rocketmq IndexFile源碼分析

IndexFile 存儲具體消息索引的文件，文件的內容結構如圖

 

## 自己拼的，以後再好好畫
IndexFile類

private static final InternalLogger log = InternalLoggerFactory.getLogger(LoggerName.STORE_LOGGER_NAME);
private static int hashSlotSize = 4;// 每個 hash 槽所佔的字節數
private static int indexSize = 20;// 每條indexFile條目佔用字節數
private static int invalidIndex = 0;// 用來驗證是否是一個有效的索引。
private final int hashSlotNum;// index 文件中 hash 槽的總個數
private final int indexNum;// indexFile中包含的條目數
private final MappedFile mappedFile;
private final FileChannel fileChannel;
private final MappedByteBuffer mappedByteBuffer;
private final IndexHeader indexHeader;// 消息頭

public IndexFile(final String fileName, final int hashSlotNum, final int indexNum,
    final long endPhyOffset, final long endTimestamp) throws IOException {
    int fileTotalSize =
        IndexHeader.INDEX_HEADER_SIZE + (hashSlotNum * hashSlotSize) + (indexNum * indexSize);
    this.mappedFile = new MappedFile(fileName, fileTotalSize);
    this.fileChannel = this.mappedFile.getFileChannel();
    this.mappedByteBuffer = this.mappedFile.getMappedByteBuffer();
    this.hashSlotNum = hashSlotNum;
    this.indexNum = indexNum;

    ByteBuffer byteBuffer = this.mappedByteBuffer.slice();
    this.indexHeader = new IndexHeader(byteBuffer);

    if (endPhyOffset > 0) {
        this.indexHeader.setBeginPhyOffset(endPhyOffset);
        this.indexHeader.setEndPhyOffset(endPhyOffset);
    }

    if (endTimestamp > 0) {
        this.indexHeader.setBeginTimestamp(endTimestamp);
        this.indexHeader.setEndTimestamp(endTimestamp);
    }
}

IndexService類

/**
 * Maximum times to attempt index file creation.
 */
private static final int MAX_TRY_IDX_CREATE = 3;
private final DefaultMessageStore defaultMessageStore;
private final int hashSlotNum;
private final int indexNum;
private final String storePath;
private final ArrayList<IndexFile> indexFileList = new ArrayList<IndexFile>();
private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();

public IndexService(final DefaultMessageStore store) {
    this.defaultMessageStore = store;
    this.hashSlotNum = store.getMessageStoreConfig().getMaxHashSlotNum(); // 槽的數量 配置文件讀取
    this.indexNum = store.getMessageStoreConfig().getMaxIndexNum(); // 條目的條數
    this.storePath =
        StorePathConfigHelper.getStorePathIndex(store.getMessageStoreConfig().getStorePathRootDir());
}

 

public boolean putKey(final String key, final long phyOffset, final long storeTimestamp) {
    if (this.indexHeader.getIndexCount() < this.indexNum) {
        // 取得hash值
        int keyHash = indexKeyHashMethod(key);
        // 求餘 取得下標 應該改 1.8hashMap獲取下標的方法 左移右移算
        int slotPos = keyHash % this.hashSlotNum;
        // 佔的字節
        int absSlotPos = IndexHeader.INDEX_HEADER_SIZE + slotPos * hashSlotSize;

        FileLock fileLock = null;

        try {

            // fileLock = this.fileChannel.lock(absSlotPos, hashSlotSize,
            // false);
            int slotValue = this.mappedByteBuffer.getInt(absSlotPos);
            if (slotValue <= invalidIndex || slotValue > this.indexHeader.getIndexCount()) {
                slotValue = invalidIndex;
            }

            // 時間差 計算消息的存儲時間與當前 IndexFile 存放的最小時間差額(單位爲秒
            long timeDiff = storeTimestamp - this.indexHeader.getBeginTimestamp();

            timeDiff = timeDiff / 1000;

            if (this.indexHeader.getBeginTimestamp() <= 0) {
                timeDiff = 0;
            } else if (timeDiff > Integer.MAX_VALUE) {
                timeDiff = Integer.MAX_VALUE;
            } else if (timeDiff < 0) {
                timeDiff = 0;
            }

            int absIndexPos =
                IndexHeader.INDEX_HEADER_SIZE + this.hashSlotNum * hashSlotSize
                    + this.indexHeader.getIndexCount() * indexSize;

            // 消息體
            this.mappedByteBuffer.putInt(absIndexPos, keyHash);
            this.mappedByteBuffer.putLong(absIndexPos + 4, phyOffset);
            this.mappedByteBuffer.putInt(absIndexPos + 4 + 8, (int) timeDiff);
            this.mappedByteBuffer.putInt(absIndexPos + 4 + 8 + 4, slotValue);

            // 槽存儲 消息的數量
            this.mappedByteBuffer.putInt(absSlotPos, this.indexHeader.getIndexCount());

            if (this.indexHeader.getIndexCount() <= 1) {
                this.indexHeader.setBeginPhyOffset(phyOffset);
                this.indexHeader.setBeginTimestamp(storeTimestamp);
            }

            this.indexHeader.incHashSlotCount();
            this.indexHeader.incIndexCount();
            this.indexHeader.setEndPhyOffset(phyOffset);
            this.indexHeader.setEndTimestamp(storeTimestamp);

            return true;
        } catch (Exception e) {
            log.error("putKey exception, Key: " + key + " KeyHashCode: " + key.hashCode(), e);
        } finally {
            if (fileLock != null) {
                try {
                    fileLock.release();
                } catch (IOException e) {
                    log.error("Failed to release the lock", e);
                }
            }
        }
    } else {
        log.warn("Over index file capacity: index count = " + this.indexHeader.getIndexCount()
            + "; index max num = " + this.indexNum);
    }

    return false;
}