git.r.bdr.sh - rbdr/cologne/blob - README.md

   1 # Cobalt #
   2
   3 Cobalt is a simple logger multiplexer that works with a JSON based format.
   4 You can instantiate it with a set of loggers or add them later
   5 (see API reference below). When logging anything, Cobalt will attempt to
   6 generate an Object that conforms to the Cobalt Log Format Definition
   7 (if required) and passes it to every logger it has by calling their `log`
   8 method.
   9
  10 Example of instantiating a cobalt logger:
  11
  12 In node:
  13 ```
  14 Cobalt = require('cobalt-log');
  15 ```
  16
  17 In the browser just require the files. Then:
  18
  19 ```
  20 this.logger = new Cobalt.Console({
  21   from : "Breezi Client",
  22   loggers : [ new Cobalt.Logger.JsConsole({
  23               formatter : Cobalt.Formatter.Token,
  24               formatterOpts : {
  25                 formatString : "{{_from}}: {{message}}",
  26                 ansiColor : true
  27               }
  28             })]
  29 });
  30 ```
  31
  32 This code will create an instance with a JsConsole logger that uses the
  33 Token formatter (See loggers and formatters below).
  34
  35 Cobalt works in a browser or inside node, so feel free to use cobalt all
  36 over! (Also, see the socket logger below for info on connecting cobalt
  37 loggers)
  38
  39 ## Quick API Reference ##
  40
  41 * **addLogger(logger)**: Adds a logger to the cobalt instance.
  42 * **removeLogger(logger)**: Removes a logger from the cobalt instance.
  43 * **buildLog(item, level=7)**: Generates a cobalt log object as if you had
  44   logged item (it will do this automatically when you log anything)
  45 * **extendLog(object)**: Creates a dummy log object and extends it with
  46   object.
  47 * **buildSeparator**: Generates a cobalt log object that defines a separator
  48 * **log, info, notice, warn, error**: Generates a log object with the
  49   appropriate severity level and sends it to all loggers.
  50 * **separator()**: Generates a separator log object and sends it to all
  51   loggers.
  52 * **space(lines)**: Logs an empty string `lines` times
  53 * **indent()**: Increases the indent level globally.
  54 * **indent(callback)**: Increases the indent level for anything logged
  55   from inside the callback.
  56 * **outdent()/outdent(callback)**: Same as indent, but decreases indent level.
  57 * **color()**: Changes the color globally. †
  58 * **color(callback)**: Changes the color for anything logged from inside the
  59   callback. †
  60 * **now()**: Returns the current time in microseconds, using performance.now()
  61   or process.hrtime() if available. If not, falls back to miliseconds.
  62
  63 † Cobalt doesn't really care about formatting or colors, but it allows you
  64 to set the `_color` property in the generated object. In the end, it's up to
  65 the formatter to decide if it will use this property. However, this maintains
  66 the old cobalt API and gives you flexibility in how you color your logs.
  67
  68
  69 ## Loggers ##
  70
  71 Cobalt doesn't depend on any particular logger, and the loggers it expects
  72 to receive is any object that responds to the log method. However, since it
  73 would pass a JSON object instead of a string, this may result in unexpected
  74 behavior for loggers that don't expect it. To ease the use of Cobalt with
  75 existing loggers, cobalt includes a couple of loggers that you can use out
  76 of the box.
  77
  78
  79 ### Cobalt.Logger.JsConsole ###
  80
  81 This logger communicates the Javascript console present in web browsers or
  82 node with cobalt. It uses the logLevel to trigger the appropriate method
  83 (e.g. info vs warn vs error). You can also initialize it with a formatter,
  84 to convert the log object to a string:
  85
  86 ```
  87  new Cobalt.Logger.JsConsole({
  88      formatter : Cobalt.Formatter.Token,
  89      formatterOpts : {
  90          formatString : "[{{_timestamp}}] {{message}} (@{{_from}})"
  91      }
  92  })
  93 ```
  94
  95 What this does is: it will trigger the method `format` on `formatter`
  96 passing the `logObject` and `formatterOpts`. This means that a formatter is
  97 any object that responds to `format(logObject, formatterOpts)`. It expects
  98 a string to be returned.
  99
 100 ### Cobalt.Logger.Socket ###
 101
 102 This logger sends the log object to a socket using Socket.IO. It does not
 103 format the output. To catch the log from the recipient, you have to listen
 104 for the `log` event, and from there you can pass it to another Cobalt
 105 instance or do whatever you want with it.
 106
 107 ### More Loggers? ###
 108
 109 You can build your own logger easily for any method of transport you find
 110 necessary (e.g. mail, database, twitter, etc). Any object that responds
 111 to `#log(logObject)` is a valid logger:
 112
 113 ```javascript
 114 // A valid, very minimalistic logger
 115 var simpleLogger = {
 116   log : function (logObject) {
 117     console.log(logObject.message);
 118   }
 119 }
 120
 121 logger.addLogger(simpleLogger);
 122 ```
 123
 124 ## Formatters ##
 125
 126 Cobalt itself makes no assumptions about the output of the logger and just
 127 passes the object to every logger it has. However, it is clear that loggers
 128 may want to manipulate this object. As shown in the JsConsole, a formatter
 129 should respond to the format method and receive a `logObject` and an
 130 `optsObject`. However, as this is not a core part of Cobalt, this is only a
 131 recommendation (as this is the way the included JsConsole logger does it)
 132 and it is up to the logger on how to transform the object it receives.
 133 Cobalt includes a very simple formatter that works well in conjuction
 134 with JsConsole.
 135
 136 ### Cobalt.Formatter.Token ###
 137
 138 The Token formatter is a very simple formatter that uses a formatString to
 139 extract values from the log object and interpolate them in a string.
 140
 141 #### Options ####
 142
 143 * **formatString**: A string that defines the format of the output. It is a
 144   string with double curly braces denoting fields. For example:
 145   `"[{{_timestamp}}] {{message}} (@{{_from}})"` would attempt to extract the
 146   \_timestamp, message and \_from fields to create a string similar to this:
 147   `"[124896126491.123] Testing the logger (@Client Application)"`
 148   (defaults to `"{{message}}"`)
 149 * **ansiColor**: A boolean value, when `true` will output the string in ANSI
 150   color depending on the severity level (defaults to `false`)
 151
 152 ### More Formatters? ###
 153
 154 As with loggers, cobalt itself does not worry about these things. However,
 155 if you wish to make a formatter that is exchangable with Token, you just
 156 need to create an object that responds to the`format(logObject, optionsObject)`
 157 method:
 158
 159 ```javascript
 160 // A valid, very minimalistic formatter
 161 var simpleFormatter = {
 162   format : function (logObject, options) {
 163     if (options.showDate) {
 164       return "[" + Date(logObject._timeStamp) + "] " + logObject.message
 165     } else {
 166       return logObject.message;
 167     }
 168   }
 169 }
 170
 171 logger.addLogger(new Cobalt.Logger.JsConsole({
 172   formatter: simpleFormatter,
 173   formatterOpts : {
 174     showDate : true
 175   }
 176 }));
 177 ```
 178
 179 ## The Cobalt Log Format ##
 180
 181 The Cobalt Log (CoLog) format is a JSON based log format used with cobalt.
 182 It is partly inspired in Greylog's GELF format, but with very notorious
 183 differences. The CoLog requires a header with certain fields that allow
 184 cobalt and its pieces to handle it. All header fields are prefixed with
 185 an underscore. Other than those fields, you can put whatever you want in
 186 the object; It's up to the loggers to make sense of the structure and
 187 display it in a way that makes sense.
 188
 189 You can attempt to build this structure on your own, or let cobalt build it for
 190 you. Any object you pass for logging will be converted. However, if you
 191 build it on your own you have two options: The first one is use buildLog
 192 to create a log object for "item" as if you had logged "item" or you can
 193 use extendLog that will create a dummy log object and extends it with
 194 whatever object you pass to it.
 195
 196 ### Required Fields ###
 197
 198 * **_version** : The version of cobalt this is designed to work with
 199 * **_timestamp** : A timestamp in microseconds.
 200 * **_cobaltLog** [true] : Cobalt will check for the \_cobaltLog to decide if
 201 transformation will happen or not.
 202
 203 ### Optional Fields ###
 204
 205 * **\_from**: The sender of the log (Defaults to Generic Cobalt Logger)
 206 * **\_level**: The level of the log (Defaults to 7)
 207 * **\_levelString**: The string corresponding to the log level (e.g. 7 ->
 208   DEBUG, 3 -> ERROR, 0 -> CRIT)
 209 * **\_indentLevel**: The indent level of the log
 210 * **\_color**: The color of the log
 211 * **\_separator**: If true, indicates that this is a separator and holds no
 212   valuable information.