Support Preemptive Authentication with RestClient (#21336)

This adds the necessary `AuthCache` needed to support preemptive authorization. By adding every host to the cache, the automatically added `RequestAuthCache` interceptor will add credentials on the first pass rather than waiting to do it after _each_ anonymous request is rejected (thus always sending everything twice when basic auth is required).

client/rest/src/main/java/org/elasticsearch/client/RestClient.java

@@ -25,6 +25,7 @@ import org.apache.http.HttpEntity;
 import org.apache.http.HttpHost;
 import org.apache.http.HttpRequest;
 import org.apache.http.HttpResponse;
+import org.apache.http.client.AuthCache;
 import org.apache.http.client.ClientProtocolException;
 import org.apache.http.client.methods.HttpEntityEnclosingRequestBase;
 import org.apache.http.client.methods.HttpHead;
@@ -34,8 +35,11 @@ import org.apache.http.client.methods.HttpPost;
 import org.apache.http.client.methods.HttpPut;
 import org.apache.http.client.methods.HttpRequestBase;
 import org.apache.http.client.methods.HttpTrace;
+import org.apache.http.client.protocol.HttpClientContext;
 import org.apache.http.client.utils.URIBuilder;
 import org.apache.http.concurrent.FutureCallback;
+import org.apache.http.impl.auth.BasicScheme;
+import org.apache.http.impl.client.BasicAuthCache;
 import org.apache.http.impl.nio.client.CloseableHttpAsyncClient;
 import org.apache.http.nio.client.methods.HttpAsyncMethods;
 import org.apache.http.nio.protocol.HttpAsyncRequestProducer;
@@ -92,7 +96,7 @@ public class RestClient implements Closeable {
     private final long maxRetryTimeoutMillis;
     private final String pathPrefix;
     private final AtomicInteger lastHostIndex = new AtomicInteger(0);
-    private volatile Set<HttpHost> hosts;
+    private volatile HostTuple<Set<HttpHost>> hostTuple;
     private final ConcurrentMap<HttpHost, DeadHostState> blacklist = new ConcurrentHashMap<>();
     private final FailureListener failureListener;
 
@@ -122,11 +126,13 @@ public class RestClient implements Closeable {
             throw new IllegalArgumentException("hosts must not be null nor empty");
         }
         Set<HttpHost> httpHosts = new HashSet<>();
+        AuthCache authCache = new BasicAuthCache();
         for (HttpHost host : hosts) {
             Objects.requireNonNull(host, "host cannot be null");
             httpHosts.add(host);
+            authCache.put(host, new BasicScheme());
         }
-        this.hosts = Collections.unmodifiableSet(httpHosts);
+        this.hostTuple = new HostTuple<>(Collections.unmodifiableSet(httpHosts), authCache);
         this.blacklist.clear();
     }
 
@@ -315,19 +321,22 @@ public class RestClient implements Closeable {
         setHeaders(request, headers);
         FailureTrackingResponseListener failureTrackingResponseListener = new FailureTrackingResponseListener(responseListener);
         long startTime = System.nanoTime();
-        performRequestAsync(startTime, nextHost().iterator(), request, ignoreErrorCodes, httpAsyncResponseConsumerFactory,
-                failureTrackingResponseListener);
+        performRequestAsync(startTime, nextHost(), request, ignoreErrorCodes, httpAsyncResponseConsumerFactory,
+                            failureTrackingResponseListener);
     }
 
-    private void performRequestAsync(final long startTime, final Iterator<HttpHost> hosts, final HttpRequestBase request,
+    private void performRequestAsync(final long startTime, final HostTuple<Iterator<HttpHost>> hostTuple, final HttpRequestBase request,
                                      final Set<Integer> ignoreErrorCodes,
                                      final HttpAsyncResponseConsumerFactory httpAsyncResponseConsumerFactory,
                                      final FailureTrackingResponseListener listener) {
-        final HttpHost host = hosts.next();
+        final HttpHost host = hostTuple.hosts.next();
         //we stream the request body if the entity allows for it
-        HttpAsyncRequestProducer requestProducer = HttpAsyncMethods.create(host, request);
-        HttpAsyncResponseConsumer<HttpResponse> asyncResponseConsumer = httpAsyncResponseConsumerFactory.createHttpAsyncResponseConsumer();
-        client.execute(requestProducer, asyncResponseConsumer, new FutureCallback<HttpResponse>() {
+        final HttpAsyncRequestProducer requestProducer = HttpAsyncMethods.create(host, request);
+        final HttpAsyncResponseConsumer<HttpResponse> asyncResponseConsumer =
+            httpAsyncResponseConsumerFactory.createHttpAsyncResponseConsumer();
+        final HttpClientContext context = HttpClientContext.create();
+        context.setAuthCache(hostTuple.authCache);
+        client.execute(requestProducer, asyncResponseConsumer, context, new FutureCallback<HttpResponse>() {
             @Override
             public void completed(HttpResponse httpResponse) {
                 try {
@@ -366,7 +375,7 @@ public class RestClient implements Closeable {
             }
 
             private void retryIfPossible(Exception exception) {
-                if (hosts.hasNext()) {
+                if (hostTuple.hosts.hasNext()) {
                     //in case we are retrying, check whether maxRetryTimeout has been reached
                     long timeElapsedMillis = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startTime);
                     long timeout = maxRetryTimeoutMillis - timeElapsedMillis;
@@ -377,7 +386,7 @@ public class RestClient implements Closeable {
                     } else {
                         listener.trackFailure(exception);
                         request.reset();
-                        performRequestAsync(startTime, hosts, request, ignoreErrorCodes, httpAsyncResponseConsumerFactory, listener);
+                        performRequestAsync(startTime, hostTuple, request, ignoreErrorCodes, httpAsyncResponseConsumerFactory, listener);
                     }
                 } else {
                     listener.onDefinitiveFailure(exception);
@@ -415,17 +424,18 @@ public class RestClient implements Closeable {
      * The iterator returned will never be empty. In case there are no healthy hosts available, or dead ones to be be retried,
      * one dead host gets returned so that it can be retried.
      */
-    private Iterable<HttpHost> nextHost() {
+    private HostTuple<Iterator<HttpHost>> nextHost() {
+        final HostTuple<Set<HttpHost>> hostTuple = this.hostTuple;
         Collection<HttpHost> nextHosts = Collections.emptySet();
         do {
-            Set<HttpHost> filteredHosts = new HashSet<>(hosts);
+            Set<HttpHost> filteredHosts = new HashSet<>(hostTuple.hosts);
             for (Map.Entry<HttpHost, DeadHostState> entry : blacklist.entrySet()) {
                 if (System.nanoTime() - entry.getValue().getDeadUntilNanos() < 0) {
                     filteredHosts.remove(entry.getKey());
                 }
             }
             if (filteredHosts.isEmpty()) {
-                //last resort: if there are no good hosts to use, return a single dead one, the one that's closest to being retried
+                //last resort: if there are no good host to use, return a single dead one, the one that's closest to being retried
                 List<Map.Entry<HttpHost, DeadHostState>> sortedHosts = new ArrayList<>(blacklist.entrySet());
                 if (sortedHosts.size() > 0) {
                     Collections.sort(sortedHosts, new Comparator<Map.Entry<HttpHost, DeadHostState>>() {
@@ -444,7 +454,7 @@ public class RestClient implements Closeable {
                 nextHosts = rotatedHosts;
             }
         } while(nextHosts.isEmpty());
-        return nextHosts;
+        return new HostTuple<>(nextHosts.iterator(), hostTuple.authCache);
     }
 
     /**
@@ -686,4 +696,18 @@ public class RestClient implements Closeable {
 
         }
     }
+
+    /**
+     * {@code HostTuple} enables the {@linkplain HttpHost}s and {@linkplain AuthCache} to be set together in a thread
+     * safe, volatile way.
+     */
+    private static class HostTuple<T> {
+        public final T hosts;
+        public final AuthCache authCache;
+
+        public HostTuple(final T hosts, final AuthCache authCache) {
+            this.hosts = hosts;
+            this.authCache = authCache;
+        }
+    }
 }

client/rest/src/test/java/org/elasticsearch/client/RestClientMultipleHostsTests.java

@@ -26,8 +26,10 @@ import org.apache.http.HttpResponse;
 import org.apache.http.ProtocolVersion;
 import org.apache.http.StatusLine;
 import org.apache.http.client.methods.HttpUriRequest;
+import org.apache.http.client.protocol.HttpClientContext;
 import org.apache.http.concurrent.FutureCallback;
 import org.apache.http.conn.ConnectTimeoutException;
+import org.apache.http.impl.auth.BasicScheme;
 import org.apache.http.impl.nio.client.CloseableHttpAsyncClient;
 import org.apache.http.message.BasicHttpResponse;
 import org.apache.http.message.BasicStatusLine;
@@ -73,13 +75,15 @@ public class RestClientMultipleHostsTests extends RestClientTestCase {
     public void createRestClient() throws IOException {
         CloseableHttpAsyncClient httpClient = mock(CloseableHttpAsyncClient.class);
         when(httpClient.<HttpResponse>execute(any(HttpAsyncRequestProducer.class), any(HttpAsyncResponseConsumer.class),
-                any(FutureCallback.class))).thenAnswer(new Answer<Future<HttpResponse>>() {
+               any(HttpClientContext.class), any(FutureCallback.class))).thenAnswer(new Answer<Future<HttpResponse>>() {
             @Override
             public Future<HttpResponse> answer(InvocationOnMock invocationOnMock) throws Throwable {
                 HttpAsyncRequestProducer requestProducer = (HttpAsyncRequestProducer) invocationOnMock.getArguments()[0];
                 HttpUriRequest request = (HttpUriRequest)requestProducer.generateRequest();
                 HttpHost httpHost = requestProducer.getTarget();
-                FutureCallback<HttpResponse> futureCallback = (FutureCallback<HttpResponse>) invocationOnMock.getArguments()[2];
+                HttpClientContext context = (HttpClientContext) invocationOnMock.getArguments()[2];
+                assertThat(context.getAuthCache().get(httpHost), instanceOf(BasicScheme.class));
+                FutureCallback<HttpResponse> futureCallback = (FutureCallback<HttpResponse>) invocationOnMock.getArguments()[3];
                 //return the desired status code or exception depending on the path
                 if (request.getURI().getPath().equals("/soe")) {
                     futureCallback.failed(new SocketTimeoutException(httpHost.toString()));

client/rest/src/test/java/org/elasticsearch/client/RestClientSingleHostIntegTests.java

@@ -26,7 +26,11 @@ import com.sun.net.httpserver.HttpServer;
 import org.apache.http.Consts;
 import org.apache.http.Header;
 import org.apache.http.HttpHost;
+import org.apache.http.auth.AuthScope;
+import org.apache.http.auth.UsernamePasswordCredentials;
 import org.apache.http.entity.StringEntity;
+import org.apache.http.impl.client.BasicCredentialsProvider;
+import org.apache.http.impl.nio.client.HttpAsyncClientBuilder;
 import org.apache.http.util.EntityUtils;
 import org.codehaus.mojo.animal_sniffer.IgnoreJRERequirement;
 import org.elasticsearch.mocksocket.MockHttpServer;
@@ -48,7 +52,10 @@ import java.util.Set;
 import static org.elasticsearch.client.RestClientTestUtil.getAllStatusCodes;
 import static org.elasticsearch.client.RestClientTestUtil.getHttpMethods;
 import static org.elasticsearch.client.RestClientTestUtil.randomStatusCode;
+import static org.hamcrest.Matchers.nullValue;
+import static org.hamcrest.Matchers.startsWith;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 
 /**
@@ -66,22 +73,10 @@ public class RestClientSingleHostIntegTests extends RestClientTestCase {
 
     @BeforeClass
     public static void startHttpServer() throws Exception {
-        String pathPrefixWithoutLeadingSlash;
-        if (randomBoolean()) {
-            pathPrefixWithoutLeadingSlash = "testPathPrefix/" + randomAsciiOfLengthBetween(1, 5);
-            pathPrefix = "/" + pathPrefixWithoutLeadingSlash;
-        } else {
-            pathPrefix = pathPrefixWithoutLeadingSlash = "";
-        }
-
+        pathPrefix = randomBoolean() ? "/testPathPrefix/" + randomAsciiOfLengthBetween(1, 5) : "";
         httpServer = createHttpServer();
         defaultHeaders = RestClientTestUtil.randomHeaders(getRandom(), "Header-default");
-        RestClientBuilder restClientBuilder = RestClient.builder(
-                new HttpHost(httpServer.getAddress().getHostString(), httpServer.getAddress().getPort())).setDefaultHeaders(defaultHeaders);
-        if (pathPrefix.length() > 0) {
-            restClientBuilder.setPathPrefix((randomBoolean() ? "/" : "") + pathPrefixWithoutLeadingSlash);
-        }
-        restClient = restClientBuilder.build();
+        restClient = createRestClient(false, true);
     }
 
     private static HttpServer createHttpServer() throws Exception {
@@ -129,6 +124,35 @@ public class RestClientSingleHostIntegTests extends RestClientTestCase {
         }
     }
 
+    private static RestClient createRestClient(final boolean useAuth, final boolean usePreemptiveAuth) {
+        // provide the username/password for every request
+        final BasicCredentialsProvider credentialsProvider = new BasicCredentialsProvider();
+        credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials("user", "pass"));
+
+        final RestClientBuilder restClientBuilder = RestClient.builder(
+            new HttpHost(httpServer.getAddress().getHostString(), httpServer.getAddress().getPort())).setDefaultHeaders(defaultHeaders);
+        if (pathPrefix.length() > 0) {
+            // sometimes cut off the leading slash
+            restClientBuilder.setPathPrefix(randomBoolean() ? pathPrefix.substring(1) : pathPrefix);
+        }
+
+        if (useAuth) {
+            restClientBuilder.setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
+                @Override
+                public HttpAsyncClientBuilder customizeHttpClient(final HttpAsyncClientBuilder httpClientBuilder) {
+                    if (usePreemptiveAuth == false) {
+                        // disable preemptive auth by ignoring any authcache
+                        httpClientBuilder.disableAuthCaching();
+                    }
+
+                    return httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider);
+                }
+            });
+        }
+
+        return restClientBuilder.build();
+    }
+
     @AfterClass
     public static void stopHttpServers() throws IOException {
         restClient.close();
@@ -159,7 +183,7 @@ public class RestClientSingleHostIntegTests extends RestClientTestCase {
 
             assertEquals(method, esResponse.getRequestLine().getMethod());
             assertEquals(statusCode, esResponse.getStatusLine().getStatusCode());
-            assertEquals((pathPrefix.length() > 0 ? pathPrefix : "") + "/" + statusCode, esResponse.getRequestLine().getUri());
+            assertEquals(pathPrefix + "/" + statusCode, esResponse.getRequestLine().getUri());
             assertHeaders(defaultHeaders, requestHeaders, esResponse.getHeaders(), standardHeaders);
             for (final Header responseHeader : esResponse.getHeaders()) {
                 String name = responseHeader.getName();
@@ -189,7 +213,41 @@ public class RestClientSingleHostIntegTests extends RestClientTestCase {
         bodyTest("GET");
     }
 
-    private void bodyTest(String method) throws IOException {
+    /**
+     * Verify that credentials are sent on the first request with preemptive auth enabled (default when provided with credentials).
+     */
+    public void testPreemptiveAuthEnabled() throws IOException  {
+        final String[] methods = { "POST", "PUT", "GET", "DELETE" };
+
+        try (final RestClient restClient = createRestClient(true, true)) {
+            for (final String method : methods) {
+                final Response response = bodyTest(restClient, method);
+
+                assertThat(response.getHeader("Authorization"), startsWith("Basic"));
+            }
+        }
+    }
+
+    /**
+     * Verify that credentials are <em>not</em> sent on the first request with preemptive auth disabled.
+     */
+    public void testPreemptiveAuthDisabled() throws IOException  {
+        final String[] methods = { "POST", "PUT", "GET", "DELETE" };
+
+        try (final RestClient restClient = createRestClient(true, false)) {
+            for (final String method : methods) {
+                final Response response = bodyTest(restClient, method);
+
+                assertThat(response.getHeader("Authorization"), nullValue());
+            }
+        }
+    }
+
+    private Response bodyTest(final String method) throws IOException {
+        return bodyTest(restClient, method);
+    }
+
+    private Response bodyTest(final RestClient restClient, final String method) throws IOException {
         String requestBody = "{ \"field\": \"value\" }";
         StringEntity entity = new StringEntity(requestBody);
         int statusCode = randomStatusCode(getRandom());
@@ -201,7 +259,9 @@ public class RestClientSingleHostIntegTests extends RestClientTestCase {
         }
         assertEquals(method, esResponse.getRequestLine().getMethod());
         assertEquals(statusCode, esResponse.getStatusLine().getStatusCode());
-        assertEquals((pathPrefix.length() > 0 ? pathPrefix : "") + "/" + statusCode, esResponse.getRequestLine().getUri());
+        assertEquals(pathPrefix + "/" + statusCode, esResponse.getRequestLine().getUri());
         assertEquals(requestBody, EntityUtils.toString(esResponse.getEntity()));
+
+        return esResponse;
     }
 }

client/rest/src/test/java/org/elasticsearch/client/RestClientSingleHostTests.java

@@ -34,10 +34,12 @@ import org.apache.http.client.methods.HttpPost;
 import org.apache.http.client.methods.HttpPut;
 import org.apache.http.client.methods.HttpTrace;
 import org.apache.http.client.methods.HttpUriRequest;
+import org.apache.http.client.protocol.HttpClientContext;
 import org.apache.http.client.utils.URIBuilder;
 import org.apache.http.concurrent.FutureCallback;
 import org.apache.http.conn.ConnectTimeoutException;
 import org.apache.http.entity.StringEntity;
+import org.apache.http.impl.auth.BasicScheme;
 import org.apache.http.impl.nio.client.CloseableHttpAsyncClient;
 import org.apache.http.message.BasicHttpResponse;
 import org.apache.http.message.BasicStatusLine;
@@ -96,11 +98,13 @@ public class RestClientSingleHostTests extends RestClientTestCase {
     public void createRestClient() throws IOException {
         httpClient = mock(CloseableHttpAsyncClient.class);
         when(httpClient.<HttpResponse>execute(any(HttpAsyncRequestProducer.class), any(HttpAsyncResponseConsumer.class),
-                any(FutureCallback.class))).thenAnswer(new Answer<Future<HttpResponse>>() {
+                any(HttpClientContext.class), any(FutureCallback.class))).thenAnswer(new Answer<Future<HttpResponse>>() {
                     @Override
                     public Future<HttpResponse> answer(InvocationOnMock invocationOnMock) throws Throwable {
                         HttpAsyncRequestProducer requestProducer = (HttpAsyncRequestProducer) invocationOnMock.getArguments()[0];
-                        FutureCallback<HttpResponse> futureCallback = (FutureCallback<HttpResponse>) invocationOnMock.getArguments()[2];
+                        HttpClientContext context = (HttpClientContext) invocationOnMock.getArguments()[2];
+                        assertThat(context.getAuthCache().get(httpHost), instanceOf(BasicScheme.class));
+                        FutureCallback<HttpResponse> futureCallback = (FutureCallback<HttpResponse>) invocationOnMock.getArguments()[3];
                         HttpUriRequest request = (HttpUriRequest)requestProducer.generateRequest();
                         //return the desired status code or exception depending on the path
                         if (request.getURI().getPath().equals("/soe")) {
@@ -156,7 +160,7 @@ public class RestClientSingleHostTests extends RestClientTestCase {
         for (String httpMethod : getHttpMethods()) {
             HttpUriRequest expectedRequest = performRandomRequest(httpMethod);
             verify(httpClient, times(++times)).<HttpResponse>execute(requestArgumentCaptor.capture(),
-                    any(HttpAsyncResponseConsumer.class), any(FutureCallback.class));
+                    any(HttpAsyncResponseConsumer.class), any(HttpClientContext.class), any(FutureCallback.class));
             HttpUriRequest actualRequest = (HttpUriRequest)requestArgumentCaptor.getValue().generateRequest();
             assertEquals(expectedRequest.getURI(), actualRequest.getURI());
             assertEquals(expectedRequest.getClass(), actualRequest.getClass());

docs/java-rest/configuration.asciidoc

@@ -81,6 +81,29 @@ RestClient restClient = RestClient.builder(new HttpHost("localhost", 9200))
         .build();
 --------------------------------------------------
 
+You can disable Preemptive Authentication, which means that every request will be sent without
+authorization headers to see if it is accepted and, upon receiving a HTTP 401 response, it will
+resend the exact same request with the basic authentication header. If you wish to do this, then
+you can do so by disabling it via the `HttpAsyncClientBuilder`:
+
+[source,java]
+--------------------------------------------------
+final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
+credentialsProvider.setCredentials(AuthScope.ANY,
+        new UsernamePasswordCredentials("user", "password"));
+
+RestClient restClient = RestClient.builder(new HttpHost("localhost", 9200))
+        .setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
+            @Override
+            public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpClientBuilder) {
+                // disable preemptive authentication
+                httpClientBuilder.disableAuthCaching();
+                return httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider);
+            }
+        })
+        .build();
+--------------------------------------------------
+
 === Encrypted communication
 
 Encrypted communication can also be configured through the

modules/reindex/src/test/java/org/elasticsearch/index/reindex/remote/RemoteScrollableHitSourceTests.java

@@ -26,6 +26,7 @@ import org.apache.http.HttpHost;
 import org.apache.http.HttpResponse;
 import org.apache.http.ProtocolVersion;
 import org.apache.http.StatusLine;
+import org.apache.http.client.protocol.HttpClientContext;
 import org.apache.http.concurrent.FutureCallback;
 import org.apache.http.entity.ContentType;
 import org.apache.http.entity.InputStreamEntity;
@@ -430,11 +431,11 @@ public class RemoteScrollableHitSourceTests extends ESTestCase {
         ContentTooLongException tooLong = new ContentTooLongException("too long!");
         CloseableHttpAsyncClient httpClient = mock(CloseableHttpAsyncClient.class);
         when(httpClient.<HttpResponse>execute(any(HttpAsyncRequestProducer.class), any(HttpAsyncResponseConsumer.class),
-                any(FutureCallback.class))).then(new Answer<Future<HttpResponse>>() {
+                any(HttpClientContext.class), any(FutureCallback.class))).then(new Answer<Future<HttpResponse>>() {
             @Override
             public Future<HttpResponse> answer(InvocationOnMock invocationOnMock) throws Throwable {
                 HeapBufferedAsyncResponseConsumer consumer = (HeapBufferedAsyncResponseConsumer) invocationOnMock.getArguments()[1];
-                FutureCallback callback = (FutureCallback) invocationOnMock.getArguments()[2];
+                FutureCallback callback = (FutureCallback) invocationOnMock.getArguments()[3];
                 assertEquals(new ByteSizeValue(100, ByteSizeUnit.MB).bytesAsInt(), consumer.getBufferLimit());
                 callback.failed(tooLong);
                 return null;
@@ -495,7 +496,7 @@ public class RemoteScrollableHitSourceTests extends ESTestCase {
 
         CloseableHttpAsyncClient httpClient = mock(CloseableHttpAsyncClient.class);
         when(httpClient.<HttpResponse>execute(any(HttpAsyncRequestProducer.class), any(HttpAsyncResponseConsumer.class),
-                any(FutureCallback.class))).thenAnswer(new Answer<Future<HttpResponse>>() {
+                any(HttpClientContext.class), any(FutureCallback.class))).thenAnswer(new Answer<Future<HttpResponse>>() {
 
             int responseCount = 0;
 
@@ -504,7 +505,7 @@ public class RemoteScrollableHitSourceTests extends ESTestCase {
                 // Throw away the current thread context to simulate running async httpclient's thread pool
                 threadPool.getThreadContext().stashContext();
                 HttpAsyncRequestProducer requestProducer = (HttpAsyncRequestProducer) invocationOnMock.getArguments()[0];
-                FutureCallback<HttpResponse> futureCallback = (FutureCallback<HttpResponse>) invocationOnMock.getArguments()[2];
+                FutureCallback<HttpResponse> futureCallback = (FutureCallback<HttpResponse>) invocationOnMock.getArguments()[3];
                 HttpEntityEnclosingRequest request = (HttpEntityEnclosingRequest)requestProducer.generateRequest();
                 URL resource = resources[responseCount];
                 String path = paths[responseCount++];