June 8-11, 2021

Virtual iRODS User Group Meeting 2021

Justin James

iRODS Consortium

iRODS Globus Connector

iRODS Globus Connector - Overview

• The iRODS Globus Connector provides access to iRODS storage resources from a Globus Connect Server.

  • ​iRODS appears as a filesystem to Globus
     

• The connector is a plugin for the Globus Connect Server and a client to the iRODS servers.
   

• All Globus requests use the iRODS C++ client API's to get information and transfer data to iRODS

iRODS Globus Connector - Overview

This is built on the work from EUDAT.  https://github.com/EUDAT-B2STAGE/B2STAGE-GridFTP

• Worked with Globus to implement a few enhancements and bug fixes.

iRODS Globus Connector - Scope of Talk

• The majority of this talk is from the iRODS perspective.  

  • Implementation details

  • Plugin limitations

  • Improvements

  • iRODS API's used by the plugin

The iRODS Globus Connector implements the globus_gfs_storage_iface_t interface.

The connector implements the following interface functions.
 

• INIT - Called when a new session is initiated.  Reads the user environment and calls clientLogin().

• DESTROY - Called at the end of the session.  Cleans up and calls rcDisconnect().

• SEND - Called when client requests to receive a file.  Calls rcDataObjRead().

• RECEIVE - Called when client requests to transfer a file to the server.  

• COMMAND - Called when a client sends a command to the server.  (See next slide).

• STAT - Called when the server needs information about the file.  Calls rcObjStat().

• REALPATH

iRODS Globus Connector - Globus Plugin Interface

iRODS Globus Connector - Globus Client Commands

The following client commands are implemented.

• GLOBUS_GFS_CMD_MKD - Creates a collection in iRODS.   Calls rcCollCreate().
   
• GLOBUS_GFS_CMD_RMD - Removes a collection.  Calls rcRmColl().
   
• GLOBUS_GFS_CMD_DELE - Deletes an object.  Calls rcDataObjUnlink().
   
• GLOBUS_GFS_CMD_CKSM - Gets the checksum for an object.  See next slide.

iRODS Globus Connector - Checksum/Hashing

Globus clients can request specific hashing algorithms.  Originally the hashing algorithm that was calculated in iRODS was returned to the client.  This did not necessarily match the algorithm the client had requested.

To support client requested hashing, the hash files are now calculated by the iRODS Globus Connector and stored in metadata as follows:
 

• AVU Name - Globus::<algorithm>
• AVU Value - <checksum value>
• AVU Units - POSIX time that the checksum was calculated

iRODS Globus Connector - Checksum/Hashing

The following pseudo-code describes roughly how a checksum request is served by the iRODS Globus Connector:

Receive request for hash for <alg1>
Query metadata for key(attr) = "Globus::alg1"
If exists:
    Compare AVU unit with object update time.
    If  AVU unit > object update time:
        Return checksum
    Else:
        Remove existing AVU for <alg1>
Download file and calculate checksum.
Write checksum to AVU.
Return checksum. 

iRODS Globus Connector - Recent Enhancements / Fixes

• Support incremental directory listings for very large directories.
  • After either X number of entries are encountered or Y seconds have passed since the last partial listing, send additional entries via globus_gridftp_server_finished_stat_partial().
     
  • Implemented heartbeats for long running checksum operations.
     
  • Implemented the realpath feature so that alternate paths don't allow users to bypass path restrictions.
     
  • Fixed some memory leaks in existing code.

iRODS Globus Connector - Future Enhancements

• Add the aforementioned PEP to calculate checksums on data object updates.
  • Administrator would specify which checksums should be calculated.
     
• Investigate and fix other performance issues.

iRODS Globus Connector - Configuring Globus

Refer to the following page for more information on configuring Globus to be used with the iRODS Globus Connector.

https://docs.globus.org/premium-storage-connectors/v5/irods/