Restarting services before a task is complete

When you perform tasks within PowerVC, those tasks may call on one or more OpenStack services as they complete. For example, when you attach a volume, both the cinder and nova services are called in the successful completion of that task. If you stop or restart one of those OpenStack services while the volume is being attached, you could experience unexpected results, such as:

• One of the resources might be put into a state that makes it unusable.
• There might be incomplete tasks on one or more of the resources involved. This can result in miscommunication between the cinder and nova services related to that resource in the future.

Services can be stopped or restarted in the following ways:

• Using the powervc-services command.
• Performing certain tasks within PowerVC. The following table lists tasks that can cause services to stop or restart:

  Table 1. Actions that cause services to stop or restart.

  Action	Service that gets stopped or restarted
  Edit storage (IP address, credentials, or display name)	Cinder (volume)
  Edit the default storage template for a storage provider
  Edit storage switches (IP address, credentials, or display name)
  Remove a storage provider
  Edit HMC or Host (IP address, credentials, or display name)	Nova (compute)
  Remove a host
  Running the powervc-ldap-config command	Keystone (identity)
  Running the powervc-config command	Varies, depending on the service being configured
  Performing a backup or restore	All

  Note: In most cases, PowerVC restricts you from performing an action when a task has not completed.

However, if you have run into problems because services have been restarted, then you may need to take the following steps to resolve the resulting problems:

• If a task failed in the middle, attempt the task again.
• Remove the affected resources from PowerVC and re-add them.
• For complex tasks (such as migration), you may have to roll back or undo the task outside of PowerVC and then perform the task again.