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Solr4.8.0源码分析(14)之SolrCloud索引深入(1)

Solr4.8.0源码分析(14) 之 SolrCloud索引深入(1)

     上一章节《Solr In Action 笔记(4) 之 SolrCloud分布式索引基础》简要学习了SolrCloud的索引过程,本节开始将通过阅读源码来深入学习下SolrCloud的索引过程。

1. SolrCloud的索引过程流程图

      这里借用下《solrCloud Update Request Handling 更新索引流程》流程图:

    由上图可以看出,SolrCloud的索引过程主要通过一个索引链过程来实现的,那么本节主要讲述下索引链以及DistributedUpdateProcessor这个过程。

2. SolrCloud update索引链

  • SolrCloud的Update索引链的类是UpdateRequestProcessorChain,这个类在Solr初始化的时候就会进行定义。
  • SolrCloud的Update索引链的组成可以通过solrconfig.xml进行自定义,比较灵活,例如:
 1  <updateRequestProcessorChain name="key" default="true"> 2    <processor class="package.Class1" /> 3    <processor class="package.Class2" > 4      <str name="someInitParam1">value</str> 5      <int name="someInitParam2">42</int> 6    </processor> 7    <processor class="solr.LogUpdateProcessorFactory" > 8      <int name="maxNumToLog">100</int> 9    </processor>10    <processor class="solr.RunUpdateProcessorFactory" />11  </updateRequestProcessorChain>
  • 如果未自定义UpdateRequestProcessorChain,那么Solr就默认以下三个过程组成索引链,依次如下:
    • LogUpdateProcessorFactory, 它对应的处理过程为LogUpdateProcessor , 主要负责对ulog的update;

    • DistributedUpdateProcessorFactory, 它对应的处理过程为DistributedUpdateProcessor ,主要负责对version的处理以及request的分发;

    • RunUpdateProcessorFactory,  它对应的处理过程为DirectUpdateHandler2 ,主要负责将记录add进本shard的lucene中;

  • 如果最后一个索引链包含了RunUpdateProcessorFactory,但是没有包含DistributedUpdateProcessorFactory,那么Solr会在索引链init的时候自动在RunUpdateProcessorFactory前面加入DistributedUpdateProcessorFactory;
  • 每一次update操作,都会重新创建一个索引链,即createProcessor,然后依次进行下去;
  • update操作包含add,delete,commit,所以上述UpdateProcessor都会分别包含processAdd,processDelete,processCommit,依次可以细分成add 索引链,delete索引链,commit索引链。

 

    明白了以上几点,那么开始学习索引链的源码

  • 首先来查看索引链的init代码,UpdateRequestProcessorChain.init()在初始化SolrCore的时候就调用了
 1  public void init(PluginInfo info) { 2     final String infomsg = "updateRequestProcessorChain \"" +  3       (null != info.name ? info.name : "") + "\"" +  4       (info.isDefault() ? " (default)" : ""); 5  6     log.info("creating " + infomsg); 7  8     // wrap in an ArrayList so we know we know we can do fast index lookups  9     // and that add(int,Object) is supported10     //从solrcore获取索引链的成员,存放成列表形式。索引链在Solrconfig.xml中是以插件的形式加入的11     List<UpdateRequestProcessorFactory> list = new ArrayList12       (solrCore.initPlugins(info.getChildren("processor"),UpdateRequestProcessorFactory.class,null));13 14     if(list.isEmpty()){15       throw new SolrException(SolrException.ErrorCode.SERVER_ERROR,16                               infomsg + " require at least one processor");17     }18 19     int numDistrib = 0;20     int runIndex = -1;21     // hi->lo incase multiple run instances, add before first one22     // (no idea why someone might use multiple run instances, but just in case)23     //从后往前遍历索引链列表,寻找DistributingUpdateProcessorFactory和RunUpdateProcessorFactory24     for (int i = list.size()-1; 0 <= i; i--) {25       UpdateRequestProcessorFactory factory = list.get(i);26       if (factory instanceof DistributingUpdateProcessorFactory) {27         numDistrib++; //DistributingUpdateProcessorFactory的个数不能超过128       }29       if (factory instanceof RunUpdateProcessorFactory) {30         runIndex = i; //RunUpdateProcessorFactory的编号31       }32     }33     if (1 < numDistrib) {34       throw new SolrException(SolrException.ErrorCode.SERVER_ERROR,35                               infomsg + " may not contain more then one " +36                               "instance of DistributingUpdateProcessorFactory");37     }38     //如果存在RunUpdateProcessorFactory且没有DistributingUpdateProcessorFactory,39     //那么会在RunUpdateProcessorFactory之前加入DistributingUpdateProcessorFactory40     if (0 <= runIndex && 0 == numDistrib) {41       // by default, add distrib processor immediately before run42       DistributedUpdateProcessorFactory distrib 43         = new DistributedUpdateProcessorFactory();44       distrib.init(new NamedList());45       list.add(runIndex, distrib);46 47       log.info("inserting DistributedUpdateProcessorFactory into " + infomsg);48     }49 50     chain = list.toArray(new UpdateRequestProcessorFactory[list.size()]); 51   }
  • 每当有update请求时候就会触发索引链的创建,UpdateRequestProcessorChain.createProcessor。
 1 public UpdateRequestProcessor createProcessor(SolrQueryRequest req,  2                                                 SolrQueryResponse rsp)  3   { 4     UpdateRequestProcessor processor = null; 5     UpdateRequestProcessor last = null; 6     //获取distribPhase 是否需要跳过DistributingUpdateProcessorFactory前面那一过程(即LogUpdateProcessor),该参数不是由客户端生成 7     final String distribPhase = req.getParams().get(DistributingUpdateProcessorFactory.DISTRIB_UPDATE_PARAM); 8     final boolean skipToDistrib = distribPhase != null; 9     boolean afterDistrib = true;  // we iterate backwards, so true to start10     //从后往前组件索引链即11     //LogUpdateProcessor.next = DistributedUpdateProcessor12     //DistributedUpdateProcessor.next = DirectUpdateHandler213     //DirectUpdateHandler2.next = null14     for (int i = chain.length-1; i>=0; i--) {15       UpdateRequestProcessorFactory factory = chain[i];16 17       if (skipToDistrib) {18         if (afterDistrib) {19           // 跳过DistributingUpdateProcessorFactory前面的索引链过程20           if (factory instanceof DistributingUpdateProcessorFactory) {21             afterDistrib = false;22           }23         } else if (!(factory instanceof UpdateRequestProcessorFactory.RunAlways)) {24           // skip anything that doesn‘t have the marker interface25           continue;26         }27       }28       //创建UpdateRequestProcessorFactory对应的UpdateProcessor,并进行连接29       processor = factory.getInstance(req, rsp, last);30       last = processor == null ? last : processor;31     }32 33     return last;34   }
  • 在UpdateRequestProcessorChain.createProcessor会调用UpdateRequestProcessorFactory的getInstance创建对应的updateProcessor,
    • LogUpdateProcessor

1   public UpdateRequestProcessor getInstance(SolrQueryRequest req, SolrQueryResponse rsp, UpdateRequestProcessor next) {2     return LogUpdateProcessor.log.isInfoEnabled() ? new LogUpdateProcessor(req, rsp, this, next) : null;3   }
    • DistributedUpdateProcessor
1   public DistributedUpdateProcessor getInstance(SolrQueryRequest req,2       SolrQueryResponse rsp, UpdateRequestProcessor next) {3 4     return new DistributedUpdateProcessor(req, rsp, next);5   }
    • RunUpdateProcessorFactory

 

1   public UpdateRequestProcessor getInstance(SolrQueryRequest req, SolrQueryResponse rsp, UpdateRequestProcessor next) 2   {3     return new RunUpdateProcessor(req, next);4   }

 

总结:本节主要学习了SolrCloud分布式索引的整体流程,以及SolrCloud建索引时候索引链的情况,下一节将详细介绍索引链的具体过程。

Solr4.8.0源码分析(14)之SolrCloud索引深入(1)