[GitHub] [rocketmq] Crearns commented on issue #1876: Broker flush when END_OF_FILE

[GitBox <gi...@apache.org>]

Crearns commented on issue #1876: Broker flush when END_OF_FILE
URL: https://github.com/apache/rocketmq/issues/1876#issuecomment-602360807
 
 
   Thanks for your reply, but sorry i am newbie, I can not understand it, I retell my understanding.
   
   when ```(msgLen + END_FILE_MIN_BLANK_LENGTH) > maxBlank```
   it will mark some data to mark the blank and return an END_OF_FILE result
   ```java
   if ((msgLen + END_FILE_MIN_BLANK_LENGTH) > maxBlank) {
                   this.resetByteBuffer(this.msgStoreItemMemory, maxBlank);
                   // 1 TOTALSIZE
                   this.msgStoreItemMemory.putInt(maxBlank);
                   // 2 MAGICCODE
                   this.msgStoreItemMemory.putInt(CommitLog.BLANK_MAGIC_CODE);
                   // 3 The remaining space may be any value
                   // Here the length of the specially set maxBlank
                   final long beginTimeMills = CommitLog.this.defaultMessageStore.now();
                   byteBuffer.put(this.msgStoreItemMemory.array(), 0, maxBlank);
                   return new AppendMessageResult(AppendMessageStatus.END_OF_FILE, wroteOffset, maxBlank, msgId, msgInner.getStoreTimestamp(),
                       queueOffset, CommitLog.this.defaultMessageStore.now() - beginTimeMills);
   }
   ```
   and in the switch statement
   
   ```java
   case END_OF_FILE:
       unlockMappedFile = mappedFile;
       // Create a new file, re-write the message
       mappedFile = this.mappedFileQueue.getLastMappedFile(0);
       if (null == mappedFile) {
           // XXX: warn and notify me
           log.error("create mapped file2 error, topic: " + msg.getTopic() + " clientAddr: " + msg.getBornHostString());
           beginTimeInLock = 0;
           return new PutMessageResult(PutMessageStatus.CREATE_MAPEDFILE_FAILED, result);
       }
       result = mappedFile.appendMessage(msg, this.appendMessageCallback);
       break;
   ```
   when the result is END_OF_FILE, it will call ```result = mappedFile.appendMessage(msg, this.appendMessageCallback);``` to put the message to a new file, it will return a new result and break.Still in memory so far, and it will call ```handleDiskFlush(result, putMessageResult, msg);``` to flush, but it only flush the new file data, the old data that mark the blank can not flush
   
   Don't know if i'm right

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