feat: add Microservices Bulkhead pattern (#3228) (#3597)

* feat: add Microservices Bulkhead pattern (#3228)

* fix: cancel queued calls on bulkhead shutdown

Shutdown now cancels the queued futures so callers do not hang, a shutdown racing a submit is no longer counted as a rejection, and interrupted inventory checks are logged. The class diagram is a rendered PNG.

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Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>

microservices-bulkhead/src/main/java/com/iluwatar/bulkhead/RemoteService.java

@@ -0,0 +1,42 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bulkhead;
+
+/**
+ * A remote dependency that a service calls over the network, such as a payment provider or an
+ * inventory system. Every call is routed through a {@link Bulkhead} so that the caller never lets
+ * one dependency monopolise its threads.
+ */
+@FunctionalInterface
+public interface RemoteService {
+
+  /**
+   * Performs the remote call.
+   *
+   * @param request identifier of the request, used in the response and in the logs
+   * @return the response of the dependency
+   */
+  String call(String request);
+}