org.apache.hadoop.http.HttpServer3.java Source code

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/**
 * 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.hadoop.http;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.io.PrintStream;
import java.net.BindException;
import java.net.InetSocketAddress;
import java.net.URI;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;

import com.google.common.collect.ImmutableMap;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.HadoopIllegalArgumentException;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.ConfServlet;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.CommonConfigurationKeys;
import org.apache.hadoop.jmx.JMXJsonServlet;
import org.apache.hadoop.log.LogLevel;
import org.apache.hadoop.metrics.MetricsServlet;
import org.apache.hadoop.security.SecurityUtil;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.security.authentication.server.AuthenticationFilter;
import org.apache.hadoop.security.authorize.AccessControlList;
import org.apache.hadoop.util.ReflectionUtils;
import org.apache.hadoop.util.Shell;
import org.mortbay.io.Buffer;
import org.mortbay.jetty.Connector;
import org.mortbay.jetty.Handler;
import org.mortbay.jetty.MimeTypes;
import org.mortbay.jetty.RequestLog;
import org.mortbay.jetty.Server;
import org.mortbay.jetty.SessionManager;
import org.mortbay.jetty.handler.ContextHandler;
import org.mortbay.jetty.handler.ContextHandlerCollection;
import org.mortbay.jetty.handler.HandlerCollection;
import org.mortbay.jetty.handler.RequestLogHandler;
import org.mortbay.jetty.nio.SelectChannelConnector;
import org.mortbay.jetty.security.SslSocketConnector;
import org.mortbay.jetty.servlet.AbstractSessionManager;
import org.mortbay.jetty.servlet.Context;
import org.mortbay.jetty.servlet.DefaultServlet;
import org.mortbay.jetty.servlet.FilterHolder;
import org.mortbay.jetty.servlet.FilterMapping;
import org.mortbay.jetty.servlet.ServletHandler;
import org.mortbay.jetty.servlet.ServletHolder;
import org.mortbay.jetty.webapp.WebAppContext;
import org.mortbay.thread.QueuedThreadPool;
import org.mortbay.util.MultiException;

import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import com.sun.jersey.spi.container.servlet.ServletContainer;

/**
 * Create a Jetty embedded server to answer http requests. The primary goal is
 * to serve up status information for the server. There are three contexts:
 * "/logs/" -> points to the log directory "/static/" -> points to common static
 * files (src/webapps/static) "/" -> the jsp server code from
 * (src/webapps/<name>)
 * 
 * HOPS this class is an intermediary solution because HTTPServer and HTTPServer2 are up to date with 
 * Apache Hadoop 2.8 while HDFS is not an need an older version of these servers
 */
@InterfaceAudience.Private
@InterfaceStability.Evolving
public final class HttpServer3 implements FilterContainer {
    public static final Log LOG = LogFactory.getLog(HttpServer3.class);

    static final String FILTER_INITIALIZER_PROPERTY = "hadoop.http.filter.initializers";
    public static final String HTTP_MAX_THREADS = "hadoop.http.max.threads";

    // The ServletContext attribute where the daemon Configuration
    // gets stored.
    public static final String CONF_CONTEXT_ATTRIBUTE = "hadoop.conf";
    public static final String ADMINS_ACL = "admins.acl";
    public static final String SPNEGO_FILTER = "SpnegoFilter";
    public static final String NO_CACHE_FILTER = "NoCacheFilter";

    public static final String BIND_ADDRESS = "bind.address";

    private final AccessControlList adminsAcl;

    protected final Server webServer;

    private final List<Connector> listeners = Lists.newArrayList();

    protected final WebAppContext webAppContext;
    protected final boolean findPort;
    protected final Map<Context, Boolean> defaultContexts = new HashMap<>();
    protected final List<String> filterNames = new ArrayList<>();
    static final String STATE_DESCRIPTION_ALIVE = " - alive";
    static final String STATE_DESCRIPTION_NOT_LIVE = " - not live";

    /**
     * Class to construct instances of HTTP server with specific options.
     */
    public static class Builder {
        private ArrayList<URI> endpoints = Lists.newArrayList();
        private String name;
        private Configuration conf;
        private String[] pathSpecs;
        private AccessControlList adminsAcl;
        private boolean securityEnabled = false;
        private String usernameConfKey;
        private String keytabConfKey;
        private boolean needsClientAuth;
        private String trustStore;
        private String trustStorePassword;
        private String trustStoreType;

        private String keyStore;
        private String keyStorePassword;
        private String keyStoreType;

        // The -keypass option in keytool
        private String keyPassword;

        private boolean findPort;

        private String hostName;

        public Builder setName(String name) {
            this.name = name;
            return this;
        }

        /**
         * Add an endpoint that the HTTP server should listen to.
         *
         * @param endpoint
         *          the endpoint of that the HTTP server should listen to. The
         *          scheme specifies the protocol (i.e. HTTP / HTTPS), the host
         *          specifies the binding address, and the port specifies the
         *          listening port. Unspecified or zero port means that the server
         *          can listen to any port.
         */
        public Builder addEndpoint(URI endpoint) {
            endpoints.add(endpoint);
            return this;
        }

        /**
         * Set the hostname of the http server. The host name is used to resolve the
         * _HOST field in Kerberos principals. The hostname of the first listener
         * will be used if the name is unspecified.
         */
        public Builder hostName(String hostName) {
            this.hostName = hostName;
            return this;
        }

        public Builder trustStore(String location, String password, String type) {
            this.trustStore = location;
            this.trustStorePassword = password;
            this.trustStoreType = type;
            return this;
        }

        public Builder keyStore(String location, String password, String type) {
            this.keyStore = location;
            this.keyStorePassword = password;
            this.keyStoreType = type;
            return this;
        }

        public Builder keyPassword(String password) {
            this.keyPassword = password;
            return this;
        }

        /**
         * Specify whether the server should authorize the client in SSL
         * connections.
         */
        public Builder needsClientAuth(boolean value) {
            this.needsClientAuth = value;
            return this;
        }

        public Builder setFindPort(boolean findPort) {
            this.findPort = findPort;
            return this;
        }

        public Builder setConf(Configuration conf) {
            this.conf = conf;
            return this;
        }

        public Builder setPathSpec(String[] pathSpec) {
            this.pathSpecs = pathSpec;
            return this;
        }

        public Builder setACL(AccessControlList acl) {
            this.adminsAcl = acl;
            return this;
        }

        public Builder setSecurityEnabled(boolean securityEnabled) {
            this.securityEnabled = securityEnabled;
            return this;
        }

        public Builder setUsernameConfKey(String usernameConfKey) {
            this.usernameConfKey = usernameConfKey;
            return this;
        }

        public Builder setKeytabConfKey(String keytabConfKey) {
            this.keytabConfKey = keytabConfKey;
            return this;
        }

        public HttpServer3 build() throws IOException {
            Preconditions.checkNotNull(name, "name is not set");
            Preconditions.checkState(!endpoints.isEmpty(), "No endpoints specified");

            if (hostName == null) {
                hostName = endpoints.get(0).getHost();
            }

            if (this.conf == null) {
                conf = new Configuration();
            }

            HttpServer3 server = new HttpServer3(this);

            if (this.securityEnabled) {
                server.initSpnego(conf, hostName, usernameConfKey, keytabConfKey);
            }

            for (URI ep : endpoints) {
                final Connector listener;
                String scheme = ep.getScheme();
                if ("http".equals(scheme)) {
                    listener = HttpServer3.createDefaultChannelConnector();
                } else if ("https".equals(scheme)) {
                    SslSocketConnector c = new SslSocketConnector();
                    c.setNeedClientAuth(needsClientAuth);
                    c.setKeyPassword(keyPassword);

                    if (keyStore != null) {
                        c.setKeystore(keyStore);
                        c.setKeystoreType(keyStoreType);
                        c.setPassword(keyStorePassword);
                    }

                    if (trustStore != null) {
                        c.setTruststore(trustStore);
                        c.setTruststoreType(trustStoreType);
                        c.setTrustPassword(trustStorePassword);
                    }
                    listener = c;

                } else {
                    throw new HadoopIllegalArgumentException("unknown scheme for endpoint:" + ep);
                }
                listener.setHost(ep.getHost());
                listener.setPort(ep.getPort() == -1 ? 0 : ep.getPort());
                server.addListener(listener);
            }
            server.loadListeners();
            return server;
        }
    }

    private HttpServer3(final Builder b) throws IOException {
        final String appDir = getWebAppsPath(b.name);
        this.webServer = new Server();
        this.adminsAcl = b.adminsAcl;
        this.webAppContext = createWebAppContext(b.name, b.conf, adminsAcl, appDir);
        this.findPort = b.findPort;
        initializeWebServer(b.name, b.hostName, b.conf, b.pathSpecs);
    }

    private void initializeWebServer(String name, String hostName, Configuration conf, String[] pathSpecs)
            throws IOException {

        Preconditions.checkNotNull(webAppContext);

        int maxThreads = conf.getInt(HTTP_MAX_THREADS, -1);
        // If HTTP_MAX_THREADS is not configured, QueueThreadPool() will use the
        // default value (currently 250).
        QueuedThreadPool threadPool = maxThreads == -1 ? new QueuedThreadPool() : new QueuedThreadPool(maxThreads);
        threadPool.setDaemon(true);
        webServer.setThreadPool(threadPool);

        SessionManager sm = webAppContext.getSessionHandler().getSessionManager();
        if (sm instanceof AbstractSessionManager) {
            AbstractSessionManager asm = (AbstractSessionManager) sm;
            asm.setHttpOnly(true);
            asm.setSecureCookies(true);
        }

        ContextHandlerCollection contexts = new ContextHandlerCollection();
        RequestLog requestLog = HttpRequestLog.getRequestLog(name);

        if (requestLog != null) {
            RequestLogHandler requestLogHandler = new RequestLogHandler();
            requestLogHandler.setRequestLog(requestLog);
            HandlerCollection handlers = new HandlerCollection();
            handlers.setHandlers(new Handler[] { contexts, requestLogHandler });
            webServer.setHandler(handlers);
        } else {
            webServer.setHandler(contexts);
        }

        final String appDir = getWebAppsPath(name);

        webServer.addHandler(webAppContext);

        addDefaultApps(contexts, appDir, conf);

        addGlobalFilter("safety", QuotingInputFilter.class.getName(), null);
        final FilterInitializer[] initializers = getFilterInitializers(conf);
        if (initializers != null) {
            conf = new Configuration(conf);
            conf.set(BIND_ADDRESS, hostName);
            for (FilterInitializer c : initializers) {
                c.initFilter(this, conf);
            }
        }

        addDefaultServlets();

        if (pathSpecs != null) {
            for (String path : pathSpecs) {
                LOG.info("adding path spec: " + path);
                addFilterPathMapping(path, webAppContext);
            }
        }
    }

    private void addListener(Connector connector) {
        listeners.add(connector);
    }

    private static WebAppContext createWebAppContext(String name, Configuration conf, AccessControlList adminsAcl,
            final String appDir) {
        WebAppContext ctx = new WebAppContext();
        ctx.setDefaultsDescriptor(null);
        ServletHolder holder = new ServletHolder(new DefaultServlet());
        Map<String, String> params = ImmutableMap.<String, String>builder().put("acceptRanges", "true")
                .put("dirAllowed", "false").put("gzip", "true").put("useFileMappedBuffer", "true").build();
        holder.setInitParameters(params);
        ctx.setWelcomeFiles(new String[] { "index.html" });
        ctx.addServlet(holder, "/");
        ctx.setDisplayName(name);
        ctx.setContextPath("/");
        ctx.setWar(appDir + "/" + name);
        ctx.getServletContext().setAttribute(CONF_CONTEXT_ATTRIBUTE, conf);
        ctx.getServletContext().setAttribute(ADMINS_ACL, adminsAcl);
        addNoCacheFilter(ctx);
        return ctx;
    }

    private static void addNoCacheFilter(WebAppContext ctxt) {
        defineFilter(ctxt, NO_CACHE_FILTER, NoCacheFilter.class.getName(), Collections.<String, String>emptyMap(),
                new String[] { "/*" });
    }

    private static class SelectChannelConnectorWithSafeStartup extends SelectChannelConnector {
        public SelectChannelConnectorWithSafeStartup() {
            super();
        }

        /* Override the broken isRunning() method (JETTY-1316). This bug is present
         * in 6.1.26. For the versions wihout this bug, it adds insignificant
         * overhead.
         */
        @Override
        public boolean isRunning() {
            if (super.isRunning()) {
                return true;
            }
            // We might be hitting JETTY-1316. If the internal state changed from
            // STARTING to STARTED in the middle of the check, the above call may
            // return false.  Check it one more time.
            LOG.warn("HttpServer Acceptor: isRunning is false. Rechecking.");
            try {
                Thread.sleep(10);
            } catch (InterruptedException ie) {
                // Mark this thread as interrupted. Someone up in the call chain
                // might care.
                Thread.currentThread().interrupt();
            }
            boolean runState = super.isRunning();
            LOG.warn("HttpServer Acceptor: isRunning is " + runState);
            return runState;
        }
    }

    @InterfaceAudience.Private
    public static Connector createDefaultChannelConnector() {
        SelectChannelConnector ret = new SelectChannelConnectorWithSafeStartup();
        ret.setLowResourceMaxIdleTime(10000);
        ret.setAcceptQueueSize(128);
        ret.setResolveNames(false);
        ret.setUseDirectBuffers(false);
        if (Shell.WINDOWS) {
            // result of setting the SO_REUSEADDR flag is different on Windows
            // http://msdn.microsoft.com/en-us/library/ms740621(v=vs.85).aspx
            // without this 2 NN's can start on the same machine and listen on 
            // the same port with indeterminate routing of incoming requests to them
            ret.setReuseAddress(false);
        }
        ret.setHeaderBufferSize(1024 * 64);
        return ret;
    }

    /** Get an array of FilterConfiguration specified in the conf */
    private static FilterInitializer[] getFilterInitializers(Configuration conf) {
        if (conf == null) {
            return null;
        }

        Class<?>[] classes = conf.getClasses(FILTER_INITIALIZER_PROPERTY);
        if (classes == null) {
            return null;
        }

        FilterInitializer[] initializers = new FilterInitializer[classes.length];
        for (int i = 0; i < classes.length; i++) {
            initializers[i] = (FilterInitializer) ReflectionUtils.newInstance(classes[i], conf);
        }
        return initializers;
    }

    /**
     * Add default apps.
     * @param appDir The application directory
     * @throws IOException
     */
    protected void addDefaultApps(ContextHandlerCollection parent, final String appDir, Configuration conf)
            throws IOException {
        // set up the context for "/logs/" if "hadoop.log.dir" property is defined. 
        String logDir = System.getProperty("hadoop.log.dir");
        if (logDir != null) {
            Context logContext = new Context(parent, "/logs");
            logContext.setResourceBase(logDir);
            logContext.addServlet(AdminAuthorizedServlet.class, "/*");
            if (conf.getBoolean(CommonConfigurationKeys.HADOOP_JETTY_LOGS_SERVE_ALIASES,
                    CommonConfigurationKeys.DEFAULT_HADOOP_JETTY_LOGS_SERVE_ALIASES)) {
                @SuppressWarnings("unchecked")
                Map<String, String> params = logContext.getInitParams();
                params.put("org.mortbay.jetty.servlet.Default.aliases", "true");
            }
            logContext.setDisplayName("logs");
            setContextAttributes(logContext, conf);
            addNoCacheFilter(webAppContext);
            defaultContexts.put(logContext, true);
        }
        // set up the context for "/static/*"
        Context staticContext = new Context(parent, "/static");
        staticContext.setResourceBase(appDir + "/static");
        staticContext.addServlet(DefaultServlet.class, "/*");
        staticContext.setDisplayName("static");
        setContextAttributes(staticContext, conf);
        defaultContexts.put(staticContext, true);
    }

    private void setContextAttributes(Context context, Configuration conf) {
        context.getServletContext().setAttribute(CONF_CONTEXT_ATTRIBUTE, conf);
        context.getServletContext().setAttribute(ADMINS_ACL, adminsAcl);
    }

    /**
     * Add default servlets.
     */
    protected void addDefaultServlets() {
        // set up default servlets
        addServlet("stacks", "/stacks", StackServlet.class);
        addServlet("logLevel", "/logLevel", LogLevel.Servlet.class);
        addServlet("metrics", "/metrics", MetricsServlet.class);
        addServlet("jmx", "/jmx", JMXJsonServlet.class);
        addServlet("conf", "/conf", ConfServlet.class);
    }

    public void addContext(Context ctxt, boolean isFiltered) {
        webServer.addHandler(ctxt);
        addNoCacheFilter(webAppContext);
        defaultContexts.put(ctxt, isFiltered);
    }

    /**
     * Set a value in the webapp context. These values are available to the jsp
     * pages as "application.getAttribute(name)".
     * @param name The name of the attribute
     * @param value The value of the attribute
     */
    public void setAttribute(String name, Object value) {
        webAppContext.setAttribute(name, value);
    }

    /** 
     * Add a Jersey resource package.
     * @param packageName The Java package name containing the Jersey resource.
     * @param pathSpec The path spec for the servlet
     */
    public void addJerseyResourcePackage(final String packageName, final String pathSpec) {
        LOG.info("addJerseyResourcePackage: packageName=" + packageName + ", pathSpec=" + pathSpec);
        final ServletHolder sh = new ServletHolder(ServletContainer.class);
        sh.setInitParameter("com.sun.jersey.config.property.resourceConfigClass",
                "com.sun.jersey.api.core.PackagesResourceConfig");
        sh.setInitParameter("com.sun.jersey.config.property.packages", packageName);
        webAppContext.addServlet(sh, pathSpec);
    }

    /**
     * Add a servlet in the server.
     * @param name The name of the servlet (can be passed as null)
     * @param pathSpec The path spec for the servlet
     * @param clazz The servlet class
     */
    public void addServlet(String name, String pathSpec, Class<? extends HttpServlet> clazz) {
        addInternalServlet(name, pathSpec, clazz, false);
        addFilterPathMapping(pathSpec, webAppContext);
    }

    /**
     * Add an internal servlet in the server. 
     * Note: This method is to be used for adding servlets that facilitate
     * internal communication and not for user facing functionality. For
     * servlets added using this method, filters are not enabled. 
     * 
     * @param name The name of the servlet (can be passed as null)
     * @param pathSpec The path spec for the servlet
     * @param clazz The servlet class
     */
    public void addInternalServlet(String name, String pathSpec, Class<? extends HttpServlet> clazz) {
        addInternalServlet(name, pathSpec, clazz, false);
    }

    /**
     * Add an internal servlet in the server, specifying whether or not to
     * protect with Kerberos authentication. 
     * Note: This method is to be used for adding servlets that facilitate
     * internal communication and not for user facing functionality. For
     +   * servlets added using this method, filters (except internal Kerberos
     * filters) are not enabled. 
     * 
     * @param name The name of the servlet (can be passed as null)
     * @param pathSpec The path spec for the servlet
     * @param clazz The servlet class
     * @param requireAuth Require Kerberos authenticate to access servlet
     */
    public void addInternalServlet(String name, String pathSpec, Class<? extends HttpServlet> clazz,
            boolean requireAuth) {
        ServletHolder holder = new ServletHolder(clazz);
        if (name != null) {
            holder.setName(name);
        }
        webAppContext.addServlet(holder, pathSpec);

        if (requireAuth && UserGroupInformation.isSecurityEnabled()) {
            LOG.info("Adding Kerberos (SPNEGO) filter to " + name);
            ServletHandler handler = webAppContext.getServletHandler();
            FilterMapping fmap = new FilterMapping();
            fmap.setPathSpec(pathSpec);
            fmap.setFilterName(SPNEGO_FILTER);
            fmap.setDispatches(Handler.ALL);
            handler.addFilterMapping(fmap);
        }
    }

    @Override
    public void addFilter(String name, String classname, Map<String, String> parameters) {

        final String[] USER_FACING_URLS = { "*.html", "*.jsp" };
        defineFilter(webAppContext, name, classname, parameters, USER_FACING_URLS);
        LOG.info(
                "Added filter " + name + " (class=" + classname + ") to context " + webAppContext.getDisplayName());
        final String[] ALL_URLS = { "/*" };
        for (Map.Entry<Context, Boolean> e : defaultContexts.entrySet()) {
            if (e.getValue()) {
                Context ctx = e.getKey();
                defineFilter(ctx, name, classname, parameters, ALL_URLS);
                LOG.info("Added filter " + name + " (class=" + classname + ") to context " + ctx.getDisplayName());
            }
        }
        filterNames.add(name);
    }

    @Override
    public void addGlobalFilter(String name, String classname, Map<String, String> parameters) {
        final String[] ALL_URLS = { "/*" };
        defineFilter(webAppContext, name, classname, parameters, ALL_URLS);
        for (Context ctx : defaultContexts.keySet()) {
            defineFilter(ctx, name, classname, parameters, ALL_URLS);
        }
        LOG.info("Added global filter '" + name + "' (class=" + classname + ")");
    }

    /**
     * Define a filter for a context and set up default url mappings.
     */
    public static void defineFilter(Context ctx, String name, String classname, Map<String, String> parameters,
            String[] urls) {

        FilterHolder holder = new FilterHolder();
        holder.setName(name);
        holder.setClassName(classname);
        holder.setInitParameters(parameters);
        FilterMapping fmap = new FilterMapping();
        fmap.setPathSpecs(urls);
        fmap.setDispatches(Handler.ALL);
        fmap.setFilterName(name);
        ServletHandler handler = ctx.getServletHandler();
        handler.addFilter(holder, fmap);
    }

    /**
     * Add the path spec to the filter path mapping.
     * @param pathSpec The path spec
     * @param webAppCtx The WebApplicationContext to add to
     */
    protected void addFilterPathMapping(String pathSpec, Context webAppCtx) {
        ServletHandler handler = webAppCtx.getServletHandler();
        for (String name : filterNames) {
            FilterMapping fmap = new FilterMapping();
            fmap.setPathSpec(pathSpec);
            fmap.setFilterName(name);
            fmap.setDispatches(Handler.ALL);
            handler.addFilterMapping(fmap);
        }
    }

    /**
     * Get the value in the webapp context.
     * @param name The name of the attribute
     * @return The value of the attribute
     */
    public Object getAttribute(String name) {
        return webAppContext.getAttribute(name);
    }

    public WebAppContext getWebAppContext() {
        return this.webAppContext;
    }

    /**
     * Get the pathname to the webapps files.
     * @param appName eg "secondary" or "datanode"
     * @return the pathname as a URL
     * @throws FileNotFoundException if 'webapps' directory cannot be found on CLASSPATH.
     */
    protected String getWebAppsPath(String appName) throws FileNotFoundException {
        URL url = getClass().getClassLoader().getResource("webapps/" + appName);
        if (url == null)
            throw new FileNotFoundException("webapps/" + appName + " not found in CLASSPATH");
        String urlString = url.toString();
        return urlString.substring(0, urlString.lastIndexOf('/'));
    }

    /**
     * Get the port that the server is on
     * @return the port
     */
    @Deprecated
    public int getPort() {
        return webServer.getConnectors()[0].getLocalPort();
    }

    /**
     * Get the address that corresponds to a particular connector.
     *
     * @return the corresponding address for the connector, or null if there's no
     *         such connector or the connector is not bounded.
     */
    public InetSocketAddress getConnectorAddress(int index) {
        Preconditions.checkArgument(index >= 0);
        if (index > webServer.getConnectors().length)
            return null;

        Connector c = webServer.getConnectors()[index];
        if (c.getLocalPort() == -1) {
            // The connector is not bounded
            return null;
        }

        return new InetSocketAddress(c.getHost(), c.getLocalPort());
    }

    /**
     * Set the min, max number of worker threads (simultaneous connections).
     */
    public void setThreads(int min, int max) {
        QueuedThreadPool pool = (QueuedThreadPool) webServer.getThreadPool();
        pool.setMinThreads(min);
        pool.setMaxThreads(max);
    }

    private void initSpnego(Configuration conf, String hostName, String usernameConfKey, String keytabConfKey)
            throws IOException {
        Map<String, String> params = new HashMap<>();
        String principalInConf = conf.get(usernameConfKey);
        if (principalInConf != null && !principalInConf.isEmpty()) {
            params.put("kerberos.principal", SecurityUtil.getServerPrincipal(principalInConf, hostName));
        }
        String httpKeytab = conf.get(keytabConfKey);
        if (httpKeytab != null && !httpKeytab.isEmpty()) {
            params.put("kerberos.keytab", httpKeytab);
        }
        params.put(AuthenticationFilter.AUTH_TYPE, "kerberos");

        defineFilter(webAppContext, SPNEGO_FILTER, AuthenticationFilter.class.getName(), params, null);
    }

    /**
     * Start the server. Does not wait for the server to start.
     */
    public void start() throws IOException {
        try {
            try {
                openListeners();
                webServer.start();
            } catch (IOException ex) {
                LOG.info("HttpServer3.start() threw a non Bind IOException", ex);
                throw ex;
            } catch (MultiException ex) {
                LOG.info("HttpServer3.start() threw a MultiException", ex);
                throw ex;
            }
            // Make sure there is no handler failures.
            Handler[] handlers = webServer.getHandlers();
            for (Handler handler : handlers) {
                if (handler.isFailed()) {
                    throw new IOException("Problem in starting http server. Server handlers failed");
                }
            }
            // Make sure there are no errors initializing the context.
            Throwable unavailableException = webAppContext.getUnavailableException();
            if (unavailableException != null) {
                // Have to stop the webserver, or else its non-daemon threads
                // will hang forever.
                webServer.stop();
                throw new IOException("Unable to initialize WebAppContext", unavailableException);
            }
        } catch (IOException e) {
            throw e;
        } catch (InterruptedException e) {
            throw (IOException) new InterruptedIOException("Interrupted while starting HTTP server").initCause(e);
        } catch (Exception e) {
            throw new IOException("Problem starting http server", e);
        }
    }

    private void loadListeners() {
        for (Connector c : listeners) {
            webServer.addConnector(c);
        }
    }

    /**
     * Open the main listener for the server
     * @throws Exception
     */
    void openListeners() throws Exception {
        for (Connector listener : listeners) {
            if (listener.getLocalPort() != -1) {
                // This listener is either started externally or has been bound
                continue;
            }
            int port = listener.getPort();
            while (true) {
                // jetty has a bug where you can't reopen a listener that previously
                // failed to open w/o issuing a close first, even if the port is changed
                try {
                    listener.close();
                    listener.open();
                    LOG.info("Jetty bound to port " + listener.getLocalPort());
                    break;
                } catch (BindException ex) {
                    if (port == 0 || !findPort) {
                        BindException be = new BindException(
                                "Port in use: " + listener.getHost() + ":" + listener.getPort());
                        be.initCause(ex);
                        throw be;
                    }
                }
                // try the next port number
                listener.setPort(++port);
                Thread.sleep(100);
            }
        }
    }

    /**
     * stop the server
     */
    public void stop() throws Exception {
        MultiException exception = null;
        for (Connector c : listeners) {
            try {
                c.close();
            } catch (Exception e) {
                LOG.error("Error while stopping listener for webapp" + webAppContext.getDisplayName(), e);
                exception = addMultiException(exception, e);
            }
        }

        try {
            // clear & stop webAppContext attributes to avoid memory leaks.
            webAppContext.clearAttributes();
            webAppContext.stop();
        } catch (Exception e) {
            LOG.error("Error while stopping web app context for webapp " + webAppContext.getDisplayName(), e);
            exception = addMultiException(exception, e);
        }

        try {
            webServer.stop();
        } catch (Exception e) {
            LOG.error("Error while stopping web server for webapp " + webAppContext.getDisplayName(), e);
            exception = addMultiException(exception, e);
        }

        if (exception != null) {
            exception.ifExceptionThrow();
        }

    }

    private MultiException addMultiException(MultiException exception, Exception e) {
        if (exception == null) {
            exception = new MultiException();
        }
        exception.add(e);
        return exception;
    }

    public void join() throws InterruptedException {
        webServer.join();
    }

    /**
     * Test for the availability of the web server
     * @return true if the web server is started, false otherwise
     */
    public boolean isAlive() {
        return webServer != null && webServer.isStarted();
    }

    @Override
    public String toString() {
        Preconditions.checkState(!listeners.isEmpty());
        StringBuilder sb = new StringBuilder("HttpServer (")
                .append(isAlive() ? STATE_DESCRIPTION_ALIVE : STATE_DESCRIPTION_NOT_LIVE)
                .append("), listening at:");
        for (Connector l : listeners) {
            sb.append(l.getHost()).append(":").append(l.getPort()).append("/,");
        }
        return sb.toString();
    }

    /**
     * Checks the user has privileges to access to instrumentation servlets.
     * <p/>
     * If <code>hadoop.security.instrumentation.requires.admin</code> is set to FALSE
     * (default value) it always returns TRUE.
     * <p/>
     * If <code>hadoop.security.instrumentation.requires.admin</code> is set to TRUE
     * it will check that if the current user is in the admin ACLS. If the user is
     * in the admin ACLs it returns TRUE, otherwise it returns FALSE.
     *
     * @param servletContext the servlet context.
     * @param request the servlet request.
     * @param response the servlet response.
     * @return TRUE/FALSE based on the logic decribed above.
     */
    public static boolean isInstrumentationAccessAllowed(ServletContext servletContext, HttpServletRequest request,
            HttpServletResponse response) throws IOException {
        Configuration conf = (Configuration) servletContext.getAttribute(CONF_CONTEXT_ATTRIBUTE);

        boolean access = true;
        boolean adminAccess = conf
                .getBoolean(CommonConfigurationKeys.HADOOP_SECURITY_INSTRUMENTATION_REQUIRES_ADMIN, false);
        if (adminAccess) {
            access = hasAdministratorAccess(servletContext, request, response);
        }
        return access;
    }

    /**
     * Does the user sending the HttpServletRequest has the administrator ACLs? If
     * it isn't the case, response will be modified to send an error to the user.
     * 
     * @param response used to send the error response if user does not have admin access.
     * @return true if admin-authorized, false otherwise
     * @throws IOException
     */
    public static boolean hasAdministratorAccess(ServletContext servletContext, HttpServletRequest request,
            HttpServletResponse response) throws IOException {
        Configuration conf = (Configuration) servletContext.getAttribute(CONF_CONTEXT_ATTRIBUTE);
        // If there is no authorization, anybody has administrator access.
        if (!conf.getBoolean(CommonConfigurationKeys.HADOOP_SECURITY_AUTHORIZATION, false)) {
            return true;
        }

        String remoteUser = request.getRemoteUser();
        if (remoteUser == null) {
            response.sendError(HttpServletResponse.SC_FORBIDDEN,
                    "Unauthenticated users are not " + "authorized to access this page.");
            return false;
        }

        if (servletContext.getAttribute(ADMINS_ACL) != null
                && !userHasAdministratorAccess(servletContext, remoteUser)) {
            response.sendError(HttpServletResponse.SC_FORBIDDEN,
                    "User " + remoteUser + " is unauthorized to access this page.");
            return false;
        }

        return true;
    }

    /**
     * Get the admin ACLs from the given ServletContext and check if the given
     * user is in the ACL.
     * 
     * @param servletContext the context containing the admin ACL.
     * @param remoteUser the remote user to check for.
     * @return true if the user is present in the ACL, false if no ACL is set or
     *         the user is not present
     */
    public static boolean userHasAdministratorAccess(ServletContext servletContext, String remoteUser) {
        AccessControlList adminsAcl = (AccessControlList) servletContext.getAttribute(ADMINS_ACL);
        UserGroupInformation remoteUserUGI = UserGroupInformation.createRemoteUser(remoteUser);
        return adminsAcl != null && adminsAcl.isUserAllowed(remoteUserUGI);
    }

    /**
     * A very simple servlet to serve up a text representation of the current
     * stack traces. It both returns the stacks to the caller and logs them.
     * Currently the stack traces are done sequentially rather than exactly the
     * same data.
     */
    public static class StackServlet extends HttpServlet {
        private static final long serialVersionUID = -6284183679759467039L;

        @Override
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            if (!HttpServer3.isInstrumentationAccessAllowed(getServletContext(), request, response)) {
                return;
            }
            response.setContentType("text/plain; charset=UTF-8");
            try (PrintStream out = new PrintStream(response.getOutputStream(), false, "UTF-8")) {
                ReflectionUtils.printThreadInfo(out, "");
            }
            ReflectionUtils.logThreadInfo(LOG, "jsp requested", 1);
        }
    }

    /**
     * A Servlet input filter that quotes all HTML active characters in the
     * parameter names and values. The goal is to quote the characters to make
     * all of the servlets resistant to cross-site scripting attacks.
     */
    public static class QuotingInputFilter implements Filter {
        private FilterConfig config;

        public static class RequestQuoter extends HttpServletRequestWrapper {
            private final HttpServletRequest rawRequest;

            public RequestQuoter(HttpServletRequest rawRequest) {
                super(rawRequest);
                this.rawRequest = rawRequest;
            }

            /**
             * Return the set of parameter names, quoting each name.
             */
            @SuppressWarnings("unchecked")
            @Override
            public Enumeration<String> getParameterNames() {
                return new Enumeration<String>() {
                    private Enumeration<String> rawIterator = rawRequest.getParameterNames();

                    @Override
                    public boolean hasMoreElements() {
                        return rawIterator.hasMoreElements();
                    }

                    @Override
                    public String nextElement() {
                        return HtmlQuoting.quoteHtmlChars(rawIterator.nextElement());
                    }
                };
            }

            /**
             * Unquote the name and quote the value.
             */
            @Override
            public String getParameter(String name) {
                return HtmlQuoting.quoteHtmlChars(rawRequest.getParameter(HtmlQuoting.unquoteHtmlChars(name)));
            }

            @Override
            public String[] getParameterValues(String name) {
                String unquoteName = HtmlQuoting.unquoteHtmlChars(name);
                String[] unquoteValue = rawRequest.getParameterValues(unquoteName);
                if (unquoteValue == null) {
                    return null;
                }
                String[] result = new String[unquoteValue.length];
                for (int i = 0; i < result.length; ++i) {
                    result[i] = HtmlQuoting.quoteHtmlChars(unquoteValue[i]);
                }
                return result;
            }

            @SuppressWarnings("unchecked")
            @Override
            public Map<String, String[]> getParameterMap() {
                Map<String, String[]> result = new HashMap<>();
                Map<String, String[]> raw = rawRequest.getParameterMap();
                for (Map.Entry<String, String[]> item : raw.entrySet()) {
                    String[] rawValue = item.getValue();
                    String[] cookedValue = new String[rawValue.length];
                    for (int i = 0; i < rawValue.length; ++i) {
                        cookedValue[i] = HtmlQuoting.quoteHtmlChars(rawValue[i]);
                    }
                    result.put(HtmlQuoting.quoteHtmlChars(item.getKey()), cookedValue);
                }
                return result;
            }

            /**
             * Quote the url so that users specifying the HOST HTTP header
             * can't inject attacks.
             */
            @Override
            public StringBuffer getRequestURL() {
                String url = rawRequest.getRequestURL().toString();
                return new StringBuffer(HtmlQuoting.quoteHtmlChars(url));
            }

            /**
             * Quote the server name so that users specifying the HOST HTTP header
             * can't inject attacks.
             */
            @Override
            public String getServerName() {
                return HtmlQuoting.quoteHtmlChars(rawRequest.getServerName());
            }
        }

        @Override
        public void init(FilterConfig config) throws ServletException {
            this.config = config;
        }

        @Override
        public void destroy() {
        }

        @Override
        public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
                throws IOException, ServletException {
            HttpServletRequestWrapper quoted = new RequestQuoter((HttpServletRequest) request);
            HttpServletResponse httpResponse = (HttpServletResponse) response;

            String mime = inferMimeType(request);
            if (mime == null) {
                httpResponse.setContentType("text/plain; charset=utf-8");
            } else if (mime.startsWith("text/html")) {
                // HTML with unspecified encoding, we want to
                // force HTML with utf-8 encoding
                // This is to avoid the following security issue:
                // http://openmya.hacker.jp/hasegawa/security/utf7cs.html
                httpResponse.setContentType("text/html; charset=utf-8");
            } else if (mime.startsWith("application/xml")) {
                httpResponse.setContentType("text/xml; charset=utf-8");
            }
            chain.doFilter(quoted, httpResponse);
        }

        /**
         * Infer the mime type for the response based on the extension of the request
         * URI. Returns null if unknown.
         */
        private String inferMimeType(ServletRequest request) {
            String path = ((HttpServletRequest) request).getRequestURI();
            ContextHandler.SContext sContext = (ContextHandler.SContext) config.getServletContext();
            MimeTypes mimes = sContext.getContextHandler().getMimeTypes();
            Buffer mimeBuffer = mimes.getMimeByExtension(path);
            return (mimeBuffer == null) ? null : mimeBuffer.toString();
        }

    }
}