terraform/internal/backend/backend.go

412 lines
16 KiB
Go
Raw Normal View History

// Package backend provides interfaces that the CLI uses to interact with
// Terraform. A backend provides the abstraction that allows the same CLI
// to simultaneously support both local and remote operations for seamlessly
// using Terraform in a team environment.
package backend
import (
"context"
"errors"
"io/ioutil"
"log"
"os"
"github.com/hashicorp/terraform/internal/addrs"
"github.com/hashicorp/terraform/internal/command/clistate"
"github.com/hashicorp/terraform/internal/command/views"
"github.com/hashicorp/terraform/internal/configs"
"github.com/hashicorp/terraform/internal/configs/configload"
"github.com/hashicorp/terraform/internal/configs/configschema"
"github.com/hashicorp/terraform/internal/plans"
"github.com/hashicorp/terraform/internal/plans/planfile"
"github.com/hashicorp/terraform/internal/states"
"github.com/hashicorp/terraform/internal/states/statemgr"
"github.com/hashicorp/terraform/internal/terraform"
"github.com/hashicorp/terraform/internal/tfdiags"
"github.com/mitchellh/go-homedir"
"github.com/zclconf/go-cty/cty"
)
// DefaultStateName is the name of the default, initial state that every
// backend must have. This state cannot be deleted.
const DefaultStateName = "default"
var (
// ErrDefaultWorkspaceNotSupported is returned when an operation does not
// support using the default workspace, but requires a named workspace to
// be selected.
ErrDefaultWorkspaceNotSupported = errors.New("default workspace not supported\n" +
"You can create a new workspace with the \"workspace new\" command.")
// ErrWorkspacesNotSupported is an error returned when a caller attempts
// to perform an operation on a workspace other than "default" for a
// backend that doesn't support multiple workspaces.
//
// The caller can detect this to do special fallback behavior or produce
// a specific, helpful error message.
ErrWorkspacesNotSupported = errors.New("workspaces not supported")
)
// InitFn is used to initialize a new backend.
type InitFn func() Backend
// Backend is the minimal interface that must be implemented to enable Terraform.
type Backend interface {
// ConfigSchema returns a description of the expected configuration
// structure for the receiving backend.
//
// This method does not have any side-effects for the backend and can
// be safely used before configuring.
ConfigSchema() *configschema.Block
// PrepareConfig checks the validity of the values in the given
// configuration, and inserts any missing defaults, assuming that its
// structure has already been validated per the schema returned by
// ConfigSchema.
//
// This method does not have any side-effects for the backend and can
// be safely used before configuring. It also does not consult any
// external data such as environment variables, disk files, etc. Validation
// that requires such external data should be deferred until the
// Configure call.
//
// If error diagnostics are returned then the configuration is not valid
// and must not subsequently be passed to the Configure method.
//
// This method may return configuration-contextual diagnostics such
// as tfdiags.AttributeValue, and so the caller should provide the
// necessary context via the diags.InConfigBody method before returning
// diagnostics to the user.
PrepareConfig(cty.Value) (cty.Value, tfdiags.Diagnostics)
// Configure uses the provided configuration to set configuration fields
// within the backend.
//
// The given configuration is assumed to have already been validated
// against the schema returned by ConfigSchema and passed validation
// via PrepareConfig.
//
// This method may be called only once per backend instance, and must be
// called before all other methods except where otherwise stated.
//
// If error diagnostics are returned, the internal state of the instance
// is undefined and no other methods may be called.
Configure(cty.Value) tfdiags.Diagnostics
// StateMgr returns the state manager for the given workspace name.
//
// If the returned state manager also implements statemgr.Locker then
// it's the caller's responsibility to call Lock and Unlock as appropriate.
//
// If the named workspace doesn't exist, or if it has no state, it will
// be created either immediately on this call or the first time
// PersistState is called, depending on the state manager implementation.
StateMgr(workspace string) (statemgr.Full, error)
// DeleteWorkspace removes the workspace with the given name if it exists.
//
// DeleteWorkspace cannot prevent deleting a state that is in use. It is
// the responsibility of the caller to hold a Lock for the state manager
// belonging to this workspace before calling this method.
DeleteWorkspace(name string) error
// States returns a list of the names of all of the workspaces that exist
// in this backend.
Workspaces() ([]string, error)
}
// Enhanced implements additional behavior on top of a normal backend.
//
// Enhanced backends allow customizing the behavior of Terraform operations.
// This allows Terraform to potentially run operations remotely, load
// configurations from external sources, etc.
type Enhanced interface {
Backend
// Operation performs a Terraform operation such as refresh, plan, apply.
// It is up to the implementation to determine what "performing" means.
// This DOES NOT BLOCK. The context returned as part of RunningOperation
// should be used to block for completion.
// If the state used in the operation can be locked, it is the
// responsibility of the Backend to lock the state for the duration of the
// running operation.
Operation(context.Context, *Operation) (*RunningOperation, error)
}
// Local implements additional behavior on a Backend that allows local
// operations in addition to remote operations.
//
// This enables more behaviors of Terraform that require more data such
// as `console`, `import`, `graph`. These require direct access to
// configurations, variables, and more. Not all backends may support this
// so we separate it out into its own optional interface.
type Local interface {
core: Functional-style API for terraform.Context Previously terraform.Context was built in an unfortunate way where all of the data was provided up front in terraform.NewContext and then mutated directly by subsequent operations. That made the data flow hard to follow, commonly leading to bugs, and also meant that we were forced to take various actions too early in terraform.NewContext, rather than waiting until a more appropriate time during an operation. This (enormous) commit changes terraform.Context so that its fields are broadly just unchanging data about the execution context (current workspace name, available plugins, etc) whereas the main data Terraform works with arrives via individual method arguments and is returned in return values. Specifically, this means that terraform.Context no longer "has-a" config, state, and "planned changes", instead holding on to those only temporarily during an operation. The caller is responsible for propagating the outcome of one step into the next step so that the data flow between operations is actually visible. However, since that's a change to the main entry points in the "terraform" package, this commit also touches every file in the codebase which interacted with those APIs. Most of the noise here is in updating tests to take the same actions using the new API style, but this also affects the main-code callers in the backends and in the command package. My goal here was to refactor without changing observable behavior, but in practice there are a couple externally-visible behavior variations here that seemed okay in service of the broader goal: - The "terraform graph" command is no longer hooked directly into the core graph builders, because that's no longer part of the public API. However, I did include a couple new Context functions whose contract is to produce a UI-oriented graph, and _for now_ those continue to return the physical graph we use for those operations. There's no exported API for generating the "validate" and "eval" graphs, because neither is particularly interesting in its own right, and so "terraform graph" no longer supports those graph types. - terraform.NewContext no longer has the responsibility for collecting all of the provider schemas up front. Instead, we wait until we need them. However, that means that some of our error messages now have a slightly different shape due to unwinding through a differently-shaped call stack. As of this commit we also end up reloading the schemas multiple times in some cases, which is functionally acceptable but likely represents a performance regression. I intend to rework this to use caching, but I'm saving that for a later commit because this one is big enough already. The proximal reason for this change is to resolve the chicken/egg problem whereby there was previously no single point where we could apply "moved" statements to the previous run state before creating a plan. With this change in place, we can now do that as part of Context.Plan, prior to forking the input state into the three separate state artifacts we use during planning. However, this is at least the third project in a row where the previous API design led to piling more functionality into terraform.NewContext and then working around the incorrect order of operations that produces, so I intend that by paying the cost/risk of this large diff now we can in turn reduce the cost/risk of future projects that relate to our main workflow actions.
2021-08-24 21:06:38 +02:00
// LocalRun uses information in the Operation to prepare a set of objects
// needed to start running that operation.
//
// The operation doesn't need a Type set, but it needs various other
// options set. This is a rather odd API that tries to treat all
// operations as the same when they really aren't; see the local and remote
// backend's implementations of this to understand what this actually
// does, because this operation has no well-defined contract aside from
// "whatever it already does".
LocalRun(*Operation) (*LocalRun, statemgr.Full, tfdiags.Diagnostics)
}
// LocalRun represents the assortment of objects that we can collect or
// calculate from an Operation object, which we can then use for local
// operations.
//
// The operation methods on terraform.Context (Plan, Apply, Import, etc) each
// generate new artifacts which supersede parts of the LocalRun object that
// started the operation, so callers should be careful to use those subsequent
// artifacts instead of the fields of LocalRun where appropriate. The LocalRun
// data intentionally doesn't update as a result of calling methods on Context,
// in order to make data flow explicit.
//
// This type is a weird architectural wart resulting from the overly-general
// way our backend API models operations, whereby we behave as if all
// Terraform operations have the same inputs and outputs even though they
// are actually all rather different. The exact meaning of the fields in
// this type therefore vary depending on which OperationType was passed to
// Local.Context in order to create an object of this type.
type LocalRun struct {
// Core is an already-initialized Terraform Core context, ready to be
// used to run operations such as Plan and Apply.
Core *terraform.Context
// Config is the configuration we're working with, which typically comes
// from either config files directly on local disk (when we're creating
// a plan, or similar) or from a snapshot embedded in a plan file
// (when we're applying a saved plan).
Config *configs.Config
// InputState is the state that should be used for whatever is the first
// method call to a context created with CoreOpts. When creating a plan
// this will be the previous run state, but when applying a saved plan
// this will be the prior state recorded in that plan.
InputState *states.State
// PlanOpts are options to pass to a Plan or Plan-like operation.
//
// This is nil when we're applying a saved plan, because the plan itself
// contains enough information about its options to apply it.
PlanOpts *terraform.PlanOpts
// Plan is a plan loaded from a saved plan file, if our operation is to
// apply that saved plan.
//
// This is nil when we're not applying a saved plan.
Plan *plans.Plan
}
// An operation represents an operation for Terraform to execute.
//
// Note that not all fields are supported by all backends and can result
// in an error if set. All backend implementations should show user-friendly
// errors explaining any incorrectly set values. For example, the local
// backend doesn't support a PlanId being set.
//
// The operation options are purposely designed to have maximal compatibility
// between Terraform and Terraform Servers (a commercial product offered by
// HashiCorp). Therefore, it isn't expected that other implementation support
// every possible option. The struct here is generalized in order to allow
// even partial implementations to exist in the open, without walling off
// remote functionality 100% behind a commercial wall. Anyone can implement
// against this interface and have Terraform interact with it just as it
// would with HashiCorp-provided Terraform Servers.
type Operation struct {
// Type is the operation to perform.
Type OperationType
// PlanId is an opaque value that backends can use to execute a specific
// plan for an apply operation.
//
// PlanOutBackend is the backend to store with the plan. This is the
// backend that will be used when applying the plan.
PlanId string
PlanRefresh bool // PlanRefresh will do a refresh before a plan
PlanOutPath string // PlanOutPath is the path to save the plan
PlanOutBackend *plans.Backend
// ConfigDir is the path to the directory containing the configuration's
// root module.
ConfigDir string
// ConfigLoader is a configuration loader that can be used to load
// configuration from ConfigDir.
ConfigLoader *configload.Loader
// Hooks can be used to perform actions triggered by various events during
// the operation's lifecycle.
Hooks []terraform.Hook
// Plan is a plan that was passed as an argument. This is valid for
// plan and apply arguments but may not work for all backends.
PlanFile *planfile.Reader
// The options below are more self-explanatory and affect the runtime
// behavior of the operation.
PlanMode plans.Mode
AutoApprove bool
Parallelism int
Targets []addrs.Targetable
ForceReplace []addrs.AbsResourceInstance
Variables map[string]UnparsedVariableValue
// Some operations use root module variables only opportunistically or
// don't need them at all. If this flag is set, the backend must treat
// all variables as optional and provide an unknown value for any required
// variables that aren't set in order to allow partial evaluation against
// the resulting incomplete context.
//
// This flag is honored only if PlanFile isn't set. If PlanFile is set then
// the variables set in the plan are used instead, and they must be valid.
AllowUnsetVariables bool
2021-02-17 19:01:30 +01:00
// View implements the logic for all UI interactions.
View views.Operation
// Input/output/control options.
UIIn terraform.UIInput
UIOut terraform.UIOutput
// StateLocker is used to lock the state while providing UI feedback to the
// user. This will be replaced by the Backend to update the context.
//
// If state locking is not necessary, this should be set to a no-op
// implementation of clistate.Locker.
StateLocker clistate.Locker
// Workspace is the name of the workspace that this operation should run
// in, which controls which named state is used.
Workspace string
}
// HasConfig returns true if and only if the operation has a ConfigDir value
// that refers to a directory containing at least one Terraform configuration
// file.
func (o *Operation) HasConfig() bool {
return o.ConfigLoader.IsConfigDir(o.ConfigDir)
}
// Config loads the configuration that the operation applies to, using the
// ConfigDir and ConfigLoader fields within the receiving operation.
func (o *Operation) Config() (*configs.Config, tfdiags.Diagnostics) {
var diags tfdiags.Diagnostics
config, hclDiags := o.ConfigLoader.LoadConfig(o.ConfigDir)
diags = diags.Append(hclDiags)
return config, diags
}
// ReportResult is a helper for the common chore of setting the status of
// a running operation and showing any diagnostics produced during that
// operation.
//
// If the given diagnostics contains errors then the operation's result
// will be set to backend.OperationFailure. It will be set to
// backend.OperationSuccess otherwise. It will then use o.View.Diagnostics
// to show the given diagnostics before returning.
//
// Callers should feel free to do each of these operations separately in
// more complex cases where e.g. diagnostics are interleaved with other
// output, but terminating immediately after reporting error diagnostics is
// common and can be expressed concisely via this method.
func (o *Operation) ReportResult(op *RunningOperation, diags tfdiags.Diagnostics) {
if diags.HasErrors() {
op.Result = OperationFailure
} else {
op.Result = OperationSuccess
}
if o.View != nil {
o.View.Diagnostics(diags)
} else {
// Shouldn't generally happen, but if it does then we'll at least
// make some noise in the logs to help us spot it.
if len(diags) != 0 {
log.Printf(
"[ERROR] Backend needs to report diagnostics but View is not set:\n%s",
diags.ErrWithWarnings(),
)
}
}
}
// RunningOperation is the result of starting an operation.
type RunningOperation struct {
// For implementers of a backend, this context should not wrap the
// passed in context. Otherwise, cancelling the parent context will
// immediately mark this context as "done" but those aren't the semantics
// we want: we want this context to be done only when the operation itself
// is fully done.
context.Context
// Stop requests the operation to complete early, by calling Stop on all
// the plugins. If the process needs to terminate immediately, call Cancel.
Stop context.CancelFunc
// Cancel is the context.CancelFunc associated with the embedded context,
// and can be called to terminate the operation early.
// Once Cancel is called, the operation should return as soon as possible
// to avoid running operations during process exit.
Cancel context.CancelFunc
// Result is the exit status of the operation, populated only after the
// operation has completed.
Result OperationResult
// PlanEmpty is populated after a Plan operation completes without error
// to note whether a plan is empty or has changes.
PlanEmpty bool
// State is the final state after the operation completed. Persisting
// this state is managed by the backend. This should only be read
// after the operation completes to avoid read/write races.
State *states.State
}
// OperationResult describes the result status of an operation.
type OperationResult int
const (
// OperationSuccess indicates that the operation completed as expected.
OperationSuccess OperationResult = 0
// OperationFailure indicates that the operation encountered some sort
// of error, and thus may have been only partially performed or not
// performed at all.
OperationFailure OperationResult = 1
)
func (r OperationResult) ExitStatus() int {
return int(r)
}
// If the argument is a path, Read loads it and returns the contents,
// otherwise the argument is assumed to be the desired contents and is simply
// returned.
func ReadPathOrContents(poc string) (string, error) {
if len(poc) == 0 {
return poc, nil
}
path := poc
if path[0] == '~' {
var err error
path, err = homedir.Expand(path)
if err != nil {
return path, err
}
}
if _, err := os.Stat(path); err == nil {
contents, err := ioutil.ReadFile(path)
if err != nil {
return string(contents), err
}
return string(contents), nil
}
return poc, nil
}