Add docs and benchmark for JSON flattening parser

benchmarks/pom.xml

@@ -51,6 +51,16 @@
       <artifactId>druid-processing</artifactId>
       <version>${project.parent.version}</version>
     </dependency>
+    <dependency>
+      <groupId>com.github.wnameless</groupId>
+      <artifactId>json-flattener</artifactId>
+      <version>0.1.0</version>
+    </dependency>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <properties>

benchmarks/src/main/java/io/druid/benchmark/FlattenJSONBenchmark.java

@@ -0,0 +1,124 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  Metamarkets 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 io.druid.benchmark;
+
+import com.metamx.common.parsers.Parser;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.RunnerException;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+
+@State(Scope.Benchmark)
+public class FlattenJSONBenchmark
+{
+  private static final int numEvents = 1000000;
+
+  List<String> flatInputs;
+  List<String> nestedInputs;
+  Parser flatParser;
+  Parser nestedParser;
+  Parser fieldDiscoveryParser;
+  Parser forcedPathParser;
+  int flatCounter = 0;
+  int nestedCounter = 0;
+
+  @Setup
+  public void prepare() throws Exception
+  {
+    FlattenJSONBenchmarkUtil gen = new FlattenJSONBenchmarkUtil();
+    flatInputs = new ArrayList<String>();
+    for (int i = 0; i < numEvents; i++) {
+      flatInputs.add(gen.generateFlatEvent());
+    }
+    nestedInputs = new ArrayList<String>();
+    for (int i = 0; i < numEvents; i++) {
+      nestedInputs.add(gen.generateNestedEvent());
+    }
+
+    flatParser = gen.getFlatParser();
+    nestedParser = gen.getNestedParser();
+    fieldDiscoveryParser = gen.getFieldDiscoveryParser();
+    forcedPathParser = gen.getForcedPathParser();
+  }
+
+  @Benchmark
+  @BenchmarkMode(Mode.AverageTime)
+  @OutputTimeUnit(TimeUnit.MICROSECONDS)
+  public Map<String, Object> baseline()
+  {
+    Map<String, Object> parsed = flatParser.parse(flatInputs.get(flatCounter));
+    flatCounter = (flatCounter + 1) % numEvents;
+    return parsed;
+  }
+
+  @Benchmark
+  @BenchmarkMode(Mode.AverageTime)
+  @OutputTimeUnit(TimeUnit.MICROSECONDS)
+  public Map<String, Object> flatten()
+  {
+    Map<String, Object> parsed = nestedParser.parse(nestedInputs.get(nestedCounter));
+    nestedCounter = (nestedCounter + 1) % numEvents;
+    return parsed;
+  }
+
+  @Benchmark
+  @BenchmarkMode(Mode.AverageTime)
+  @OutputTimeUnit(TimeUnit.MICROSECONDS)
+  public Map<String, Object> preflattenNestedParser()
+  {
+    Map<String, Object> parsed = fieldDiscoveryParser.parse(flatInputs.get(nestedCounter));
+    nestedCounter = (nestedCounter + 1) % numEvents;
+    return parsed;
+  }
+
+  @Benchmark
+  @BenchmarkMode(Mode.AverageTime)
+  @OutputTimeUnit(TimeUnit.MICROSECONDS)
+  public Map<String, Object> forcedRootPaths()
+  {
+    Map<String, Object> parsed = forcedPathParser.parse(flatInputs.get(nestedCounter));
+    nestedCounter = (nestedCounter + 1) % numEvents;
+    return parsed;
+  }
+
+  public static void main(String[] args) throws RunnerException {
+    Options opt = new OptionsBuilder()
+        .include(FlattenJSONBenchmark.class.getSimpleName())
+        .warmupIterations(1)
+        .measurementIterations(25)
+        .forks(1)
+        .build();
+
+    new Runner(opt).run();
+  }
+}
+