Merge pull request #6311 from flouthoc/correctly-burst-cache

build: `--mount=type=bind` ignore `modTime` for cache candidates

imagebuildah/util.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"time"
 
 	"github.com/containers/buildah"
 	digest "github.com/opencontainers/go-digest"
@@ -69,6 +70,11 @@ func generatePathChecksum(sourcePath string) (string, error) {
 		}
 		header.Name = filepath.ToSlash(relPath)
 
+		// Zero out timestamp fields to ignore modification time in checksum calculation
+		header.ModTime = time.Time{}
+		header.AccessTime = time.Time{}
+		header.ChangeTime = time.Time{}
+
 		if err := tarWriter.WriteHeader(header); err != nil {
 			return err
 		}

imagebuildah/util_test.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"path/filepath"
 	"testing"
+	"time"
 
 	"github.com/opencontainers/go-digest"
 	"github.com/stretchr/testify/assert"
@@ -52,6 +53,11 @@ func TestGeneratePathChecksum(t *testing.T) {
 		}
 		header.Name = filepath.ToSlash(relPath)
 
+		// Zero out timestamp fields to match the modified generatePathChecksum function
+		header.ModTime = time.Time{}
+		header.AccessTime = time.Time{}
+		header.ChangeTime = time.Time{}
+
 		if err := tarWriter.WriteHeader(header); err != nil {
 			return err
 		}

tests/bud.bats

@@ -662,6 +662,38 @@ _EOF
   expect_output --substring "Cache burst add diff"
 }
 
+@test "bud --layers with --mount type bind should preserve cache when file mod time changes but content stays same" {
+  _prefetch alpine
+  local contextdir=${TEST_SCRATCH_DIR}/bud/platform
+  mkdir -p $contextdir
+
+  cat > $contextdir/samplefile << _EOF
+samplefile content unchanged
+_EOF
+
+  cat > $contextdir/Containerfile << _EOF
+FROM alpine
+RUN --mount=type=bind,source=samplefile,target=file,Z cat file
+_EOF
+
+  # on first run since there is no cache so content must be printed
+  run_buildah build $WITH_POLICY_JSON --layers -t source -f $contextdir/Containerfile $contextdir
+  expect_output --substring "samplefile content unchanged"
+
+  # on second run since there is cache so content should not be printed
+  run_buildah build $WITH_POLICY_JSON --layers -t source -f $contextdir/Containerfile $contextdir
+  # output should not contain content from the file since entire build is cached
+  assert "$output" !~ "samplefile content unchanged"
+
+  # Change mod time of this file (this changes modification time)
+ touch -d "@1577836800" $contextdir/samplefile
+
+  # on third run since content is unchanged, cache should still be used despite different mod time
+  run_buildah build $WITH_POLICY_JSON --layers -t source -f $contextdir/Containerfile $contextdir
+  # output should not contain content from the file since cache should still be valid
+  assert "$output" !~ "samplefile content unchanged"
+}
+
 @test "bud --layers should not hit cache if heredoc is changed - with ARG" {
   _prefetch alpine
   local contextdir=${TEST_SCRATCH_DIR}/bud/platform