差異處

這裏顯示兩個版本的差異處。

--- java:apache_camel:throttler:helloworld [2019/03/17 20:38]
tony 建立
+++ java:apache_camel:throttler:helloworld [2023/06/25 09:48]
@@ 行 1: / 行 1: @@
-{{tag>camel}}
-====== Camel - Throttler Hello World ======
-===== Introduction =====
-在設計web應用程式時，有時會需要一個節流器，去幫我控制單位時間內能處理的請求數量，以避免過載；又或者是要根據不同使用者所買的授權，去控制單位時間內能呼叫的API次數等。Camel提供了Throttler，讓我們能輕鬆透過設定，去達到這些效果。我將透過HTTP GET請求/events/{id}做為範例，說明如何使用Throttler。首先介紹這個範例中的兩個RouteBuilder。
-===== RestRouteBuilder =====
-REST核心設定集中在這個builder中，它負責宣告用什麼port與component去建立REST服務:
-<code java>
-package org.tonylin.practice.camel.rest;
-import org.apache.camel.builder.RouteBuilder;
-import org.apache.camel.model.rest.RestBindingMode;
-public class RestRouteBuilder extends RouteBuilder {
-	@Override
-	public void configure() throws Exception {
-		restConfiguration().component("netty4-http").port(8080).bindingMode(RestBindingMode.auto).endpointProperty("ssl",  "false");
-	}
-}
-</code>
-(我以http當範例，如果對https用法有興趣，可以參考[[java:apache_camel:rest_with_netty_http_and_ssl|這篇]])
-===== ThrottlerRouteBuilder =====
-接下來是今天的主角，我先列出程式碼內容，後面再針對重點configure做說明:
-<code java>
-package org.tonylin.practice.camel.throttler;
-import static com.google.common.base.Preconditions.checkState;
-import org.apache.camel.Exchange;
-import org.apache.camel.Processor;
-import org.apache.camel.builder.RouteBuilder;
-import org.apache.camel.processor.ThrottlerRejectedExecutionException;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-public class ThrottlerRouteBuilder extends RouteBuilder {
-	private static Logger logger = LoggerFactory.getLogger(ThrottlerRouteBuilder.class);
-	private final static String GET_EVENTS = "GET_EVENTS";
-	private Object eventHandler;
-	private int limit = 2;
-	private int period = 200;
-	public ThrottlerRouteBuilder(Object eventHandler) {
-		this.eventHandler = eventHandler;
-	}
-	public void setLimit(int limit) {
-		this.limit = limit;
-	}
-	public void setPeriod(int period) {
-		this.period = period;
-	}
-	@Override
-	public void configure() throws Exception {
-		checkState(eventHandler!=null, "Can't find eventHandler");
-		onException(ThrottlerRejectedExecutionException.class)
-		.process(new Processor() {
-			@Override
-			public void process(Exchange exchange) throws Exception {
-				logger.debug("handle ThrottlerRejectedExecutionException");
-				exchange.getOut().setHeader(Exchange.HTTP_RESPONSE_CODE, "503");
-			}
-		})
-		.handled(true);
-		rest("/events/{id}").get().route().id(GET_EVENTS)
-		.throttle(limit)
-		.timePeriodMillis(period)
-		.rejectExecution(true)
-		.bean(eventHandler).endRest();
-	}
-}
-</code>
-我首要說明的是throttler的configure:
-<code java>
-rest("/events/{id}").get().route().id(GET_EVENTS)
-	.throttle(limit)
-	.timePeriodMillis(period)
-	.rejectExecution(true)
-	.bean(eventHandler).endRest();
-</code>
-除了HTTP GET的宣告外，這些程式碼代表著以下意義:
-  * throttle(limit): 限制的存取次數。
-  * timePeriodMillis(period): 限制存取次數的單位時間，預設是1000ms。
-  * rejectExecution(true): 當超過此限制時，是否要reject請求，預設為false。假如沒reject，後續超過限制的請求會block至單位時間後執行。
-  * bean(eventHandler): 請求的處理者。
-在我設定rejectExecution為true後，我發現camel會拋出ThrottlerRejectedExecutionException，且client會block住；因此這個設定必須與camel的errorHandler一同使用，這是我的使用範例:
-<code java>
-onException(ThrottlerRejectedExecutionException.class)
-	.process(new Processor() {
-		@Override
-		public void process(Exchange exchange) throws Exception {
-			logger.debug("handle ThrottlerRejectedExecutionException");
-			exchange.getOut().setHeader(Exchange.HTTP_RESPONSE_CODE, "503");
-		}
-	})
-.handled(true);
-</code>
-我宣告當發生ThrottlerRejectedExecutionException例外時，會將回應給client的response code設為503以代表server過載。除此之外，別忘記把handled設為true，代表例外已被處理。
-===== Unit Test =====
-最後我以單元測試來展示效果，包含testOverload與testThrottlePeriod兩個測試；而throttler的limit為2，period為200ms，testcase會在後面做說明:
-<code java>
-package org.tonylin.practice.camel.throttler;
-import java.util.ArrayList;
-import java.util.List;
-import org.apache.camel.RoutesBuilder;
-import org.apache.camel.test.junit4.CamelTestSupport;
-import org.apache.http.HttpResponse;
-import org.apache.http.client.HttpClient;
-import org.apache.http.client.methods.HttpGet;
-import org.apache.http.impl.client.HttpClientBuilder;
-import org.junit.Test;
-import org.tonylin.practice.camel.rest.RestHandler;
-import org.tonylin.practice.camel.rest.RestRouteBuilder;
-public class ThrottlerRouteBuilderTest extends CamelTestSupport {
-	private RestHandler hander = new RestHandler();
-	private static final int limit = 2;
-	private static final int period = 200;
-	private HttpClient client = HttpClientBuilder.create().build();
-	private HttpGet httpGet = new HttpGet("http://localhost:8080/events/123");
-	@Override
-	protected RoutesBuilder[] createRouteBuilders() throws Exception {
-		ThrottlerRouteBuilder throttlerRouteBuilder = new ThrottlerRouteBuilder(hander);
-		throttlerRouteBuilder.setLimit(limit);
-		throttlerRouteBuilder.setPeriod(period);
-		return new RoutesBuilder[] {
-				new RestRouteBuilder(),
-				throttlerRouteBuilder
-		};
-	}
-	private List<HttpResponse> batchRequest(int times) throws Exception {
-		List<HttpResponse> responses = new ArrayList<HttpResponse>();
-		for( int i = 0 ; i < times ; i++ ) {
-			responses.add(client.execute(httpGet));
-		}
-		return responses;
-	}
-	@Test
-	public void testOverload() throws Exception {
-		// skip
-	}
-	@Test
-	public void testThrottlePeriod() throws Exception  {
-		// skip
-	}
-}
-</code>
-測試中使用的RestHandler，負責收集請求的event id，用以確認請求內容是否正確:
-<code java>
-public class RestHandler {
-	private static Logger logger = LoggerFactory.getLogger(RestHandler.class);
-	private List<String> requestIds = new ArrayList<String>();
-	@Handler
-	public void handle(Exchange exchange) {
-		String requestId = exchange.getIn().getHeader("id", String.class);
-		logger.debug("Request id: {}", requestId);
-		requestIds.add(requestId);
-	}
-	public List<String> getRequestIds(){
-		return requestIds;
-	}
-}
-</code>
-針對testOverload測試，是用來確認throttler單位時間內的請求是否有效；因此測試中，連續做了3次請求，最後會去確認這三次的請求結果是否正確:
-<code java>
-@Test
-public void testOverload() throws Exception {
-	// when request 3 times
-	List<HttpResponse> responses = batchRequest(3);
-	// then
-	assertEquals(2, hander.getRequestIds().size());
-	assertEquals(200, responses.get(0).getStatusLine().getStatusCode());
-	assertEquals(200, responses.get(1).getStatusLine().getStatusCode());
-	assertEquals(503, responses.get(2).getStatusLine().getStatusCode());
-}
-</code>
-而testThrottlePeriod測試，用以確認throttler單位時間是否有作用；因此測試中，會先發3次請求，再等待此單位時間後，再發3次請求。最後確認請求結果:
-<code java>
-@Test
-public void testThrottlePeriod() throws Exception  {
-	// when
-	List<HttpResponse> responses = batchRequest(3);
-	Thread.sleep(period+1);
-	responses.addAll(batchRequest(3));
-	// then
-	assertEquals(2, hander.getRequestIds().size());
-	assertEquals(200, responses.get(0).getStatusLine().getStatusCode());
-	assertEquals(200, responses.get(1).getStatusLine().getStatusCode());
-	assertEquals(503, responses.get(2).getStatusLine().getStatusCode());
-	assertEquals(200, responses.get(3).getStatusLine().getStatusCode());
-	assertEquals(200, responses.get(4).getStatusLine().getStatusCode());
-	assertEquals(503, responses.get(5).getStatusLine().getStatusCode());
-}
-</code>
-透過這兩個測試範例，我們可以簡單地了解throttler的用法。
-===== Library Info =====
-以下是我在寫這篇文章時，所使用的libraries版本:
-<code>
-ext {
-	camelVersion='2.23.1'
-	nettyAllVersion='4.1.34.Final'
-	guavaVersion='27.1-jre'
-	log4jVersion='1.2.17'
-	slf4jVersion='1.7.26'
-	httpClientVersion='4.5.7'
-}
-dependencies {
-    compile group: 'org.apache.camel', name: 'camel-core', version: "$camelVersion"
-    compile group: 'org.apache.camel', name: 'camel-netty4-http', version: "$camelVersion"
-    compile group: 'org.apache.camel', name: 'camel-http-common', version: "$camelVersion"
-    compile group: 'org.apache.camel', name: 'camel-netty4', version: "$camelVersion"
-    compile group: 'io.netty', name: 'netty-all', version: "$nettyAllVersion"
-    compile group: 'com.google.guava', name: 'guava', version: "$guavaVersion"
-    compile group: 'log4j', name: 'log4j', version: "$log4jVersion"
-    compile group: 'org.slf4j', name: 'slf4j-api', version: "$slf4jVersion"
-    runtime group: 'org.slf4j', name: 'slf4j-log4j12', version: "$slf4jVersion"
-    testCompile group: 'org.apache.camel', name: 'camel-test', version: "$camelVersion"
-    testCompile group: 'org.apache.httpcomponents', name: 'httpclient', version: "$httpClientVersion"
-    testCompile 'junit:junit:4.12'
-}
-</code>
-===== Reference =====
-  * [[http://camel.apache.org/throttler.html|Camel - Throttler]]
-=====    =====
-----
-\\
-~~DISQUS~~