prune: support clearing build cache using CleanCacheMount

`podman builder prune` and `podman image prune` should also support
cleaning build cache using buildah's public `CleanCacheMount` API.

Reference: https://docs.docker.com/reference/cli/docker/builder/prune/
Context: containers#15612 (reply in thread)
Context: containers/buildah#4490

Signed-off-by: flouthoc <[email protected]>

Author: flouthoc

cmd/podman/images/prune.go

@@ -46,6 +46,7 @@ func init() {
 
 	flags := pruneCmd.Flags()
 	flags.BoolVarP(&pruneOpts.All, "all", "a", false, "Remove all images not in use by containers, not just dangling ones")
+	flags.BoolVarP(&pruneOpts.BuildCache, "build-cache", "", false, "Remove persistent build cache created by --mount=type=cache")
 	flags.BoolVarP(&pruneOpts.External, "external", "", false, "Remove images even when they are used by external containers (e.g., by build containers)")
 	flags.BoolVarP(&force, "force", "f", false, "Do not prompt for confirmation")
 

docs/source/markdown/podman-image-prune.1.md

@@ -17,6 +17,10 @@ The image prune command does not prune cache images that only use layers that ar
 
 Remove dangling images and images that have no associated containers.
 
+#### **--build-cache**
+
+Remove persistent build cache create for `--mount=type=cache`.
+
 #### **--external**
 
 Remove images even when they are used by external containers (e.g., build containers).

pkg/api/handlers/libpod/images.go

@@ -118,8 +118,9 @@ func PruneImages(w http.ResponseWriter, r *http.Request) {
 	runtime := r.Context().Value(api.RuntimeKey).(*libpod.Runtime)
 	decoder := r.Context().Value(api.DecoderKey).(*schema.Decoder)
 	query := struct {
-		All      bool `schema:"all"`
-		External bool `schema:"external"`
+		All        bool `schema:"all"`
+		External   bool `schema:"external"`
+		BuildCache bool `schema:"buildcache"`
 	}{
 		// override any golang type defaults
 	}
@@ -157,9 +158,10 @@ func PruneImages(w http.ResponseWriter, r *http.Request) {
 	imageEngine := abi.ImageEngine{Libpod: runtime}
 
 	pruneOptions := entities.ImagePruneOptions{
-		All:      query.All,
-		External: query.External,
-		Filter:   libpodFilters,
+		All:        query.All,
+		External:   query.External,
+		Filter:     libpodFilters,
+		BuildCache: query.BuildCache,
 	}
 	imagePruneReports, err := imageEngine.Prune(r.Context(), pruneOptions)
 	if err != nil {

pkg/api/server/register_images.go

@@ -1129,6 +1129,12 @@ func (s *APIServer) registerImagesHandlers(r *mux.Router) error {
 	//    description: |
 	//      Remove images even when they are used by external containers (e.g, by build containers)
 	//  - in: query
+	//    name: buildcache
+	//    default: false
+	//    type: boolean
+	//    description: |
+	//      Remove persistent build cache created by build instructions such as `--mount=type=cache`.
+	//  - in: query
 	//    name: filters
 	//    type: string
 	//    description: |

pkg/bindings/images/types.go

@@ -93,6 +93,8 @@ type PruneOptions struct {
 	All *bool
 	// Prune images even when they're used by external containers
 	External *bool
+	// Prune persistent build cache
+	BuildCache *bool
 	// Filters to apply when pruning images
 	Filters map[string][]string
 }

pkg/bindings/images/types_prune_options.go

@@ -249,9 +249,10 @@ type ImageListOptions struct {
 }
 
 type ImagePruneOptions struct {
-	All      bool     `json:"all" schema:"all"`
-	External bool     `json:"external" schema:"external"`
-	Filter   []string `json:"filter" schema:"filter"`
+	All        bool     `json:"all" schema:"all"`
+	External   bool     `json:"external" schema:"external"`
+	BuildCache bool     `json:"buildcache" schema:"buildcache"`
+	Filter     []string `json:"filter" schema:"filter"`
 }
 
 type ImageTagOptions struct{}

pkg/domain/entities/images.go

@@ -19,6 +19,7 @@ import (
 	"time"
 
 	bdefine "github.com/containers/buildah/define"
+	"github.com/containers/buildah/pkg/volumes"
 	"github.com/containers/common/libimage"
 	"github.com/containers/common/libimage/filter"
 	"github.com/containers/common/pkg/config"
@@ -107,6 +108,13 @@ func (ir *ImageEngine) Prune(ctx context.Context, opts entities.ImagePruneOption
 		numPreviouslyRemovedImages = numRemovedImages
 	}
 
+	if opts.BuildCache || opts.All {
+		// Clean build cache if any
+		if err := volumes.CleanCacheMount(); err != nil {
+			return nil, err
+		}
+	}
+
 	return pruneReports, nil
 }
 

pkg/domain/infra/abi/images.go

@@ -102,7 +102,7 @@ func (ir *ImageEngine) Prune(ctx context.Context, opts entities.ImagePruneOption
 		f := strings.Split(filter, "=")
 		filters[f[0]] = f[1:]
 	}
-	options := new(images.PruneOptions).WithAll(opts.All).WithFilters(filters).WithExternal(opts.External)
+	options := new(images.PruneOptions).WithAll(opts.All).WithFilters(filters).WithExternal(opts.External).WithBuildCache(opts.BuildCache)
 	reports, err := images.Prune(ir.ClientCtx, options)
 	if err != nil {
 		return nil, err

pkg/domain/infra/tunnel/images.go

@@ -0,0 +1,4 @@
+FROM alpine
+RUN mkdir /test
+# use option z if selinux is enabled
+RUN --mount=type=cache,target=/test,z cat /test/world

test/e2e/build/buildkit-mount/Containerfilecacheread

@@ -0,0 +1,4 @@
+FROM alpine
+RUN mkdir /test
+# use option z if selinux is enabled
+RUN --mount=type=cache,target=/test,z echo hello > /test/world

test/e2e/build/buildkit-mount/Containerfilecachewrite

@@ -41,6 +41,37 @@ var _ = Describe("Podman build", func() {
 		Expect(session).Should(ExitCleanly())
 	})
 
+	It("podman image prune should clean build cache", Serial, func() {
+		// try writing something to persistent cache
+		session := podmanTest.Podman([]string{"build", "-f", "build/buildkit-mount/Containerfilecachewrite"})
+		session.WaitWithDefaultTimeout()
+		Expect(session).Should(ExitCleanly())
+
+		// try reading something from persistent cache
+		session = podmanTest.Podman([]string{"build", "-f", "build/buildkit-mount/Containerfilecacheread"})
+		session.WaitWithDefaultTimeout()
+		Expect(session).Should(ExitCleanly())
+		Expect(session.OutputToString()).To(ContainSubstring("hello"))
+
+		// Prune build cache
+		session = podmanTest.Podman([]string{"image", "prune", "-f", "--build-cache"})
+		session.WaitWithDefaultTimeout()
+		Expect(session).Should(ExitCleanly())
+
+		expectedErr := "open '/test/world': No such file or directory"
+		// try reading something from persistent cache should fail
+		session = podmanTest.Podman([]string{"build", "-f", "build/buildkit-mount/Containerfilecacheread"})
+		session.WaitWithDefaultTimeout()
+		if IsRemote() {
+			// In the case of podman remote the error from build is not being propogated to `stderr` instead it appears
+			// on the `stdout` this could be a potential bug in `remote build` which needs to be fixed and visited.
+			Expect(session.OutputToString()).To(ContainSubstring(expectedErr))
+			Expect(session).Should(ExitWithError(1, "exit status 1"))
+		} else {
+			Expect(session).Should(ExitWithError(1, expectedErr))
+		}
+	})
+
 	It("podman build and remove basic alpine with TMPDIR as relative", func() {
 		// preserve TMPDIR if it was originally set
 		if cacheDir, found := os.LookupEnv("TMPDIR"); found {