How does the slave replicate

最新推荐文章于 2025-08-15 10:14:10 发布

转载最新推荐文章于 2025-08-15 10:14:10 发布 · 169 阅读

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本文详细阐述了Apache Solr集群中从节点如何通过不断轮询主节点来获取最新的索引版本，并在本地进行同步复制的过程。包括从节点发起文件列表请求、检查本地索引文件、下载缺失文件、文件移动到本地索引目录以及最终执行commit命令加载新索引等关键步骤。

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http://wiki.apache.org/solr/SolrReplication

How does the slave replicate?

The master is totally unaware of the slaves. The slave continuously keeps polling the master (depending on the 'pollInterval' parameter) to check the current index version the master. If the slave finds out that the master has a newer version of the index it initiates a replication process. The steps are as follows,

Slave issues a filelist command to get the list of the files. This command returns the names of the files as well as some metadata (size,lastmodified,alias if any)

http://localhost:8080/solr/core2/replication?command=filelist&indexversion=1302400909042

The slave checks with its own index if it has any of those files in the local index. It then proceeds to download the missing files (The command name is 'filecontent' ). This uses a custom format (akin to the HTTP chunked encoding) to download the full content or a part of each file . If the connection breaks in between , the download resumes from the point it failed. At any point, it tries 5 times before giving up a replication altogether.

The files are downloaded into a temp dir. So if the slave or master crashes in between it does not corrupt anything. It just aborts the current replication.
After the download completes, all the new files are 'mov'ed to the slave's live index directory and the files' timestamps will match the timestamps in the master.
A 'commit' command is issued on the slave by the Slave's ReplicationHandler and the new index is loaded.