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Discussion items

March Sprint Demo 

  • gcov
    • We could try. Hoping SQUARE will provide "central" support
  • DM-854
  • db module - improvements
    • revisit implementation of createTable (and createDb?)
    • current implementation confused data loader, see DM-2417
    • should behave like mysql does
    • created ticket: DM-2502
  • db module - documentation
    • doxygenize
    • created ticket: DM-2503
  • ddl info in metaserv
    • rethink how to store metadata about schema if we have 100s of database with exactly the same schema
    • created tickets DM-2504, DM-2505
    • related ticket DM-2139
    • also, document what is supported, cat/sql/baselineSchema.sql not enough
    • created ticket DM-2506
  • defining stories
    • try to clearly define goals / deliverables / "acceptance list" 

information exchange between processes

  • usecase: need to exchange info about "index of chunks managed by the worker" between cmsd and xrootd
  • considering shared memory (if we can keep it simple)
  • ~1000 elements, easy, can lock entire block, auto release lock
  •  don't want to do it through xrootd directly, or via database. Messes up scheduling I/O heavy requests
  • having it will allow incremental updates to the structure of the index of chunks without restarting the services
  • create stories for Andy
  • created DM-2507, DM-2508

Deleting tables

  • related story: DM-1896
  • worry about race condition: one czar marks  table delete-pending, other czar schedules query related to that table
  • decided to introduce small delay, rely on fast synchronization between czars and CSS
  • considered stamping schema with "schema version", incremented when table deleted etc. Worry, it can stop perfectly valid queries that need tables not affected
  • considered cross-czar communication