FLS engine

Applicable in the context of the fields rule

FLS engine specifies how ROR handles field-level security internally. Previously FLS was based entirely on Lucene - that's why ROR needed to be installed on all nodes to make the fields rule work properly. Now the fields rule is more flexible and part of FLS responsibilities is handled solely by ES. Increasing ES usage and reducing Lucene exploitation in FLS implementation makes the rule more efficient.

Unfortunately, a few FLS functionalities still have to be handled at the Lucene level, and cannot benefit of the new ES level implementation (see supported at ES level requests ) Lucene is still used by fields rule when ES is not able to handle a request properly (as kind of a fallback).


FLS engine can be configured with global, optional property fls_engine set under the readonlyrest: section.

There are two engines available:

  • es_with_lucene (default)

⚠️IMPORTANT As Lucene is part of this engine, the ReadonlyREST plugin still needs to be installed in all the cluster nodes that contain data.

Default hybrid approach - the major part of FLS is handled by ES. Corner cases are passed to Lucene. This solution handles all requests properly being more performant than the old full Lucene-based approach.

  • es

FLS is handled only by ES, without fallback to Lucene. When ES is not able to handle FLS properly, the fields rule is not matched. In the es engine, FLS is not available for some types of requests (requirements listed below). The major advantage of this approach is to not rely on Lucene, so ROR doesn't need to be installed on all nodes.

If a lack of full FLS support is unacceptable and all type of requests needs to be handled properly (rule matching, no rejection) it's advised to use a more reliable es_with_lucene engine.

ES limitations

Supported by es FLS engine requests are:

  • all Get/MGet API requests

  • Search/MSearch/AsyncSearch API requests with the following restrictions:

    • not using script fields

    • the used query is one of

      • common terms

      • match bool

      • match

      • match phrase

      • match phrase prefix

      • exists

      • fuzzy

      • prefix

      • range

      • regexp

      • term

      • wildcard

      • terms set

      • bool

      • boosting

      • constant score

      • dis max

    • the defined query doesn't use wildcards in field names

    • defined compound queries using only listed above supported queries as inner queries

    • the Search request doesn't use scroll

If the request doesn't meet above requirements (e.g. it's using query_string or script fields), the es engine will reject it.

Example configuration (ROR using es FLS engine):

 fls_engine: "es"

   - name: "user_using_fields"
     auth_key: user:pass
     fields: ["~someNotAllowedField"]

Property fls_engine can be omitted, then by default, ROR uses es_with_lucene FLS engine.

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