SolrCloud HOWTO

What is the most important change in 4.x version of Apache Solr? I think there are many of them but Solr Cloud is definitely something that changed a lot in Solr architecture. Until now, bigger installations suffered from single point of failure (SPOF) – there was only the one master server and when this server was going down, the whole cluster lose the ability to receive new data. Of course you could go for multiple masters, where a single master was responsible for indexing some part of the data, but still, there was a SPOF present in your deployment. Even if everything worked, due to commit interval and the fact that slave instances checked the presence of new data periodically, the solution was far from ideal – the new data in the cluster appeared minutes after commit.

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