Hyrax - Configuring The OLFS To Work With Multiple BES's

Configuring Hyrax to use multiple BES backends is straight forward. It will require that you edit the olfs.xml file and possible the catalog.xml file.

Top Level BES

Every installation of Hyrax requires a top level (or root level) BES.** This BES has a prefix of "/" (the forward slash character).

In a single BES deployment this BES would contain all of the data resources to be made visible in Hyrax. In the THREDDS catalog.xml file each top level directory/collection would have it's own <datasetScan> element.

**Note: The word root here has absolutely nothing to do with the login account called root associated with the super user or system administrator.

Mount points

In a multiple BES installation each additional BES must have a mount point within the exposed hierarchy of collections for it to be visible in Hyrax. Eh? What's that you said? Allow me to explain by example.

Simple

Here is the <BESConfig> section of an olfs.xml file that configures the OLFS to use a single BES, the default configuration arrangement for Hyrax:

    <BESConfig>
        <BES>
            <prefix>/</prefix>
            <host>localhost</host>
            <port>10002</port>
            <ClientPool maximum="10" />
        </BES>
    </BESConfig>

The BES is running on the same system as the OLFS, and it's prefix is correctly set "/". This BES will handle all data requests direct at the OLFS and will expose it's top level directory/collection/catalog in the URI space of the OLFS here:

http://localhost:8080/opendap/

The THREDDS catalog.xml file for this should contain a <datasetScan> element for each of the top level directories/collections/catalogs that the BES exposes at the above URI.

Complex

Using multiple BES's requires you to think about the concept of mount points

Here is the <BESConfig> section of an olfs.xml file:

    <BESConfig>
        <BES>
            <prefix>/</prefix>
            <host>localhost</host>
            <port>10002</port>
            <ClientPool maximum="10" />
        </BES>
        
        <BES>
            <prefix>/sst</prefix>
            <host>comet.test.org</host>
            <port>10002</port>
            <ClientPool maximum="10" />
        </BES>
    </BESConfig>

Examples

Complex

Example: