vlogger

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 Go to latest Published: Jan 13, 2021 License: Apache-2.0 Imports: 4 Imported by: 0

README

vlogger

import "github.com/f5devcentral/testipam/pkg/vlogger"

Package vlogger implements an interface around basic logging features so that end-user and library writers can code to the interface without worrying about the specific type of logging package that is being used.

LIBRARY USAGE

To support logging in a user-defined library, you need to include the vlogger package. Once that is included, you can simply call one of the following package-level functions:

func Debug(msg string)
func Debugf(format string, params ... interface{})
func Info(msg string)
func Infof(format string, params ... interface{})
func Warning(msg string)
func Warningf(format string, params ... interface{})
func Error(msg string)
func Errorf(format string, params ... interface{})
func Critical(msg string)
func Criticalf(format string, params ... interface{})
func Fatal(msg string)
func Fatalf(format string, params ... interface{})
func Panic(msg string)
func Panicf(format string, params ... interface{})
APPLICATION USAGE

Logging in the main application is similar to logging in a library. However, additional steps must be taken to setup and breakdown the vlogger.

When creating an application, you should specify the concrete vlogger that you would like to use in your main module's init function. This will guarantee that the vlogger will be available for any library that supports vlogger (otherwise logging will default to the console).

The following types of loggers are currently provided as subpackages:

func NewConsoleLogger() Logger
func NewSyslogLogger(facility syslog.Priority, progname string) Logger
func NewSeelogLogger(filename string) Logger
func NewLogrusLogger() Logger

The first two use standard GO packages to implement logging. The last two uses more sophisticated third-party library that supports features such as multiple logging streams and various levels of filtering. Logging using these last two packages can be directed to any combination of outputs including syslog. Users can also provide their own implementations by adhering to the vlogger interface.

Some logging subpackages have an extended version of the New function that provides additional customization of that particular logger. These functions end with an 'Ext' suffix (for instance, NewConsoleLoggerExt).

Logger types need to be registered for use by the vlogger package-level functions using the following call:

func RegisterLogger(minLogLevel, maxLogLevel, Logger)

The RegisterLogger function allows you to use different loggers for different log levels (for instance, sending critical messages to a blocking logger while sending all other messages to a non-blocking version).

For proper cleanup, the main routine should have a defer statement that calls the vlogger Close() function:

func Close()
LOG LEVELS

To control the global logging level, several package level functions are provided:

SetLogLevel(level LogLevel)
GetLogLevel() LogLevel

The following log levels are currently defined (do not make an assumption of the values assigned to these constants):

LL_DEBUG
LL_INFO
LL_WARNING
LL_ERROR
LL_CRITICAL

Two related defines can also be used (mainly as a convenience for logger registration):

LL_MIN_LEVEL
LL_MAX_LEVEL

Note that certain concrete packages will have their own fine-grained filtering for logging. However, the package-level controls will supercede these finer controls.

COMPATIBILITY ISSUES

Log levels do not always map 1-to-1 with the underlying 3rd-party logging library. The issues mainly involve the LL_CRITICAL level. Packages that do not provide this level will be mapped to LL_ERROR.

EXAMPLE

The following is a simple example of an application that sends several log statements to the console:

    package main

    import (
      log  "github.com/f5devcentral/testipam/pkg/vlogger"
      "github.com/f5devcentral/testipam/pkg/vlogger/console"

    func init() {
      // Log all messages to the user's console
      log.RegisterLogger(log.LL_MIN_LEVEL, log.LL_MAX_LEVEL, console.NewConsoleLogger())
      // only report errors at the LL_INFO level and above
      log.SetLogLevel(log.LL_INFO)
    }

    func main() {
      defer log.Close()

      log.Debug("This debug message won't print");
      log.Info("This is an info message")
      log.Warning("This is a warning message")
      log.Errorf("This is an error message with %v", "formatting")
      log.Criticalf("This is a critical message %v formatting", "with")
      log.Fatal("This is a fatal message")
      log.Info("This will never print due to log.Fatal() causing the application to exit")
    }
MODULES

log.go:

This module provides the generic interface that end-user libraries and apps should program to.

Usage

func RegisterLogger
func RegisterLogger(minLogLevel, maxLogLevel LogLevel, log Logger)

RegisterLogger must be called to map a concrete logger object with each log level.

func Close
func Close()

Close informs the configured loggers that they are being closed and should cleanup (for instance, flushing any queued log messages)

func Panic
func Panic(msg string)

Panic sends a CRITICAL message to the logger object and then calls panic. NOTE: This call should not be made in packages that are meant to serve as libraries for other developers.

func Panicf
func Panicf(format string, params ...interface{})

Panicf sends a formatted CRITICAL message to the logger object and then calls panic. NOTE: This call should not be made in packages that are meant to serve as libraries for other developers.

func Fatal
func Fatal(msg string)

Fatal sends a CRITICAL message to the logger object and then exits. NOTE: This call should not be made in packages that are meant to serve as libraries for other developers.

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

Fatalf sends a formatted CRITICAL message to the logger object and then exits. NOTE: This call should not be made in packages that are meant to serve as libraries for other developers.

func Critical
func Critical(msg string)

Critical sends a message to the logger object to record critical level statements (these indicate conditions that should never occur and might cause a failure/crash of the executing program or unexpected outcome from the requested action).

func Criticalf
func Criticalf(format string, params ...interface{})

Criticalf formats a message before sending it to the logger object to record critical level statements (these indicate conditions that should never occur and might cause a failure/crash of the executing program or unexpected outcome from the requested action).

func Error
func Error(msg string)

Error sends a message to the logger object to record error level statements (these indicate conditions that should not occur and may indicate a failure in performing the requested action).

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

Errorf formats a message before sending it to the logger object to record error level statements (these indicate conditions that should not occur and may indicate a failure in performing the requested action).

func Warning
func Warning(msg string)

Warning sends a message to the logger object to record warning level statements (these indication conditions that are unexpected or may cause issues but are not normally going to affect the program execution).

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

Warningf formats a message before sending it to the logger object to record warning level statements (these indication conditions that are unexpected or may cause issues but are not normally going to affect the program execution).

func Info
func Info(msg string)

Info sends a message to the logger object to record informational level statements (these should be statements that can normally be logged without causing performance issues).

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

Infof formats a message before sending it to the logger object to record informational level statements (there should be statements that can normally be logged without causing performance issues).

func Debug
func Debug(msg string)

Debug sends a message to the logger object to record debug/trace level statements

func Debugf
func Debugf(format string, params ...interface{})

Debugf formats a message before sending it to the logger object to record debug/trace level statements

func SetLogLevel
func SetLogLevel(level LogLevel)

SetLogLevel sets the current package-level filtering

func GetLogLevel
func GetLogLevel() LogLevel

GetLogLevel returns the current package-level filtering

type LogLevel
type LogLevel int

LogLevel is used for global (package-level) filtering of log messages based on their priority (this filtering is applied before all other filtering which might be provided by the concrete logger).

const (
	// Must be in sequential ascending order based on priority
	// (higher priorities have higher numeric values)
	LL_DEBUG LogLevel = iota
	LL_INFO
	LL_WARNING
	LL_ERROR
	LL_CRITICAL
	LL_LOGLEVEL_SIZE
	LL_MIN_LEVEL = LL_DEBUG
	LL_MAX_LEVEL = LL_LOGLEVEL_SIZE - 1
)
type Logger
type Logger interface {
	Debug(string)
	Debugf(string, ...interface{})
	Info(string)
	Infof(string, ...interface{})
	Warning(string)
	Warningf(string, ...interface{})
	Error(string)
	Errorf(string, ...interface{})
	Critical(string)
	Criticalf(string, ...interface{})
	GetLogLevel() syslog.Priority
	SetLogLevel(syslog.Priority)
	Close()
}

Generic interface that all concrete loggers must implement. Using this interface directly isolates user code from a particular logger implementation.

Documentation

Overview

Package vlogger implements an interface around basic logging features so that end-user and library writers can code to the interface without worrying about the specific type of logging package that is being used.

LIBRARY USAGE

To support logging in a user-defined library, you need to include the vlogger package. Once that is included, you can simply call one of the following package-level functions: 

func Debug(msg string)
func Debugf(format string, params ... interface{})
func Info(msg string)
func Infof(format string, params ... interface{})
func Warning(msg string)
func Warningf(format string, params ... interface{})
func Error(msg string)
func Errorf(format string, params ... interface{})
func Critical(msg string)
func Criticalf(format string, params ... interface{})
func Fatal(msg string)
func Fatalf(format string, params ... interface{})
func Panic(msg string)
func Panicf(format string, params ... interface{})

APPLICATION USAGE

Logging in the main application is similar to logging in a library. However, additional steps must be taken to setup and breakdown the vlogger.

When creating an application, you should specify the concrete vlogger that you would like to use in your main module's init function. This will guarantee that the vlogger will be available for any library that supports vlogger (otherwise logging will default to the console).

The following types of loggers are currently provided as subpackages: 

func NewConsoleLogger() Logger
func NewSyslogLogger(facility syslog.Priority, progname string) Logger
func NewSeelogLogger(filename string) Logger
func NewLogrusLogger() Logger

The first two use standard GO packages to implement logging. The last two uses more sophisticated third-party library that supports features such as multiple logging streams and various levels of filtering. Logging using these last two packages can be directed to any combination of outputs including syslog. Users can provide their own implementations by adhering to the vlogger interface.

Some logging subpackages have an extended version of the New function that provides additional customization of that particular logger. These functions end with an 'Ext' suffix (for instance, NewConsoleLoggerExt).

Logger types need to be registered for use by the vlogger package-level functions using the following call: 

func RegisterLogger(minLogLevel, maxLogLevel, Logger)

The RegisterLogger function allows you to use different loggers for different log levels (for instance, sending critical messages to a blocking logger while sending all other messages to a non-blocking version).

For proper cleanup, the main routine should have a defer statement that calls the vlogger Close() function: 

func Close()

LOG LEVELS

To control the global logging level, several package level functions are provided: 

SetLogLevel(level LogLevel)
GetLogLevel() LogLevel

The following log levels are currently defined (do not make an assumption of the values assigned to these constants): 

LL_DEBUG
LL_INFO
LL_WARNING
LL_ERROR
LL_CRITICAL

Two related defines can also be used (mainly as a convenience for logger registration): 

LL_MIN_LEVEL
LL_MAX_LEVEL

Note that certain concrete packages will have their own fine-grained filtering for logging. However, the package-level controls will supercede these finer controls.

COMPATIBILITY ISSUES

Log levels do not always map 1-to-1 with the underlying 3rd-party logging library. The issues mainly involve the LL_CRITICAL level. Packages that do not provide this level will be mapped to LL_ERROR.

EXAMPLE

The following is a simple example of an application that sends several log statements to the console: 

package main

import (
  log  "github.com/f5devcentral/testipam/pkg/vlogger"
  "github.com/f5devcentral/testipam/pkg/vlogger/console"

func init() {
  // Log all messages to the user's console
  log.RegisterLogger(log.LL_MIN_LEVEL, log.LL_MAX_LEVEL, console.NewConsoleLogger())
  // only report errors at the LL_INFO level and above
  log.SetLogLevel(log.LL_INFO)
}

func main() {
  defer log.Close()

  log.Debug("This debug message won't print");
  log.Info("This is an info message")
  log.Warning("This is a warning message")
  log.Errorf("This is an error message with %v", "formatting")
  log.Criticalf("This is a critical message %v formatting", "with")
  log.Fatal("This is a fatal message")
  log.Info("This will never print due to log.Fatal() causing the application to exit")
}

MODULES

log.go: 

This module provides the generic interface that end-user libraries and apps should program to.

log_null.go: 

Turns off all logging.

Index

Constants

View Source 
const (
	// Must be in sequential ascending order based on priority
	// (higher priorities have higher numeric values)
	LL_DEBUG = iota
	LL_INFO
	LL_WARNING
	LL_ERROR
	LL_CRITICAL
	LL_LOGLEVEL_SIZE

	LL_MIN_LEVEL = LL_DEBUG
	LL_MAX_LEVEL = LL_LOGLEVEL_SIZE - 1
)

Variables

This section is empty.

Functions

func Close 

func Close()

Close informs the configured loggers that they are being closed and should cleanup (for instance, flushing any queued log messages)

func Critical 

func Critical(msg string)

Critical sends a message to the logger object to record critical level statements (these indicate conditions that should never occur and might cause a failure/crash of the executing program or unexpected outcome from the requested action).

func Criticalf 

func Criticalf(format string, params ...interface{})

Criticalf formats a message before sending it to the logger object to record critical level statements (these indicate conditions that should never occur and might cause a failure/crash of the executing program or unexpected outcome from the requested action).

func Debug 

func Debug(msg string)

Debug sends a message to the logger object to record debug/trace level statements

func Debugf 

func Debugf(format string, params ...interface{})

Debugf formats a message before sending it to the logger object to record debug/trace level statements

func Error 

func Error(msg string)

Error sends a message to the logger object to record error level statements (these indicate conditions that should not occur and may indicate a failure in performing the requested action).

func Errorf 

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

Errorf formats a message before sending it to the logger object to record error level statements (these indicate conditions that should not occur and may indicate a failure in performing the requested action).

func Fatal 

func Fatal(msg string)

Fatal sends a CRITICAL message to the logger object and then exits. NOTE: This call should not be made in packages that are meant to serve as libraries for other developers.

func Fatalf 

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

Fatalf sends a formatted CRITICAL message to the logger object and then exits. NOTE: This call should not be made in packages that are meant to serve as libraries for other developers.

func Info 

func Info(msg string)

Info sends a message to the logger object to record informational level statements (these should be statements that can normally be logged without causing performance issues).

func Infof 

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

Infof formats a message before sending it to the logger object to record informational level statements (there should be statements that can normally be logged without causing performance issues).

func Panic 

func Panic(msg string)

Panic sends a CRITICAL message to the logger object and then calls panic. NOTE: This call should not be made in packages that are meant to serve as libraries for other developers.

func Panicf 

func Panicf(format string, params ...interface{})

Panicf sends a formatted CRITICAL message to the logger object and then calls panic. NOTE: This call should not be made in packages that are meant to serve as libraries for other developers.

func RegisterLogger 

func RegisterLogger(minLogLevel, maxLogLevel LogLevel, log Logger)

RegisterLogger must be called to map a concrete logger object with each log level.

func SetLogLevel 

func SetLogLevel(level LogLevel)

SetLogLevel sets the current package-level filtering

func Warning 

func Warning(msg string)

Warning sends a message to the logger object to record warning level statements (these indication conditions that are unexpected or may cause issues but are not normally going to affect the program execution).

func Warningf 

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

Warningf formats a message before sending it to the logger object to record warning level statements (these indication conditions that are unexpected or may cause issues but are not normally going to affect the program execution).

Types

type LogLevel 

type LogLevel int

LogLevel is used for global (package-level) filtering of log messages based on their priority (this filtering is applied before all other filtering which might be provided by the concrete logger).

func GetLogLevel 

func GetLogLevel() LogLevel

GetLogLevel returns the current package-level filtering

func NewLogLevel 

func NewLogLevel(s string) *LogLevel

NewLogLevel converts a string to a log level.

func (LogLevel) MarshalJSON 

func (ll LogLevel) MarshalJSON() ([]byte, error)

MarshalJSON converts a LogLevel to a quoted string for JSON output.

func (LogLevel) String 

func (ll LogLevel) String() string

String converts a LogLevel to a string for serializing.

func (*LogLevel) UnmarshalJSON 

func (ll *LogLevel) UnmarshalJSON(data []byte) error

type Logger 

type Logger interface {
	Debug(string)
	Debugf(string, ...interface{})
	Info(string)
	Infof(string, ...interface{})
	Warning(string)
	Warningf(string, ...interface{})
	Error(string)
	Errorf(string, ...interface{})
	Critical(string)
	Criticalf(string, ...interface{})
	GetLogLevel() syslog.Priority
	SetLogLevel(syslog.Priority)
	Close()
}

Generic interface that all concrete loggers must implement. Using this interface directly isolates user code from a particular logger implementation.

Source Files

View all Source files

Directories

Path Synopsis
log_console.go: Provides console logging through the common interface.
 log_console.go: Provides console logging through the common interface.

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