README.md

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Sling Capabilities - JCR sources
=======================================

This module is part of the [Apache Sling](https://sling.apache.org) project.

It provides information about the JCR repository to the [Sling Capabilities](https://github.com/apache/sling-org-apache-sling-capabilities) module.

It is implemented separately to avoid making the core module dependent on JCR APIs.

Usage
-----
For now, this module's `SearchSource` provides just one capability that indicates whether the Oak similarity search feature is available. Here's typical JSON output of the `CapabilitiesServlet` when this source is active:

    {
      "org.apache.sling.capabilities": {
        "data": {
          "org.apache.sling.jcr.search": {
            "similarity.search.active": "false"
          }
        }
      }
    }

To compute this value, the `SearchSource` needs to make a JCR query to find out whether similarity search is available - that is the case if there is at least one Oak index configuration which has `@useInSimilarity = true`.

That query is configurable in the `SearchSource` component, with a default value that should work for common cases.

The cache lifetime of that value in the `SearchSource` component is also configurable, with a default of 60 seconds. The component caches the query result for that amount of time to avoid making too many queries.

To execute this query, the `SearchSource` uses a Service User that needs read access under `/oak:index`. 

The following feature model excerpt can be used to set that up. It also creates a `/var/capabilities/public` path that every user can read. Resources with the `sling/capabilities` resource type can be created under that path to provide access to the capabilities. See the Capabilities module documentation for more information.

    "configurations": {
        "org.apache.sling.serviceusermapping.impl.ServiceUserMapperImpl.amended~cq-capabilities-jcr": {
          "user.mapping": [
            "org.apache.sling.capabilities.jcr:search=[capabilities-search]"
          ]
        },
        "org.apache.sling.capabilities.internal.CapabilitiesServlet": {
          "resourcePathPatterns" : "/var/capabilities/.*"
        }
      },
      "repoinit:TEXT|true": [
        "create service user capabilities-search",
        "",
        "set ACL for capabilities-search",
        "allow jcr:read on /oak:index",
        "end",
        "",
        "create path /var/capabilities/public(nt:unstructured)",
        "",
        "set ACL on /var/capabilities/public",
        "allow jcr:read for everyone",
        "end"
    ]