Searchlight Indexing

Searchlight Indexing

In order for the Searchlight API service to return results, information must be indexed. The two primary mechanisms by which this happens are indexing from the source (which allows a complete index rebuild) and incrementally updating the index based on information received via notifications. The information indexed is determined by a plugin model.

Search plugins

The search service determines the type of information that is indexed and searchable via a plugin mechanism.

See Searchlight Plugin Documentation for plugin installation and general configuration information.

See each plugin below for detailed information about specific plugins:

Indexing model

The Mitaka Searchlight release introduced the ability to continue executing search requests while reindexing operations are running. This feature is called zero-downtime reindexing. In order to implement zero-downtime indexing, the concept of a resource group was introduced.

A resource group is a collection of plugins that share an Elasticsearch index. Since each plugin represents a resource type, you can think of a resource group as a collection of resource types.

For each resource group, Searchlight creates an index whose name consists of the resource group name appended with a timestamp. Each resource group is referred to by a pair of Elasticsearch aliases. One alias is used for searching by the API (the search alias), and the other (the listener alias) is used to index incoming events.

During reindexing, a new index is created, and the listener alias is pointed at both the old and new indices. Incoming events are therefore indexed into both indices. The search alias is left pointing at the old index. Once indexing is finished, both aliases are pointed solely at the new index and the old index is deleted.

In order to improve the performance of reindexing, index refresh of the new index is disabled during reindexing, and turned on after reindexing is done. As a consequence, Documents synced to the new index are not searchable until index is refreshed, but document retrieval by IDs still works, because GET operation in Elasticsearch is realtime.

It is important to note that zero-downtime reindexing requires that all plugins in a resource group are indexed together. When it’s desired to index an individual resource type, an optimization copies existing data directly from the old index to the new one to avoid re-harvesting the data from each service API.


Due to some limitations discovered during the Mitaka release, indexing into multiple indices (multiple plugin resource groups) is disabled. The newton release implemented full support for specifying different resource groups for different resource types.

Sorting across resource groups

Using multiple resource groups will impact sort behavior when sorting on fields across resource types when all the resource types don’t have the requested ‘sort-by field’. Follow the guidelines below to avoid errors:

Bulk indexing

To initially create the catalog index (or add new resource typs to it later), run the following command:

$ searchlight-manage index sync

This will iterate through all registered and enabled search plugins and request that they perform a full indexing of all data that’s available to them.

It is also possible to index just a single resource, or all resources belonging to a resource group. For instance, to index all glance images:

$ searchlight-manage index sync --type OS::Glance::Image

As described above, this will create a new index for all plugins that share a resource group with OS::Glance::Image. The management command will retrieve up-to-date information from the Glance API. Data for other plugins will be bulk-copied from a preexisting index into the new one using the scroll and bulk features of Elasticsearch.

You can use the wildcard character * at the end of the type argument. For instance, the following will match all cinder plugins:

$ searchlight-manage index sync --type OS::Cinder::*

Wildcard characters are only allowed at the end of the argument; they will not be matched anywhere else.

To index all resources in the ‘searchlight’ resource group:

$ searchlight-manage index sync --index searchlight

You will be prompted to confirm unless --force is provided.

To reindex resources only without notification:

$ searchlight-manage index sync --notification-less


We strongly recommend putting the notification-less plugins in their own resource group and scheduling a cron job to periodically re-sync the notification plugins to keep the documents up to date.

The searchlight-manage index sync command may be re-run at any time to perform a full re-index of the data. As described above, there should be no or very little impact on search requests during this process.

Parent/child relationships

Some plugins contain multiple resources with parent/child relationships; the Designate plugins are an example. Because reindexing parent data independent of child documents does not logically make sense (without orphaning them), it is not possible to request indexing of a child resource type:

$ searchlight-manage index sync --type OS::Designate::RecordSet

'OS::Designate::RecordSet' is a child of 'OS::Designate::Zone' and cannot be indexed separately.
Indexing 'OS::Designate::Zone' will re-index all child resource types.

You can see parent/child relationships in the list of resources presented prior to indexing:

$ searchlight-manage index sync --type OS::Designate::Zone

Resource types (and indices) matching selection:
  OS::Designate::Zone (designate)
      ---->  OS::Designate::RecordSet

Child plugins will inherit their resource group name from their parent. Any child configuration setting for resource_group_name will be ignored.

Incremental Updates

Once a resource has been indexed, typically you will only need to consume incremental updates rather than re-index the entire data set again. The preferred methodolgy is to set up notification listening.


Many services publish notifications when there are changes to the resources they own. The searchlight listener consumes these notifications and will perform incremental updates to the index based on those notifications.

To start this service, run the following command:

$ searchlight-listener

Note, this will typically require that you have configured notifications properly for the service which owns the resource. For example, the glance service owns images and metadata definitions. Please check the plugin documentation for each service’s specific configuration requirements.

Multi-Thread Support

The Newton Searchlight release introduced multiple thread support for indexing. Previously when the searchlight-manage index sync command was executed, all indexing occurred in a single thread. To boost the performance of the indexing functionality, each resource type will now index in its own thread. Multiple indexing threads will run concurrently.

By default, the maximum number of simultaneous threads is 3. This limit can be modified in the Searchlight configuration file. The setting is called workers and lives under [manage]. For example, to increase the maximum number of threads to 6, the following can be added to the Searchlight configuration file:


The use of threads can also affect the parsing of the log files. The default formatting of the log messages include only the process ID, but no thread-specific information. This can be changed by modifying the formatting string settings in the Searchlight configuration file. To add the thread ID for a message, add %(thread)d. To add the thread name, add %(threadName)s. For example, to add the thread ID and the thread name after the process ID to the logging message, the following setting can be added to the Searchlight configuration file:

logging_default_format_string = %(asctime)s.%(msecs)03d %(process)d %(thread)d %(threadName)s %(levelname)s %(name)s [-] %(instance)s%(message)s

Force Elasticsearch indexing

The Newton Searchlight release introduced the ability to reindex from Elasticsearch only, bypassing the plugin APIs altogether. This option is useful if there has been a change to the mapping definitions or the index settings. This functionality is enabled with the option --apply-mapping-changes for the index command.

A sample usage would be:

$ searchlight-manage index aliases --apply-mapping-changes

The --type option is not compatible with the --apply-mapping-changes option. Specifying both options on the command line will result in an error.


The resource group cannot be changed when using this option. If you do change the resource group, the underlying index will be changed and will result in an empty index.

Elasticsearch Index Cleanup

In some cases, there may be orphaned Searchlight indices in Elasticsearch. An orphaned index is one that is no longer used by Searchlight, either directly or through an alias.

To help detect which Searchlight-related indices may be orphaned in Elasticsearch, the searchlight-manage command will display all indices that are currently being used by Searchlight. This is the aliases option to the index command:

$ searchlight-manage index aliases

This command outputs a listing of all indices that are used by Searchlight (based on the current configuration file). The aliases associated with each index is also shown. A sample output will look like this:

$ searchlight-manage index aliases
List of Elasticsearch indices (and their associated aliases) used by Searchlight.

The indices are based on the current config file.
To view indices used by other Searchlight config files, use the --config-file option.

Indices are denoted with a '*'
Aliases are denoted with a '+'

    * searchlight-2016_07_13_17_09_27
        + searchlight-listener
        + searchlight-search
    * sl-swift-2016_07_13_17_09_26
        + sl-swift-listener
        + sl-swift-search

The example shows that Searchlight is using two indices in Elasticsearch: searchlight-2016_07_13_17_09_27 and sl-swift-2016_07_13_17_09_26. The index searchlight-2016_07_13_17_09_27 has two aliases: searchlight-listener and searchlight-search. The index sl-swift-2016_07_13_17_09_26 has two aliases: sl-swift-listener and sl-swift-search.

Any other indices or aliases in Elasticsearch are not used by this specific Searchlight configuration. NOTE: If there are other Searchlight instances running with a different configuration, their indices and aliases will not by displayed by this command. The user will need to rerun the index aliases command using these other configuration files.

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