There are a few situations that we've seen arise quite commonly for folks
upgrading from Terraform 0.11 to 0.12. These particular problems are not
things that Terraform 0.12 can fix automatically during upgrading, but
we can at least give some better feedback to users that they ought to be
addressed _before_ upgrading.
The provider address problem is already detected and flagged by the
"terraform 0.11checklist" command that folks should run as part of their
upgrade process, but the module address problem is not something we
noticed was lacking validation in 0.11 and so the checklist tool doesn't
cover it. Due to the lack of coverage in the checklist tool, this commit
also includes an additional section in the upgrade guide that mentions
the problem and gives instructions on how to address it.
The state refactoring command "terraform state mv" in Terraform 0.11 does
not update existing dependency addresses recorded in the state when it
moves objects around, and Terraform only updates the dependency addresses
in the state when it performs a full update on a resource instance, and
so it's a common problem for folks updating from Terraform 0.11 with
resource names that are not valid identifiers to run into state upgrade
errors even though they have followed the instructions produced by
"terraform 0.12checklist".
Dependencies are synced from config during every refresh walk anyway, so
in practice we can get away with just discarding invalid dependency
addresses and letting the refresh walk update them. In practice these
addresses are unlikely to be pointing at a resource that actually exists
anyway, because if so Terraform 0.12's configuration parser wouldn't be
able to interpret it.
Discarding invalid dependency addresses allows the state upgrade to
complete successfully in such cases and thus gives the refresh step an
opportunity to repair the problem.
Some of our errors returned here were lacking context about what part of
the file was problematic, which led to some useless error reporting for
some real-world situations that this upgrade process doesn't seem to be
catching.
Here we add additional context to those error cases, as a step towards
tracking down exactly which upgrade cases are missing here so that we can
potentially fix them in a subsequent release.
We're going to allow the provider to encode whatever it wants in here, so
a provider can use whatever is most convenient for its implementation
language and to avoid some of the bugs we saw with the prior model where
the forced round-trip through JSON and back into interface{} would cause
some loss of fidelity, leading to bugs.
Due to how often the state and plan types are referenced throughout
Terraform, there isn't a great way to switch them out gradually. As a
consequence, this huge commit gets us from the old world to a _compilable_
new world, but still has a large number of known test failures due to
key functionality being stubbed out.
The stubs here are for anything that interacts with providers, since we
now need to do the follow-up work to similarly replace the old
terraform.ResourceProvider interface with its replacement in the new
"providers" package. That work, along with work to fix the remaining
failing tests, will follow in subsequent commits.
The aim here was to replace all references to terraform.State and its
downstream types with states.State, terraform.Plan with plans.Plan,
state.State with statemgr.State, and switch to the new implementations of
the state and plan file formats. However, due to the number of times those
types are used, this also ended up affecting numerous other parts of core
such as terraform.Hook, the backend.Backend interface, and most of the CLI
commands.
Just as with 5861dbf3fc49b19587a31816eb06f511ab861bb4 before, I apologize
in advance to the person who inevitably just found this huge commit while
spelunking through the commit history.
Whereas the parent directory "states" contains the models that represent
state in memory, this package's responsibility is in serializing a subset
of that data to a JSON-based file format and then reloading that data
back into memory later.
For reading, this package supports state file formats going back to
version 1, using lightly-adapted versions of the migration code previously
used in the "terraform" package. State data is upgraded to the latest
version step by step and then transformed into the in-memory state
representation, which is distinct from any of the file format structs in
this package to enable these to evolve separately.
For writing, only the latest version (4) is supported, which is a new
format that is a slightly-flattened version of the new in-memory state
models introduced in the prior commit. This format retains the outputs
from only the root module and it flattens out the module and instance
parts of the hierarchy by including the identifiers for these inside
the child object. The loader then reconstructs the multi-layer structure
we use for more convenient access in memory.
For now, the only testing in this package is of round-tripping different
versions of state through a read and a write, ensuring the output is
as desired. This exercises all of the reading, upgrading, and writing
functions but should be augmented in later commits to improve coverage
and introduce more focused tests for specific parts of the functionality.
Martin Atkins