parallel_plan blocks multiple environments using the default workspace

[jrobison-sb]

I've got a repository with multiple environments structured like this:

terraform/environments/dev
terraform/environments/test
terraform/environments/prod

Each environment uses only the default workspace.

When I enable parallel_plan: true, this breaks Atlantis' ability to run plans in parallel as expected, with the error saying The default workspace is currently locked by another command that is running for this pull request.

Atlantis shouldn't behave this way because each environment is separate and each plan lock is based on the directory: "msg": "acquired lock with id \"terraform/environments/production/default\"",. A lock with ID terraform/environments/production/default shouldn't block Atlantis from simultaneously using another lock with ID terraform/environments/test/default.

[brandon-fryslie]

I was suffering from this same issue. Here is a potential workaround: #260 (comment)

[matthewmrichter]

The underlying locking issue that causes this is addressed in #6376.

The write lock in Clone() serializes all parallel plan goroutines against the read locks held by runSteps(). The fix uses a read-lock fast path for the common case where the clone directory is already at the correct commit, enabling true parallel execution.