BlockingHttpServer.java

/*
 * Copyright 2017 the original author or authors.
 *
 * Licensed 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.gradle.test.fixtures.server.http;

import com.sun.net.httpserver.HttpServer;
import org.junit.rules.ExternalResource;

import java.io.File;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * An HTTP server that allows a test to synchronize and make assertions about concurrent activities that happen in another process.
 * For example, can be used to that certain tasks do or do not execute in parallel.
 */
public class BlockingHttpServer extends ExternalResource {
    private static final AtomicInteger COUNTER = new AtomicInteger();
    private static final ExecutorService EXECUTOR_SERVICE = Executors.newCachedThreadPool();
    private final Lock lock = new ReentrantLock();
    private final HttpServer server;
    private final ChainingHttpHandler handler;
    private final int timeoutMs;
    private final int serverId;
    private boolean running;

    public BlockingHttpServer() throws IOException {
        this(30000);
    }

    public BlockingHttpServer(int timeoutMs) throws IOException {
        // Use an OS selected port
        server = HttpServer.create(new InetSocketAddress(0), 10);
        server.setExecutor(EXECUTOR_SERVICE);
        serverId = COUNTER.incrementAndGet();
        handler = new ChainingHttpHandler(lock, COUNTER);
        server.createContext("/", handler);
        this.timeoutMs = timeoutMs;
    }

    /**
     * Returns the URI for this server.
     */
    public URI getUri() {
        try {
            return new URI("http://localhost:" + getPort());
        } catch (URISyntaxException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Returns the URI for the given call.
     */
    public URI uri(String call) {
        try {
            return new URI("http", null, "localhost", getPort(), "/" + call, null, null);
        } catch (URISyntaxException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Returns Java statements that invoke the given call.
     */
    public String callFromBuild(String call) {
        URI uri = uri(call);
        return "System.out.println(\"calling " + uri + "\"); try { new java.net.URL(\"" + uri + "\").openConnection().getContentLength(); } catch(Exception e) { throw new RuntimeException(e); }; System.out.println(\"response received\");";
    }

    /**
     * Returns a Java statements that invokes a call, using the given expression to calculate the call to make.
     */
    public String callFromBuildUsingExpression(String expression) {
        String uriExpression = "\"" + getUri() + "/\" + " + expression;
        return "System.out.println(\"calling \" + " + uriExpression + "); try { new java.net.URL(" + uriExpression + ").openConnection().getContentLength(); } catch(Exception e) { throw new RuntimeException(e); }; System.out.println(\"response received\");";
    }

    /**
     * Expects the given requests to be made concurrently. Blocks each request until they have all been received then releases them all.
     */
    public void expectConcurrentExecution(String expectedCall, String... additionalExpectedCalls) {
        List<ResourceHandler> resourceHandlers = new ArrayList<ResourceHandler>();
        resourceHandlers.add(new SimpleResourceHandler(expectedCall));
        for (String call : additionalExpectedCalls) {
            resourceHandlers.add(new SimpleResourceHandler(call));
        }
        handler.addHandler(new CyclicBarrierRequestHandler(lock, timeoutMs, resourceHandlers));
    }

    /**
     * Expects the given requests to be made concurrently. Blocks each request until they have all been received then releases them all.
     */
    public void expectConcurrentExecution(Collection<String> expectedCalls) {
        List<ResourceHandler> resourceHandlers = new ArrayList<ResourceHandler>();
        for (String call : expectedCalls) {
            resourceHandlers.add(new SimpleResourceHandler(call));
        }
        handler.addHandler(new CyclicBarrierRequestHandler(lock, timeoutMs, resourceHandlers));
    }

    /**
     * Expects the given requests to be made concurrently. Blocks each request until they have all been received then releases them all.
     */
    public void expectConcurrentExecutionTo(Collection<? extends Resource> expectedCalls) {
        List<ResourceHandler> resourceHandlers = new ArrayList<ResourceHandler>();
        for (Resource call : expectedCalls) {
            resourceHandlers.add((ResourceHandler) call);
        }
        handler.addHandler(new CyclicBarrierRequestHandler(lock, timeoutMs, resourceHandlers));
    }

    /**
     * Expect a GET request to the given path, and return the contents of the given file.
     */
    public Resource file(String path, File file) {
        return new FileResourceHandler(path, file);
    }

    /**
     * Expect a GET request to the given path, and return some arbitrary content.
     */
    public Resource resource(String path) {
        return new SimpleResourceHandler(path);
    }

    /**
     * Expect a GET request to the given path, and return the given content (UTF-8 encoded)
     */
    public Resource resource(String path, String content) {
        return new SimpleResourceHandler(path, content);
    }

    /**
     * Expects exactly the given number of calls to be made concurrently from any combination of the expected calls. Blocks each call until they are explicitly released.
     * Is not considered "complete" until all expected calls have been received.
     */
    public BlockingHandler blockOnConcurrentExecutionAnyOf(int concurrent, String... expectedCalls) {
        List<ResourceHandler> resourceHandlers = new ArrayList<ResourceHandler>();
        for (String call : expectedCalls) {
            resourceHandlers.add(new SimpleResourceHandler(call));
        }
        CyclicBarrierAnyOfRequestHandler requestHandler = new CyclicBarrierAnyOfRequestHandler(lock, serverId, timeoutMs, concurrent, resourceHandlers);
        handler.addHandler(requestHandler);
        return requestHandler;
    }

    /**
     * Expects exactly the given number of calls to be made concurrently from any combination of the expected calls. Blocks each call until they are explicitly released.
     * Is not considered "complete" until all expected calls have been received.
     */
    public BlockingHandler blockOnConcurrentExecutionAnyOfToResources(int concurrent, Collection<? extends Resource> expectedCalls) {
        List<ResourceHandler> resourceHandlers = new ArrayList<ResourceHandler>();
        for (Resource call : expectedCalls) {
            resourceHandlers.add((ResourceHandler) call);
        }
        CyclicBarrierAnyOfRequestHandler requestHandler = new CyclicBarrierAnyOfRequestHandler(lock, serverId, timeoutMs, concurrent, resourceHandlers);
        handler.addHandler(requestHandler);
        return requestHandler;
    }

    /**
     * Expects the given request to be made.
     */
    public void expectSerialExecution(String expectedCall) {
        handler.addHandler(new CyclicBarrierRequestHandler(lock, timeoutMs, Collections.singleton(new SimpleResourceHandler(expectedCall))));
    }

    /**
     * Expects the given request to be made.
     */
    public void expectSerialExecution(Resource expectedCall) {
        handler.addHandler(new CyclicBarrierRequestHandler(lock, timeoutMs, Collections.singleton((ResourceHandler) expectedCall)));
    }

    public void start() {
        server.start();
        running = true;
    }

    public void stop() {
        handler.assertComplete();
        running = false;
        // Stop is very slow, clean it up later
        EXECUTOR_SERVICE.execute(new Runnable() {
            @Override
            public void run() {
                server.stop(10);
            }
        });
    }

    /**
     * For testing this fixture only.
     */
    void waitForRequests(int requestCount) {
        handler.waitForRequests(requestCount);
    }

    @Override
    protected void after() {
        stop();
    }

    private int getPort() {
        if (!running) {
            throw new IllegalStateException("Cannot get HTTP port as server is not running.");
        }
        return server.getAddress().getPort();
    }

    /**
     * Represents some HTTP resource.
     */
    public interface Resource {
    }

    /**
     * Allows the test to synchronise with and unblock requests.
     */
    public interface BlockingHandler {
        /**
         * Releases the given number of blocked requests. Fails when fewer than the given number of requests are waiting to be released.
         */
        void release(int count);

        /**
         * Releases the given request. Fails when the given request is not waiting to be released.
         */
        void release(String path);

        /**
         * Releases all requests. Fails when there are requests yet to be received.
         */
        void releaseAll();

        /**
         * Waits for the expected number of concurrent requests to be received.
         */
        void waitForAllPendingCalls();
    }

}