Active the node.js agent log (#46)

* Active the node.js agent log

* add link

docs/README.md

@@ -4,4 +4,5 @@
     * [Quick start](quick-start.md)
     * [Install nodejs agent](install-agent.md)
   * [Skywalking Backend Compatibility List](compatibility-list.md)
-    
+  * FAQ
+    * [How to active agent log](how-to-active-agent-log.org)

docs/how-to-active-agent-log.org

+* How to active Node.js Agent log
+  Node.js agent uses [[https://www.npmjs.com/package/debug][debug]] framework for output log, and your can active the log before you deploy application currently.
+  Note: *Node.js Agent only support that output the log to console currently.*
+  
+  To active all level log, You should add following variable into environment variables before you deploy application.
+  #+BEGIN_SRC 
+  DEBUG=skywalking:*
+  #+END_SRC
+  
+  Maybe you just want to active *error* level log, That's fine, just add the variable into environment variables. The Agent support four log level: *debug* *info* *warn* *error* currently.
+  #+BEGIN_SRC 
+  DEBUG=skywalking:error
+  #+END_SRC
+
+
+

modules/nodejs-agent/lib/logger/index.js

@@ -16,32 +16,36 @@
  */
 
 const Logger = function() {
-  let _logger = require("debug");
-
-  this.debug = function(className, format, ...args) {
-    _logger(className + ":debug")(format, ...args);
-  };
-
-  this.info = function(className, format, ...args) {
-    _logger(className + ":info")(format, ...args);
-  };
-
-  this.warn = function(className, format, ...args) {
-    _logger(className + ":warn")(format, ...args);
-  };
-
-  this.error = function(className, format, ...args) {
-    _logger(className + ":error")(format, ...args);
-  };
+    let _debug = require("debug");
+    let _debugLogger = _debug("skywalking:debug");
+    let _infoLogger = _debug("skywalking:info");
+    let _warnLogger = _debug("skywalking:warn");
+    let _errorLogger = _debug("skywalking:error");
+
+    this.debug = function(className, format, ...args) {
+        _debugLogger("[%s] " + format, className, ...args);
+    };
+
+    this.info = function(className, format, ...args) {
+        _infoLogger("[%s] " + format, className, ...args);
+    };
+
+    this.warn = function(className, format, ...args) {
+        _warnLogger("[%s] " + format, className, ...args);
+    };
+
+    this.error = function(className, format, ...args) {
+        _errorLogger("[%s] " + format, className, ...args);
+    };
 };
 
 Logger.instance = null;
 
 Logger.getInstance = function() {
-  if (this.instance === null) {
-    this.instance = new Logger();
-  }
-  return this.instance;
+    if (this.instance === null) {
+        this.instance = new Logger();
+    }
+    return this.instance;
 };
 
 module.exports = Logger.getInstance();