Direct ICAT communication

Step 1 towards solving #2848 (closed)

There are now two ICAT clients with the same API:

1. bliss.icat.client.IcatClient: communicates directly with ICAT
2. bliss.icat.client.IcatTangoProxy: communicates through tango servers

IcatClient is used when configured in the beacon configuration (same controller as for configuring metadata gathering)

icat_servers:
    metadata_urls: [URL1, URL2]
    elogbook_url: URL3
    elogbook_token: elogbook-00000000-0000-0000-0000-000000000000

The default URL prefix is "tcp://" for the metadata and "https://" for the e-logbook.

BLISS will fall back to IcatTangoProxy when IcatClient is not configured. As a reminder, it requires two TANGO devices per BLISS session with names "id00/metaexp/session_name" and "id00/metadata/session_name". The configuration is done in the TANGO device class properties.

Implementation

• bliss.icat.client.IcatClient: direct communication with ICAT: e-logbook and metadata. Has one IcatElogbookClient and one IcatMessagingClient.
• bliss.icat.client.elogbook.IcatElogbookClient: client for the e-logbook part of the ICAT+ REST API.
• bliss.icat.client.metadata.IcatMetadataClient: client for storing dataset metadata in ICAT. Has one IcatMessagingClient.
• bliss.icat.client.messaging.IcatMessagingClient: client for the ICAT message broker (currently activemq). It also uses the broker's REST server (jolokia) for monitoring.

Maintenance

Apart from being able to add failure handling, we have huge improvements in terms of maintenance.

Code:

• IcatTangoProxy requires ~800 lines of code + all the code in the tango_metadata project.
• IcatClient requires ~400 lines of code.

Infrastructure:

• IcatTangoProxy requires 2 tango devices per BLISS session per beamline.
• IcatClient requires 1 ICATmeta configuration per beamline (see above).