atris commented on a change in pull request #1686: URL: https://github.com/apache/lucene-solr/pull/1686#discussion_r460693175
########## File path: solr/core/src/java/org/apache/solr/servlet/RequestRateLimiter.java ########## @@ -0,0 +1,199 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You 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.apache.solr.servlet; + +import javax.servlet.AsyncContext; +import javax.servlet.AsyncEvent; +import javax.servlet.AsyncListener; +import javax.servlet.FilterConfig; +import javax.servlet.http.HttpServletRequest; +import javax.servlet.http.HttpServletResponse; +import java.io.IOException; +import java.lang.invoke.MethodHandles; +import java.util.Queue; +import java.util.concurrent.ConcurrentLinkedQueue; +import java.util.concurrent.Semaphore; +import java.util.concurrent.TimeUnit; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * Handles rate limiting for a specific request type. + * + * The control flow is as follows: + * Handle request -- Check if slot is available -- If available, acquire slot and proceed -- + * else asynchronously queue the request. + * + * When an active request completes, a check is performed to see if there are any pending requests. + * If there is an available pending request, process the same. + */ +public class RequestRateLimiter { + private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass()); + + private Semaphore allowedConcurrentRequests; + private RateLimiterConfig rateLimiterConfig; + private Queue<AsyncContext> waitQueue; + private Queue<AsyncListener> listenerQueue; + + public RequestRateLimiter(RateLimiterConfig rateLimiterConfig) { + this.rateLimiterConfig = rateLimiterConfig; + this.allowedConcurrentRequests = new Semaphore(rateLimiterConfig.allowedRequests); + this.waitQueue = new ConcurrentLinkedQueue<>(); + this.listenerQueue = new ConcurrentLinkedQueue<>(); + } + + public boolean handleRequest(HttpServletRequest request) throws InterruptedException { + + if (!rateLimiterConfig.isEnabled) { + return true; + } + + boolean accepted = allowedConcurrentRequests.tryAcquire(rateLimiterConfig.waitForSlotAcquisition, TimeUnit.MILLISECONDS); + + if (!accepted) { + AsyncContext asyncContext = request.startAsync(); Review comment: I dont think so -- an async request should just return its current context here. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org For additional commands, e-mail: issues-h...@lucene.apache.org
