[GitHub] [arrow] davisusanibar commented on a diff in pull request #12847: ARROW-15577: [Java][Doc] Add Arrow Flight documentation

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

davisusanibar commented on code in PR #12847:
URL: https://github.com/apache/arrow/pull/12847#discussion_r848772739


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docs/source/java/flight.rst:
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+.. 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 ``CallContext`` for common parameters. To indicate
+failure, pass an exception to the "listener" if present, or else 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, create a `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 option!"));
+        }
+    } 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 ``Location.forGrpcTls`` to create the Location for the client.
+
+Enabling Authentication
+=======================
+
+.. warning:: Authentication is insecure without enabling TLS.
+
+Handshake-based authentication can be enabled by implementing
+on the client side through authenticates against the Flight service
+``FlightClient.authenticate``, or by authenticates with a username
+and password through ``FlightClient.authenticateBasic`` and
+``FlightClient.authenticateBasicToken``. And on the server side
+through ``FlightServer.Builder().authHandler`` or by
+``FlightServer.Builder().headerAuthenticator``.

Review Comment:
   Updated



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