[GitHub] [druid] kfaraz commented on a change in pull request #11495: Select broker based on query context parameter `brokerService`

[GitBox <gi...@apache.org>]

kfaraz commented on a change in pull request #11495:
URL: https://github.com/apache/druid/pull/11495#discussion_r677152826



##########
File path: server/src/main/java/org/apache/druid/server/router/QueryContextTieredBrokerSelectorStrategy.java
##########
@@ -0,0 +1,97 @@
+/*
+ * 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.druid.server.router;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Optional;
+import org.apache.commons.lang.StringUtils;
+import org.apache.druid.java.util.common.logger.Logger;
+import org.apache.druid.query.Query;
+import org.apache.druid.query.QueryContexts;
+
+import javax.annotation.Nullable;
+
+/**
+ * Implementation of {@link TieredBrokerSelectorStrategy} which uses the parameter
+ * {@link QueryContexts#BROKER_SERVICE_NAME} in the Query context to select the
+ * Broker Service.
+ * <p>
+ * If the {@link #fallbackBrokerService} is set to a valid Broker Service Name,
+ * then all queries that do not specify a valid value for
+ * {@link QueryContexts#BROKER_SERVICE_NAME} would be directed to the
+ * {@code #fallbackBrokerService}. Note that the {@code fallbackBrokerService}
+ * can be different from the {@link TieredBrokerConfig#getDefaultBrokerServiceName()}.
+ */
+public class QueryContextTieredBrokerSelectorStrategy implements TieredBrokerSelectorStrategy
+{
+  private static final Logger log = new Logger(QueryContextTieredBrokerSelectorStrategy.class);
+
+  private final String fallbackBrokerService;
+
+  @JsonCreator
+  public QueryContextTieredBrokerSelectorStrategy(
+      @JsonProperty("fallbackBrokerService") @Nullable String fallbackBrokerService
+  )
+  {
+    this.fallbackBrokerService = fallbackBrokerService;
+  }
+
+  @Override
+  public Optional<String> getBrokerServiceName(TieredBrokerConfig tierConfig, Query query)
+  {
+    try {
+      final String contextBrokerService = QueryContexts.getBrokerServiceName(query);
+
+      if (isValidBrokerService(contextBrokerService, tierConfig)) {
+        // If the broker service in the query context is valid, use that
+        return Optional.of(contextBrokerService);
+      } else if (isValidBrokerService(fallbackBrokerService, tierConfig)) {

Review comment:
       I don't have the `TieredBrokerConfig` in the constructor, because the object is being constructed from deserialization of config and not by Guice.




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