Solr uses a directory called Solr Home for configuration files and additional libraries. It is specified with parameter -s of the "bin/solr start" script or as environment property SOLR_HOME, for example, in bin/solr.in.sh. The directory has the following general structure:

<solr-home>/
    solr.xml
    configsets/
        <configset1>/
            conf/
                schema.xml
                solrconfig.xml
                ...
        <configset2>/
        ...
    lib/
        <additional jar files>

solr.xml

The file solr.xml is the central Solr configuration file. It contains just a few settings, which you do not need to change. Most of Solr's configuration is placed in other configuration files.

It specifies the coreRootDirectory, which is the directory where Solr cores and their data are stored. The default solr.xml uses the directory that is set with system property coreRootDirectory. If no such system property is set, Solr will store cores in the directory <solr-home>/cores. It's recommended to configure a different absolute path outside of Solr Home.

You can set the coreRootDirectory system property with the parameter "-a -DcoreRootDirectory=<path>" when invoking "bin/solr start". Alternatively, you can set the environment variable SOLR_OPTS, for example in bin/solr.in.sh:

SOLR_OPTS="$SOLR_OPTS -DcoreRootDirectory=/var/coremedia/solr-data"

You can find more information about the solr.xml file in the Solr Reference Guide at https://solr.apache.org/guide/8_11/format-of-solr-xml.html.

Config Sets

Index-specific configuration files are organized as named config sets, which are subdirectories of the configsets directory. A config set defines an index schema with index fields and types in conf/schema.xml and lots of configuration options for indexing, searching and additional features in conf/solrconfig.xml. The latter file for example contains search request handler definitions with default settings such as the default index field to search in.

The CoreMedia Search Engine comes with three config sets: "content" for Content Feeder indices, "cae" for CAE Feeder indices and "elastic" for Elastic Social indices. They configure different index fields and Solr features such as search request handlers as required. Projects may customize these files or create additional config sets according to their needs. Note that some index fields are required for operation. See the comments in the configuration files for details.

Lib directory

The directory <solr-home>/lib contains additional libraries that can be used by all Solr cores and are not available in the Solr distribution itself. This includes some required CoreMedia extensions.

Core Root Directory

The coreRootDirectory contains the actual Solr cores, which are the indices used by CoreMedia applications. The directory must be writable and should provide fast disk I/O for good performance. Solr automatically discovers cores by looking for core.properties files below that directory. Each directory with a core.properties file represents a Solr Core. CoreMedia Feeder applications create cores dynamically, so the directory can be empty at first start.

With the default configuration, Content Feeder and CAE Feeders will create these Solr cores when started the first time:

Further cores will be created by Elastic Social applications for users and comments for different tenants, for example:

The coreRootDirectory has the following general structure:

<coreRootDirectory>/
    <core1>/
        core.properties
        data/
            index/
                <index files>
            tlog/
                <transaction log files>
    <core2>/
    ...

The file core.properties contains Solr core configuration properties, most importantly the name of the used config set with the configSet property. The core "studio" uses the "content" config set, the cores "preview" and "live" use the "cae" config set, and Elastic Social cores use the "elastic" config set.

Index Data

Each Solr core has its own data directory with index files and transaction log. The actual index files are written to the directory data/index. In addition to the index, Solr maintains a transaction log with latest and/or pending changes for the index files. The transaction log is stored in the directory data/tlog.