[ISSUE #2334] Polish the log and response remark when service not available (#2335)

* enhancement(response & log):polish the log and response remark when service not available

* enhancement(response remark & log): make log and response remark better understand

* chore(style): modify code style to pass CI tests

broker/src/main/java/org/apache/rocketmq/broker/processor/ReplyMessageProcessor.java

@@ -251,28 +251,29 @@ public class ReplyMessageProcessor extends AbstractSendMessageProcessor implemen
 
             // Failed
             case CREATE_MAPEDFILE_FAILED:
-                log.info("create mapped file failed, server is busy or broken.");
+                log.warn("create mapped file failed, server is busy or broken.");
                 break;
             case MESSAGE_ILLEGAL:
-                log.info(
+                log.warn(
                     "the message is illegal, maybe msg properties length limit 32k.");
                 break;
             case PROPERTIES_SIZE_EXCEEDED:
-                log.info(
+                log.warn(
                     "the message is illegal, maybe msg body or properties length not matched. msg body length limit 128k.");
                 break;
             case SERVICE_NOT_AVAILABLE:
-                log.info(
-                    "service not available now, maybe disk full, maybe your broker machine memory too small.");
+                log.warn(
+                    "service not available now. It may be caused by one of the following reasons: " +
+                        "the broker's disk is full, messages are put to the slave, message store has been shut down, etc.");
                 break;
             case OS_PAGECACHE_BUSY:
-                log.info("[PC_SYNCHRONIZED]broker busy, start flow control for a while");
+                log.warn("[PC_SYNCHRONIZED]broker busy, start flow control for a while");
                 break;
             case UNKNOWN_ERROR:
-                log.info("UNKNOWN_ERROR");
+                log.warn("UNKNOWN_ERROR");
                 break;
             default:
-                log.info("UNKNOWN_ERROR DEFAULT");
+                log.warn("UNKNOWN_ERROR DEFAULT");
                 break;
         }
 

broker/src/main/java/org/apache/rocketmq/broker/processor/SendMessageProcessor.java

@@ -480,7 +480,8 @@ public class SendMessageProcessor extends AbstractSendMessageProcessor implement
             case SERVICE_NOT_AVAILABLE:
                 response.setCode(ResponseCode.SERVICE_NOT_AVAILABLE);
                 response.setRemark(
-                    "service not available now, maybe disk full, " + diskUtil() + ", maybe your broker machine memory too small.");
+                    "service not available now. It may be caused by one of the following reasons: " +
+                        "the broker's disk is full [" + diskUtil() + "], messages are put to the slave, message store has been shut down, etc.");
                 break;
             case OS_PAGECACHE_BUSY:
                 response.setCode(ResponseCode.SYSTEM_ERROR);

store/src/main/java/org/apache/rocketmq/store/DefaultMessageStore.java

@@ -392,7 +392,7 @@ public class DefaultMessageStore implements MessageStore {
         if (BrokerRole.SLAVE == this.messageStoreConfig.getBrokerRole()) {
             long value = this.printTimes.getAndIncrement();
             if ((value % 50000) == 0) {
-                log.warn("message store has shutdown, so putMessage is forbidden");
+                log.warn("broke role is slave, so putMessage is forbidden");
             }
             return PutMessageStatus.SERVICE_NOT_AVAILABLE;
         }
@@ -400,7 +400,8 @@ public class DefaultMessageStore implements MessageStore {
         if (!this.runningFlags.isWriteable()) {
             long value = this.printTimes.getAndIncrement();
             if ((value % 50000) == 0) {
-                log.warn("message store has shutdown, so putMessage is forbidden");
+                log.warn("the message store is not writable. It may be caused by one of the following reasons: " +
+                    "the broker's disk is full, write to logic queue error, write to index file error, etc");
             }
             return PutMessageStatus.SERVICE_NOT_AVAILABLE;
         } else {