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Revision as of 22:08, 13 January 2017 by Melwitt (talk | contribs)

Nova Cells v2



  • The deployment/upgrade process needs to be documented in more than just the release notes.
    • dansmith was going to work on a blog post to start this.
    • On a side note, we should also have man pages for the cell_v2 commands because there is confusion around the inputs and outputs and how return codes should be treated, i.e. is 1 an error or not?
    • alaski's older docs patch (which is probably out of date now but might be useful) is here: https://review.openstack.org/#/c/267153/
    • Summary of current commands:
      • map_cell0: creates a cell mapping for cell0
      • simple_cell_setup: creates a cell mapping for cell0 and creates a cell mapping and associates hosts with it (requires unmapped compute hosts registered already). Intended as a lightweight way for non-cells-v1 users to setup cells v2 during an upgrade.
      • map_cell_and_hosts: creates a cell mapping and associates hosts with it (requires unmapped compute hosts registered already)
      • discover_hosts: associates unmapped hosts with an existing cell mapping
    • Commands TODO?:
      • create_cell: creates a cell mapping intended for association with hosts later via discover_hosts
      • list_cells: list current cell mappings, noting any that are empty (to help with 1. knowing whether a cell needs to be created 2. finding empty cells for use or for cleanup)
      • delete_cell: delete a cell mapping, for use in cleaning up erroneously created cell mappings or wrong cell mappings, etc.
  • Integrate the 'nova-status upgrade check' CLI into the CI/QA system (grenade).
  • Older tracking etherpads (these may be out of date):

Open Questions

  • Should the computes self-register with a cell when the compute_nodes record is created from the ResourceTracker? https://review.openstack.org/#/c/369634/
    • How would the computes know which cell to map to? We could add something to the model to flag a 'default' or 'staging' cell mapping, or put something into nova.conf on the compute node.
    • If we auto-register into a default/staging cell, how do we move hosts to other cells? nova-manage CLI?
  • Why can't we create an empty cell, i.e. a cell mapping with no computes? This is a fresh-install scenario.
    • Note that the nova-status upgrade check command does not consider it a failure if there are cell mappings but no compute nodes yet but simple_cell_setup does consider that a failure, see bug 1656276.
    • There has been a review up for this for awhile: https://review.openstack.org/#/c/332713/
      • This way, a fresh install would do something like: 'nova-manage cell_v2 map_cell0' 'nova-manage cell_v2 create_cell' and then once compute hosts are available, operator runs 'nova-manage cell_v2 discover_hosts'





DB Table Analysis


Scheduling requirements


Code Review