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itemtype=http://schema.org/CreativeWork><meta content="聊一下 RocketMQ 的消息存储四 | Nicksxs's Blog" itemprop=name><meta content="IndexFile 结构 hash 结构能够通过 key 寻找到对应在 CommitLog 中的位置" itemprop=description></span><header class=post-header><h1 itemprop="name headline" class=post-title>聊一下 RocketMQ 的消息存储四</h1><div class=post-meta-container><div class=post-meta><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-calendar"></i> </span><span class=post-meta-item-text>发表于</span> <time itemprop="dateCreated datePublished" title="创建时间:2021-10-17 20:41:34" datetime=2021-10-17T20:41:34+08:00>2021-10-17</time> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-folder"></i> </span><span class=post-meta-item-text>分类于</span> <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/MQ/ itemprop=url rel=index><span itemprop=name>MQ</span></a> </span>, <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/MQ/RocketMQ/ itemprop=url rel=index><span itemprop=name>RocketMQ</span></a> </span>, <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/MQ/RocketMQ/%E6%B6%88%E6%81%AF%E9%98%9F%E5%88%97/ itemprop=url rel=index><span itemprop=name>消息队列</span></a> </span></span><span class="post-meta-item cloudflare-page-counter" data-title="聊一下 RocketMQ 的消息存储四" data-increment=true data-path=/2021/10/17/%E8%81%8A%E4%B8%80%E4%B8%8B-RocketMQ-%E7%9A%84%E6%B6%88%E6%81%AF%E5%AD%98%E5%82%A8%E5%9B%9B/ title=阅读次数><span class=post-meta-item-icon><i class="far fa-eye"></i> </span><span class=post-meta-item-text>阅读次数:</span> <span class=cloudflare-page-counter-count></span></span></div><div class=post-description>IndexFile 结构 hash 结构能够通过 key 寻找到对应在 CommitLog 中的位置</div></div></header><div class=post-body itemprop=articleBody><p>IndexFile 结构 hash 结构能够通过 key 寻找到对应在 CommitLog 中的位置<p>IndexFile 的构建则是分发给这个进行处理<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br><span class=line>12</span><br><span class=line>13</span><br><span class=line>14</span><br><span class=line>15</span><br><span class=line>16</span><br><span class=line>17</span><br><span class=line>18</span><br><span class=line>19</span><br><span class=line>20</span><br><span class=line>21</span><br><span class=line>22</span><br><span class=line>23</span><br><span class=line>24</span><br><span class=line>25</span><br><span class=line>26</span><br><span class=line>27</span><br><span class=line>28</span><br><span class=line>29</span><br><span class=line>30</span><br><span class=line>31</span><br><span class=line>32</span><br><span class=line>33</span><br><span class=line>34</span><br><span class=line>35</span><br><span class=line>36</span><br><span class=line>37</span><br><span class=line>38</span><br><span class=line>39</span><br><span class=line>40</span><br><span class=line>41</span><br><span class=line>42</span><br><span class=line>43</span><br><span class=line>44</span><br><span class=line>45</span><br><span class=line>46</span><br><span class=line>47</span><br><span class=line>48</span><br><span class=line>49</span><br><span class=line>50</span><br><span class=line>51</span><br><span class=line>52</span><br><span class=line>53</span><br><span class=line>54</span><br><span class=line>55</span><br></pre><td class=code><pre><span class=line><span class=keyword>class</span> <span class="title class_">CommitLogDispatcherBuildIndex</span> <span class=keyword>implements</span> <span class="title class_">CommitLogDispatcher</span> {</span><br><span class=line></span><br><span class=line> <span class=meta>@Override</span></span><br><span class=line> <span class=keyword>public</span> <span class=keyword>void</span> <span class="title function_">dispatch</span><span class=params>(DispatchRequest request)</span> {</span><br><span class=line> <span class=keyword>if</span> (DefaultMessageStore.<span class=built_in>this</span>.messageStoreConfig.isMessageIndexEnable()) {</span><br><span class=line> DefaultMessageStore.<span class=built_in>this</span>.indexService.buildIndex(request);</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line>}</span><br><span class=line><span class=keyword>public</span> <span class=keyword>void</span> <span class="title function_">buildIndex</span><span class=params>(DispatchRequest req)</span> {</span><br><span class=line> <span class=type>IndexFile</span> <span class=variable>indexFile</span> <span class=operator>=</span> retryGetAndCreateIndexFile();</span><br><span class=line> <span class=keyword>if</span> (indexFile != <span class=literal>null</span>) {</span><br><span class=line> <span class=type>long</span> <span class=variable>endPhyOffset</span> <span class=operator>=</span> indexFile.getEndPhyOffset();</span><br><span class=line> <span class=type>DispatchRequest</span> <span class=variable>msg</span> <span class=operator>=</span> req;</span><br><span class=line> <span class=type>String</span> <span class=variable>topic</span> <span class=operator>=</span> msg.getTopic();</span><br><span class=line> <span class=type>String</span> <span class=variable>keys</span> <span class=operator>=</span> msg.getKeys();</span><br><span class=line> <span class=keyword>if</span> (msg.getCommitLogOffset() < endPhyOffset) {</span><br><span class=line> <span class=keyword>return</span>;</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=keyword>final</span> <span class=type>int</span> <span class=variable>tranType</span> <span class=operator>=</span> MessageSysFlag.getTransactionValue(msg.getSysFlag());</span><br><span class=line> <span class=keyword>switch</span> (tranType) {</span><br><span class=line> <span class=keyword>case</span> MessageSysFlag.TRANSACTION_NOT_TYPE:</span><br><span class=line> <span class=keyword>case</span> MessageSysFlag.TRANSACTION_PREPARED_TYPE:</span><br><span class=line> <span class=keyword>case</span> MessageSysFlag.TRANSACTION_COMMIT_TYPE:</span><br><span class=line> <span class=keyword>break</span>;</span><br><span class=line> <span class=keyword>case</span> MessageSysFlag.TRANSACTION_ROLLBACK_TYPE:</span><br><span class=line> <span class=keyword>return</span>;</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=keyword>if</span> (req.getUniqKey() != <span class=literal>null</span>) {</span><br><span class=line> indexFile = putKey(indexFile, msg, buildKey(topic, req.getUniqKey()));</span><br><span class=line> <span class=keyword>if</span> (indexFile == <span class=literal>null</span>) {</span><br><span class=line> log.error(<span class=string>"putKey error commitlog {} uniqkey {}"</span>, req.getCommitLogOffset(), req.getUniqKey());</span><br><span class=line> <span class=keyword>return</span>;</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=keyword>if</span> (keys != <span class=literal>null</span> && keys.length() > <span class=number>0</span>) {</span><br><span class=line> String[] keyset = keys.split(MessageConst.KEY_SEPARATOR);</span><br><span class=line> <span class=keyword>for</span> (<span class=type>int</span> <span class=variable>i</span> <span class=operator>=</span> <span class=number>0</span>; i < keyset.length; i++) {</span><br><span class=line> <span class=type>String</span> <span class=variable>key</span> <span class=operator>=</span> keyset[i];</span><br><span class=line> <span class=keyword>if</span> (key.length() > <span class=number>0</span>) {</span><br><span class=line> indexFile = putKey(indexFile, msg, buildKey(topic, key));</span><br><span class=line> <span class=keyword>if</span> (indexFile == <span class=literal>null</span>) {</span><br><span class=line> log.error(<span class=string>"putKey error commitlog {} uniqkey {}"</span>, req.getCommitLogOffset(), req.getUniqKey());</span><br><span class=line> <span class=keyword>return</span>;</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> log.error(<span class=string>"build index error, stop building index"</span>);</span><br><span class=line> }</span><br><span class=line> }</span><br></pre></table></figure><p>配置的数量<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br></pre><td class=code><pre><span class=line><span class=keyword>private</span> <span class=type>boolean</span> <span class=variable>messageIndexEnable</span> <span class=operator>=</span> <span class=literal>true</span>;</span><br><span class=line><span class=keyword>private</span> <span class=type>int</span> <span class=variable>maxHashSlotNum</span> <span class=operator>=</span> <span class=number>5000000</span>;</span><br><span class=line><span class=keyword>private</span> <span class=type>int</span> <span class=variable>maxIndexNum</span> <span class=operator>=</span> <span class=number>5000000</span> * <span class=number>4</span>;</span><br></pre></table></figure><p>最核心的其实是 IndexFile 的结构和如何写入<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br><span class=line>12</span><br><span class=line>13</span><br><span class=line>14</span><br><span class=line>15</span><br><span class=line>16</span><br><span class=line>17</span><br><span class=line>18</span><br><span class=line>19</span><br><span class=line>20</span><br><span class=line>21</span><br><span class=line>22</span><br><span class=line>23</span><br><span class=line>24</span><br><span class=line>25</span><br><span class=line>26</span><br><span class=line>27</span><br><span class=line>28</span><br><span class=line>29</span><br><span class=line>30</span><br><span class=line>31</span><br><span class=line>32</span><br><span class=line>33</span><br><span class=line>34</span><br><span class=line>35</span><br><span class=line>36</span><br><span class=line>37</span><br><span class=line>38</span><br><span class=line>39</span><br><span class=line>40</span><br><span class=line>41</span><br><span class=line>42</span><br><span class=line>43</span><br><span class=line>44</span><br><span class=line>45</span><br><span class=line>46</span><br><span class=line>47</span><br><span class=line>48</span><br><span class=line>49</span><br><span class=line>50</span><br><span class=line>51</span><br><span class=line>52</span><br><span class=line>53</span><br><span class=line>54</span><br><span class=line>55</span><br><span class=line>56</span><br><span class=line>57</span><br><span class=line>58</span><br><span class=line>59</span><br><span class=line>60</span><br><span class=line>61</span><br><span class=line>62</span><br><span class=line>63</span><br><span class=line>64</span><br><span class=line>65</span><br><span class=line>66</span><br><span class=line>67</span><br><span class=line>68</span><br><span class=line>69</span><br><span class=line>70</span><br><span class=line>71</span><br><span class=line>72</span><br><span class=line>73</span><br><span class=line>74</span><br></pre><td class=code><pre><span class=line><span class=keyword>public</span> <span class=type>boolean</span> <span class="title function_">putKey</span><span class=params>(<span class=keyword>final</span> String key, <span class=keyword>final</span> <span class=type>long</span> phyOffset, <span class=keyword>final</span> <span class=type>long</span> storeTimestamp)</span> {</span><br><span class=line> <span class=keyword>if</span> (<span class=built_in>this</span>.indexHeader.getIndexCount() < <span class=built_in>this</span>.indexNum) {</span><br><span class=line> <span class=comment>// 获取 key 的 hash</span></span><br><span class=line> <span class=type>int</span> <span class=variable>keyHash</span> <span class=operator>=</span> indexKeyHashMethod(key);</span><br><span class=line> <span class=comment>// 计算属于哪个 slot</span></span><br><span class=line> <span class=type>int</span> <span class=variable>slotPos</span> <span class=operator>=</span> keyHash % <span class=built_in>this</span>.hashSlotNum;</span><br><span class=line> <span class=comment>// 计算 slot 位置 因为结构是有个 indexHead,主要是分为三段 header,slot 和 index</span></span><br><span class=line> <span class=type>int</span> <span class=variable>absSlotPos</span> <span class=operator>=</span> IndexHeader.INDEX_HEADER_SIZE + slotPos * hashSlotSize;</span><br><span class=line></span><br><span class=line> <span class=type>FileLock</span> <span class=variable>fileLock</span> <span class=operator>=</span> <span class=literal>null</span>;</span><br><span class=line></span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line></span><br><span class=line> <span class=comment>// fileLock = this.fileChannel.lock(absSlotPos, hashSlotSize,</span></span><br><span class=line> <span class=comment>// false);</span></span><br><span class=line> <span class=type>int</span> <span class=variable>slotValue</span> <span class=operator>=</span> <span class=built_in>this</span>.mappedByteBuffer.getInt(absSlotPos);</span><br><span class=line> <span class=keyword>if</span> (slotValue <= invalidIndex || slotValue > <span class=built_in>this</span>.indexHeader.getIndexCount()) {</span><br><span class=line> slotValue = invalidIndex;</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=type>long</span> <span class=variable>timeDiff</span> <span class=operator>=</span> storeTimestamp - <span class=built_in>this</span>.indexHeader.getBeginTimestamp();</span><br><span class=line></span><br><span class=line> timeDiff = timeDiff / <span class=number>1000</span>;</span><br><span class=line></span><br><span class=line> <span class=keyword>if</span> (<span class=built_in>this</span>.indexHeader.getBeginTimestamp() <= <span class=number>0</span>) {</span><br><span class=line> timeDiff = <span class=number>0</span>;</span><br><span class=line> } <span class=keyword>else</span> <span class=keyword>if</span> (timeDiff > Integer.MAX_VALUE) {</span><br><span class=line> timeDiff = Integer.MAX_VALUE;</span><br><span class=line> } <span class=keyword>else</span> <span class=keyword>if</span> (timeDiff < <span class=number>0</span>) {</span><br><span class=line> timeDiff = <span class=number>0</span>;</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=comment>// 计算索引存放位置,头部 + slot 数量 * slot 大小 + 已有的 index 数量 + index 大小</span></span><br><span class=line> <span class=type>int</span> <span class=variable>absIndexPos</span> <span class=operator>=</span></span><br><span class=line> IndexHeader.INDEX_HEADER_SIZE + <span class=built_in>this</span>.hashSlotNum * hashSlotSize</span><br><span class=line> + <span class=built_in>this</span>.indexHeader.getIndexCount() * indexSize;</span><br><span class=line> </span><br><span class=line> <span class=built_in>this</span>.mappedByteBuffer.putInt(absIndexPos, keyHash);</span><br><span class=line> <span class=built_in>this</span>.mappedByteBuffer.putLong(absIndexPos + <span class=number>4</span>, phyOffset);</span><br><span class=line> <span class=built_in>this</span>.mappedByteBuffer.putInt(absIndexPos + <span class=number>4</span> + <span class=number>8</span>, (<span class=type>int</span>) timeDiff);</span><br><span class=line> <span class=built_in>this</span>.mappedByteBuffer.putInt(absIndexPos + <span class=number>4</span> + <span class=number>8</span> + <span class=number>4</span>, slotValue);</span><br><span class=line></span><br><span class=line> <span class=comment>// 存放的是数量位移,不是绝对位置</span></span><br><span class=line> <span class=built_in>this</span>.mappedByteBuffer.putInt(absSlotPos, <span class=built_in>this</span>.indexHeader.getIndexCount());</span><br><span class=line></span><br><span class=line> <span class=keyword>if</span> (<span class=built_in>this</span>.indexHeader.getIndexCount() <= <span class=number>1</span>) {</span><br><span class=line> <span class=built_in>this</span>.indexHeader.setBeginPhyOffset(phyOffset);</span><br><span class=line> <span class=built_in>this</span>.indexHeader.setBeginTimestamp(storeTimestamp);</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=built_in>this</span>.indexHeader.incHashSlotCount();</span><br><span class=line> <span class=built_in>this</span>.indexHeader.incIndexCount();</span><br><span class=line> <span class=built_in>this</span>.indexHeader.setEndPhyOffset(phyOffset);</span><br><span class=line> <span class=built_in>this</span>.indexHeader.setEndTimestamp(storeTimestamp);</span><br><span class=line></span><br><span class=line> <span class=keyword>return</span> <span class=literal>true</span>;</span><br><span class=line> } <span class=keyword>catch</span> (Exception e) {</span><br><span class=line> log.error(<span class=string>"putKey exception, Key: "</span> + key + <span class=string>" KeyHashCode: "</span> + key.hashCode(), e);</span><br><span class=line> } <span class=keyword>finally</span> {</span><br><span class=line> <span class=keyword>if</span> (fileLock != <span class=literal>null</span>) {</span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> fileLock.release();</span><br><span class=line> } <span class=keyword>catch</span> (IOException e) {</span><br><span class=line> log.error(<span class=string>"Failed to release the lock"</span>, e);</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> log.warn(<span class=string>"Over index file capacity: index count = "</span> + <span class=built_in>this</span>.indexHeader.getIndexCount()</span><br><span class=line> + <span class=string>"; index max num = "</span> + <span class=built_in>this</span>.indexNum);</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=keyword>return</span> <span class=literal>false</span>;</span><br><span class=line> }</span><br></pre></table></figure><p>具体可以看一下这个简略的示意图<br><img loading=lazy src=https://img.nicksxs.me/uPic/kqfruz.png></div><footer class=post-footer><div class="affiliate-creative affiliate-creative--post-end" data-affiliate-id=tencent-cloud-general><a rel="sponsored noopener" aria-label=腾讯云产品优惠 href=https://cloud.tencent.com/act/cps/redirect?redirect=2446&cps_key=2e33a1eedb380997d03618b4a5ba6ca7&from=console target=_blank><img alt=腾讯云服务器、数据库和云产品优惠 decoding=async height=419 loading=lazy src=/uploads/affiliate/tencent-cloud-general.webp width=690> </a><span class=affiliate-disclosure>推广</span></div><div class=reward-container><div>请我一杯咖啡吧!</div><button>赞赏</button><div class=post-reward><div><img alt="Nicksxs 微信" src=https://i.loli.net/2020/01/12/NUlWanT31E8LQGx.png><span>微信</span></div><div><img alt="Nicksxs 支付宝" 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