Clean up cached machine images

When initing machines, we download a machine image, and uncompress and
copy the image for the actual vm image. When a user constantly pulls new
machines, there may be a buildup of old, unused machine images. This
commit cleans ups the unused cached images.

Changes:
- If the machine is pulled from a URL or from the FCOS releases, we pull
  them into XDG_DATA_HOME/containers/podman/machine/vmType/cache
- Cache cleanups only happen if there is a cache miss, and we need to
  pull a new image
- For Fedora and FCOS, we actually use the cache, so we go through the
  cache dir and remove any images older than 2 weeks (FCOS's release cycle), on a cache miss.
- For generic files pulled from a URL, we don't actually cache, so we
  delete the pulled file immediately after creating a machine image
- For generic files from a local path, the original file will never be
  cleaned up

Note that because we cache in a different dir, this will not clean up
old images pulled before this commit.

[NO NEW TESTS NEEDED]

Signed-off-by: Ashley Cui <acui@redhat.com>

1 files changed, 16 insertions, 3 deletions

diff --git a/pkg/machine/fcos.go b/pkg/machine/fcos.go
index 4ccb99e96..246f92a19 100644
--- a/pkg/machine/fcos.go
+++ b/pkg/machine/fcos.go
@@ -13,6 +13,7 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
+	"time"
 
 	"github.com/coreos/stream-metadata-go/fedoracoreos"
 	"github.com/coreos/stream-metadata-go/release"
@@ -53,7 +54,7 @@ func NewFcosDownloader(vmType, vmName, imageStream string) (DistributionDownload
 		return nil, err
 	}
 
-	dataDir, err := GetDataDir(vmType)
+	cacheDir, err := GetCacheDir(vmType)
 	if err != nil {
 		return nil, err
 	}
@@ -62,15 +63,20 @@ func NewFcosDownloader(vmType, vmName, imageStream string) (DistributionDownload
 		Download: Download{
 			Arch:      getFcosArch(),
 			Artifact:  artifact,
+			CacheDir:  cacheDir,
 			Format:    Format,
 			ImageName: imageName,
-			LocalPath: filepath.Join(dataDir, imageName),
+			LocalPath: filepath.Join(cacheDir, imageName),
 			Sha256sum: info.Sha256Sum,
 			URL:       url,
 			VMName:    vmName,
 		},
 	}
-	fcd.Download.LocalUncompressedFile = fcd.getLocalUncompressedName()
+	dataDir, err := GetDataDir(vmType)
+	if err != nil {
+		return nil, err
+	}
+	fcd.Download.LocalUncompressedFile = fcd.getLocalUncompressedFile(dataDir)
 	return fcd, nil
 }
 
@@ -108,6 +114,13 @@ func (f FcosDownload) HasUsableCache() (bool, error) {
 	return sum.Encoded() == f.Sha256sum, nil
 }
 
+func (f FcosDownload) CleanCache() error {
+	// Set cached image to expire after 2 weeks
+	// FCOS refreshes around every 2 weeks, assume old images aren't needed
+	expire := 14 * 24 * time.Hour
+	return removeImageAfterExpire(f.CacheDir, expire)
+}
+
 func getFcosArch() string {
 	var arch string
 	// TODO fill in more architectures