Control plane simulations allow you to preview changes to your resources before applying them to your control planes. Like a plan or dry-run operation, simulations expose the impact of updates to compositions or claims without changing your actual resources.
A control plane simulation creates a temporary copy of your control plane and returns a preview of the desired changes. The simulation change plan helps you reduce the risk of unexpected behavior based on your changes.
Simulation benefits
Control planes are dynamic systems that automatically reconcile resources to match your desired state. Simulations provide visibility into this reconciliation process by showing:
- New resources to create
- Existing resources to change
- Existing resources to delete
- How configuration changes propagate through the system
These insights are crucial when planning complex changes or upgrading Crossplane packages.
Requirements
Simulations are available to select customers on Upbound Cloud with Team Tier or higher. For more information, reach out to Upbound.
How to simulate your control planes
Before you start a simulation, build your project and use the up project run command to run your control plane.
Use the up project simulate command with your control plane name to start the
simulation:
up project simulate --complete-after=60s --terminate-on-finish
The complete-after flag determines how long to run the simulation before it completes and calculates the results. Depending on the change, a simulation may not complete within your defined interval leaving unaffected resources as unchanged.
The terminate-on-finish flag terminates the simulation after the time
you set - deleting the control plane that ran the simulation.
At the end of your simulation, your CLI returns:
- A summary of the resources created, modified, or deleted
- Diffs for each resource affected
View your simulation in the Upbound Console
You can also view your simulation results in the Upbound Console:
- Navigate to your base control plane in the Upbound Console
- Select the “Simulations” tab in the menu
- Select a simulation object for a change list of all resources affected.
The Console provides visual indications of changes:
- Created Resources: Marked with green
- Modified Resources: Marked with yellow
- Deleted Resources: Marked with red
- Unchanged Resources: Displayed in gray
Considerations
Simulations is a private preview feature.
Be aware of the following limitations:
Simulations can’t predict the exact behavior of external systems due to the complexity and non-deterministic reconciliation pattern in Crossplane.
The only completion criteria for a simulation is time. Your simulation may not receive a conclusive result within that interval. Upbound recommends the default
60svalue.Providers don’t run in simulations. Simulations can’t compose resources that rely on the status of Managed Resources.
The Upbound team is working to improve these limitations. Your feedback is always appreciated.
Next steps
For more information, follow the tutorial on Simulations.
