emkornfield commented on a change in pull request #8265:
URL: https://github.com/apache/arrow/pull/8265#discussion_r513165104



##########
File path: 
java/flight/flight-grpc/src/main/java/org/apache/arrow/flight/FlightHandlerRegistry.java
##########
@@ -0,0 +1,170 @@
+/*
+ * 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.arrow.flight;
+
+import java.util.Objects;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.apache.arrow.flight.impl.Flight;
+import org.apache.arrow.memory.BufferAllocator;
+
+import io.grpc.Context;
+import io.grpc.HandlerRegistry;
+import io.grpc.Metadata;
+import io.grpc.MethodDescriptor;
+import io.grpc.ServerCall;
+import io.grpc.ServerCallHandler;
+import io.grpc.ServerMethodDefinition;
+import io.grpc.ServerServiceDefinition;
+import io.grpc.Status;
+
+/**
+ * A gRPC HandlerRegistry that creates a new Arrow allocator for each call to 
a Flight "data" method
+ * (DoGet, DoPut, or DoExchange).
+ */
+public final class FlightHandlerRegistry extends HandlerRegistry {
+  private final BufferAllocator allocator;
+  private final ServerServiceDefinition delegate;
+  private final ServerMethodDefinition<Flight.Ticket, ArrowMessage> 
doGetMethod;
+  private final ServerMethodDefinition<ArrowMessage, Flight.PutResult> 
doPutMethod;
+  private final ServerMethodDefinition<ArrowMessage, ArrowMessage> 
doExchangeMethod;
+  private final AtomicInteger counter;
+
+  @SuppressWarnings("unchecked")
+  FlightHandlerRegistry(BufferAllocator allocator, ServerServiceDefinition 
delegate) {
+    this.allocator = allocator;
+    this.delegate = delegate;
+    // Unchecked cast
+    this.doGetMethod = (ServerMethodDefinition<Flight.Ticket, ArrowMessage>)
+        
Objects.requireNonNull(delegate.getMethod(FlightBindingService.DO_GET));
+    this.doPutMethod = (ServerMethodDefinition<ArrowMessage, Flight.PutResult>)
+        
Objects.requireNonNull(delegate.getMethod(FlightBindingService.DO_PUT));
+    this.doExchangeMethod = (ServerMethodDefinition<ArrowMessage, 
ArrowMessage>)
+        
Objects.requireNonNull(delegate.getMethod(FlightBindingService.DO_EXCHANGE));
+    this.counter = new AtomicInteger(0);
+  }
+
+  @Override
+  public ServerMethodDefinition<?, ?> lookupMethod(String methodName, String 
authority) {
+    if (FlightBindingService.DO_GET.equals(methodName)) {
+      final String allocatorName = allocator.getName() + "-DoGet-" + 
counter.getAndIncrement();
+      final BufferAllocator childAllocator = 
allocator.newChildAllocator(allocatorName, 0, allocator.getLimit());

Review comment:
       i don't know if this is a concern, but does this potentially over 
reserve space on the parent allocator?  I suppose this doesn't really change 
existing semantics?




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