ConnectionDrainingFilter.java

ConnectionDrainingFilter.java

/*
Copyright (c) 2017, Sky UK Ltd All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided
that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list of conditions and the
following disclaimer.

Redistributions in binary form must reproduce the above copyright notice, this list of conditions and
the following disclaimer in the documentation and/or other materials provided with the distribution.

Neither the name of feed nor the names of its contributors may be used to endorse or promote products
derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

package uk.sky;

import com.google.common.util.concurrent.Uninterruptibles;
import io.dropwizard.Configuration;
import io.dropwizard.jetty.setup.ServletEnvironment;
import io.dropwizard.setup.Environment;
import org.eclipse.jetty.util.component.AbstractLifeCycle;
import org.eclipse.jetty.util.component.LifeCycle;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import java.io.IOException;
import java.time.Duration;
import java.util.EnumSet;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * ConnectionDrainingFilter provides a filter for gracefully terminating a dropwizard application, allowing
 * clients to terminate the connection before the server shuts down.
 * <p>
 * When used, it forces Jetty to wait for the provided duration before shutting down. During this time it
 * attaches a `Connection: close` header on all responses so that clients will close their persistent connections.
 * <p>
 * To use, call {@link #addToDropwizard} in your {@link io.dropwizard.Application#run(Configuration, Environment)} method.
 */
public final class ConnectionDrainingFilter extends AbstractLifeCycle.AbstractLifeCycleListener implements Filter {

    private static final Logger LOG = LoggerFactory.getLogger(ConnectionDrainingFilter.class);
    private static final String PATH_SPEC = "/*";
    public static final String FILTER_NAME = "ConnectionDrainingFilter";
    private final AtomicBoolean connectionCloseHeaderEnabled = new AtomicBoolean(false);
    private final Duration drainDuration;

    private ConnectionDrainingFilter(Duration drainDuration) {
        this.drainDuration = drainDuration;
    }

    /**
     * Create a new servlet filter. It should be added as a filter, and also registered with Jetty's container lifecycle.
     *
     * @param drainDuration amount of time to drain client connections before shutdown. Should be slightly larger than idle timeouts.
     * @return a new servlet filter and lifecycle listener
     */
    public static ConnectionDrainingFilter create(Duration drainDuration) {
        return new ConnectionDrainingFilter(drainDuration);
    }

    /**
     * Adds the filter to your Dropwizard environment, which will register it with Jetty.
     *
     * @param environment   dropwizard environment
     * @param drainDuration amount of time to drain client connections before shutdown. Should be slightly larger than idle timeouts.
     */
    public static void addToDropwizard(Environment environment, io.dropwizard.util.Duration drainDuration) {
        ConnectionDrainingFilter connectionDrainingFilter = new ConnectionDrainingFilter(Duration.ofNanos(drainDuration.toNanoseconds()));

        registerFilterWithServletEnvironment(connectionDrainingFilter, environment.servlets());
        registerFilterWithServletEnvironment(connectionDrainingFilter, environment.admin());

        environment.lifecycle().addLifeCycleListener(connectionDrainingFilter);
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // nada
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        if (!connectionCloseHeaderEnabled.get()) {
            chain.doFilter(request, response);
            return;
        }

        if (!(response instanceof HttpServletResponse)) {
            LOG.warn("Unable to drain connections safely, unexpected response type %s", response.getClass());
            chain.doFilter(request, response);
            return;
        }

        HttpServletResponseWrapper connectionCloseResponse = new HttpServletResponseWrapper((HttpServletResponse) response);
        connectionCloseResponse.addHeader("Connection", "close");
        chain.doFilter(request, connectionCloseResponse);
    }

    @Override
    public void destroy() {
        // nada
    }

    @Override
    public void lifeCycleStopping(LifeCycle event) {
        LOG.info("Draining server before shutdown");
        connectionCloseHeaderEnabled.set(true);
        Uninterruptibles.sleepUninterruptibly(drainDuration.toNanos(), TimeUnit.NANOSECONDS);
        LOG.info("Finished drain, exiting");
    }

    private static void registerFilterWithServletEnvironment(ConnectionDrainingFilter connectionDrainingFilter, ServletEnvironment servletEnvironment) {
        EnumSet<DispatcherType> dispatcherTypes = EnumSet.of(DispatcherType.REQUEST);
        servletEnvironment.addFilter(FILTER_NAME, connectionDrainingFilter)
                .addMappingForUrlPatterns(dispatcherTypes, true, PATH_SPEC);
    }
}

For Dropwizard 1.0.