Give search nodes same cache defaults as frozen (#94032)

Currently search nodes operate with the same partially cached search
shards design as frozen nodes. Therefore, it makes sense to give them
the same shared cache defaults as frozen nodes.

x-pack/plugin/blob-cache/src/main/java/org/elasticsearch/blobcache/shared/SharedBlobCacheService.java

@@ -109,7 +109,7 @@ public class SharedBlobCacheService<KeyType> implements Releasable {
     public static final Setting<RelativeByteSizeValue> SHARED_CACHE_SIZE_SETTING = new Setting<>(
         new Setting.SimpleKey(SHARED_CACHE_SETTINGS_PREFIX + "size"),
         (settings) -> {
-            if (DiscoveryNode.isDedicatedFrozenNode(settings)) {
+            if (DiscoveryNode.isDedicatedFrozenNode(settings) || DiscoveryNode.hasRole(settings, DiscoveryNodeRole.SEARCH_ROLE)) {
                 return "90%";
             } else {
                 return ByteSizeValue.ZERO.getStringRep();
@@ -167,7 +167,8 @@ public class SharedBlobCacheService<KeyType> implements Releasable {
     public static final Setting<ByteSizeValue> SHARED_CACHE_SIZE_MAX_HEADROOM_SETTING = new Setting<>(
         new Setting.SimpleKey(SHARED_CACHE_SETTINGS_PREFIX + "size.max_headroom"),
         (settings) -> {
-            if (SHARED_CACHE_SIZE_SETTING.exists(settings) == false && DiscoveryNode.isDedicatedFrozenNode(settings)) {
+            if (SHARED_CACHE_SIZE_SETTING.exists(settings) == false
+                && (DiscoveryNode.isDedicatedFrozenNode(settings) || DiscoveryNode.hasRole(settings, DiscoveryNodeRole.SEARCH_ROLE))) {
                 return "100GB";
             }
 

x-pack/plugin/blob-cache/src/test/java/org/elasticsearch/blobcache/shared/SharedBlobCacheServiceTests.java

@@ -307,6 +307,18 @@ public class SharedBlobCacheServiceTests extends ESTestCase {
         assertThat(SharedBlobCacheService.SHARED_CACHE_SIZE_MAX_HEADROOM_SETTING.get(settings), equalTo(ByteSizeValue.ofBytes(-1)));
     }
 
+    public void testSearchNodeCacheSizeDefaults() {
+        final Settings settings = Settings.builder()
+            .putList(NodeRoleSettings.NODE_ROLES_SETTING.getKey(), DiscoveryNodeRole.SEARCH_ROLE.roleName())
+            .build();
+
+        RelativeByteSizeValue relativeCacheSize = SharedBlobCacheService.SHARED_CACHE_SIZE_SETTING.get(settings);
+        assertThat(relativeCacheSize.isAbsolute(), is(false));
+        assertThat(relativeCacheSize.isNonZeroSize(), is(true));
+        assertThat(relativeCacheSize.calculateValue(ByteSizeValue.ofBytes(10000), null), equalTo(ByteSizeValue.ofBytes(9000)));
+        assertThat(SharedBlobCacheService.SHARED_CACHE_SIZE_MAX_HEADROOM_SETTING.get(settings), equalTo(ByteSizeValue.ofGb(100)));
+    }
+
     public void testMaxHeadroomRejectedForAbsoluteCacheSize() {
         String cacheSize = ByteSizeValue.ofBytes(size(500)).getStringRep();
         final Settings settings = Settings.builder()