	Flush()
}

func NewDefaultFormatter 

func NewDefaultFormatter(out io.Writer) Formatter

func NewDefaultSyslogFormatter 

func NewDefaultSyslogFormatter(tag string) (Formatter, error)

func NewJournaldFormatter 

func NewJournaldFormatter() (Formatter, error)

func NewLogFormatter 

func NewLogFormatter(w io.Writer, prefix string, flag int) Formatter

NewLogFormatter is a helper to produce a new LogFormatter struct. It uses the golang log package to actually do the logging work so that logs look similar.

func NewNilFormatter 

func NewNilFormatter() Formatter

NewNilFormatter is a helper to produce a new LogFormatter struct. It logs no messages so that you can cause part of your logging to be silent.

func NewPrettyFormatter 

func NewPrettyFormatter(w io.Writer, debug bool) Formatter

func NewStringFormatter 

func NewStringFormatter(w io.Writer) Formatter

func NewSyslogFormatter 

func NewSyslogFormatter(w *syslog.Writer) Formatter

type GlogFormatter 

type GlogFormatter struct {
	StringFormatter
}

func NewGlogFormatter 

func NewGlogFormatter(w io.Writer) *GlogFormatter

func (GlogFormatter) Format 

func (g GlogFormatter) Format(pkg string, level LogLevel, depth int, entries ...interface{})

type LogFormatter 

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

LogFormatter emulates the form of the traditional built-in logger.

func (*LogFormatter) Flush 

func (lf *LogFormatter) Flush()

Flush is included so that the interface is complete, but is a no-op.

func (*LogFormatter) Format 

func (lf *LogFormatter) Format(pkg string, _ LogLevel, _ int, entries ...interface{})

Format builds a log message for the LogFormatter. The LogLevel is ignored.

type LogLevel 

type LogLevel int8

LogLevel is the set of all log levels. 

const (
	// CRITICAL is the lowest log level; only errors which will end the program will be propagated.
	CRITICAL LogLevel = iota - 1
	// ERROR is for errors that are not fatal but lead to troubling behavior.
	ERROR
	// WARNING is for errors which are not fatal and not errors, but are unusual. Often sourced from misconfigurations.
	WARNING
	// NOTICE is for normal but significant conditions.
	NOTICE
	// INFO is a log level for common, everyday log updates.
	INFO
	// DEBUG is the default hidden level for more verbose updates about internal processes.
	DEBUG
	// TRACE is for (potentially) call by call tracing of programs.
	TRACE
)

func ParseLevel 

func ParseLevel(s string) (LogLevel, error)

ParseLevel translates some potential loglevel strings into their corresponding levels.

func (LogLevel) Char 

func (l LogLevel) Char() string

Char returns a single-character representation of the log level.

func (*LogLevel) Set 

func (l *LogLevel) Set(s string) error

Update using the given string value. Fulfills the flag.Value interface.

func (LogLevel) String 

func (l LogLevel) String() string

String returns a multi-character representation of the log level.

func (*LogLevel) Type 

func (l *LogLevel) Type() string

Returns an empty string, only here to fulfill the pflag.Value interface.

type NilFormatter 

type NilFormatter struct {
}

NilFormatter is a no-op log formatter that does nothing.

func (*NilFormatter) Flush 

func (_ *NilFormatter) Flush()

Flush is included so that the interface is complete, but is a no-op.

func (*NilFormatter) Format 

func (_ *NilFormatter) Format(_ string, _ LogLevel, _ int, _ ...interface{})

Format does nothing.

type PackageLogger 

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

func NewPackageLogger 

func NewPackageLogger(repo string, pkg string) (p *PackageLogger)

NewPackageLogger creates a package logger object. This should be defined as a global var in your package, referencing your repo.

func (*PackageLogger) Debug 

func (p *PackageLogger) Debug(entries ...interface{})

func (*PackageLogger) Debugf 

func (p *PackageLogger) Debugf(format string, args ...interface{})

func (*PackageLogger) Error 

func (p *PackageLogger) Error(entries ...interface{})

func (*PackageLogger) Errorf 

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

func (*PackageLogger) Fatal 

func (p *PackageLogger) Fatal(args ...interface{})

func (*PackageLogger) Fatalf 

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

func (*PackageLogger) Fatalln 

func (p *PackageLogger) Fatalln(args ...interface{})

func (*PackageLogger) Flush 

func (p *PackageLogger) Flush()

func (*PackageLogger) Info 

func (p *PackageLogger) Info(entries ...interface{})

func (*PackageLogger) Infof 

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

func (*PackageLogger) LevelAt 

func (p *PackageLogger) LevelAt(l LogLevel) bool

LevelAt checks if the given log level will be outputted under current setting.

func (*PackageLogger) Log 

func (p *PackageLogger) Log(l LogLevel, args ...interface{})

Log a message at any level between ERROR and TRACE

func (*PackageLogger) Logf 

func (p *PackageLogger) Logf(l LogLevel, format string, args ...interface{})

Log a formatted string at any level between ERROR and TRACE

func (*PackageLogger) Notice 

func (p *PackageLogger) Notice(entries ...interface{})

func (*PackageLogger) Noticef 

func (p *PackageLogger) Noticef(format string, args ...interface{})

func (*PackageLogger) Panic 

func (p *PackageLogger) Panic(args ...interface{})

func (*PackageLogger) Panicf 

func (p *PackageLogger) Panicf(format string, args ...interface{})

func (*PackageLogger) Panicln 

func (p *PackageLogger) Panicln(args ...interface{})

func (*PackageLogger) Print 

func (p *PackageLogger) Print(args ...interface{})

func (*PackageLogger) Printf 

func (p *PackageLogger) Printf(format string, args ...interface{})

func (*PackageLogger) Println 

func (p *PackageLogger) Println(args ...interface{})

func (*PackageLogger) SetLevel 

func (p *PackageLogger) SetLevel(l LogLevel)

SetLevel allows users to change the current logging level.

func (*PackageLogger) Trace 

func (p *PackageLogger) Trace(entries ...interface{})

func (*PackageLogger) Tracef 

func (p *PackageLogger) Tracef(format string, args ...interface{})

func (*PackageLogger) Warning 

func (p *PackageLogger) Warning(entries ...interface{})

func (*PackageLogger) Warningf 

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

type PrettyFormatter 

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

func (*PrettyFormatter) Flush 

func (c *PrettyFormatter) Flush()

func (*PrettyFormatter) Format 

func (c *PrettyFormatter) Format(pkg string, l LogLevel, depth int, entries ...interface{})

type Priority 

type Priority int

Priority of a journal message 

const (
	PriEmerg Priority = iota
	PriAlert
	PriCrit
	PriErr
	PriWarning
	PriNotice
	PriInfo
	PriDebug
)

type RepoLogger 

type RepoLogger map[string]*PackageLogger

func GetRepoLogger 

func GetRepoLogger(repo string) (RepoLogger, error)

GetRepoLogger may return the handle to the repository's set of packages' loggers.

func MustRepoLogger 

func MustRepoLogger(repo string) RepoLogger

MustRepoLogger returns the handle to the repository's packages' loggers.

func (RepoLogger) ParseLogLevelConfig 

func (r RepoLogger) ParseLogLevelConfig(conf string) (map[string]LogLevel, error)

ParseLogLevelConfig parses a comma-separated string of "package=loglevel", in order, and returns a map of the results, for use in SetLogLevel.

func (RepoLogger) SetLogLevel 

func (r RepoLogger) SetLogLevel(m map[string]LogLevel)

SetLogLevel takes a map of package names within a repository to their desired loglevel, and sets the levels appropriately. Unknown packages are ignored. "*" is a special package name that corresponds to all packages, and will be processed first.

func (RepoLogger) SetRepoLogLevel 

func (r RepoLogger) SetRepoLogLevel(l LogLevel)

SetRepoLogLevel sets the log level for all packages in the repository.

type StringFormatter 

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

func (*StringFormatter) Flush 

func (s *StringFormatter) Flush()

func (*StringFormatter) Format 

func (s *StringFormatter) Format(pkg string, l LogLevel, i int, entries ...interface{})

Source Files

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