Add comments for sniffer Config.

skywalking-sniffer/skywalking-api/src/main/java/com/a/eye/skywalking/api/conf/Config.java

 package com.a.eye.skywalking.api.conf;
 
 import com.a.eye.skywalking.api.logging.LogLevel;
+import com.a.eye.skywalking.api.logging.WriterFactory;
 
+/**
+ * This is the core config in sniffer agent.
+ *
+ * @author wusheng
+ */
 public class Config {
 
     public static class Agent {
+        /**
+         * Application code is showed in sky-walking-ui.
+         * Suggestion: set a unique name for each application, one application's nodes share the same code.
+         */
         public static String APPLICATION_CODE = "";
 
+        /**
+         * One, means sampling OFF.
+         * Greater than one, select one trace in every N traces.
+         * Zero and negative number are illegal.
+         */
         public static int SAMPLING_CYCLE = 1;
     }
 
     public static class Collector {
+        /**
+         * Collector REST-Service address.
+         * e.g.
+         * SERVERS="127.0.0.1:8080"  for single collector node.
+         * SERVERS="10.2.45.126:8080,10.2.45.127:7600"  for multi collector nodes.
+         */
         public static String SERVERS = "";
 
+        /**
+         * Collector receive segments REST-Service name.
+         */
         public static String SERVICE_NAME = "/segments";
 
+        /**
+         * The max size to send traces per rest-service call.
+         */
         public static int BATCH_SIZE = 50;
     }
 
     public static class Buffer {
+        /**
+         * The in-memory buffer size. Based on Disruptor, this value must be 2^n.
+         *
+         * @see {https://github.com/LMAX-Exchange/disruptor}
+         */
         public static int SIZE = 512;
     }
 
     public static class Logging {
-        // log文件名
+        /**
+         * Log file name.
+         */
         public static String FILE_NAME = "skywalking-api.log";
-        // log文件文件夹名字
+
+        /**
+         * Log files directory.
+         * Default is blank string, means, use "system.out" to output logs.
+         *
+         * @see {@link WriterFactory#getLogWriter()}
+         */
         public static String DIR = "";
-        // 最大文件大小
+
+        /**
+         * The max size of log file.
+         * If the size is bigger than this, archive the current file, and write into a new file.
+         */
         public static int MAX_FILE_SIZE = 300 * 1024 * 1024;
 
+        /**
+         * The log level. Default is debug.
+         *
+         * @see {@link LogLevel}
+         */
         public static LogLevel LEVEL = LogLevel.DEBUG;
     }
 }