import quincy 17.2.0

[ceph.git] / ceph / src / arrow / java / flight / flight-core / src / main / java / org / apache / arrow / flight / FlightServerMiddleware.java

diff --git a/ceph/src/arrow/java/flight/flight-core/src/main/java/org/apache/arrow/flight/FlightServerMiddleware.java b/ceph/src/arrow/java/flight/flight-core/src/main/java/org/apache/arrow/flight/FlightServerMiddleware.java
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+++ b/ceph/src/arrow/java/flight/flight-core/src/main/java/org/apache/arrow/flight/FlightServerMiddleware.java
@@ -0,0 +1,100 @@
+/*
+ * 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;
+
+/**
+ * Server-side middleware for Flight calls.
+ *
+ * <p>Middleware are instantiated per-call.
+ *
+ * <p>Methods are not guaranteed to be called on any particular thread, relative to the thread that Flight requests are
+ * executed on. Do not depend on thread-local storage; instead, use state on the middleware instance. Service
+ * implementations may communicate with middleware implementations through
+ * {@link org.apache.arrow.flight.FlightProducer.CallContext#getMiddleware(Key)}. Methods on the middleware instance
+ * are non-reentrant, that is, a particular RPC will not make multiple concurrent calls to methods on a single
+ * middleware instance. However, methods on the factory instance are expected to be thread-safe, and if the factory
+ * instance returns the same middleware object more than once, then that middleware object must be thread-safe.
+ */
+public interface FlightServerMiddleware {
+
+  /**
+   * A factory for Flight server middleware.
+   * @param <T> The middleware type.
+   */
+  interface Factory<T extends FlightServerMiddleware> {
+    /**
+     * A callback for when the call starts.
+     *
+     * @param info Details about the call.
+     * @param incomingHeaders A mutable set of request headers.
+     * @param context Context about the current request.
+     *
+     * @throws FlightRuntimeException if the middleware wants to reject the call with the given status
+     */
+    T onCallStarted(CallInfo info, CallHeaders incomingHeaders, RequestContext context);
+  }
+
+  /**
+   * A key for Flight server middleware. On a server, middleware instances are identified by this key.
+   *
+   * <p>Keys use reference equality, so instances should be shared.
+   *
+   * @param <T> The middleware class stored in this key. This provides a compile-time check when retrieving instances.
+   */
+  class Key<T extends FlightServerMiddleware> {
+    final String key;
+
+    Key(String key) {
+      this.key = Objects.requireNonNull(key, "Key must not be null.");
+    }
+
+    /**
+     * Create a new key for the given type.
+     */
+    public static <T extends FlightServerMiddleware> Key<T> of(String key) {
+      return new Key<>(key);
+    }
+  }
+
+  /**
+   * Callback for when the underlying transport is about to send response headers.
+   *
+   * @param outgoingHeaders A mutable set of response headers. These can be manipulated to send different headers to the
+   *     client.
+   */
+  void onBeforeSendingHeaders(CallHeaders outgoingHeaders);
+
+  /**
+   * Callback for when the underlying transport has completed a call.
+   * @param status Whether the call completed successfully or not.
+   */
+  void onCallCompleted(CallStatus status);
+
+  /**
+   * Callback for when an RPC method implementation throws an uncaught exception.
+   *
+   * <p>May be called multiple times, and may be called before or after {@link #onCallCompleted(CallStatus)}.
+   * Generally, an uncaught exception will end the call with a error {@link CallStatus}, and will be reported to {@link
+   * #onCallCompleted(CallStatus)}, but not necessarily this method.
+   *
+   * @param err The exception that was thrown.
+   */
+  void onCallErrored(Throwable err);
+}