When using the enhanced remote backend, a subset of all Terraform
operations are supported. Of these, only plan and apply can be executed
on the remote infrastructure (e.g. Terraform Cloud). Other operations
run locally and use the remote backend for state storage.
This causes problems when the local version of Terraform does not match
the configured version from the remote workspace. If the two versions
are incompatible, an `import` or `state mv` operation can cause the
remote workspace to be unusable until a manual fix is applied.
To prevent this from happening accidentally, this commit introduces a
check that the local Terraform version and the configured remote
workspace Terraform version are compatible. This check is skipped for
commands which do not write state, and can also be disabled by the use
of a new command-line flag, `-ignore-remote-version`.
Terraform version compatibility is defined as:
- For all releases before 0.14.0, local must exactly equal remote, as
two different versions cannot share state;
- 0.14.0 to 1.0.x are compatible, as we will not change the state
version number until at least Terraform 1.1.0;
- Versions after 1.1.0 must have the same major and minor versions, as
we will not change the state version number in a patch release.
If the two versions are incompatible, a diagnostic is displayed,
advising that the error can be suppressed with `-ignore-remote-version`.
When this flag is used, the diagnostic is still displayed, but as a
warning instead of an error.
Commands which will not write state can assert this fact by calling the
helper `meta.ignoreRemoteBackendVersionConflict`, which will disable the
checks. Those which can write state should instead call the helper
`meta.remoteBackendVersionCheck`, which will return diagnostics for
display.
In addition to these explicit paths for managing the version check, we
have an implicit check in the remote backend's state manager
initialization method. Both of the above helpers will disable this
check. This fallback is in place to ensure that future code paths which
access state cannot accidentally skip the remote version check.
This includes a new TargetAddrs field on both Run and RunCreateOptions
which we'll use to send resource addresses that were specified using
-target on the CLI command line when using the remote backend.
There were some unrelated upstream breaking changes compared to the last
version we had vendored, so this commit also includes some changes to the
backend/remote package to work with this new API, which now requires the
remote backend to be aware of the remote system's opaque workspace id.
* backend/remote: Filter environment variables when loading context
Following up on #23122, the remote system (Terraform Cloud or
Enterprise) serves environment and Terraform variables using a single
type of object. We only should load Terraform variables into the
Terraform context.
Fixes https://github.com/hashicorp/terraform/issues/23283.
For remote operations, the remote system (Terraform Cloud or Enterprise)
writes the stored variable values into a .tfvars file before running the
remote copy of Terraform CLI.
By contrast, for operations that only run locally (like
"terraform import"), we fetch the stored variable values from the remote
API and add them into the set of available variables directly as part
of creating the local execution context.
Previously in the local-only case we were assuming that all stored
variables are strings, which isn't true: the Terraform Cloud/Enterprise UI
allows users to specify that a particular variable is given as an HCL
expression, in which case the correct behavior is to parse and evaluate
the expression to obtain the final value.
This also addresses a related issue whereby previously we were forcing
all sensitive values to be represented as a special string "<sensitive>".
That leads to type checking errors for any variable specified as having
a type other than string, so instead here we use an unknown value as a
placeholder so that type checking can pass.
Unpopulated sensitive values may cause errors downstream though, so we'll
also produce a warning for each of them to let the user know that those
variables are not available for local-only operations. It's a warning
rather than an error so that operations that don't rely on known values
for those variables can potentially complete successfully.
This can potentially produce errors in situations that would've been
silently ignored before: if a remote variable is marked as being HCL
syntax but is not valid HCL then it will now fail parsing at this early
stage, whereas previously it would've just passed through as a string
and failed only if the operation tried to interpret it as a non-string.
However, in situations like these the remote operations like
"terraform plan" would already have been failing with an equivalent
error message anyway, so it's unlikely that any existing workspace that
is being used for routine operations would have such a broken
configuration.
Some commands don't use variables at all or use them in a way that doesn't
require them to all be fully valid and consistent. For those, we don't
want to fetch variable values from the remote system and try to validate
them because that's wasteful and likely to cause unnecessary error
messages.
Furthermore, the variables endpoint in Terraform Cloud and Enterprise only
works for personal access tokens, so it's important that we don't assume
we can _always_ use it. If we do, then we'll see problems when commands
are run inside Terraform Cloud and Enterprise remote execution contexts,
where the variables map always comes back as empty.
Alisdair McDiarmid