solr源码分析--recovery

恢复机制比较复杂，慢慢写写。

概述

　　恢复的流程主要就是三个，一个replay，一个peersync还有一个replicate。下面结合场景，从源码角度分析三个数据恢复场景的流程。

replay

　　这个还是先从solr启动说起，分析一下整体的代码流程。

SolrDispatcher.init()

  @Override
  public void init(FilterConfig config) throws ServletException
  {
    log.info("SolrDispatchFilter.init(): {}", this.getClass().getClassLoader());

    String exclude = config.getInitParameter("excludePatterns");
    if(exclude != null) {
      String[] excludeArray = exclude.split(",");
      excludePatterns = new ArrayList<>();
      for (String element : excludeArray) {
        excludePatterns.add(Pattern.compile(element));
      }
    }
    try {
      Properties extraProperties = (Properties) config.getServletContext().getAttribute(PROPERTIES_ATTRIBUTE);
      if (extraProperties == null)
        extraProperties = new Properties();

      String solrHome = (String) config.getServletContext().getAttribute(SOLRHOME_ATTRIBUTE);
      ExecutorUtil.addThreadLocalProvider(SolrRequestInfo.getInheritableThreadLocalProvider());

      this.cores = createCoreContainer(solrHome == null ? SolrResourceLoader.locateSolrHome() : Paths.get(solrHome),
                                       extraProperties); // 创建一个CoreContainer
      this.httpClient = cores.getUpdateShardHandler().getHttpClient();
      log.info("user.dir=" + System.getProperty("user.dir"));
    }
    catch( Throwable t ) {
      // catch this so our filter still works
      log.error( "Could not start Solr. Check solr/home property and the logs");
      SolrCore.log( t );
      if (t instanceof Error) {
        throw (Error) t;
      }
    }

    log.info("SolrDispatchFilter.init() done");
  }

  protected CoreContainer createCoreContainer(Path solrHome, Properties extraProperties) {
    NodeConfig nodeConfig = loadNodeConfig(solrHome, extraProperties);
    cores = new CoreContainer(nodeConfig, extraProperties, true);
    cores.load();
    return cores;
  }

CoreContainer.load()

...... 
      for (final CoreDescriptor cd : cds) {
        if (cd.isTransient() || !cd.isLoadOnStartup()) {
          solrCores.putDynamicDescriptor(cd.getName(), cd);
        } else if (asyncSolrCoreLoad) {
          solrCores.markCoreAsLoading(cd);
        }
        if (cd.isLoadOnStartup()) {
          futures.add(coreLoadExecutor.submit(() -> {
            SolrCore core;
            try {
              if (zkSys.getZkController() != null) {
                zkSys.getZkController().throwErrorIfReplicaReplaced(cd);
              }

              core = create(cd, false); // 创建，加载之前的数据
            } finally {
              if (asyncSolrCoreLoad) {
                solrCores.markCoreAsNotLoading(cd);
              }
            }
            try {
              zkSys.registerInZk(core, true); // zk中进行注册
            } catch (RuntimeException e) {
              SolrException.log(log, "Error registering SolrCore", e);
            }
            return