log

import "github.com/go-coldbrew/log"

Package log provides a minimal interface for structured logging in services. ColdBrew uses this log package for all logs.

How To Use

The simplest way to use this package is by calling static log functions to report particular level (error/warning/info/debug)

log.Error(...)
log.Warn(...)
log.Info(...)
log.Debug(...)

You can also initialize a new logger by calling 'log.NewLogger' and passing a loggers.BaseLogger implementation (loggers package provides a number of pre built implementations)

logger := log.NewLogger(gokit.NewLogger())
logger.Info(ctx, "key", "value")

Note: Preferred logging output is in either logfmt or json format, so to facilitate these log function arguments should be in pairs of key-value

Contextual Logs

log package uses context.Context to pass additional information to logs, you can use 'loggers.AddToLogContext' function to add additional information to logs. For example in access log from service

{"@timestamp":"2018-07-30T09:58:18.262948679Z","caller":"http/http.go:66","error":null,"grpcMethod":"/AuthSvc.AuthService/Authenticate","level":"info","method":"POST","path":"/2.0/authenticate/","took":"1.356812ms","trace":"15592e1b-93df-11e8-bdfd-0242ac110002","transport":"http"}

we pass 'grpcMethod' from context, this information gets automatically added to all log calls called inside the service and makes debugging services much easier. ColdBrew also generates a 'trace' ID per request, this can be used to trace an entire request path in logs.

this package is based on https://github.com/carousell/Orion/tree/master/utils/log

Index

• func Debug(ctx context.Context, args ...interface{})
• func Error(ctx context.Context, args ...interface{})
• func GetLevel() loggers.Level
• func GetOverridenLogLevel(ctx context.Context) (loggers.Level, bool)
• func Info(ctx context.Context, args ...interface{})
• func OverrideLogLevel(ctx context.Context, level loggers.Level) context.Context
• func SetLevel(level loggers.Level)
• func SetLogger(l Logger)
• func Warn(ctx context.Context, args ...interface{})
• type Logger
  • func GetLogger() Logger
  • func NewLogger(log loggers.BaseLogger) Logger

func Debug

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

Debug writes out a debug log to global logger This is a convenience function for GetLogger().Log(loggers.DebugLevel, 1, args...)

func Error

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

Error writes out an error log to global logger This is a convenience function for GetLogger().Log(loggers.ErrorLevel, 1, args...)

func GetLevel

func GetLevel() loggers.Level

GetLevel returns the current log level This is useful for checking if a log level is enabled

func GetOverridenLogLevel

func GetOverridenLogLevel(ctx context.Context) (loggers.Level, bool)

GetOverridenLogLevel fetches overriden log level from context If no log level is overriden, it returns false If log level is overriden, it returns the log level and true

func Info

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

Info writes out an info log to global logger This is a convenience function for GetLogger().Log(loggers.InfoLevel, 1, args...)

func OverrideLogLevel

func OverrideLogLevel(ctx context.Context, level loggers.Level) context.Context

OverrideLogLevel allows the default log level to be overridden from request context This is useful when you want to override the log level for a specific request For example, you can set the log level to debug for a specific request while the default log level is set to info

func SetLevel

func SetLevel(level loggers.Level)

SetLevel sets the log level to filter logs

func SetLogger

func SetLogger(l Logger)

SetLogger sets the global logger

func Warn

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

Warn writes out a warning log to global logger This is a convenience function for GetLogger().Log(loggers.WarnLevel, 1, args...)

type Logger

Logger interface is implemnted by the log implementation to provide the log methods to the application code.

type Logger interface {
    loggers.BaseLogger
    // Debug logs a message at level Debug.
    // ctx is used to extract the request id and other context information.
    Debug(ctx context.Context, args ...interface{})
    // Info logs a message at level Info.
    // ctx is used to extract the request id and other context information.
    Info(ctx context.Context, args ...interface{})
    // Warn logs a message at level Warn.
    // ctx is used to extract the request id and other context information.
    Warn(ctx context.Context, args ...interface{})
    // Error logs a message at level Error.
    // ctx is used to extract the request id and other context information.
    Error(ctx context.Context, args ...interface{})
}

func GetLogger

func GetLogger() Logger

GetLogger returns the global logger If the global logger is not set, it will create a new one with gokit logger

func NewLogger

func NewLogger(log loggers.BaseLogger) Logger

NewLogger creates a new logger with a provided BaseLogger The default logger is gokit logger

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