Experiment 4 : Test context propagation with RxJava

This is where we fail. RxJava executes all of its processing outside
main thread, therefore even the interceptor gets executed on async
thread.

In ideal case it would be best if the interceptor can get control before
passing control to RxInvokerProvider, so we can guarantee it still
happens on calling thread.

While it is true, that rx request might not even fire ever, this is only
chance for service provider to propagate context.

ext/rx/rx-client-rxjava/src/test/java/org/glassfish/jersey/client/rx/rxjava/RxTracingWithInterceptorTest.java

@@ -0,0 +1,132 @@
+/*
+ *    DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+ *
+ *    Copyright (c) [2019] Payara Foundation and/or its affiliates. All rights reserved.
+ *
+ *    The contents of this file are subject to the terms of either the GNU
+ *    General Public License Version 2 only ("GPL") or the Common Development
+ *    and Distribution License("CDDL") (collectively, the "License").  You
+ *    may not use this file except in compliance with the License.  You can
+ *    obtain a copy of the License at
+ *    https://github.com/payara/Payara/blob/master/LICENSE.txt
+ *    See the License for the specific
+ *    language governing permissions and limitations under the License.
+ *
+ *    When distributing the software, include this License Header Notice in each
+ *    file and include the License file at glassfish/legal/LICENSE.txt.
+ *
+ *    GPL Classpath Exception:
+ *    The Payara Foundation designates this particular file as subject to the "Classpath"
+ *    exception as provided by the Payara Foundation in the GPL Version 2 section of the License
+ *    file that accompanied this code.
+ *
+ *    Modifications:
+ *    If applicable, add the following below the License Header, with the fields
+ *    enclosed by brackets [] replaced by your own identifying information:
+ *    "Portions Copyright [year] [name of copyright owner]"
+ *
+ *    Contributor(s):
+ *    If you wish your version of this file to be governed by only the CDDL or
+ *    only the GPL Version 2, indicate your decision by adding "[Contributor]
+ *    elects to include this software in this distribution under the [CDDL or GPL
+ *    Version 2] license."  If you don't indicate a single choice of license, a
+ *    recipient has the option to distribute your version of this file under
+ *    either the CDDL, the GPL Version 2 or to extend the choice of license to
+ *    its licensees as provided above.  However, if you add GPL Version 2 code
+ *    and therefore, elected the GPL Version 2 license, then the option applies
+ *    only if the new code is made subject to such option by the copyright
+ *    holder.
+ */
+
+package org.glassfish.jersey.client.rx.rxjava;
+
+import org.glassfish.jersey.client.spi.PreInvocationInterceptor;
+import org.glassfish.jersey.internal.guava.ThreadFactoryBuilder;
+import org.glassfish.jersey.process.JerseyProcessingUncaughtExceptionHandler;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import javax.ws.rs.NotFoundException;
+import javax.ws.rs.client.Client;
+import javax.ws.rs.client.ClientBuilder;
+import javax.ws.rs.client.ClientRequestContext;
+import javax.ws.rs.client.ClientRequestFilter;
+import javax.ws.rs.core.GenericType;
+import javax.ws.rs.core.Response;
+import java.io.IOException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.ScheduledThreadPoolExecutor;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.core.Is.is;
+
+public class RxTracingWithInterceptorTest {
+    static final String KEY = "thread_name";
+    static final String EXECUTING_THREAD = Thread.currentThread().getName();
+
+    private Client client;
+
+    @Before
+    public void setUp() throws Exception {
+        client = ClientBuilder.newClient().register(TerminalClientRequestFilter.class);
+        client.register(RxObservableInvokerProvider.class)
+                .register(ContextPropagator.class)
+                .register(new OtherThreadChecker(EXECUTING_THREAD))
+                .register(TerminalClientRequestFilter.class)
+                .register(RxObservableInvokerProvider.class);
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        client.close();
+        client = null;
+    }
+
+    @Test
+    public void testReadEntityViaClass() throws Throwable {
+        final String response = client.target("http://jersey.java.net")
+                .request()
+                .rx(RxObservableInvoker.class)
+                .get(String.class)
+                .toBlocking()
+                .toFuture()
+                .get();
+
+        assertThat(response, is("NO-ENTITY"));
+    }
+
+    static class ContextPropagator implements PreInvocationInterceptor {
+
+        @Override
+        public void beforeRequest(ClientRequestContext requestContext) {
+            System.out.println("Setting context in thead " + Thread.currentThread().getName());
+            requestContext.setProperty(KEY, Thread.currentThread().getName());
+        }
+    }
+
+    static class OtherThreadChecker implements ClientRequestFilter {
+
+        private String callingThread;
+
+        public OtherThreadChecker(String callingThread) {
+            this.callingThread = callingThread;
+        }
+
+        @Override
+        public void filter(ClientRequestContext requestContext) throws IOException {
+            String currentThread = Thread.currentThread().getName();
+            System.out.println("Executing in thread " + currentThread);
+            if (!currentThread.equals(callingThread)) {
+                String context = (String) requestContext.getProperty(KEY);
+                System.out.println("Tracing context is " + context);
+                if (!callingThread.equals(context)) {
+                    requestContext.abortWith(Response.serverError().entity("unexpected request in context: " + context).build());
+                }
+            } else {
+                requestContext.abortWith(Response.serverError().entity("Request executed at calling thread").build());
+            }
+        }
+    }
+
+}