Operator Tool to migrate stacks to the convergence mode.


It would be useful for operators to make sure all stacks are being run under the same logic in order to support the service better.

Problem description

Whether or not a stack action is run under convergence is sticky, meaning that if the current “convergence_engine” setting is True when the stack-create is run, then that stack will always be run with the convergence logic (the same is also true for convergence_engine=False).

Proposed change

This spec proposes a new tool for operators that migrates any stack created under the legacy mode to convergence mode.

This will only convert stack that are in a sane state (*_COMPLETE) and will warn the operator if they need to re-run the command to catch stacks currently have actions in progress.

The steps the operator will need to take are:

  1. edit /etc/heat/heat.conf change convergence_engine to what they want

  2. restart heat-engine

  3. run “heat-manage migrate-convergence-1 <stack_id>”


  1. Stacks could be left to run in both modes and eventually users would re-create stacks thus migrating them to the new mode (this could take a long time though).

  2. We could automatically convert stacks on the next stack-update. This takes the control out of the operators hands, but has the advantage of doing this operation piecemeal and the end-user could fix any issues that arise. (asalkeld: I think this could be an attractive option).

  3. Grow some balls and decide that we are going with convergence and make this a migration script (aka no-going-back).


Extend heat-manage as follows:

heat-manage migrate-convergence-1 <stack_id>

This command will call code in stack.py to get stack with stack_id and all it nested stuff. We need to set convergence = True, prev_raw_template_id = None and remove appropriate raw template, generate and add new traversal_id and set current_template_id for all resources in these stacks. Also we need to fill needed_by and requires columns in the database with corresponding dependencies.


Primary assignee:



Target Milestone for completion:


Work Items