admin: Add purge interface

This commit adds a new option to the admin interface to purge an
instance. This requires the user to manually confirm the name of the
instance.

internal/dis/component/instances/purger/purger.go

@@ -0,0 +1,86 @@
+package purger
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	"github.com/FAU-CDI/wisski-distillery/internal/dis/component"
+	"github.com/FAU-CDI/wisski-distillery/internal/dis/component/instances"
+	"github.com/FAU-CDI/wisski-distillery/pkg/logging"
+	"github.com/tkw1536/goprogram/exit"
+)
+
+// Purger purges instances from the distillery
+type Purger struct {
+	component.Base
+	Dependencies struct {
+		Instances     *instances.Instances
+		Provisionable []component.Provisionable
+	}
+}
+
+var errPurgeNoDetails = exit.Error{
+	Message:  "unable to find instance details for purge: %s",
+	ExitCode: exit.ExitGeneric,
+}
+var errPurgeGeneric = exit.Error{
+	Message:  "unable to purge instance %q: %s",
+	ExitCode: exit.ExitGeneric,
+}
+
+// Purge permanently purges an instance from the distillery.
+// The instance does not have to exist; in which case the resources are also deleted.
+func (purger *Purger) Purge(ctx context.Context, out io.Writer, slug string) error {
+	logging.LogMessage(out, ctx, "Checking bookkeeping table")
+	instance, err := purger.Dependencies.Instances.WissKI(ctx, slug)
+	if err == instances.ErrWissKINotFound {
+		fmt.Fprintln(out, "Not found in bookkeeping table, assuming defaults")
+		instance, err = purger.Dependencies.Instances.Create(slug)
+	}
+	if err != nil {
+		return errPurgeNoDetails.WithMessageF(err)
+	}
+
+	// remove docker stack
+	logging.LogMessage(out, ctx, "Stopping and removing docker container")
+	if err := instance.Barrel().Stack().Down(ctx, out); err != nil {
+		fmt.Fprintln(out, err)
+	}
+
+	// remove the filesystem
+	logging.LogMessage(out, ctx, "Removing from filesystem %s", instance.FilesystemBase)
+	if err := purger.Environment.RemoveAll(instance.FilesystemBase); err != nil {
+		fmt.Fprintln(out, err)
+	}
+
+	// purge all the instance specific resources
+	if err := logging.LogOperation(func() error {
+		domain := instance.Domain()
+		for _, pc := range purger.Dependencies.Provisionable {
+			logging.LogMessage(out, ctx, "Purging %s resources", pc.Name())
+			err := pc.Purge(ctx, instance.Instance, domain)
+			if err != nil {
+				return err
+			}
+		}
+
+		return nil
+	}, out, ctx, "Purging instance-specific resources"); err != nil {
+		return errPurgeGeneric.WithMessageF(slug, err)
+	}
+
+	// remove from bookkeeping
+	logging.LogMessage(out, ctx, "Removing instance from bookkeeping")
+	if err := instance.Bookkeeping().Delete(ctx); err != nil {
+		fmt.Fprintln(out, err)
+	}
+
+	// remove the filesystem
+	logging.LogMessage(out, ctx, "Remove lock data")
+	if instance.Locker().TryUnlock(ctx) {
+		fmt.Fprintln(out, "instance was not locked")
+	}
+
+	return nil
+}