Activities and Priorities

Current state:

FTS3 multi-dimentional scheduling offers two features:

• activities shares, which allow to divide the assigned slots acording to weights decided by the VO
• priorities, which allow to reshuffle the jobs within an activity share

Currently CMS does not rely on these features. PhEDEx has its own intricate scheduling mechanism, and FTS3 acts simply as a FIFO queue.

Rucio provides interface for both features; however, ATLAS is only using activity shares, as setting different priorities may cause starvation.

Proposal:

We propose to introduce the following activity shares in CMS Rucio (initial weights to be decided):

• tier-0 transfers
• pre-production transfers
• post-production transfers
• debug transfers
• popularity based replication
• user transfers
• crab staging
• ASO
• default (pre-existing)

Activity and priority can be specified as an attribute of the replication rule. Activity weights are defined in FTS configuration and can be adjusted via FTS API using VO production role.

References:

1. FTS scheduling: http://fts3-docs.web.cern.ch/fts3-docs/docs/features.html#multidimensional-scheduler
2. Rucio interface: https://rucio.readthedocs.io/en/latest/api/rule.html
3. FTS interface: http://fts3-docs.web.cern.ch/fts3-docs/fts-rest/docs/api.html#activity-shares-configuration
4. PhEDEx scheduling: https://twiki.cern.ch/twiki/bin/view/CMS/PhedexAdminDocsPriorityQueues

Backup:

Brief summary of prioritization in PhEDEx:

• Priority levels (high, normal, low, reserved) are specified by user in transfer request.
• Approved request turn into subscriptions.
• Subscribed files are allocated for transfer in order of priority and the time the data was requested, older request first.
• Files are allocated for routing until 50 TB request windows per priority are filled.
• Priority changes are propagated to the allocated file requests.
• Once data are routed, transfer tasks are created with task_priority, time_assigned, and rank . The rank is ordered by priority and then the file's logical name.
• Transfer tasks are fetched by the site FileDownload agent, sorted by time_assigned and rank and submitted to FTS in that order.