Core overview

Selecting one of the available cores in the drop-down list on the left side of the Administration Console will open a core dedicated area, with several other sections. The first section is an overview of the selected core. It reports more or less the same information that we saw in the dashboard and in the core admin page.

Here, there is additional information about the health check (heartbeat information enabled only if you configured the ping request handler) and the replication status.

The replication section shows the index status of the master and slave (only if the current Solr instance acts as a slave) in terms of replicability.

Tip

The replication section is useful for monitoring master-repeater-slave instances, especially when you get some synchronization issues within the Solr ensemble. Note that the console also has a dedicated Replication section where that information is more detailed.

The master-slave replication architecture is explained in the next chapter.

Caches

To speed up query execution, Solr stores data using several types of in-memory caches. Caches transparently store filters, documents, and identifiers so that future requests for the same data can be served faster. If you run the same search twice, you will see in the Solr logs a marked difference between the first and the second query in terms of response time, as shown in the following example:

… params={q=history&fq=catalog:NRA} hits=17298 status=0 QTime=78
…
… params={q=history&fq=catalog:NRA} hits=17298 status=0 QTime=2

Solr comes with several kinds of caches. They can be configured and tuned in solrconfig.xml:

<filterCache class="solr.FastLRUCache" size="512" initialSize="512" autowarmCount="0"/>
<queryResultCache class="solr.LRUCache" size="512" initialSize="512" autowarmCount="0"/>
<documentCache class="solr.LRUCache" size="512" initialSize="512" autowarmCount="0"/>
<fieldValueCache class="solr.FastLRUCache" size="512" autowarmCount="128" showItems="32" />

The following table briefly describes the types of caches available in Solr:

Cache

Description

FilterCache

Holds the document identifiers associated with filter queries that have been executed.

QueryResultCache

Holds the document identifiers resulting from queries that have been executed.

DocumentCache

Holds Lucene document instances for quick access to their stored fields.

FieldCache

A low-level Lucene field cache that is not managed by Solr (in other words, it cannot be configured). It is used for sorting and faceting.

FieldValueCache

This is a field cache very similar to FieldCache, but it can be configured. It is mainly used for faceting.

CustomCache

Application-level caches used to hold custom user/application data.

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