log

Basic logging with batteries

• APIs to prefix log-level in log messages.
• Global option to redirect logs to a file.
• Include/Exclude/Format log time.
• Colorize log messages for different levels.
• Console logging.
• Stable APIs, existing APIs are not going to change.

How to use golog

Packages can import golog and use its methods

import github.com/bnclabs/golog
func myfunc() {
    ..
    log.Fatalf(...)
    ..
    log.Warnf(...)
    ..
    log.Debugf(...)
}

Note here that log is not an object name, importing golog resolves to log package that has exported methods Fatalf() Warnf() etc ... For more information please read the go-documentation for log package.

By default, importing the package will initialize the logger to default-logger that shall log to standard output. To use custom logger use the following initializer function in your package or application:

import github.com/bnclabs/golog

var mylogger = newmylogger()
func init() {
    setts := map[string]interface{}{
        "log.level": "info",
        "log.file":  "",
    }
    SetLogger(mylogger, setts)
}

mylogger should implement the log.Logger interface{}.

Order of log levels

const (
	logLevelIgnore LogLevel = iota + 1
	logLevelFatal
	logLevelError
	logLevelWarn
	logLevelInfo
	logLevelVerbose
	logLevelDebug
	logLevelTrace
)

Console Logging

By default log APIs will worry about log-level, prefix format, time-format sometimes it become too much of clutter on the screen to communicate simple messages with user via console. In such cases use the Consolef API.

    log.Consolef("goledger version - goledger%v\n", api.LedgerVersion)

Consolef does not print the log time, log level and always outputs to stdout.

Settings

• log.level, filter all messages logged at level greater than the configured value. Can be one of the following names - ignore, fatal, error, warn, info, verbose, debug, trace
• log.flag, comma separated value of log.Flags, eg: Ldate,Ltime,Llongfile, described further down.
• log.file, if not empty string, all log messages are appended to configured file.
• log.timeformat, format of time string prefixed to log message, should confirm to time.Now().Format().
• log.prefix, fmt.Sprintf format string for log level, by default [<leve>] format is used.
• log.colorfatal, comma separated value of attribute names - bold, underline, blinkslow, blinkrapid, crossedout, red, green, yellow, blue, magenta, cyan, white, hired, higreen, hiyellow, hiblue, himagenta, hicyan, hiwhite. Attribute-settings available for all log levels.

Ignore ignore level can be used to ignore all log messages. Note that only log-level can be specified as ignore, no corresponding API is supported.

log.flags

const (
    // Bits or'ed together to control what's printed.
    // There is no control over the order they appear (the order listed
    // here) or the format they present (as described in the comments).
    // The prefix is followed by a colon only when Llongfile or Lshortfile
    // is specified.
    // For example, flags Ldate | Ltime (or LstdFlags) produce,
    //  2009/01/23 01:23:23 message
    // while flags Ldate | Ltime | Lmicroseconds | Llongfile produce,
    //  2009/01/23 01:23:23.123123 /a/b/c/d.go:23: message
    Ldate         = 1 << iota     // the date in the local time zone: 2009/01/23
    Ltime                         // the time in the local time zone: 01:23:23
    Lmicroseconds                 // microsecond resolution: 01:23:23.123123.  assumes Ltime.
    Llongfile                     // full file name and line number: /a/b/c/d.go:23
    Lshortfile                    // final file name element and line number: d.go:23. overrides Llongfile
    LUTC                          // if Ldate or Ltime is set, use UTC rather than the local time zone
    LstdFlags     = Ldate | Ltime // initial values for the standard logger
)

Default log.level is Info.

Panic and recovery

• API SetLogger()
  • If log.file is not string.
  • If creating or opening log.file fails.
  • If log.level is not an allowed log string.
  • If log.prefix is neither string, nor bool.
• API SetLogLevel()
  • If log.level is not an allowed log string.
• API SetLogprefix()
  • If log.prefix is neither string, nor bool.

Typically all the above panic cases needs to be fixed during development, and should never occur during production. If panics become unavoidable please use panic/recover.

How to contribute

• Pick an issue, or create an new issue. Provide adequate documentation for the issue.
• Assign the issue or get it assigned.
• Work on the code, once finished, raise a pull request.
• Golog is written in golang, hence expected to follow the global guidelines for writing go programs.
• As of now, branch master is the development branch.