Feature: handle rate limiting of UAA server.

Author: Lokowandtg

README.md

@@ -253,7 +253,7 @@ Beyond that, it is helpful to capture the following information:
 If you open a Github issue with a request for help, please include as much of the information above as possible and do not forget to sanitize any request/response data posted.
 
 ## Development
-The project depends on Java 8. To build from source and install to your local Maven cache, run the following:
+The project depends on Java 8 to 21. To build from source and install to your local Maven cache, run the following:
 
 ```shell
 $ git submodule update --init --recursive
@@ -297,6 +297,7 @@ Name | Description
 `TEST_PROXY_PORT` | _(Optional)_ The port of a proxy to route all requests through. Defaults to `8080`.
 `TEST_PROXY_USERNAME` | _(Optional)_ The username for a proxy to route all requests through
 `TEST_SKIPSSLVALIDATION` | _(Optional)_ Whether to skip SSL validation when connecting to the Cloud Foundry instance.  Defaults to `false`.
+`UAA_API_REQUEST_LIMIT` | _(Optional)_ If your UAA server does rate limiting and returns 429 errors, set this variable to a value smaller than the limit. Defaults to `0` (no limit)
 
 If you do not have access to a CloudFoundry instance with admin access, you can run one locally using [bosh-deployment](https://github.com/cloudfoundry/bosh-deployment) & [cf-deployment](https://github.com/cloudfoundry/cf-deployment/) and Virtualbox.
 

cloudfoundry-client-reactor/src/main/java/org/cloudfoundry/reactor/uaa/AbstractUaaOperations.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2013-2025 the original author or authors.
+ *
+ * Licensed 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.cloudfoundry.reactor.uaa;
+
+import java.util.Map;
+import org.cloudfoundry.reactor.ConnectionContext;
+import org.cloudfoundry.reactor.TokenProvider;
+import org.cloudfoundry.uaa.ratelimit.Ratelimit;
+import org.cloudfoundry.uaa.ratelimit.RatelimitRequest;
+import org.cloudfoundry.uaa.ratelimit.RatelimitResponse;
+import reactor.core.publisher.Mono;
+
+public final class ReactorRatelimit extends AbstractUaaOperations implements Ratelimit {
+
+    /**
+     * Creates an instance
+     *
+     * @param connectionContext the {@link ConnectionContext} to use when communicating with the server
+     * @param root              the root URI of the server. Typically something like {@code https://uaa.run.pivotal.io}.
+     * @param tokenProvider     the {@link TokenProvider} to use when communicating with the server
+     * @param requestTags       map with custom http headers which will be added to web request
+     */
+    public ReactorRatelimit(
+            ConnectionContext connectionContext,
+            Mono<String> root,
+            TokenProvider tokenProvider,
+            Map<String, String> requestTags) {
+        super(connectionContext, root, tokenProvider, requestTags);
+    }
+
+    @Override
+    public Mono<RatelimitResponse> getRatelimit(RatelimitRequest request) {
+        return get(
+                        request,
+                        RatelimitResponse.class,
+                        builder -> builder.pathSegment("RateLimitingStatus"))
+                .checkpoint();
+    }
+}

cloudfoundry-client-reactor/src/main/java/org/cloudfoundry/reactor/uaa/ReactorRatelimit.java

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2013-2025 the original author or authors.
+ *
+ * Licensed 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.cloudfoundry.reactor.uaa;
+
+import io.netty.handler.codec.http.HttpHeaders;
+import java.util.Objects;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import org.cloudfoundry.reactor.uaa.UaaThrottler.Token;
+import org.cloudfoundry.reactor.util.ErrorPayloadMapper;
+import org.cloudfoundry.reactor.util.Operator;
+import org.cloudfoundry.reactor.util.OperatorContext;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import reactor.core.publisher.Mono;
+import reactor.netty.http.client.HttpClient;
+
+public class UaaOperator extends Operator {
+
+    private Token token = null;
+    private static final Logger LOGGER = LoggerFactory.getLogger("cloudfoundry-client.test");
+
+    public UaaOperator(OperatorContext context, HttpClient httpClient, Token value, String caller) {
+        super(context, httpClient);
+        token = Objects.requireNonNull(value, "value must not be null");
+        if (token != UaaThrottler.NON_UAA_TOKEN) {
+            LOGGER.trace("UaaOperator creating instance for " + value.id() + " caller " + caller);
+        }
+    }
+
+    @Override
+    public UaaOperator followRedirects() {
+        return new UaaOperator(
+                this.context, super.getHttpClient().followRedirect(true), this.token, "follow");
+    }
+
+    @Override
+    public UaaOperator headers(Consumer<HttpHeaders> headersTransformer) {
+        return new UaaOperator(
+                this.context,
+                super.getHttpClient().headers(headersTransformer),
+                this.token,
+                "headers");
+    }
+
+    @Override
+    public UaaOperator headersWhen(
+            Function<HttpHeaders, Mono<? extends HttpHeaders>> headersWhenTransformer) {
+        return new UaaOperator(
+                this.context,
+                super.getHttpClient().headersWhen(headersWhenTransformer),
+                this.token,
+                "headersWhen");
+    }
+
+    @Override
+    public UaaOperator withErrorPayloadMapper(ErrorPayloadMapper errorPayloadMapper) {
+        return new UaaOperator(
+                this.context.withErrorPayloadMapper(errorPayloadMapper),
+                super.getHttpClient(),
+                this.token,
+                "errorPayload");
+    }
+
+    @Override
+    protected HttpClient attachRequestLogger(HttpClient httpClient) {
+        return super.attachRequestLogger(httpClient)
+                .doAfterRequest((response, connection) -> token.activate());
+    }
+}