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Apache Solr Reference Guide Covering Apache Solr 6.0

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CDC Replicator<br />

The CDC Replicator is a background thread that is responsible for replicating updates from a Source Data<br />

Center to one or more Target Data Centers. It will also be responsible in providing monitoring information on a<br />

per-shard basis. As there can be a large number of collections and shards in a cluster, we will use a fixed-size<br />

pool of CDC Replicator threads that will be shared across shards.<br />

Limitations<br />

The current design of CDCR has some limitations. CDCR will continue to evolve over time and many of these<br />

limitations will be addressed. Among them are:<br />

CDCR is unlikely to be satisfactory for bulk-load situations where the update rate is high, especially if the<br />

bandwidth between the Source and Target clusters is restricted. In this scenario, the initial bulk load<br />

should be performed, the Source and Target data centers synchronized and CDCR be utilized for<br />

incremental updates.<br />

CDCR is currently only active-passive; data is pushed from the Source cluster to the Target cluster. There<br />

is active work being done in this area in the 6x code line to remove this limitation.<br />

Configuration<br />

The Source and Target configurations differ in the case of the data centers being in separate clusters. "Cluster"<br />

here means separate ZooKeeper ensembles controlling disjoint <strong>Solr</strong> instances. Whether these data centers are<br />

physically separated or not is immaterial for this discussion.<br />

Source Configuration<br />

Here is a sample of a Source configuration file, a section in solrconfig.xml. The presence of the <br />

section causes CDCR to use this cluster as the Source and should not be present in the Target collections in the<br />

cluster-to-cluster case. Details about each setting are after the two examples:<br />

<br />

<br />

10.240.18.211:2181<br />

collection1<br />

collection1<br />

<br />

<br />

8<br />

1000<br />

128<br />

<br />

<br />

1000<br />

<br />

<br />

<br />

${solr.ulog.dir:}<br />

<br />

<br />

<br />

<strong>Apache</strong> <strong>Solr</strong> <strong>Reference</strong> <strong>Guide</strong> <strong>6.0</strong><br />

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