make image metadata cache size configurable

Signed-off-by: Kent Rancourt <[email protected]>

Author: krancour

charts/kargo/templates/controller/configmap.yaml

@@ -33,6 +33,7 @@ data:
   {{- end }}
   ALLOW_IMAGE_TAG_CACHING: {{ quote .Values.controller.imageCache.allowUseCachedTags }}
   REQUIRE_IMAGE_TAG_CACHING: {{ quote .Values.controller.imageCache.requireUseCachedTags }}
+  MAX_IMAGE_CACHE_ENTRIES: {{ .Values.controller.imageCache.maxEntries | quote }}
   ARGOCD_INTEGRATION_ENABLED: {{ quote .Values.controller.argocd.integrationEnabled }}
   {{- if .Values.controller.argocd.integrationEnabled }}
   {{- if .Values.kubeconfigSecrets.argocd }}

charts/kargo/values.yaml

@@ -519,10 +519,12 @@ controller:
       type: ""
 
   imageCache:
-    ## @param controller.imageCache.allowUseCachedTags ALLOWS container image repository subscriptions to improve performance by opting into more aggressive caching. That option is safe only for cases where it is known with certainty that relevant tags are "immutable" (i.e. the exact images referenced by tags remain constant over time and tags are never "re-used" to point to new/different images). If an operator wishes not to run the risk that users will inappropriately opt into this, this setting can be set to `false` to disallow it. Artifact discovery will FAIL if that policy is violated. Note that this setting does not apply at all to the Digest selection strategy, which always assumes tags are mutable.
+    ## @param controller.imageCache.allowUseCachedTags ALLOWS container image repository subscriptions to improve performance by opting into more aggressive image metadata caching. That option is safe only for cases where it is known with certainty that relevant tags are "immutable" (i.e. the exact images referenced by tags remain constant over time and tags are never "re-used" to point to new/different images). If an operator wishes not to run the risk that users will inappropriately opt into this, this setting can be set to `false` to disallow it. Artifact discovery will FAIL if that policy is violated. Note that this setting does not apply at all to the Digest selection strategy, which always assumes tags are mutable.
     allowUseCachedTags: true
-    ## @param controller.imageCache.requireUseCachedTags REQUIRES container images repository subscriptions to improve performance by opting into more aggressive caching. That option is safe only for cases where it is known with certainty that relevant tags are "immutable" (i.e. the exact images referenced by tags remain constant over time and tags are never "re-used" to point to new/different images). If an operator wishes to ensure performance, this setting can be set to `true`. Artifact discovery will FAIL if that policy is violated. Note that this setting does not apply at all to the Digest selection strategy, which always assumes tags are mutable.
+    ## @param controller.imageCache.requireUseCachedTags REQUIRES container images repository subscriptions to improve performance by opting into more aggressive image metadata caching. That option is safe only for cases where it is known with certainty that relevant tags are "immutable" (i.e. the exact images referenced by tags remain constant over time and tags are never "re-used" to point to new/different images). If an operator wishes to ensure performance, this setting can be set to `true`. Artifact discovery will FAIL if that policy is violated. Note that this setting does not apply at all to the Digest selection strategy, which always assumes tags are mutable.
     requireUseCachedTags: false
+    ## @param controller.imageCache.maxEntries specifies the maximum number of entries in the internal image metadata cache.
+    maxEntries: 100000
 
   ## All settings relating to the Argo CD control plane this controller might
   ## integrate with.

pkg/image/cache.go

@@ -1,12 +1,18 @@
 package image
 
-import "github.com/akuity/kargo/pkg/cache"
+import (
+	"github.com/akuity/kargo/pkg/cache"
+	"github.com/akuity/kargo/pkg/os"
+	"github.com/akuity/kargo/pkg/types"
+)
 
 var imageCache cache.Cache[Image]
 
 func init() {
 	var err error
-	imageCache, err = cache.NewInMemoryCache[Image](100000)
+	imageCache, err = cache.NewInMemoryCache[Image](
+		types.MustParseInt(os.GetEnv("MAX_IMAGE_CACHE_ENTRIES", "100000")),
+	)
 	if err != nil {
 		panic("failed to initialize image cache: " + err.Error())
 	}