[GitHub] [druid] kroeders commented on a change in pull request #10427: ServerSelectorStrategy to filter servers with missing required lookups

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

kroeders commented on a change in pull request #10427:
URL: https://github.com/apache/druid/pull/10427#discussion_r493903568



##########
File path: extensions-contrib/lookup-aware-server-selector/src/main/java/org/apache/druid/client/selector/filter/lookup/LookupAwareFilterStrategy.java
##########
@@ -0,0 +1,181 @@
+/*
+ * 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.client.selector.filter.lookup;
+
+import com.fasterxml.jackson.annotation.JacksonInject;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonTypeName;
+import org.apache.druid.client.selector.QueryableDruidServer;
+import org.apache.druid.client.selector.filter.ServerFilterStrategy;
+import org.apache.druid.java.util.common.ISE;
+import org.apache.druid.math.expr.Expr;
+import org.apache.druid.query.DataSource;
+import org.apache.druid.query.JoinDataSource;
+import org.apache.druid.query.LookupDataSource;
+import org.apache.druid.query.Query;
+import org.apache.druid.query.dimension.DimensionSpec;
+import org.apache.druid.query.dimension.ExtractionDimensionSpec;
+import org.apache.druid.query.extraction.CascadeExtractionFn;
+import org.apache.druid.query.extraction.ExtractionFn;
+import org.apache.druid.query.groupby.GroupByQuery;
+import org.apache.druid.query.lookup.RegisteredLookupExtractionFn;
+import org.apache.druid.query.search.SearchQuery;
+import org.apache.druid.query.topn.TopNQuery;
+import org.apache.druid.segment.VirtualColumn;
+import org.apache.druid.segment.VirtualColumns;
+import org.apache.druid.segment.virtual.ExpressionVirtualColumn;
+
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+
+@JsonTypeName("lookupsLoaded")
+public class LookupAwareFilterStrategy implements ServerFilterStrategy
+{
+  public static final String LOOKUPS_CONTEXT_KEY = "lookups";
+  public static final String QUERY_LOOKUPS_CACHE_KEY = "__lookups";
+  private final LookupStatusView lookupStatusView;
+
+  @JsonCreator
+  public LookupAwareFilterStrategy(@JacksonInject LookupStatusView lookupStatusView)
+  {
+    this.lookupStatusView = lookupStatusView;
+  }
+
+  @Override
+  public <T> Set<QueryableDruidServer> filter(Query<T> query, Set<QueryableDruidServer> servers)
+  {
+    if (query == null) {
+      return servers;
+    }
+    final Set<String> lookups;
+    if (query.getContext() != null

Review comment:
       I'm not sure about this use of context, but I would prefer to not calculate the associated lookups in each selection. The withOverridenContext methods return a new Query, so maybe some other way to cache it? I was also wondering if it would be better to calculate a blocked list of servers once and then make the FilteringServerSelectorStrategy operate  on that list, which would allow stacking filters to handle other resiliency issues. 




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