Software config notify deployment progress

https://blueprints.launchpad.net/heat/+spec/software-config-progress

Currently when a deployment resource remains IN_PROGRESS there is no way of knowing whether configuration is taking a long time, or if an unrelated problem occured before or after. The only option is to ssh into a server to diagnose the issue. This blueprint proposes that the server signal to heat when any deployment activity starts.

Problem description

Currently when a deployment resource remains IN_PROGRESS the configuration may be taking a legitimately long time. In other cases there may be a failure due to one of the following problems.

The potential problems during server boot include:

  1. Nova says the server has booted but the image failed to actually boot
  2. The server booted, but was not successfully assigned an IP address
  3. Nova metadata server cannot be reached on boot to poll for initial metadata

The potential problems which occur after boot but before a specific deployment is executed include:

  1. Misconfiguration in the installed server agent, hooks and config tools

5. Failure to poll deployment metadata from heat (or other configured polling source)

And finally the potential problems when actually executing the deployment:

6. Inability for the server to signal the results back to heat, either due to authentication or connectivity issues.

Currently there is no feedback that the actual deployment has started. If the user had earlier feedback that deployment has started then they can eliminate the above six failures as the cause of the deployment being IN_PROGRESS.

Proposed change

Currently SoftwareDeployment.signal assumes that as soon as a signal is received the deployment task is complete. This will be changed so that the signal details are checked for extra data which indicates that this is an IN_PROGRESS signal rather than a COMPLETE/FAILED signal. The software-config hooks will be modified to send an IN_PROGRESS signal before they start the deployment task.

The signal details are currently a JSON map with entries for each output value, plus deploy_stdout, deploy_stderr and deploy_status_code. Two new entries will be expected, deploy_status and deploy_status_reason. SoftwareDeployment.signal will check for this and if deploy_status is IN_PROGRESS then the deployment resource will remain in an IN_PROGRESS state. However there will be a resource event generated to give the user some feedback that their deployment task has started.

Backwards-compatibility concerns need to be considered both with old images running on new heat, and new images running on old heat.

Old image, new heat

There is nothing special to consider here. The server will not signal heat that a deployment is starting, but the deployment resource will already be in an IN_PROGRESS state. The only implication is that the user will not see the extra IN_PROGRESS event telling them that the deployment has started.

New image, old heat

Since old heat assumes that the deployment is complete as soon as a signal is received, the hooks need to suppress sending any IN_PROGRESS signals. This can be achieved by the hooks checking for the input deploy_status_aware being set to true. Only new heat will set this input value to true so the hook can check this input and behave accordingly.

Alternatives

None

Implementation

Assignee(s)

Primary assignee:
<steve-stevebaker>

Milestones

Target Milestone for completion:
Kilo-1

Work Items

Work items or tasks – break the feature up into the things that need to be done to implement it. Those parts might end up being done by different people, but we’re mostly trying to understand the timeline for implementation.

Dependencies

There are no blueprint or library dependencies for this blueprint