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* 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. --------- Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>
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@@ -0,0 +1,134 @@
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/*
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* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
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*
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* The MIT License
|
||||
* Copyright © 2014-2022 Ilkka Seppälä
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*
|
||||
* 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
|
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.bulkhead;
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import java.time.Duration;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.concurrent.ExecutionException;
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import java.util.concurrent.Future;
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import java.util.concurrent.TimeUnit;
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import java.util.concurrent.TimeoutException;
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import lombok.extern.slf4j.Slf4j;
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/**
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* The Bulkhead pattern partitions the resources of a service so that a failure or an overload in
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* one dependency cannot sink the whole service, just like the watertight compartments in a ship's
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* hull keep a single leak from flooding the entire vessel.
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*
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* <p>In this example an order service calls two downstream dependencies: a payment provider that
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* has become very slow and an inventory system that is perfectly healthy. The demo first sends both
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* kinds of calls through one shared thread pool. The slow payment calls fill every thread and the
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* queue, so a request for the healthy inventory system is rejected although nothing is wrong with
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* it. The demo then gives each dependency its own {@link Bulkhead}. The payment compartment still
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* saturates and rejects the excess calls fast, but the inventory compartment keeps answering
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* immediately because the payment calls can no longer consume its threads.
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*/
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@Slf4j
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public class App {
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private static final Duration PAYMENT_LATENCY = Duration.ofMillis(300);
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private static final Duration WAIT_TIMEOUT = Duration.ofSeconds(5);
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/**
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* Program entry point.
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*
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* @param args command line arguments, not used
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*/
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public static void main(String[] args) {
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var payment = new PaymentService(PAYMENT_LATENCY);
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var inventory = new InventoryService();
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LOGGER.info("--- Scenario 1: one shared thread pool for every downstream call ---");
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try (var sharedPool = new Bulkhead("shared-pool", 2, 2)) {
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var paymentFutures = flood(sharedPool, payment, "order", 4);
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callInventory(sharedPool, inventory, "order-5");
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awaitAll(paymentFutures);
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}
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LOGGER.info("--- Scenario 2: a dedicated bulkhead for each downstream dependency ---");
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try (var paymentBulkhead = new Bulkhead("payment", 2, 2);
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var inventoryBulkhead = new Bulkhead("inventory", 2, 2)) {
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var paymentFutures = flood(paymentBulkhead, payment, "order", 10);
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for (var i = 1; i <= 3; i++) {
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callInventory(inventoryBulkhead, inventory, "order-" + i);
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}
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awaitAll(paymentFutures);
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LOGGER.info(
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"Bulkhead '{}' rejected {} of 10 calls, bulkhead '{}' rejected {} of 3 calls",
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paymentBulkhead.getName(),
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paymentBulkhead.getRejectedCalls(),
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inventoryBulkhead.getName(),
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inventoryBulkhead.getRejectedCalls());
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}
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}
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static List<Future<String>> flood(
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Bulkhead bulkhead, RemoteService service, String requestPrefix, int calls) {
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var accepted = new ArrayList<Future<String>>();
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for (var i = 1; i <= calls; i++) {
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var request = requestPrefix + "-" + i;
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try {
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accepted.add(bulkhead.submit(() -> service.call(request)));
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} catch (BulkheadFullException e) {
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LOGGER.info("Request '{}' rejected immediately: {}", request, e.getMessage());
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}
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}
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return accepted;
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}
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static void callInventory(Bulkhead bulkhead, RemoteService inventory, String request) {
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try {
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var response = bulkhead.submit(() -> inventory.call(request));
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LOGGER.info(
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"Inventory response: {}", response.get(WAIT_TIMEOUT.toMillis(), TimeUnit.MILLISECONDS));
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} catch (BulkheadFullException e) {
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LOGGER.error(
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"Inventory check for '{}' rejected although the inventory system is healthy: {}",
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request,
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e.getMessage());
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} catch (ExecutionException | TimeoutException e) {
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LOGGER.error("Inventory check for '{}' failed", request, e);
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} catch (InterruptedException e) {
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Thread.currentThread().interrupt();
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LOGGER.warn(
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"Inventory check for '{}' was interrupted while waiting for the response", request);
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}
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}
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static void awaitAll(List<Future<String>> futures) {
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for (var future : futures) {
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try {
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LOGGER.info(
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"Payment response: {}", future.get(WAIT_TIMEOUT.toMillis(), TimeUnit.MILLISECONDS));
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} catch (ExecutionException | TimeoutException e) {
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LOGGER.error("Payment call failed", e);
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} catch (InterruptedException e) {
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Thread.currentThread().interrupt();
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return;
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}
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}
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}
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}
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@@ -0,0 +1,157 @@
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/*
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* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
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*
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* The MIT License
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* Copyright © 2014-2022 Ilkka Seppälä
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*
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* 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,
|
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
|
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* THE SOFTWARE.
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*/
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package com.iluwatar.bulkhead;
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import java.util.concurrent.ArrayBlockingQueue;
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import java.util.concurrent.BlockingQueue;
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import java.util.concurrent.Callable;
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import java.util.concurrent.Future;
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import java.util.concurrent.RejectedExecutionException;
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import java.util.concurrent.SynchronousQueue;
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import java.util.concurrent.ThreadPoolExecutor;
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import java.util.concurrent.TimeUnit;
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import java.util.concurrent.atomic.AtomicInteger;
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import java.util.concurrent.atomic.AtomicLong;
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import lombok.Getter;
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import lombok.extern.slf4j.Slf4j;
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/**
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* Isolates the calls made to one downstream dependency inside a dedicated, bounded thread pool.
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*
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* <p>The pool has a fixed number of worker threads and a bounded waiting queue. When both are full
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* the bulkhead does not block the caller and it cannot borrow threads from anywhere else: the call
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* fails fast with a {@link BulkheadFullException}. Each dependency gets its own instance, so a slow
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* or hanging dependency can only exhaust its own compartment while the rest of the system keeps
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* serving requests.
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*/
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@Slf4j
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public class Bulkhead implements AutoCloseable {
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@Getter private final String name;
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@Getter private final int maxConcurrentCalls;
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@Getter private final int maxQueueSize;
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private final ThreadPoolExecutor executor;
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private final AtomicLong rejectedCalls = new AtomicLong();
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/**
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* Creates a bulkhead with its own thread pool.
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*
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* @param name name of the compartment, used in logs and worker thread names
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* @param maxConcurrentCalls number of calls that may run at the same time
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* @param maxQueueSize number of calls that may wait for a free thread; zero disables queueing
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*/
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public Bulkhead(String name, int maxConcurrentCalls, int maxQueueSize) {
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if (maxConcurrentCalls < 1) {
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throw new IllegalArgumentException("maxConcurrentCalls must be at least 1");
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}
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if (maxQueueSize < 0) {
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throw new IllegalArgumentException("maxQueueSize must not be negative");
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}
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this.name = name;
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this.maxConcurrentCalls = maxConcurrentCalls;
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this.maxQueueSize = maxQueueSize;
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BlockingQueue<Runnable> queue =
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maxQueueSize == 0 ? new SynchronousQueue<>() : new ArrayBlockingQueue<>(maxQueueSize);
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var threadCounter = new AtomicInteger();
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this.executor =
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new ThreadPoolExecutor(
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maxConcurrentCalls,
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maxConcurrentCalls,
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0L,
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TimeUnit.MILLISECONDS,
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queue,
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runnable ->
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new Thread(runnable, "bulkhead-" + name + "-" + threadCounter.incrementAndGet()),
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new ThreadPoolExecutor.AbortPolicy());
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}
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/**
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* Submits a call to this compartment.
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*
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* @param task the call to execute
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* @param <T> type of the result
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* @return a future that completes with the result of the call
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* @throws BulkheadFullException if every thread is busy and the queue is full
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* @throws IllegalStateException if the bulkhead has been shut down
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*/
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public <T> Future<T> submit(Callable<T> task) {
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if (executor.isShutdown()) {
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throw new IllegalStateException("Bulkhead '" + name + "' is shut down");
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}
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try {
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var future = executor.submit(task);
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LOGGER.debug(
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"Bulkhead '{}' accepted call ({} active, {} queued)",
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name,
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executor.getActiveCount(),
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executor.getQueue().size());
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return future;
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} catch (RejectedExecutionException e) {
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if (executor.isShutdown()) {
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throw new IllegalStateException("Bulkhead '" + name + "' is shut down");
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}
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rejectedCalls.incrementAndGet();
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LOGGER.warn(
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"Bulkhead '{}' is full ({} active, {} queued), rejecting call",
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name,
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executor.getActiveCount(),
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executor.getQueue().size());
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throw new BulkheadFullException(name);
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}
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}
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/** Number of calls currently running. */
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public int getActiveCalls() {
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return executor.getActiveCount();
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}
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/** Number of calls waiting for a free thread. */
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public int getQueuedCalls() {
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return executor.getQueue().size();
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}
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/** Number of calls rejected since the bulkhead was created. */
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public long getRejectedCalls() {
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return rejectedCalls.get();
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}
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/**
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* Stops the compartment, interrupting calls that are still running and cancelling the calls that
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* were still waiting in the queue, so that callers blocked on their future are released instead
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* of waiting for a result that will never be produced.
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*/
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public void shutdown() {
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for (var pending : executor.shutdownNow()) {
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if (pending instanceof Future<?> future) {
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future.cancel(false);
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}
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}
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}
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@Override
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public void close() {
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shutdown();
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}
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}
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@@ -0,0 +1,46 @@
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/*
|
||||
* 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.
|
||||
*/
|
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package com.iluwatar.bulkhead;
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/**
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* Thrown by a {@link Bulkhead} when a call cannot be accepted because every worker thread is busy
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* and the waiting queue is full. The caller receives this exception immediately instead of
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* blocking, which is the fail-fast behaviour the pattern relies on: the caller can degrade
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* gracefully while the overloaded dependency keeps consuming only the capacity reserved for it.
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*/
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public class BulkheadFullException extends RuntimeException {
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private final String bulkheadName;
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public BulkheadFullException(String bulkheadName) {
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super("Bulkhead '" + bulkheadName + "' is full, call rejected");
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this.bulkheadName = bulkheadName;
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}
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/** Name of the bulkhead that rejected the call. */
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public String getBulkheadName() {
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return bulkheadName;
|
||||
}
|
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}
|
||||
@@ -0,0 +1,41 @@
|
||||
/*
|
||||
* 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;
|
||||
|
||||
import lombok.extern.slf4j.Slf4j;
|
||||
|
||||
/**
|
||||
* Simulates a healthy inventory system that answers immediately. It represents the dependency that
|
||||
* should keep working even while another dependency is overloaded.
|
||||
*/
|
||||
@Slf4j
|
||||
public class InventoryService implements RemoteService {
|
||||
|
||||
@Override
|
||||
public String call(String request) {
|
||||
LOGGER.info("Inventory system received '{}'", request);
|
||||
return "Inventory reserved for " + request;
|
||||
}
|
||||
}
|
||||
@@ -0,0 +1,60 @@
|
||||
/*
|
||||
* 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;
|
||||
|
||||
import java.time.Duration;
|
||||
import lombok.extern.slf4j.Slf4j;
|
||||
|
||||
/**
|
||||
* Simulates a payment provider that has become slow. Every call takes the configured latency, so a
|
||||
* burst of payment requests keeps the threads that serve it busy for a long time. Without a
|
||||
* bulkhead these calls would also occupy the threads needed by healthy dependencies.
|
||||
*/
|
||||
@Slf4j
|
||||
public class PaymentService implements RemoteService {
|
||||
|
||||
private final Duration latency;
|
||||
|
||||
/**
|
||||
* Creates a payment service.
|
||||
*
|
||||
* @param latency time every call takes to complete
|
||||
*/
|
||||
public PaymentService(Duration latency) {
|
||||
this.latency = latency;
|
||||
}
|
||||
|
||||
@Override
|
||||
public String call(String request) {
|
||||
LOGGER.info("Payment provider received '{}', it will take {} ms", request, latency.toMillis());
|
||||
try {
|
||||
Thread.sleep(latency);
|
||||
} catch (InterruptedException e) {
|
||||
Thread.currentThread().interrupt();
|
||||
throw new IllegalStateException("Payment for '" + request + "' was interrupted", e);
|
||||
}
|
||||
return "Payment approved for " + request;
|
||||
}
|
||||
}
|
||||
@@ -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);
|
||||
}
|
||||
Reference in new issue
Block a user