Small improvements for `sentinel-transport`

- Modify the init order of command center init func to -1 (prioritized than before)
- Add CommandConstants for common use

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

sentinel-transport/sentinel-transport-common/src/main/java/com/alibaba/csp/sentinel/command/CommandConstants.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright 1999-2018 Alibaba Group Holding Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.alibaba.csp.sentinel.command;
+
+/**
+ * @author Eric Zhao
+ * @since 1.4.1
+ */
+public final class CommandConstants {
+
+    public static final String VERSION_COMMAND = "version";
+
+    public static final String MSG_INVALID_COMMAND = "Invalid command";
+    public static final String MSG_UNKNOWN_COMMAND_PREFIX = "Unknown command";
+
+    public static final String MSG_SUCCESS = "success";
+    public static final String MSG_FAIL = "failed";
+
+    private CommandConstants() {}
+}

sentinel-transport/sentinel-transport-common/src/main/java/com/alibaba/csp/sentinel/transport/init/CommandCenterInitFunc.java

@@ -19,12 +19,14 @@ import java.util.Iterator;
 import java.util.ServiceLoader;
 
 import com.alibaba.csp.sentinel.init.InitFunc;
+import com.alibaba.csp.sentinel.init.InitOrder;
 import com.alibaba.csp.sentinel.log.RecordLog;
 import com.alibaba.csp.sentinel.transport.CommandCenter;
 
 /**
  * @author Eric Zhao
  */
+@InitOrder(-1)
 public class CommandCenterInitFunc implements InitFunc {
 
     @Override

sentinel-transport/sentinel-transport-simple-http/src/main/java/com/alibaba/csp/sentinel/transport/command/http/HttpEventTask.java

@@ -72,7 +72,7 @@ public class HttpEventTask implements Runnable {
                 new OutputStreamWriter(outputStream, Charset.forName(SentinelConfig.charset())));
 
             String line = in.readLine();
-            CommandCenterLog.info("[CommandCenter] socket income:" + line
+            CommandCenterLog.info("[SimpleHttpCommandCenter] socket income: " + line
                 + "," + socket.getInetAddress());
             CommandRequest request = parseRequest(line);
 
@@ -95,10 +95,10 @@ public class HttpEventTask implements Runnable {
             printWriter.flush();
 
             long cost = System.currentTimeMillis() - start;
-            CommandCenterLog.info("[CommandCenter] deal a socket task:" + line
-                + "," + socket.getInetAddress() + ", time cost=" + cost + " ms");
+            CommandCenterLog.info("[SimpleHttpCommandCenter] Deal a socket task: " + line
+                + ", address: " + socket.getInetAddress() + ", time cost: " + cost + " ms");
         } catch (Throwable e) {
-            CommandCenterLog.info("CommandCenter error", e);
+            CommandCenterLog.warn("[SimpleHttpCommandCenter] CommandCenter error", e);
             try {
                 if (printWriter != null) {
                     String errorMessage = SERVER_ERROR_MESSAGE;
@@ -110,7 +110,7 @@ public class HttpEventTask implements Runnable {
                     printWriter.flush();
                 }
             } catch (Exception e1) {
-                CommandCenterLog.info("CommandCenter close serverSocket failed", e);
+                CommandCenterLog.warn("[SimpleHttpCommandCenter] Close server socket failed", e);
             }
         } finally {
             closeResource(in);
@@ -124,7 +124,7 @@ public class HttpEventTask implements Runnable {
             try {
                 closeable.close();
             } catch (Exception e) {
-                CommandCenterLog.info("CommandCenter close resource failed", e);
+                CommandCenterLog.warn("[SimpleHttpCommandCenter] Close resource failed", e);
             }
         }
     }