Dynamic Config Resolver

polaris-server.yml

@@ -73,6 +73,9 @@ featureConfiguration:
     - AZURE
     - FILE
 
+dynamicFeatureConfigResolver:
+  type: no-op
+
 callContextResolver:
   type: default
 

polaris-service/src/main/java/org/apache/polaris/service/config/DefaultConfigurationStore.java

@@ -28,23 +28,33 @@
 public class DefaultConfigurationStore implements PolarisConfigurationStore {
   private final Map<String, Object> config;
   private final Map<String, Map<String, Object>> realmConfig;
+  private final DynamicFeatureConfigResolver dynamicFeatureConfigResolver;
 
   public DefaultConfigurationStore(Map<String, Object> config) {
     this.config = config;
     this.realmConfig = Map.of();
+    this.dynamicFeatureConfigResolver = new NoOpDynamicFeatureConfigResolver();
   }
 
   public DefaultConfigurationStore(
-      Map<String, Object> config, Map<String, Map<String, Object>> realmConfig) {
+      Map<String, Object> config,
+      Map<String, Map<String, Object>> realmConfig,
+      DynamicFeatureConfigResolver dynamicFeatureConfigResolver) {
     this.config = config;
     this.realmConfig = realmConfig;
+    this.dynamicFeatureConfigResolver = dynamicFeatureConfigResolver;
   }
 
   @SuppressWarnings("unchecked")
   @Override
   public <T> @Nullable T getConfiguration(@NotNull PolarisCallContext ctx, String configName) {
     String realm = CallContext.getCurrentContext().getRealmContext().getRealmIdentifier();
     return (T)
-        realmConfig.getOrDefault(realm, Map.of()).getOrDefault(configName, config.get(configName));
+        dynamicFeatureConfigResolver
+            .resolve(configName)
+            .orElse(
+                realmConfig
+                    .getOrDefault(realm, Map.of())
+                    .getOrDefault(configName, config.get(configName)));
   }
 }

polaris-service/src/main/java/org/apache/polaris/service/config/DynamicFeatureConfigResolver.java

@@ -0,0 +1,39 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.polaris.service.config;
+
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import io.dropwizard.jackson.Discoverable;
+import java.util.Optional;
+
+/**
+ * DynamicFeatureConfigResolvers dynamically resolve featureConfigurations. This is useful for
+ * integration with feature flag systems which are intended for fetching configs at runtime.
+ */
+@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")
+public interface DynamicFeatureConfigResolver extends Discoverable {
+  /**
+   * Resolves a dynamic config by its key name.
+   *
+   * @param key
+   * @return The config value or Optional.empty() if the config should not be dynamically resolved.
+   *     If it's not dynamically resolved, it will be deferred to the application config.
+   */
+  Optional<Object> resolve(String key);
+}

polaris-service/src/main/java/org/apache/polaris/service/config/NoOpDynamicFeatureConfigResolver.java

@@ -0,0 +1,31 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.polaris.service.config;
+
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import java.util.Optional;
+
+/** An empty dynamic config resolver. */
+@JsonTypeName("no-op")
+public class NoOpDynamicFeatureConfigResolver implements DynamicFeatureConfigResolver {
+  @Override
+  public Optional<Object> resolve(String key) {
+    return Optional.empty();
+  }
+}

polaris-service/src/main/java/org/apache/polaris/service/config/PolarisApplicationConfig.java

@@ -63,6 +63,7 @@ public class PolarisApplicationConfig extends Configuration {
   private String awsSecretKey;
   private FileIOFactory fileIOFactory;
   private RateLimiter rateLimiter;
+  private DynamicFeatureConfigResolver dynamicFeatureConfigResolver;
 
   private AccessToken gcpAccessToken;
 
@@ -89,6 +90,17 @@ public FileIOFactory getFileIOFactory() {
     return fileIOFactory;
   }
 
+  @JsonProperty("dynamicFeatureConfigResolver")
+  public void setDynamicFeatureConfigResolver(
+      DynamicFeatureConfigResolver dynamicFeatureConfigResolver) {
+    this.dynamicFeatureConfigResolver = dynamicFeatureConfigResolver;
+  }
+
+  @JsonProperty("dynamicFeatureConfigResolver")
+  public DynamicFeatureConfigResolver getDynamicFeatureConfigResolver() {
+    return dynamicFeatureConfigResolver;
+  }
+
   @JsonProperty("authenticator")
   public void setPolarisAuthenticator(
       DiscoverableAuthenticator<String, AuthenticatedPolarisPrincipal> polarisAuthenticator) {
@@ -194,7 +206,8 @@ public long getMaxRequestBodyBytes() {
   }
 
   public PolarisConfigurationStore getConfigurationStore() {
-    return new DefaultConfigurationStore(globalFeatureConfiguration, realmConfiguration);
+    return new DefaultConfigurationStore(
+        globalFeatureConfiguration, realmConfiguration, dynamicFeatureConfigResolver);
   }
 
   public List<String> getDefaultRealms() {

polaris-service/src/main/resources/META-INF/services/io.dropwizard.jackson.Discoverable

@@ -19,6 +19,7 @@
 
 org.apache.polaris.service.auth.DiscoverableAuthenticator
 org.apache.polaris.core.persistence.MetaStoreManagerFactory
+org.apache.polaris.service.config.DynamicFeatureConfigResolver
 org.apache.polaris.service.config.OAuth2ApiService
 org.apache.polaris.service.context.RealmContextResolver
 org.apache.polaris.service.context.CallContextResolver

polaris-service/src/main/resources/META-INF/services/org.apache.polaris.service.config.DynamicFeatureConfigResolver

@@ -0,0 +1,20 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+org.apache.polaris.service.config.NoOpDynamicFeatureConfigResolver

polaris-service/src/test/java/org/apache/polaris/service/config/DefaultConfigurationStoreTest.java

@@ -20,14 +20,18 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 
+import java.util.HashMap;
 import java.util.Map;
+import java.util.Optional;
+import java.util.stream.Stream;
 import org.apache.polaris.core.PolarisCallContext;
 import org.apache.polaris.core.PolarisDefaultDiagServiceImpl;
 import org.apache.polaris.service.persistence.InMemoryPolarisMetaStoreManagerFactory;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
 
 public class DefaultConfigurationStoreTest {
-
   @Test
   public void testGetConfiguration() {
     DefaultConfigurationStore defaultConfigurationStore =
@@ -65,7 +69,8 @@ public void testGetRealmConfiguration() {
                 "realm1",
                 Map.of("key1", realm1KeyOneValue),
                 "realm2",
-                Map.of("key1", realm2KeyOneValue, "key2", realm2KeyTwoValue)));
+                Map.of("key1", realm2KeyOneValue, "key2", realm2KeyTwoValue)),
+            new NoOpDynamicFeatureConfigResolver());
     InMemoryPolarisMetaStoreManagerFactory metastoreFactory =
         new InMemoryPolarisMetaStoreManagerFactory();
 
@@ -106,4 +111,77 @@ public void testGetRealmConfiguration() {
     String keyTwoRealm3 = defaultConfigurationStore.getConfiguration(realm3Ctx, "key2");
     assertThat(keyTwoRealm3).isEqualTo(defaultKeyTwoValue);
   }
+
+  @Test
+  public void testDynamicConfig() {
+    InMemoryPolarisMetaStoreManagerFactory metastoreFactory =
+        new InMemoryPolarisMetaStoreManagerFactory();
+    PolarisCallContext polarisCtx =
+        new PolarisCallContext(
+            metastoreFactory.getOrCreateSessionSupplier(() -> "realm1").get(),
+            new PolarisDefaultDiagServiceImpl());
+
+    String key = "k1";
+    Map<String, Object> staticConfig = Map.of(key, 10);
+
+    assertThat(
+            new DefaultConfigurationStore(staticConfig, Map.of(), k -> Optional.empty())
+                .<Integer>getConfiguration(polarisCtx, key))
+        .as("The DynamicFeatureConfigResolver always returns Optional.empty()")
+        .isEqualTo(10);
+
+    assertThat(
+            new DefaultConfigurationStore(staticConfig, Map.of(), k -> Optional.of(5))
+                .<Integer>getConfiguration(polarisCtx, key))
+        .as("The DynamicFeatureConfigResolver always returns 5")
+        .isEqualTo(5);
+  }
+
+  @ParameterizedTest
+  @MethodSource("getTestConfigs")
+  public void testPrecedenceIsDynamicThenStaticPerRealmThenStaticGlobal(TestConfig testConfig) {
+    InMemoryPolarisMetaStoreManagerFactory metastoreFactory =
+        new InMemoryPolarisMetaStoreManagerFactory();
+
+    String realm = "realm1";
+    PolarisCallContext polarisCtx =
+        new PolarisCallContext(
+            metastoreFactory.getOrCreateSessionSupplier(() -> realm).get(),
+            new PolarisDefaultDiagServiceImpl());
+
+    String key = "k1";
+
+    Map<String, Object> staticConfig = new HashMap<>();
+    if (testConfig.staticConfig != null) {
+      staticConfig.put(key, testConfig.staticConfig);
+    }
+
+    Map<String, Object> realmConfig = new HashMap<>();
+    if (testConfig.realmConfig != null) {
+      realmConfig.put(key, testConfig.realmConfig);
+    }
+
+    DefaultConfigurationStore configStore =
+        new DefaultConfigurationStore(
+            staticConfig,
+            Map.of(realm, realmConfig),
+            (k) -> Optional.ofNullable(testConfig.dynamicConfig));
+    assertThat(configStore.<Integer>getConfiguration(polarisCtx, key))
+        .isEqualTo(testConfig.expectedValue);
+  }
+
+  private static Stream<TestConfig> getTestConfigs() {
+    return Stream.of(
+        new TestConfig(null, null, null, null),
+        new TestConfig(5, null, null, 5),
+        new TestConfig(5, 6, null, 6),
+        new TestConfig(5, 6, 7, 7),
+        new TestConfig(5, null, 7, 7),
+        new TestConfig(null, null, 7, 7),
+        new TestConfig(null, 6, 7, 7),
+        new TestConfig(null, 6, null, 6));
+  }
+
+  public record TestConfig(
+      Integer staticConfig, Integer realmConfig, Integer dynamicConfig, Integer expectedValue) {}
 }

polaris-service/src/test/resources/polaris-server-integrationtest.yml

@@ -79,6 +79,9 @@ featureConfiguration:
     - GCS
     - AZURE
 
+dynamicFeatureConfigResolver:
+  type: no-op
+
 metaStoreManager:
   type: in-memory