CommitLog 結構
CommitLog、MappedFileQueue、MappedFile 的關系如下：
CommitLog : MappedFileQueue : MappedFile = 1 : 1 : N。
反應到系統文件如下：
···
Yunai-MacdeMacBook-Pro-2:commitlog yunai$ pwd
/Users/yunai/store/commitlog
Yunai-MacdeMacBook-Pro-2:commitlog yunai$ ls -l
total 10485760
-rw-r--r-- 1 yunai staff 1073741824 4 21 16:27 00000000000000000000
-rw-r--r-- 1 yunai staff 1073741824 4 21 16:29 00000000001073741824
-rw-r--r-- 1 yunai staff 1073741824 4 21 16:32 00000000002147483648
-rw-r--r-- 1 yunai staff 1073741824 4 21 16:33 00000000003221225472
-rw-r--r-- 1 yunai staff 1073741824 4 21 16:32 00000000004294967296
···
CommitLog、MappedFileQueue、MappedFile 的定義如下：
MappedFile ：00000000000000000000、00000000001073741824、00000000002147483648等文件。
MappedFileQueue ：MappedFile 所在的文件夾，對 MappedFile 進行封裝成文件隊列，對上層提供可無限使用的文件容量。
每個 MappedFile 統一文件大小。
文件命名方式：fileName[n] = fileName[n - 1] + mappedFileSize。在 CommitLog 里默認為 1GB。
CommitLog ：針對 MappedFileQueue 的封裝使用。
CommitLog 目前存儲在 MappedFile 有兩種內容類型：
MESSAGE ：消息。
BLANK ：文件不足以存儲消息時的空白占位。
CommitLog 存儲在 MappedFile的結構：
MESSAGE[1] MESSAGE[2] … MESSAGE[n - 1] MESSAGE[n] BLANK
MESSAGE 在 CommitLog 存儲結構：
第幾位 字段 說明 數據類型 字節數
1 MsgLen 消息總長度 Int 4
2 MagicCode MESSAGE_MAGIC_CODE Int 4
3 BodyCRC 消息內容CRC Int 4
4 QueueId 消息隊列編號 Int 4
5 Flag flag Int 4
6 QueueOffset 消息隊列位置 Long 8
7 PhysicalOffset 物理位置。在 CommitLog 的順序存儲位置。 Long 8
8 SysFlag MessageSysFlag Int 4
9 BornTimestamp 生成消息時間戳 Long 8
10 BornHost 生效消息的地址+端口 Long 8
11 StoreTimestamp 存儲消息時間戳 Long 8
12 StoreHost 存儲消息的地址+端口 Long 8
13 ReconsumeTimes 重新消費消息次數 Int 4
14 PreparedTransationOffset Long 8
15 BodyLength + Body 內容長度 + 內容 Int + Bytes 4 + bodyLength
16 TopicLength + Topic Topic長度 + Topic Byte + Bytes 1 + topicLength
17 PropertiesLength + Properties 拓展字段長度 + 拓展字段 Short + Bytes 2 + PropertiesLength
BLANK 在 CommitLog 存儲結構：
第幾位 字段 說明 數據類型 字節數
1 maxBlank 空白長度 Int 4
2 MagicCode BLANK_MAGIC_CODE Int 4
CommitLog 存儲消息
1: public PutMessageResult putMessage(final MessageExtBrokerInner msg) {
2: // Set the storage time
3: msg.setStoreTimestamp(System.currentTimeMillis());
4: // Set the message body BODY CRC (consider the most appropriate setting
5: // on the client)
6: msg.setBodyCRC(UtilAll.crc32(msg.getBody()));
7: // Back to Results
8: AppendMessageResult result = null;
9:
10: StoreStatsService storeStatsService = this.defaultMessageStore.getStoreStatsService();
11:
12: String topic = msg.getTopic();
13: int queueId = msg.getQueueId();
14:
15: // 事務相關 TODO 待讀：事務相關
16: final int tranType = MessageSysFlag.getTransactionValue(msg.getSysFlag());
17: if (tranType == MessageSysFlag.TRANSACTION_NOT_TYPE//
18: || tranType == MessageSysFlag.TRANSACTION_COMMIT_TYPE) {
19: // Delay Delivery
20: if (msg.getDelayTimeLevel() > 0) {
21: if (msg.getDelayTimeLevel() > this.defaultMessageStore.getScheduleMessageService().getMaxDelayLevel()) {
22: msg.setDelayTimeLevel(this.defaultMessageStore.getScheduleMessageService().getMaxDelayLevel());
23: }
24:
25: topic = ScheduleMessageService.SCHEDULE_TOPIC;
26: queueId = ScheduleMessageService.delayLevel2QueueId(msg.getDelayTimeLevel());
27:
28: // Backup real topic, queueId
29: MessageAccessor.putProperty(msg, MessageConst.PROPERTY_REAL_TOPIC, msg.getTopic());
30: MessageAccessor.putProperty(msg, MessageConst.PROPERTY_REAL_QUEUE_ID, String.valueOf(msg.getQueueId()));
31: msg.setPropertiesString(MessageDecoder.messageProperties2String(msg.getProperties()));
32:
33: msg.setTopic(topic);
34: msg.setQueueId(queueId);
35: }
36: }
37:
38: long eclipseTimeInLock = 0;
39:
40: // 獲取寫入映射文件
41: MappedFile unlockMappedFile = null;
42: MappedFile mappedFile = this.mappedFileQueue.getLastMappedFile();
43:
44: // 獲取寫入鎖
45: lockForPutMessage(); //spin...
46: try {
47: long beginLockTimestamp = this.defaultMessageStore.getSystemClock().now();
48: this.beginTimeInLock = beginLockTimestamp;
49:
50: // Here settings are stored timestamp, in order to ensure an orderly
51: // global
52: msg.setStoreTimestamp(beginLockTimestamp);
53:
54: // 當不存在映射文件時，進行創建
55: if (null == mappedFile || mappedFile.isFull()) {
56: mappedFile = this.mappedFileQueue.getLastMappedFile(0); // Mark: NewFile may be cause noise
57: }
58: if (null == mappedFile) {
59: log.error("create maped file1 error, topic: " + msg.getTopic() + " clientAddr: " + msg.getBornHostString());
60: beginTimeInLock = 0;
61: return new PutMessageResult(PutMessageStatus.CREATE_MAPEDFILE_FAILED, null);
62: }
63:
64: // 存儲消息
65: result = mappedFile.appendMessage(msg, this.appendMessageCallback);
66: switch (result.getStatus()) {
67: case PUT_OK:
68: break;
69: case END_OF_FILE: // 當文件尾時，獲取新的映射文件，並進行插入
70: unlockMappedFile = mappedFile;
71: // Create a new file, re-write the message
72: mappedFile = this.mappedFileQueue.getLastMappedFile(0);
73: if (null == mappedFile) {
74: // XXX: warn and notify me
75: log.error("create maped file2 error, topic: " + msg.getTopic() + " clientAddr: " + msg.getBornHostString());
76: beginTimeInLock = 0;
77: return new PutMessageResult(PutMessageStatus.CREATE_MAPEDFILE_FAILED, result);
78: }
79: result = mappedFile.appendMessage(msg, this.appendMessageCallback);
80: break;
81: case MESSAGE_SIZE_EXCEEDED:
82: case PROPERTIES_SIZE_EXCEEDED:
83: beginTimeInLock = 0;
84: return new PutMessageResult(PutMessageStatus.MESSAGE_ILLEGAL, result);
85: case UNKNOWN_ERROR:
86: beginTimeInLock = 0;
87: return new PutMessageResult(PutMessageStatus.UNKNOWN_ERROR, result);
88: default:
89: beginTimeInLock = 0;
90: return new PutMessageResult(PutMessageStatus.UNKNOWN_ERROR, result);
91: }
92:
93: eclipseTimeInLock = this.defaultMessageStore.getSystemClock().now() - beginLockTimestamp;
94: beginTimeInLock = 0;
95: } finally {
96: // 釋放寫入鎖
97: releasePutMessageLock();
98: }
99:
100: if (eclipseTimeInLock > 500) {
101: log.warn("[NOTIFYME]putMessage in lock cost time(ms)={}, bodyLength={} AppendMessageResult={}", eclipseTimeInLock, msg.getBody().length, result);
102: }
103:
104: //
105: if (null != unlockMappedFile && this.defaultMessageStore.getMessageStoreConfig().isWarmMapedFileEnable()) {
106: this.defaultMessageStore.unlockMappedFile(unlockMappedFile);
107: }
108:
109: PutMessageResult putMessageResult = new PutMessageResult(PutMessageStatus.PUT_OK, result);
110:
111: // Statistics
112: storeStatsService.getSinglePutMessageTopicTimesTotal(msg.getTopic()).incrementAndGet();
113: storeStatsService.getSinglePutMessageTopicSizeTotal(topic).addAndGet(result.getWroteBytes());
114:
115: // 進行同步||異步 flush||commit
116: GroupCommitRequest request = null;
117: // Synchronization flush
118: if (FlushDiskType.SYNC_FLUSH == this.defaultMessageStore.getMessageStoreConfig().getFlushDiskType()) {
119: final GroupCommitService service = (GroupCommitService) this.flushCommitLogService;
120: if (msg.isWaitStoreMsgOK()) {
121: request = new GroupCommitRequest(result.getWroteOffset() + result.getWroteBytes());
122: service.putRequest(request);
123: boolean flushOK = request.waitForFlush(this.defaultMessageStore.getMessageStoreConfig().getSyncFlushTimeout());
124: if (!flushOK) {
125: log.error("do groupcommit, wait for flush failed, topic: " + msg.getTopic() + " tags: " + msg.getTags()
126: + " client address: " + msg.getBornHostString());
127: putMessageResult.setPutMessageStatus(PutMessageStatus.FLUSH_DISK_TIMEOUT);
128: }
129: } else {
130: service.wakeup();
131: }
132: }
133: // Asynchronous flush
134: else {
135: if (!this.defaultMessageStore.getMessageStoreConfig().isTransientStorePoolEnable()) {
136: flushCommitLogService.wakeup(); // important：喚醒commitLog線程，進行flush
137: } else {
138: commitLogService.wakeup();
139: }
140: }
141:
142: // Synchronous write double 如果是同步Master，同步到從節點 // TODO 待讀：數據同步
143: if (BrokerRole.SYNC_MASTER == this.defaultMessageStore.getMessageStoreConfig().getBrokerRole()) {
144: HAService service = this.defaultMessageStore.getHaService();
145: if (msg.isWaitStoreMsgOK()) {
146: // Determine whether to wait
147: if (service.isSlaveOK(result.getWroteOffset() + result.getWroteBytes())) {
148: if (null == request) {
149: request = new GroupCommitRequest(result.getWroteOffset() + result.getWroteBytes());
150: }
151: service.putRequest(request);
152:
153: service.getWaitNotifyObject().wakeupAll();
154:
155: boolean flushOK =
156: // TODO
157: request.waitForFlush(this.defaultMessageStore.getMessageStoreConfig().getSyncFlushTimeout());
158: if (!flushOK) {
159: log.error("do sync transfer other node, wait return, but failed, topic: " + msg.getTopic() + " tags: "
160: + msg.getTags() + " client address: " + msg.getBornHostString());
161: putMessageResult.setPutMessageStatus(PutMessageStatus.FLUSH_SLAVE_TIMEOUT);
162: }
163: }
164: // Slave problem
165: else {
166: // Tell the producer, slave not available
167: putMessageResult.setPutMessageStatus(PutMessageStatus.SLAVE_NOT_AVAILABLE);
168: }
169: }
170: }
171:
172: return putMessageResult;
173: }
說明 ：存儲消息，並返回存儲結果。
第 2 行 ：設置存儲時間等。
第 16 至 36 行 ：事務消息相關，暫未了解。
第 45 & 97 行 ：獲取鎖與釋放鎖。
第 52 行 ：再次設置存儲時間。目前會有多處地方設置存儲時間。
第 55 至 62 行 ：獲取 MappedFile，若不存在或已滿，則進行創建。詳細解析見：MappedFileQueue#getLastMappedFile(…)。
第 65 行 ：插入消息到 MappedFile，解析解析見：MappedFile#appendMessage(…)。
第 69 至 80 行 ：MappedFile 已滿，創建新的，再次插入消息。
第 116 至 140 行 ：消息刷盤，即持久化到文件。上面插入消息實際未存儲到硬盤。此處，根據不同的刷盤策略，執行會有不同。詳細解析見：FlushCommitLogService。
第 143 至 173 行 ：Broker 主從同步。后面的文章會詳細解析😈。
MappedFileQueue#getLastMappedFile(…)
1: public MappedFile getLastMappedFile(final long startOffset, boolean needCreate) {
2: long createOffset = -1; // 創建文件開始offset。-1時，不創建
3: MappedFile mappedFileLast = getLastMappedFile();
4:
5: if (mappedFileLast == null) { // 一個映射文件都不存在
6: createOffset = startOffset - (startOffset % this.mappedFileSize);
7: }
8:
9: if (mappedFileLast != null && mappedFileLast.isFull()) { // 最后一個文件已滿
10: createOffset = mappedFileLast.getFileFromOffset() + this.mappedFileSize;
11: }
12:
13: if (createOffset != -1 && needCreate) { // 創建文件
14: String nextFilePath = this.storePath + File.separator + UtilAll.offset2FileName(createOffset);
15: String nextNextFilePath = this.storePath + File.separator
16: + UtilAll.offset2FileName(createOffset + this.mappedFileSize);
17: MappedFile mappedFile = null;
18:
19: if (this.allocateMappedFileService != null) {
20: mappedFile = this.allocateMappedFileService.putRequestAndReturnMappedFile(nextFilePath,
21: nextNextFilePath, this.mappedFileSize);
22: } else {
23: try {
24: mappedFile = new MappedFile(nextFilePath, this.mappedFileSize);
25: } catch (IOException e) {
26: log.error("create mappedFile exception", e);
27: }
28: }
29:
30: if (mappedFile != null) {
31: if (this.mappedFiles.isEmpty()) {
32: mappedFile.setFirstCreateInQueue(true);
33: }
34: this.mappedFiles.add(mappedFile);
35: }
36:
37: return mappedFile;
38: }
39:
40: return mappedFileLast;
41: }
說明 ：獲取最后一個 MappedFile，若不存在或文件已滿，則進行創建。
第 5 至 11 行 ：計算當文件不存在或已滿時，新創建文件的 createOffset。
第 14 行 ：計算文件名。從此處我們可
以得知，MappedFile的文件命名規則：
fileName[n] = fileName[n - 1] + n * mappedFileSize
fileName[0] = startOffset - (startOffset % this.mappedFileSize)
目前 CommitLog 的 startOffset 為 0。
此處有個疑問，為什么需要 (startOffset % this.mappedFileSize)。例如：
| startOffset | mappedFileSize | createOffset |
| — | :– | :– |
| 5 | 1 | 5 |
| 5 | 2 | 4 |
| 5 | 3 | 3 |
| 5 | 4 | 4 |
| 5 | > 5 | 0 |
如果有知道的同學，麻煩提示下。😈
解答：fileName[0] = startOffset - (startOffset % this.mappedFileSize) 計算出來的是，以 this.mappedFileSize 為每個文件大小時，startOffset 所在文件的開始offset
第 30 至 35 行 ：設置 MappedFile是否是第一個創建的文件。該標識用於 ConsumeQueue 對應的 MappedFile ，詳見 ConsumeQueue#fillPreBlank。
MappedFile#appendMessage(…)
1: public AppendMessageResult appendMessage(final MessageExtBrokerInner msg, final AppendMessageCallback cb) {
2: assert msg != null;
3: assert cb != null;
4:
5: int currentPos = this.wrotePosition.get();
6:
7: if (currentPos < this.fileSize) {
8: ByteBuffer byteBuffer = writeBuffer != null ? writeBuffer.slice() : this.mappedByteBuffer.slice();
9: byteBuffer.position(currentPos);
10: AppendMessageResult result =
11: cb.doAppend(this.getFileFromOffset(), byteBuffer, this.fileSize - currentPos, msg);
12: this.wrotePosition.addAndGet(result.getWroteBytes());
13: this.storeTimestamp = result.getStoreTimestamp();
14: return result;
15: }
16:
17: log.error("MappedFile.appendMessage return null, wrotePosition: " + currentPos + " fileSize: "
18: + this.fileSize);
19: return new AppendMessageResult(AppendMessageStatus.UNKNOWN_ERROR);
20: }
說明 ：插入消息到 MappedFile，並返回插入結果。
第 8 行 ：獲取需要寫入的字節緩沖區。為什么會有 writeBuffer != null 的判斷后，使用不同的字節緩沖區，見：FlushCommitLogService。
第 9 至 11 行 ：設置寫入 position，執行寫入，更新 wrotePosition(當前寫入位置，下次開始寫入開始位置)。
DefaultAppendMessageCallback#doAppend(…)
class DefaultAppendMessageCallback implements AppendMessageCallback {
2: // File at the end of the minimum fixed length empty
3: private static final int END_FILE_MIN_BLANK_LENGTH = 4 + 4;
4:
7: private final ByteBuffer msgIdMemory;
8:
13: private final ByteBuffer msgStoreItemMemory;
14:
18: private final int maxMessageSize;
19:
24: private final StringBuilder keyBuilder = new StringBuilder();
25:
29: private final ByteBuffer hostHolder = ByteBuffer.allocate(8);
30:
31: DefaultAppendMessageCallback(final int size) {
32: this.msgIdMemory = ByteBuffer.allocate(MessageDecoder.MSG_ID_LENGTH);
33: this.msgStoreItemMemory = ByteBuffer.allocate(size + END_FILE_MIN_BLANK_LENGTH);
34: this.maxMessageSize = size;
35: }
36:
37: public ByteBuffer getMsgStoreItemMemory() {
38: return msgStoreItemMemory;
39: }
40:
41: public AppendMessageResult doAppend(final long fileFromOffset, final ByteBuffer byteBuffer, final int maxBlank, final MessageExtBrokerInner msgInner) {
42: // STORETIMESTAMP + STOREHOSTADDRESS + OFFSET <br>
43:
44: // PHY OFFSET
45: long wroteOffset = fileFromOffset + byteBuffer.position();
46:
47: // 計算commitLog里的msgId
48: this.resetByteBuffer(hostHolder, 8);
49: String msgId = MessageDecoder.createMessageId(this.msgIdMemory, msgInner.getStoreHostBytes(hostHolder), wroteOffset);
50:
51: // Record ConsumeQueue information 獲取隊列offset
52: keyBuilder.setLength(0);
53: keyBuilder.append(msgInner.getTopic());
54: keyBuilder.append('-');
55: keyBuilder.append(msgInner.getQueueId());
56: String key = keyBuilder.toString();
57: Long queueOffset = CommitLog.this.topicQueueTable.get(key);
58: if (null == queueOffset) {
59: queueOffset = 0L;
60: CommitLog.this.topicQueueTable.put(key, queueOffset);
61: }
62:
63: // Transaction messages that require special handling // TODO 疑問：用途
64: final int tranType = MessageSysFlag.getTransactionValue(msgInner.getSysFlag());
65: switch (tranType) {
66: // Prepared and Rollback message is not consumed, will not enter the
67: // consumer queue
68: case MessageSysFlag.TRANSACTION_PREPARED_TYPE:
69: case MessageSysFlag.TRANSACTION_ROLLBACK_TYPE:
70: queueOffset = 0L;
71: break;
72: case MessageSysFlag.TRANSACTION_NOT_TYPE:
73: case MessageSysFlag.TRANSACTION_COMMIT_TYPE:
74: default:
75: break;
76: }
77:
78: // 計算消息長度
79: final byte[] propertiesData =
80: msgInner.getPropertiesString() == null ? null : msgInner.getPropertiesString().getBytes(MessageDecoder.CHARSET_UTF8);
81: final int propertiesLength = propertiesData == null ? 0 : propertiesData.length;
82: if (propertiesLength > Short.MAX_VALUE) {
83: log.warn("putMessage message properties length too long. length={}", propertiesData.length);
84: return new AppendMessageResult(AppendMessageStatus.PROPERTIES_SIZE_EXCEEDED);
85: }
86: final byte[] topicData = msgInner.getTopic().getBytes(MessageDecoder.CHARSET_UTF8);
87: final int topicLength = topicData.length;
88: final int bodyLength = msgInner.getBody() == null ? 0 : msgInner.getBody().length;
89: final int msgLen = calMsgLength(bodyLength, topicLength, propertiesLength);
90: // Exceeds the maximum message
91: if (msgLen > this.maxMessageSize) {
92: CommitLog.log.warn("message size exceeded, msg total size: " + msgLen + ", msg body size: " + bodyLength
93: + ", maxMessageSize: " + this.maxMessageSize);
94: return new AppendMessageResult(AppendMessageStatus.MESSAGE_SIZE_EXCEEDED);
95: }
96:
97: // Determines whether there is sufficient(足夠) free space
98: if ((msgLen + END_FILE_MIN_BLANK_LENGTH) > maxBlank) {
99: this.resetByteBuffer(this.msgStoreItemMemory, maxBlank);
100: // 1 TOTAL_SIZE
101: this.msgStoreItemMemory.putInt(maxBlank);
102: // 2 MAGIC_CODE
103: this.msgStoreItemMemory.putInt(CommitLog.BLANK_MAGIC_CODE);
104: // 3 The remaining space may be any value
105: //
106:
107: // Here the length of the specially set maxBlank
108: final long beginTimeMills = CommitLog.this.defaultMessageStore.now();
109: byteBuffer.put(this.msgStoreItemMemory.array(), 0, maxBlank);
110: return new AppendMessageResult(AppendMessageStatus.END_OF_FILE, wroteOffset, maxBlank, msgId, msgInner.getStoreTimestamp(),
111: queueOffset, CommitLog.this.defaultMessageStore.now() - beginTimeMills);
112: }
113:
114: // Initialization of storage space
115: this.resetByteBuffer(msgStoreItemMemory, msgLen);
116: // 1 TOTAL_SIZE
117: this.msgStoreItemMemory.putInt(msgLen);
118: // 2 MAGIC_CODE
119: this.msgStoreItemMemory.putInt(CommitLog.MESSAGE_MAGIC_CODE);
120: // 3 BODY_CRC
121: this.msgStoreItemMemory.putInt(msgInner.getBodyCRC());
122: // 4 QUEUE_ID
123: this.msgStoreItemMemory.putInt(msgInner.getQueueId());
124: // 5 FLAG
125: this.msgStoreItemMemory.putInt(msgInner.getFlag());
126: // 6 QUEUE_OFFSET
127: this.msgStoreItemMemory.putLong(queueOffset);
128: // 7 PHYSICAL_OFFSET
129: this.msgStoreItemMemory.putLong(fileFromOffset + byteBuffer.position());
130: // 8 SYS_FLAG
131: this.msgStoreItemMemory.putInt(msgInner.getSysFlag());
132: // 9 BORN_TIMESTAMP
133: this.msgStoreItemMemory.putLong(msgInner.getBornTimestamp());
134: // 10 BORN_HOST
135: this.resetByteBuffer(hostHolder, 8);
136: this.msgStoreItemMemory.put(msgInner.getBornHostBytes(hostHolder));
137: // 11 STORE_TIMESTAMP
138: this.msgStoreItemMemory.putLong(msgInner.getStoreTimestamp());
139: // 12 STORE_HOST_ADDRESS
140: this.resetByteBuffer(hostHolder, 8);
141: this.msgStoreItemMemory.put(msgInner.getStoreHostBytes(hostHolder));
142: //this.msgStoreItemMemory.put(msgInner.getStoreHostBytes());
143: // 13 RECONSUME_TIMES
144: this.msgStoreItemMemory.putInt(msgInner.getReconsumeTimes());
145: // 14 Prepared Transaction Offset
146: this.msgStoreItemMemory.putLong(msgInner.getPreparedTransactionOffset());
147: // 15 BODY
148: this.msgStoreItemMemory.putInt(bodyLength);
149: if (bodyLength > 0)
150: this.msgStoreItemMemory.put(msgInner.getBody());
151: // 16 TOPIC
152: this.msgStoreItemMemory.put((byte) topicLength);
153: this.msgStoreItemMemory.put(topicData);
154: // 17 PROPERTIES
155: this.msgStoreItemMemory.putShort((short) propertiesLength);
156: if (propertiesLength > 0)
157: this.msgStoreItemMemory.put(propertiesData);
158:
159: final long beginTimeMills = CommitLog.this.defaultMessageStore.now();
160: // Write messages to the queue buffer
161: byteBuffer.put(this.msgStoreItemMemory.array(), 0, msgLen);
162:
163: AppendMessageResult result = new AppendMessageResult(AppendMessageStatus.PUT_OK, wroteOffset, msgLen, msgId,
164: msgInner.getStoreTimestamp(), queueOffset, CommitLog.this.defaultMessageStore.now() - beginTimeMills);
165:
166: switch (tranType) {
167: case MessageSysFlag.TRANSACTION_PREPARED_TYPE:
168: case MessageSysFlag.TRANSACTION_ROLLBACK_TYPE:
169: break;
170: case MessageSysFlag.TRANSACTION_NOT_TYPE:
171: case MessageSysFlag.TRANSACTION_COMMIT_TYPE:
172: // The next update ConsumeQueue information 更新隊列的offset
173: CommitLog.this.topicQueueTable.put(key, ++queueOffset);
174: break;
175: default:
176: break;
177: }
178: return result;
179: }
180:
181:
187: private void resetByteBuffer(final ByteBuffer byteBuffer, final int limit) {
188: byteBuffer.flip();
189: byteBuffer.limit(limit);
190: }
191: }
說明 ：插入消息到字節緩沖區。
第 45 行 ：計算物理位置。在 CommitLog 的順序存儲位置。
第 47 至 49 行 ：計算 CommitLog 里的 offsetMsgId。這里一定要和 msgId 區分開。
計算方式 長度
offsetMsgId Broker存儲時生成 Hex(storeHostBytes, wroteOffset) 32
msgId Client發送消息時生成 Hex(進程編號, IP, ClassLoader, startTime, currentTime, 自增序列) 32 《RocketMQ 源碼分析 —— Message 基礎》
第 51 至 61 行 ：獲取隊列位置(offset)。
第 78 至 95 行 ：計算消息總長度。
第 98 至 112 行 ：當文件剩余空間不足時，寫入 BLANK 占位，返回結果。
第 114 至 161 行 ：寫入 MESSAGE 。
第 173 行 ：更新隊列位置(offset)。
FlushCommitLogService
線程服務 場景 插入消息性能
CommitRealTimeService 異步刷盤 && 開啟內存字節緩沖區 第一
FlushRealTimeService 異步刷盤 && 關閉內存字節緩沖區 第二
GroupCommitService 同步刷盤 第三
MappedFile#落盤
方式
方式一 寫入內存字節緩沖區(writeBuffer) 從內存字節緩沖區(write buffer)提交(commit)到文件通道(fileChannel) 文件通道(fileChannel)flush
方式二 寫入映射文件字節緩沖區(mappedByteBuffer) 映射文件字節緩沖區(mappedByteBuffer)flush
flush相關代碼
考慮到寫入性能，滿足 flushLeastPages * OS_PAGE_SIZE 才進行 flush。
1:
7: public int flush(final int flushLeastPages) {
8: if (this.isAbleToFlush(flushLeastPages)) {
9: if (this.hold()) {
10: int value = getReadPosition();
11:
12: try {
13: //We only append data to fileChannel or mappedByteBuffer, never both.
14: if (writeBuffer != null || this.fileChannel.position() != 0) {
15: this.fileChannel.force(false);
16: } else {
17: this.mappedByteBuffer.force();
18: }
19: } catch (Throwable e) {
20: log.error("Error occurred when force data to disk.", e);
21: }
22:
23: this.flushedPosition.set(value);
24: this.release();
25: } else {
26: log.warn("in flush, hold failed, flush offset = " + this.flushedPosition.get());
27: this.flushedPosition.set(getReadPosition());
28: }
29: }
30: return this.getFlushedPosition();
31: }
32:
33:
42: private boolean isAbleToFlush(final int flushLeastPages) {
43: int flush = this.flushedPosition.get();
44: int write = getReadPosition();
45:
46: if (this.isFull()) {
47: return true;
48: }
49:
50: if (flushLeastPages > 0) {
51: return ((write / OS_PAGE_SIZE) - (flush / OS_PAGE_SIZE)) >= flushLeastPages;
52: }
53:
54: return write > flush;
55: }
FlushRealTimeService
class FlushRealTimeService extends FlushCommitLogService {
2:
5: private long lastFlushTimestamp = 0;
6:
10: private long printTimes = 0;
11:
12: public void run() {
13: CommitLog.log.info(this.getServiceName() + " service started");
14:
15: while (!this.isStopped()) {
16: boolean flushCommitLogTimed = CommitLog.this.defaultMessageStore.getMessageStoreConfig().isFlushCommitLogTimed();
17: int interval = CommitLog.this.defaultMessageStore.getMessageStoreConfig().getFlushIntervalCommitLog();
18: int flushPhysicQueueLeastPages = CommitLog.this.defaultMessageStore.getMessageStoreConfig().getFlushCommitLogLeastPages();
19: int flushPhysicQueueThoroughInterval = CommitLog.this.defaultMessageStore.getMessageStoreConfig().getFlushCommitLogThoroughInterval();
20:
21: // Print flush progress
22: // 當時間滿足flushPhysicQueueThoroughInterval時，即使寫入的數量不足flushPhysicQueueLeastPages，也進行flush
23: boolean printFlushProgress = false;
24: long currentTimeMillis = System.currentTimeMillis();
25: if (currentTimeMillis >= (this.lastFlushTimestamp + flushPhysicQueueThoroughInterval)) {
26: this.lastFlushTimestamp = currentTimeMillis;
27: flushPhysicQueueLeastPages = 0;
28: printFlushProgress = (printTimes++ % 10) == 0;
29: }
30:
31: try {
32: // 等待執行
33: if (flushCommitLogTimed) {
34: Thread.sleep(interval);
35: } else {
36: this.waitForRunning(interval);
37: }
38:
39: if (printFlushProgress) {
40: this.printFlushProgress();
41: }
42:
43: // flush commitLog
44: long begin = System.currentTimeMillis();
45: CommitLog.this.mappedFileQueue.flush(flushPhysicQueueLeastPages);
46: long storeTimestamp = CommitLog.this.mappedFileQueue.getStoreTimestamp();
47: if (storeTimestamp > 0) {
48: CommitLog.this.defaultMessageStore.getStoreCheckpoint().setPhysicMsgTimestamp(storeTimestamp);
49: }
50: long past = System.currentTimeMillis() - begin;
51: if (past > 500) {
52: log.info("Flush data to disk costs {} ms", past);
53: }
54: } catch (Throwable e) {
55: CommitLog.log.warn(this.getServiceName() + " service has exception. ", e);
56: this.printFlushProgress();
57: }
58: }
59:
60: // Normal shutdown, to ensure that all the flush before exit
61: boolean result = false;
62: for (int i = 0; i < RETRY_TIMES_OVER && !result; i++) {
63: result = CommitLog.this.mappedFileQueue.flush(0);
64: CommitLog.log.info(this.getServiceName() + " service shutdown, retry " + (i + 1) + " times " + (result ? "OK" : "Not OK"));
65: }
66:
67: this.printFlushProgress();
68:
69: CommitLog.log.info(this.getServiceName() + " service end");
70: }
71:
72: @Override
73: public String getServiceName() {
74: return FlushRealTimeService.class.getSimpleName();
75: }
76:
77: private void printFlushProgress() {
78: // CommitLog.log.info("how much disk fall behind memory, "
79: // + CommitLog.this.mappedFileQueue.howMuchFallBehind());
80: }
81:
82: @Override
83: @SuppressWarnings("SpellCheckingInspection")
84: public long getJointime() {
85: return 1000 * 60 * 5;
86: }
87: }
說明：實時 flush線程服務，調用 MappedFile#flush 相關邏輯。
第 23 至 29 行 ：每 flushPhysicQueueThoroughInterval 周期，執行一次 flush 。因為不是每次循環到都能滿足 flushCommitLogLeastPages 大小，因此，需要一定周期進行一次強制 flush 。當然，不能每次循環都去執行強制 flush，這樣性能較差。
第 33 行 至 37 行 ：根據 flushCommitLogTimed 參數，可以選擇每次循環是固定周期還是等待喚醒。默認配置是后者，所以，每次插入消息完成，會去調用 commitLogService.wakeup() 。
第 45 行 ：調用 MappedFile 進行 flush。
第 61 至 65 行 ：Broker 關閉時，強制 flush，避免有未刷盤的數據。