terraform/backend/local/backend_refresh.go

package local

import (
	"context"
	"fmt"
	"log"
	"os"
	"strings"

	"github.com/hashicorp/errwrap"
	"github.com/hashicorp/go-multierror"
	"github.com/hashicorp/terraform/backend"
	"github.com/hashicorp/terraform/command/clistate"
	"github.com/hashicorp/terraform/config/module"
	"github.com/hashicorp/terraform/state"
	"github.com/hashicorp/terraform/terraform"
)

func (b *Local) opRefresh(
	ctx context.Context,
	op *backend.Operation,
	runningOp *backend.RunningOperation) {
	// Check if our state exists if we're performing a refresh operation. We
	// only do this if we're managing state with this backend.
	if b.Backend == nil {
		if _, err := os.Stat(b.StatePath); err != nil {
			if os.IsNotExist(err) {
				err = nil
			}

			if err != nil {
				runningOp.Err = fmt.Errorf(
					"There was an error reading the Terraform state that is needed\n"+
						"for refreshing. The path and error are shown below.\n\n"+
						"Path: %s\n\nError: %s",
					b.StatePath, err)
				return
			}
		}
	}

	// If we have no config module given to use, create an empty tree to
	// avoid crashes when Terraform.Context is initialized.
	if op.Module == nil {
		op.Module = module.NewEmptyTree()
	}

	// Get our context
	tfCtx, opState, err := b.context(op)
	if err != nil {
		runningOp.Err = err
		return
	}

	if op.LockState {
		lockCtx, cancel := context.WithTimeout(ctx, op.StateLockTimeout)
		defer cancel()

		lockInfo := state.NewLockInfo()
		lockInfo.Operation = op.Type.String()
		lockID, err := clistate.Lock(lockCtx, opState, lockInfo, b.CLI, b.Colorize())
		if err != nil {
			runningOp.Err = errwrap.Wrapf("Error locking state: {{err}}", err)
			return
		}

		defer func() {
			if err := clistate.Unlock(opState, lockID, b.CLI, b.Colorize()); err != nil {
				runningOp.Err = multierror.Append(runningOp.Err, err)
			}
		}()
	}

	// Set our state
	runningOp.State = opState.State()
	if runningOp.State.Empty() || !runningOp.State.HasResources() {
		if b.CLI != nil {
			b.CLI.Output(b.Colorize().Color(
				strings.TrimSpace(refreshNoState) + "\n"))
		}
	}

	// Perform the refresh in a goroutine so we can be interrupted
	var newState *terraform.State
	var refreshErr error
	doneCh := make(chan struct{})
	go func() {
		defer close(doneCh)
		newState, refreshErr = tfCtx.Refresh()
		log.Printf("[INFO] backend/local: refresh calling Refresh")
	}()

	select {
	case <-ctx.Done():
		if b.CLI != nil {
			b.CLI.Output("stopping refresh operation...")
		}

		// Stop execution
		go tfCtx.Stop()

		// Wait for completion still
		<-doneCh
	case <-doneCh:
	}

	// write the resulting state to the running op
	runningOp.State = newState
	if refreshErr != nil {
		runningOp.Err = errwrap.Wrapf("Error refreshing state: {{err}}", refreshErr)
		return
	}

	// Write and persist the state
	if err := opState.WriteState(newState); err != nil {
		runningOp.Err = errwrap.Wrapf("Error writing state: {{err}}", err)
		return
	}
	if err := opState.PersistState(); err != nil {
		runningOp.Err = errwrap.Wrapf("Error saving state: {{err}}", err)
		return
	}
}

const refreshNoState = `
[reset][bold][yellow]Empty or non-existent state file.[reset][yellow]

Refresh will do nothing. Refresh does not error or return an erroneous
exit status because many automation scripts use refresh, plan, then apply
and may not have a state file yet for the first run.
`