Simplify the use of clistate.Lock by creating a clistate.Locker
instance, which stores the context of locking a state, to allow unlock
to be called without knowledge of how the state was locked.
This alows the backend code to bring the needed UI methods to the point
where the state is locked, and still unlock the state from an outer
scope.
Provide a NoopLocker as well, so that callers can always call Unlock
without verifying the status of the lock.
Add the StateLocker field to the backend.Operation, so that the state
lock can be carried between the different function scopes of the backend
code. This will allow the backend context to lock the state before it's
read, while allowing the different operations to unlock the state when
they complete.
If the user wishes to interrupt the running operation, only the first
interrupt was communicated to the operation by canceling the provided
context. A second interrupt would start the shutdown process, but not
communicate this to the running operation. This order of event could
cause partial writes of state.
What would happen is that once the command returns, the plugin system
would stop the provider processes. Once the provider processes dies, all
pending Eval operations would return return with an error, and quickly
cause the operation to complete. Since the backend code didn't know that
the process was shutting down imminently, it would continue by
attempting to write out the last known state. Under the right
conditions, the process would exit part way through the writing of the
state file.
Add Stop and Cancel CancelFuncs to the RunningOperation, to allow it to
easily differentiate between the two signals. The backend will then be
able to detect a shutdown and abort more gracefully.
In order to ensure that the backend is not in the process of writing the
state out, the command will always attempt to wait for the process to
complete after cancellation.
A common reason to want to use `terraform plan` is to have a chance to
review and confirm a plan before running it. If in fact that is the
only reason you are running plan, this new `terraform apply -auto-approve=false`
flag provides an easier alternative to
P=$(mktemp -t plan)
terraform refresh
terraform plan -refresh=false -out=$P
terraform apply $P
rm $P
The flag defaults to true for now, but in a future version of Terraform it will
default to false.
Add fields required to create an appropriate context for all calls to
clistate.Lock.
Add missing checks for Meta.stateLock, where we would attempt to lock,
even if locking should be skipped.
What will hopfully be the final version of the Backend interface. This
combines the MultiState interface into Backend since it will be required
to implement, and simplifies the interface because the Backend is no
longer responsible for tracking the current state.
Split the interface to change environments out from the minimal Backend
interface, to make it optional for backend implementations. If
backend.MultiState isn't implemented, return a "not implemented" from
environment related methods.
Have the Local backend delegate the MultiState methods to the proper
backend.
Backends are a mechanism that allow abstracting the behavior of
Terraform CLI from the actual core. This allows us to slip in special
behavior such as state loading, remote operations, etc.
James Bardin