CoreAdmin API

The Core Admin API is primarily used under the covers by the Collections API when running a SolrCloud cluster.

SolrCloud users should not typically use the CoreAdmin API directly, but the API may be useful for users of single-node or master/slave Solr installations for core maintenance operations.

The CoreAdmin API is implemented by the CoreAdminHandler, which is a special purpose request handler that is used to manage Solr cores. Unlike other request handlers, the CoreAdminHandler is not attached to a single core. Instead, there is a single instance of the CoreAdminHandler in each Solr node that manages all the cores running in that node and is accessible at the /solr/admin/cores path.

CoreAdmin actions can be executed by via HTTP requests that specify an action request parameter, with additional action specific arguments provided as additional parameters.

All action names are uppercase, and are defined in depth in the sections below.


The STATUS action returns the status of all running Solr cores, or status for only the named core.


STATUS Parameters

The name of a core, as listed in the "name" attribute of a <core> element in solr.xml.
If false, information about the index will not be returned with a core STATUS request. In Solr implementations with a large number of cores (i.e., more than hundreds), retrieving the index information for each core can take a lot of time and isn’t always required. The default is true.


The CREATE action creates a new core and registers it.

If a Solr core with the given name already exists, it will continue to handle requests while the new core is initializing. When the new core is ready, it will take new requests and the old core will be unloaded.


Note that this command is the only one of the Core Admin API commands that does not support the core parameter. Instead, the name parameter is required, as shown below.

CREATE must be able to find a configuration!

Your CREATE call must be able to find a configuration, or it will not succeed.

When you are running SolrCloud and create a new core for a collection, the configuration will be inherited from the collection. Each collection is linked to a configName, which is stored in ZooKeeper. This satisfies the configuration requirement. There is something to note, though: if you’re running SolrCloud, you should NOT use the CoreAdmin API at all. Use the Collections API.

When you are not running SolrCloud, if you have Config Sets defined, you can use the configSet parameter as documented below. If there are no configsets, then the instanceDir specified in the CREATE call must already exist, and it must contain a conf directory which in turn must contain solrconfig.xml, your schema (usually named either managed-schema or schema.xml), and any files referenced by those configs.

The config and schema filenames can be specified with the config and schema parameters, but these are expert options. One thing you could do to avoid creating the conf directory is use config and schema parameters that point at absolute paths, but this can lead to confusing configurations unless you fully understand what you are doing.

CREATE and the file

The file is built as part of the CREATE command. If you create a file yourself in a core directory and then try to use CREATE to add that core to Solr, you will get an error telling you that another core is already defined there. The file must NOT exist before calling the CoreAdmin API with the CREATE command.

CREATE Core Parameters

The name of the new core. Same as name on the <core> element. This parameter is required.
The directory where files for this core should be stored. Same as instanceDir on the <core> element. The default is the value specified for the name parameter if not supplied.
Name of the config file (i.e., solrconfig.xml) relative to instanceDir.
Name of the schema file to use for the core. Please note that if you are using a "managed schema" (the default behavior) then any value for this property which does not match the effective managedSchemaResourceName will be read once, backed up, and converted for managed schema use. See Schema Factory Definition in SolrConfig for details.
Name of the data directory relative to instanceDir.
Name of the configset to use for this core. For more information, see the section Config Sets.

The name of the collection to which this core belongs. The default is the name of the core. collection.param=value causes a property of param=value to be set if a new collection is being created. Use collection.configName=config-name to point to the configuration for a new collection.

While it’s possible to create a core for a non-existent collection, this approach is not supported and not recommended. Always create a collection using the Collections API before creating a core directly for it.
The shard id this core represents. Normally you want to be auto-assigned a shard id.
Sets the core property name to value. See the section on defining file contents.
Request ID to track this action which will be processed asynchronously.

Use collection.configName=configname to point to the config for a new collection.

CREATE Example



The RELOAD action loads a new core from the configuration of an existing, registered Solr core. While the new core is initializing, the existing one will continue to handle requests. When the new Solr core is ready, it takes over and the old core is unloaded.


This is useful when you’ve made changes to a Solr core’s configuration on disk, such as adding new field definitions. Calling the RELOAD action lets you apply the new configuration without having to restart Solr.

RELOAD performs "live" reloads of SolrCore, reusing some existing objects. Some configuration options, such as the dataDir location and IndexWriter-related settings in solrconfig.xml can not be changed and made active with a simple RELOAD action.

RELOAD Core Parameters

The name of the core, as listed in the "name" attribute of a <core> element in solr.xml. This parameter is required.


The RENAME action changes the name of a Solr core.


RENAME Parameters

The name of the Solr core to be renamed. This parameter is required.
The new name for the Solr core. If the persistent attribute of <solr> is true, the new name will be written to solr.xml as the name attribute of the <core> attribute. This parameter is required.
Request ID to track this action which will be processed asynchronously.


SWAP atomically swaps the names used to access two existing Solr cores. This can be used to swap new content into production. The prior core remains available and can be swapped back, if necessary. Each core will be known by the name of the other, after the swap.


Do not use SWAP with a SolrCloud node. It is not supported and can result in the core being unusable.

SWAP Parameters

The name of one of the cores to be swapped. This parameter is required.
The name of one of the cores to be swapped. This parameter is required.
Request ID to track this action which will be processed asynchronously.


The UNLOAD action removes a core from Solr. Active requests will continue to be processed, but no new requests will be sent to the named core. If a core is registered under more than one name, only the given name is removed.


The UNLOAD action requires a parameter (core) identifying the core to be removed. If the persistent attribute of <solr> is set to true, the <core> element with this name attribute will be removed from solr.xml.

Unloading all cores in a SolrCloud collection causes the removal of that collection’s metadata from ZooKeeper.

UNLOAD Parameters

The name of a core to be removed. This parameter is required.
If true, will remove the index when unloading the core. The default is false.
If true, removes the data directory and all sub-directories. The default is false.
If true, removes everything related to the core, including the index directory, configuration files and other related files. The default is false.
Request ID to track this action which will be processed asynchronously.


The MERGEINDEXES action merges one or more indexes to another index. The indexes must have completed commits, and should be locked against writes until the merge is complete or the resulting merged index may become corrupted. The target core index must already exist and have a compatible schema with the one or more indexes that will be merged to it. Another commit on the target core should also be performed after the merge is complete.


In this example, we use the indexDir parameter to define the index locations of the source cores. The core parameter defines the target index. A benefit of this approach is that we can merge any Lucene-based index that may not be associated with a Solr core.

Alternatively, we can instead use a srcCore parameter, as in this example:


This approach allows us to define cores that may not have an index path that is on the same physical server as the target core. However, we can only use Solr cores as the source indexes. Another benefit of this approach is that we don’t have as high a risk for corruption if writes occur in parallel with the source index.

We can make this call run asynchronously by specifying the async parameter and passing a request-id. This id can then be used to check the status of the already submitted task using the REQUESTSTATUS API.


The name of the target core/index. This parameter is required.
Multi-valued, directories that would be merged.
Multi-valued, source cores that would be merged.
Request ID to track this action which will be processed asynchronously.


The SPLIT action splits an index into two or more indexes. The index being split can continue to handle requests. The split pieces can be placed into a specified directory on the server’s filesystem or it can be merged into running Solr cores.

The SPLIT action supports five parameters, which are described in the table below.

SPLIT Parameters

The name of the core to be split. This parameter is required.
Multi-valued, the directory path in which a piece of the index will be written. Either this parameter or targetCore must be specified. If this is specified, the targetCore parameter may not be used.
Multi-valued, the target Solr core to which a piece of the index will be merged. Either this parameter or path must be specified. If this is specified, the path parameter may not be used.
A comma-separated list of hash ranges in hexadecimal format. If this parameter is used, split.key should not be. See the SPLIT Examples below for an example of how this parameter can be used.
The key to be used for splitting the index. If this parameter is used, ranges should not be. See the SPLIT Examples below for an example of how this parameter can be used.
Request ID to track this action which will be processed asynchronously.

SPLIT Examples

The core index will be split into as many pieces as the number of path or targetCore parameters.

Usage with two targetCore parameters:


Here the core index will be split into two pieces and merged into the two targetCore indexes.

Usage with two path parameters:


The core index will be split into two pieces and written into the two directory paths specified.

Usage with the split.key parameter:


Here all documents having the same route key as the split.key i.e., 'A!' will be split from the core index and written to the targetCore.

Usage with ranges parameter:


This example uses the ranges parameter with hash ranges 0-500, 501-1000 and 1001-1500 specified in hexadecimal. Here the index will be split into three pieces with each targetCore receiving documents matching the hash ranges specified i.e., core1 will get documents with hash range 0-500, core2 will receive documents with hash range 501-1000 and finally, core3 will receive documents with hash range 1001-1500. At least one hash range must be specified. Please note that using a single hash range equal to a route key’s hash range is NOT equivalent to using the split.key parameter because multiple route keys can hash to the same range.

The targetCore must already exist and must have a compatible schema with the core index. A commit is automatically called on the core index before it is split.

This command is used as part of the SPLITSHARD command but it can be used for non-cloud Solr cores as well. When used against a non-cloud core without split.key parameter, this action will split the source index and distribute its documents alternately so that each split piece contains an equal number of documents. If the split.key parameter is specified then only documents having the same route key will be split from the source index.


Request the status of an already submitted asynchronous CoreAdmin API call.



The REQUESTSTATUS command has only one parameter.

The user defined request-id for the asynchronous request. This parameter is required.

The call below will return the status of an already submitted asynchronous CoreAdmin call.



The REQUESTRECOVERY action manually asks a core to recover by synching with the leader. This should be considered an "expert" level command and should be used in situations where the node (SorlCloud replica) is unable to become active automatically.



The name of the core to re-sync. This parameter is required.



The core to specify can be found by expanding the appropriate ZooKeeper node via the admin UI.