davisusanibar commented on code in PR #12847: URL: https://github.com/apache/arrow/pull/12847#discussion_r848513939
########## docs/source/java/flight.rst: ########## @@ -0,0 +1,216 @@ +.. 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. + +================ +Arrow Flight RPC +================ + +Arrow Flight is an RPC framework for efficient transfer of Arrow data +over the network. + +.. contents:: + +.. seealso:: + + :doc:`Flight protocol documentation <../format/Flight>` + Documentation of the Flight protocol, including how to use + Flight conceptually. + + `Java Cookbook <https://arrow.apache.org/cookbook/java/flight.html>`_ + Recipes for using Arrow Flight in Java. + +Writing a Flight Service +======================== + +Flight servers implement the `FlightProducer`_ interface. For convenience, +they can subclass `NoOpFlightProducer`_ instead, which offers default +implementations of all the RPC methods. + +.. code-block:: Java + + public class TutorialFlightProducer implements FlightProducer { + @Override + // Override methods or use NoOpFlightProducer for only methods needed + } + +Each RPC method always takes a `CallStatus` for common parameters. To indicate +failure, raise an exception. + +.. code-block:: Java + + // Server + @Override + public void listFlights(CallContext context, Criteria criteria, StreamListener<FlightInfo> listener) { + // ... + listener.onError( + CallStatus.UNAUTHENTICATED.withDescription( + "Custom UNAUTHENTICATED description message.").toRuntimeException()); + // ... + } + + // Client + try{ + Iterable<FlightInfo> flightInfosBefore = flightClient.listFlights(Criteria.ALL); + // ... + } catch (FlightRuntimeException e){ + // Catch UNAUTHENTICATED exception + } + +To start a server, create a `Location`_ to specify where to listen, and then create +a `FlightServer`_ with an instance of a producer. This will start the server, but +won't block the rest of the program. Call ``FlightServer.awaitTermination`` +to block until the server stops. + +.. code-block:: Java + + class TutorialFlightProducer implements FlightProducer { + @Override + // Override methods or use NoOpFlightProducer for only methods needed + } + + Location location = Location.forGrpcInsecure("0.0.0.0", 0); + try( + BufferAllocator allocator = new RootAllocator(); + FlightServer server = FlightServer.builder( + allocator, + location, + new TutorialFlightProducer() + ).build(); + ){ + server.start(); + System.out.println("Server listening on port " + server.getPort()); + server.awaitTermination(); + } catch (Exception e) { + e.printStackTrace(); + } + +.. code-block:: shell + + Server listening on port 58104 + +Using the Flight Client +======================= + +To connect to a Flight service, call `FlightClient`_ with a location. + +.. code-block:: Java + + Location location = Location.forGrpcInsecure("0.0.0.0", 58104); + + try(BufferAllocator allocator = new RootAllocator(); + FlightClient client = FlightClient.builder(allocator, location).build()){ + // ... Consume operations exposed by Flight server + } catch (Exception e) { + e.printStackTrace(); + } + +Cancellation and Timeouts +========================= + +When making a call, clients can optionally provide `CallOptions`. This allows +clients to set a timeout on calls. Also, some objects returned by client RPC calls +expose a cancel method which allows terminating a call early. + +.. code-block:: Java + + Location location = Location.forGrpcInsecure("0.0.0.0", 58609); + + try(BufferAllocator allocator = new RootAllocator(); + FlightClient tutorialFlightClient = FlightClient.builder(allocator, location).build()){ + + Iterator<Result> resultIterator = tutorialFlightClient.doAction( + new Action("test-timeout"), + CallOptions.timeout(2, TimeUnit.SECONDS) + ); + } catch (Exception e) { + e.printStackTrace(); + } + +On the server side, timeouts are transparent. For cancellation, the server needs to manually poll +`setOnCancelHandler` or `isCancelled` to check if the client has cancelled the call, and if so, +break out of any processing the server is currently doing. + +.. code-block:: Java + + // Client + Location location = Location.forGrpcInsecure("0.0.0.0", 58609); + try(BufferAllocator allocator = new RootAllocator(); + FlightClient tutorialFlightClient = FlightClient.builder(allocator, location).build()){ + try(FlightStream flightStream = flightClient.getStream(new Ticket(new byte[]{}))) { + // ... + flightStream.cancel("tutorial-cancel", new Exception("Testing cancellation opion!")); + } + } catch (Exception e) { + e.printStackTrace(); + } + // Server + @Override + public void getStream(CallContext context, Ticket ticket, ServerStreamListener listener) { + // ... + listener.setOnCancelHandler(()->{ + // Implement logic to handle cancellation option + }); + } + +Enabling TLS +============ + +TLS can be enabled when setting up a server by providing a +certificate and key pair to `FlightServer.builder.useTls`. + +On the client side, use `FlightClient.builder.trustedCertificates`. + +Enabling Authentication +======================= + +.. warning:: Authentication is insecure without enabling TLS. + +Handshake-based authentication can be enabled by implementing +`ServerAuthHandler`. Authentication consists of two parts: on +initial client connection, the server and client authentication +implementations can perform any negotiation needed; then, on each RPC +thereafter, the client provides a token. The server authentication +handler validates the token and provides the identity of the +client. This identity can be obtained from the +`CallContext.peerIdentity`. + +.. code-block:: Java + + // Client + FlightClient client = FlightClient.builder().build(); + client.authenticateBasic("user", "password"); + // Server + FlightServer server = FlightServer.builder().authHandler(new BasicServerAuthHandler(validator)).build(); + // CallHeaders printed on the Flight Server: + Metadata(content-type=application/grpc,user-agent=grpc-java-netty/1.44.1,auth-token-bin=bXlfdG9rZW4,grpc-accept-encoding=gzip) Review Comment: Deleted -- This is an automated message from the Apache Git Service. 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