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Nova Cells v2



  • The deployment/upgrade process needs to be documented in more than just the release notes.
    • dansmith has a start on the docs here: https://review.openstack.org/#/c/420198/ (merged)
    • (diana will take 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? Put the CLI docs here: http://docs.openstack.org/developer/nova/man/nova-manage.html
    • alaski's older docs patch (which is probably out of date now but might be useful) is here: https://review.openstack.org/#/c/267153/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 (or all cell mappings if a specific cell isn't specified)
  • Integrate the 'nova-status upgrade check' CLI into the CI/QA system (grenade).
  • mriedem is working on setting up multiple cells in the multinode job: https://review.openstack.org/#/c/420976/
    • That's probably going to cause issues for the live migration tests since we can't migrate between cells and we only have two computes in that job, and with my change each is in a cell.
    • sdague also pointed out some design issues in the dependent change which means needing to callback into devstack from devstack-gate at the end of the deploy to run discover_hosts.
  • Release notes for Ocata
  • Older tracking etherpads (these may be out of date):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