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David Medina Orozco
d45dcb1a63
* Translate Iterator pattern to Spanish * Translate to Spanish: Servant pattern Sharding pattern Spatial-partition pattern Special-case pattern specification pattern State pattern Strategy pattern Subclass-case pattern * Update language to es * Fixing Missing translation * Translate to Spanish: template method pattern throttling pattern trampoline pattern transaction-script pattern type object pattern Update method pattern visitor pattern * Fixing Missing translation
219 lines
8.9 KiB
Markdown
219 lines
8.9 KiB
Markdown
---
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title: Throttling
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category: Behavioral
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language: es
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tag:
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- Performance
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- Cloud distributed
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---
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## Propósito
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Garantizar que un cliente determinado no pueda acceder a los recursos del servicio más allá del límite asignado.
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## Explicación
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Ejemplo del mundo real
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> Un joven humano y un viejo enano entran en un bar. Empiezan a pedir cervezas al camarero.
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> El camarero se da cuenta inmediatamente de que el joven humano no debe consumir demasiadas bebidas demasiado rápido
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> y se niega a servir si no ha pasado suficiente tiempo. Para el viejo enano, el ritmo de servicio puede ser mayor.
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> ser mayor.
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En palabras sencillas
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> El patrón de Throttling se utiliza para limitar la velocidad de acceso a un recurso.
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[Microsoft documentation](https://docs.microsoft.com/en-us/azure/architecture/patterns/throttling) dice
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> Controlar el consumo de recursos utilizados por una instancia de una aplicación, un tenant individual,
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> o un servicio completo. Esto puede permitir que el sistema continúe funcionando y cumpla con los acuerdos de nivel de servicio, incluso cuando un aumento de la demanda impone una carga extrema sobre los recursos.
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**Ejemplo programático**
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La clase `BarCustomer` presenta los clientes de la API `Bartender`. La clase `CallsCount` registra el número de
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llamadas por `BarCustomer`.
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```java
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public class BarCustomer {
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@Getter
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private final String name;
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@Getter
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private final int allowedCallsPerSecond;
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public BarCustomer(String name, int allowedCallsPerSecond, CallsCount callsCount) {
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if (allowedCallsPerSecond < 0) {
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throw new InvalidParameterException("Number of calls less than 0 not allowed");
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}
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this.name = name;
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this.allowedCallsPerSecond = allowedCallsPerSecond;
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callsCount.addTenant(name);
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}
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}
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@Slf4j
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public final class CallsCount {
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private final Map<String, AtomicLong> tenantCallsCount = new ConcurrentHashMap<>();
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public void addTenant(String tenantName) {
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tenantCallsCount.putIfAbsent(tenantName, new AtomicLong(0));
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}
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public void incrementCount(String tenantName) {
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tenantCallsCount.get(tenantName).incrementAndGet();
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}
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public long getCount(String tenantName) {
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return tenantCallsCount.get(tenantName).get();
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}
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public void reset() {
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tenantCallsCount.replaceAll((k, v) -> new AtomicLong(0));
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LOGGER.info("reset counters");
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}
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}
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```
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A continuación, se introduce el servicio al que llaman los inquilinos. Para realizar un seguimiento del número de llamadas, se utiliza un temporizador de estrangulamiento.
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```java
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public interface Throttler {
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void start();
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}
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public class ThrottleTimerImpl implements Throttler {
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private final int throttlePeriod;
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private final CallsCount callsCount;
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public ThrottleTimerImpl(int throttlePeriod, CallsCount callsCount) {
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this.throttlePeriod = throttlePeriod;
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this.callsCount = callsCount;
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}
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@Override
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public void start() {
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new Timer(true).schedule(new TimerTask() {
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@Override
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public void run() {
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callsCount.reset();
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}
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}, 0, throttlePeriod);
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}
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}
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```
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El `Bartender` ofrece el servicio `orderDrink` a los `BarCustomer`s. Los clientes probablemente no
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saben que la tasa de servicio de cerveza está limitada por su apariencia.
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```java
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class Bartender {
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private static final Logger LOGGER = LoggerFactory.getLogger(Bartender.class);
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private final CallsCount callsCount;
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public Bartender(Throttler timer, CallsCount callsCount) {
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this.callsCount = callsCount;
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timer.start();
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}
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public int orderDrink(BarCustomer barCustomer) {
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var tenantName = barCustomer.getName();
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var count = callsCount.getCount(tenantName);
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if (count >= barCustomer.getAllowedCallsPerSecond()) {
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LOGGER.error("I'm sorry {}, you've had enough for today!", tenantName);
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return -1;
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}
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callsCount.incrementCount(tenantName);
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LOGGER.debug("Serving beer to {} : [{} consumed] ", barCustomer.getName(), count+1);
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return getRandomCustomerId();
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}
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private int getRandomCustomerId() {
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return ThreadLocalRandom.current().nextInt(1, 10000);
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}
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}
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```
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Ahora es posible ver el ejemplo completo en acción. BarCustomer` el joven humano está limitado a 2
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llamadas por segundo y el viejo enano a 4.
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```java
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public static void main(String[] args) {
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var callsCount = new CallsCount();
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var human = new BarCustomer("young human", 2, callsCount);
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var dwarf = new BarCustomer("dwarf soldier", 4, callsCount);
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var executorService = Executors.newFixedThreadPool(2);
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executorService.execute(() -> makeServiceCalls(human, callsCount));
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executorService.execute(() -> makeServiceCalls(dwarf, callsCount));
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executorService.shutdown();
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try {
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executorService.awaitTermination(10, TimeUnit.SECONDS);
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} catch (InterruptedException e) {
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LOGGER.error("Executor service terminated: {}", e.getMessage());
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}
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}
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private static void makeServiceCalls(BarCustomer barCustomer, CallsCount callsCount) {
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var timer = new ThrottleTimerImpl(1000, callsCount);
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var service = new Bartender(timer, callsCount);
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// Sleep is introduced to keep the output in check and easy to view and analyze the results.
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IntStream.range(0, 50).forEach(i -> {
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service.orderDrink(barCustomer);
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try {
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Thread.sleep(100);
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} catch (InterruptedException e) {
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LOGGER.error("Thread interrupted: {}", e.getMessage());
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}
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});
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}
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```
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Un extracto de la salida de consola del ejemplo:
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```
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18:46:36.218 [Timer-0] INFO com.iluwatar.throttling.CallsCount - reset counters
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18:46:36.218 [Timer-1] INFO com.iluwatar.throttling.CallsCount - reset counters
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18:46:36.242 [pool-1-thread-2] DEBUG com.iluwatar.throttling.Bartender - Serving beer to dwarf soldier : [1 consumed]
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18:46:36.242 [pool-1-thread-1] DEBUG com.iluwatar.throttling.Bartender - Serving beer to young human : [1 consumed]
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18:46:36.342 [pool-1-thread-2] DEBUG com.iluwatar.throttling.Bartender - Serving beer to dwarf soldier : [2 consumed]
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18:46:36.342 [pool-1-thread-1] DEBUG com.iluwatar.throttling.Bartender - Serving beer to young human : [2 consumed]
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18:46:36.443 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
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18:46:36.443 [pool-1-thread-2] DEBUG com.iluwatar.throttling.Bartender - Serving beer to dwarf soldier : [3 consumed]
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18:46:36.544 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
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18:46:36.544 [pool-1-thread-2] DEBUG com.iluwatar.throttling.Bartender - Serving beer to dwarf soldier : [4 consumed]
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18:46:36.645 [pool-1-thread-2] ERROR com.iluwatar.throttling.Bartender - I'm sorry dwarf soldier, you've had enough for today!
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18:46:36.645 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
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18:46:36.745 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
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18:46:36.745 [pool-1-thread-2] ERROR com.iluwatar.throttling.Bartender - I'm sorry dwarf soldier, you've had enough for today!
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18:46:36.846 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
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18:46:36.846 [pool-1-thread-2] ERROR com.iluwatar.throttling.Bartender - I'm sorry dwarf soldier, you've had enough for today!
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18:46:36.947 [pool-1-thread-2] ERROR com.iluwatar.throttling.Bartender - I'm sorry dwarf soldier, you've had enough for today!
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18:46:36.947 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
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18:46:37.048 [pool-1-thread-2] ERROR com.iluwatar.throttling.Bartender - I'm sorry dwarf soldier, you've had enough for today!
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18:46:37.048 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
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18:46:37.148 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
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18:46:37.148 [pool-1-thread-2] ERROR com.iluwatar.throttling.Bartender - I'm sorry dwarf soldier, you've had enough for today!
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```
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## Diagrama de clases
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## Aplicabilidad
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El patrón Throttling debe utilizarse:
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* Cuando se necesita restringir el acceso al servicio para no tener un alto impacto en el rendimiento del mismo.
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* Cuando varios clientes consumen los mismos recursos del servicio y la restricción debe hacerse en función del uso por cliente.
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## Créditos
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* [Throttling pattern](https://docs.microsoft.com/en-us/azure/architecture/patterns/throttling)
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* [Cloud Design Patterns: Prescriptive Architecture Guidance for Cloud Applications (Microsoft patterns & practices)](https://www.amazon.com/gp/product/B00ITGHBBS/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=B00ITGHBBS&linkId=12aacdd0cec04f372e7152689525631a)
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