Allow to exclude build-args and env vars from cache key

cmd/executor/cmd/root.go

@@ -257,6 +257,8 @@ func addKanikoOptionsFlags() {
 	RootCmd.PersistentFlags().VarP(&opts.Compression, "compression", "", "Compression algorithm (gzip, zstd)")
 	RootCmd.PersistentFlags().IntVarP(&opts.CompressionLevel, "compression-level", "", -1, "Compression level")
 	RootCmd.PersistentFlags().BoolVarP(&opts.Cache, "cache", "", false, "Use cache when building image")
+	RootCmd.PersistentFlags().VarP(&opts.ExcludeBuildArgsFromCacheKey, "exclude-build-arg-from-cache-key", "", "This flag allows you to exclude ARG values from the cache key. Set it repeatedly for multiple values.")
+	RootCmd.PersistentFlags().VarP(&opts.ExcludeEnvsFromCacheKey, "exclude-env-from-cache-key", "", "This flag allows you to exclude ENV values from the cache key. Set it repeatedly for multiple values.")
 	RootCmd.PersistentFlags().BoolVarP(&opts.CompressedCaching, "compressed-caching", "", true, "Compress the cached layers. Decreases build time, but increases memory usage.")
 	RootCmd.PersistentFlags().BoolVarP(&opts.Cleanup, "cleanup", "", false, "Clean the filesystem at the end")
 	RootCmd.PersistentFlags().DurationVarP(&opts.CacheTTL, "cache-ttl", "", time.Hour*336, "Cache timeout, requires value and unit of duration -> ex: 6h. Defaults to two weeks.")

pkg/config/options.go

@@ -28,6 +28,9 @@ import (
 type CacheOptions struct {
 	CacheDir string
 	CacheTTL time.Duration
+
+	ExcludeBuildArgsFromCacheKey multiArg
+	ExcludeEnvsFromCacheKey      multiArg
 }
 
 // RegistryOptions are all the options related to the registries, set by command line arguments.

pkg/executor/build.go

@@ -199,20 +199,39 @@ func isOCILayout(path string) bool {
 }
 
 func (s *stageBuilder) populateCompositeKey(command commands.DockerCommand, files []string, compositeKey CompositeCache, args *dockerfile.BuildArgs, env []string) (CompositeCache, error) {
-	// First replace all the environment variables or args in the command
-	replacementEnvs := args.ReplacementEnvs(env)
-	// The sort order of `replacementEnvs` is basically undefined, sort it
-	// so we can ensure a stable cache key.
-	sort.Strings(replacementEnvs)
-	// Use the special argument "|#" at the start of the args array. This will
-	// avoid conflicts with any RUN command since commands can not
-	// start with | (vertical bar). The "#" (number of build envs) is there to
-	// help ensure proper cache matches.
-
 	if command.IsArgsEnvsRequiredInCache() {
-		if len(replacementEnvs) > 0 {
+		filteredEnvs := []string{}
-			compositeKey.AddKey(fmt.Sprintf("|%d", len(replacementEnvs)))
+		for _, e := range env {
-			compositeKey.AddKey(replacementEnvs...)
+			envName := strings.SplitN(e, "=", 2)[0]
+			if s.opts.ExcludeEnvsFromCacheKey.Contains(envName) {
+				continue
+			}
+			filteredEnvs = append(filteredEnvs, e)
+		}
+
+		// First replace all the environment variables or args in the command
+		envsAndBuildArgs := args.ReplacementEnvs(filteredEnvs)
+
+		filteredEnvsAndBuildArgs := []string{}
+		for i, env := range envsAndBuildArgs {
+			envArgName := strings.SplitN(env, "=", 2)[0]
+			if s.opts.ExcludeBuildArgsFromCacheKey.Contains(envArgName) {
+				continue
+			}
+			filteredEnvsAndBuildArgs = append(filteredEnvs, envsAndBuildArgs[i])
+		}
+
+		// The sort order of `filteredEnvs` is basically undefined, sort it
+		// so we can ensure a stable cache key.
+		sort.Strings(filteredEnvsAndBuildArgs)
+
+		if len(filteredEnvsAndBuildArgs) > 0 {
+			// Use the special argument "|#" at the start of the args array. This will
+			// avoid conflicts with any RUN command since commands can not
+			// start with | (vertical bar). The "#" (number of build envs) is there to
+			// help ensure proper cache matches.
+			compositeKey.AddKey(fmt.Sprintf("|%d", len(filteredEnvsAndBuildArgs)))
+			compositeKey.AddKey(filteredEnvsAndBuildArgs...)
 		}
 	}
 

pkg/executor/build_test.go

@@ -655,10 +655,12 @@ func newStageContext(command string, args map[string]string, env []string) stage
 
 func Test_stageBuilder_populateCompositeKey(t *testing.T) {
 	type testcase struct {
-		description string
+		description                  string
-		cmd1        stageContext
+		cmd1                         stageContext
-		cmd2        stageContext
+		cmd2                         stageContext
-		shdEqual    bool
+		shdEqual                     bool
+		excludeBuildArgsFromCacheKey []string
+		excludeEnvsFromCacheKey      []string
 	}
 	testCases := []testcase{
 		{
@@ -744,6 +746,21 @@ func Test_stageBuilder_populateCompositeKey(t *testing.T) {
 				[]string{},
 			),
 		},
+		{
+			description: "cache key for same command [RUN] with a build arg values, with excludeBuildArgsFromCacheKey set",
+			cmd1: newStageContext(
+				"RUN echo $ARG > test",
+				map[string]string{"ARG": "foo"},
+				[]string{},
+			),
+			cmd2: newStageContext(
+				"RUN echo $ARG > test",
+				map[string]string{"ARG": "bar"},
+				[]string{},
+			),
+			shdEqual:                     true,
+			excludeBuildArgsFromCacheKey: []string{"ARG"},
+		},
 		{
 			description: "cache key for same command [RUN] with different env values",
 			cmd1: newStageContext(
@@ -798,6 +815,21 @@ func Test_stageBuilder_populateCompositeKey(t *testing.T) {
 			),
 			shdEqual: false,
 		},
+		{
+			description: "cache key for command [RUN] with different env values, when excludeEnvsFromCacheKey is set",
+			cmd1: newStageContext(
+				"RUN echo ${APP_VERSION%.*} ${APP_VERSION%-*} > test",
+				map[string]string{"ARG": "foo"},
+				[]string{"ENV=1"},
+			),
+			cmd2: newStageContext(
+				"RUN echo ${APP_VERSION%.*} ${APP_VERSION%-*} > test",
+				map[string]string{"ARG": "foo"},
+				[]string{"ENV=2"},
+			),
+			shdEqual:                true,
+			excludeEnvsFromCacheKey: []string{"ENV"},
+		},
 		func() testcase {
 			dir, files := tempDirAndFile(t)
 			file := files[0]
@@ -867,7 +899,15 @@ func Test_stageBuilder_populateCompositeKey(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		t.Run(tc.description, func(t *testing.T) {
-			sb := &stageBuilder{fileContext: util.FileContext{Root: "workspace"}}
+			sb := &stageBuilder{
+				fileContext: util.FileContext{Root: "workspace"},
+				opts: &config.KanikoOptions{
+					CacheOptions: config.CacheOptions{
+						ExcludeBuildArgsFromCacheKey: tc.excludeBuildArgsFromCacheKey,
+						ExcludeEnvsFromCacheKey:      tc.excludeEnvsFromCacheKey,
+					},
+				},
+			}
 			ck := CompositeCache{}
 
 			instructions1, err := dockerfile.ParseCommands([]string{tc.cmd1.command.String()})