Configuring solrconfig.xml

The solrconfig.xml file is the configuration file with the most parameters affecting Solr itself.

While configuring Solr, you’ll work with solrconfig.xml often, either directly or via the Config API to create "configuration overlays" (configoverlay.json) to override the values in solrconfig.xml.

In solrconfig.xml, you configure important features such as:

request handlers, which process the requests to Solr, such as requests to add documents to the index or requests to return results for a query
listeners, processes that "listen" for particular query-related events; listeners can be used to trigger the execution of special code, such as invoking some common queries to warm-up caches
the Request Dispatcher for managing HTTP communications
the Admin Web interface
parameters related to replication and duplication (these parameters are covered in detail in Legacy Scaling and Distribution)

The solrconfig.xml file is located in the conf/ directory for each collection. Several well-commented example files can be found in the server/solr/configsets/ directories demonstrating best practices for many different types of installations.

We’ve covered the options in the following sections:

Substituting Properties in Solr Config Files

Solr supports variable substitution of property values in config files, which allows runtime specification of various configuration options in solrconfig.xml. The syntax is ${propertyname[:option default value]}. This allows defining a default that can be overridden when Solr is launched. If a default value is not specified, then the property must be specified at runtime or the configuration file will generate an error when parsed.

There are multiple methods for specifying properties that can be used in configuration files. Of those below, strongly consider "config overlay" as the preferred approach, as it stays local to the config set and because it’s easy to modify.

JVM System Properties

Any JVM System properties, usually specified using the -D flag when starting the JVM, can be used as variables in any XML configuration file in Solr.

For example, in the sample solrconfig.xml files, you will see this value which defines the locking type to use:

<lockType>${solr.lock.type:native}</lockType>

Which means the lock type defaults to "native" but when starting Solr, you could override this using a JVM system property by launching the Solr it with:

bin/solr start -Dsolr.lock.type=none

In general, any Java system property that you want to set can be passed through the bin/solr script using the standard -Dproperty=value syntax. Alternatively, you can add common system properties to the SOLR_OPTS environment variable defined in the Solr include file (bin/solr.in.sh or bin/solr.in.cmd). For more information about how the Solr include file works, refer to: Taking Solr to Production.

Config API

The Config API allows you to use an API to modify Solr’s configuration, specifically user defined properties. Changes made with this API are stored in a file named configoverlay.json. This file should only be edited with the API, but will look like this example:

{"userProps":{
    "dih.db.url":"jdbc:oracle:thin:@localhost:1521",
    "dih.db.user":"username",
    "dih.db.pass":"password"}}

For more details, see the section Config API.

solrcore.properties

If the configuration directory for a Solr core contains a file named solrcore.properties that file can contain any arbitrary user defined property names and values using the Java standard properties file format, and those properties can be used as variables in the XML configuration files for that Solr core.

For example, the following solrcore.properties file could be created in the conf/ directory of a collection using one of the example configurations, to override the lockType used.

#conf/solrcore.properties
solr.lock.type=none

Deprecation

solrcore.properties won’t work in SolrCloud mode (it is not read from ZooKeeper). This feature is likely to be removed in the future. Instead, use another mechanism like a config overlay.

The path and name of the solrcore.properties file can be overridden using the properties property in core.properties.

User-Defined Properties in `core.properties`

Every Solr core has a core.properties file, automatically created when using the APIs. When you create a SolrCloud collection, you can pass through custom parameters to go into each core.properties that will be created, by prefixing the parameter name with "property." as a URL parameter. Example:

http://localhost:8983/solr/admin/collections?action=CREATE&name=gettingstarted&numShards=1&property.my.custom.prop=edismax

That would create a core.properties file that has at least the following properties (others omitted for brevity):

#core.properties
name=gettingstarted
my.custom.prop=edismax

The my.custom.prop property can then be used as a variable, such as in solrconfig.xml:

<requestHandler name="/select">
  <lst name="defaults">
    <str name="defType">${my.custom.prop}</str>
  </lst>
</requestHandler>

Implicit Core Properties

Several attributes of a Solr core are available as "implicit" properties that can be used in variable substitution, independent of where or how they underlying value is initialized. For example: regardless of whether the name for a particular Solr core is explicitly configured in core.properties or inferred from the name of the instance directory, the implicit property solr.core.name is available for use as a variable in that core’s configuration file…

<requestHandler name="/select">
  <lst name="defaults">
    <str name="collection_name">${solr.core.name}</str>
  </lst>
</requestHandler>

All implicit properties use the solr.core. name prefix, and reflect the runtime value of the equivalent core.properties property:

solr.core.name
solr.core.config
solr.core.schema
solr.core.dataDir
solr.core.transient
solr.core.loadOnStartup

The Well-Configured Solr Instance DataDir and DirectoryFactory in SolrConfig