Upgrade should respect the stack_order about motherbrain HOT 2 CLOSED

I have been working on this and wanted to see what people thought. This is also including functionality for #668.

Two new options to the upgrade task.
-C, --concurrency - Specifies the max number of nodes that can be converged concurrently.
-b, --bootstrap-order - Specifies that nodes are converged in the order specified in the stack_order.

Here is how these things work together. Consider the stack order

stack_order do
  bootstrap 'app::database'
  bootstrap 'app::service'
end

and a manifest

{
  "nodes": [
    {
      "groups": ["app::database"],
      "hosts": ["db1", "db2", "db3"]
    },
    {
      "groups": ["app::service"],
      "hosts": ["app1", "app2", "app3"]
    }
  ]
}

The first thing I am doing is getting the task_queue from the bootstrap_routine and then using that to group all hostnames in the correct order. So, in the above example I have

[["db1", "db2", "db3"], ["app1", "app2", "app3"]]

Now depending on the combination of the --concurrency and --bootstrap flags this array is transformed into an array of "concurrency groups". In other words it is an array of arrays where each sub array can be converged in parallel.

If --concurrency 2

# We don't care that db nodes and app nodes are converged in parallel. 
# We just are restricting the max number of parallel converges
[["db1", "db2"], ["db3", "app1"], ["app2", "app3"]]

if --concurrency 2 and --bootstrap-order

# We want all the database nodes to go first followed by all of the app nodes but we want 
# at most 2 nodes converging at any given time
[["db1", "db2"], ["db3"], ["app1", "app2"], ["app3"]]

If just --bootstrap-order

# We want all the db nodes to converge in parallel then the app nodes in parallel
[["db1", "db2", "db3"], ["app1", "app2", "app3"]]

And finally the behavior when neither flag is specified

# All nodes can be converged in parallel.
[["db1", "db2", "db3", "app1", "app2", "app3"]]

I would love to get some feedback on this. Thanks.

from motherbrain.

Given the associated PR was merged, I'm closing this for now. Let me know if there's more to do on this front.

from motherbrain.