source: src/main/java/geniusweb/partiesserver/RunParty.java@ 3

package geniusweb.partiesserver;

import java.io.IOException;
import java.util.logging.Level;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import geniusweb.partiesserver.repository.AvailablePartiesRepo;
import geniusweb.partiesserver.repository.AvailableParty;
import geniusweb.partiesserver.repository.RunningPartiesRepo;
import geniusweb.partiesserver.repository.RunningParty;
import tudelft.utilities.logging.ReportToLogger;
import tudelft.utilities.logging.Reporter;
import tudelft.utilities.repository.NoResourcesNowException;

/**
 * Servlet implementation class RunParty. It's behind the url
 * partiesserver/run/NAME where NAME is the name of the party that needs to be
 * run.
 */
public class RunParty extends HttpServlet {
        private static final int DEFAULT_TIMEOUT = 3000; // ms
        private static final long serialVersionUID = 1L;
        private final Reporter log;

        /**
         * @see HttpServlet#HttpServlet()
         */
        public RunParty() {
                this(new ReportToLogger("partiesserver"));
        }

        /**
         * 
         * @param reporter the reporter where we log issues to.
         */
        public RunParty(Reporter reporter) {
                this.log = reporter;
        }

        /**
         * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
         *      response). Returns
         *      <ul>
         *      <li>URL with websocket address to contact the now running agent.
         *      <li>SC_NOT_FOUND (404) if attempt is made to access non-running
         *      party.
         *      <li>SC_SERVICE_UNAVAILABLE (503) if there are no free slots to run
         *      the party.
         *      <li>SC_EXPECTATION_FAILED (417) if something else goes wrong during
         *      instantiating the party (then see logs for more details)
         *      </ul>
         */
        @Override
        protected void doGet(HttpServletRequest request,
                        HttpServletResponse response) throws ServletException, IOException {
                String name = request.getPathInfo().substring(1);
                log.log(Level.INFO, "request to run " + name);

                AvailableParty party = AvailablePartiesRepo.instance().get(name);
                if (party == null) {
                        log.log(Level.INFO, "party " + name + " does not exist");
                        response.sendError(HttpServletResponse.SC_NOT_FOUND);
                        return;
                }
                // try to avoid needless creation of the party.
                if (RunningPartiesRepo.instance().availableSlots() <= 0) {
                        tryLater(response, name);
                        return;
                }

                RunningParty running;
                try {
                        running = RunningParty.create(party, DEFAULT_TIMEOUT);
                } catch (Throwable e1) {
                        log.log(Level.WARNING, "Failed to instantiate party " + name, e1);
                        response.sendError(HttpServletResponse.SC_EXPECTATION_FAILED,
                                        "Failed to instantiate party " + name + ":"
                                                        + e1.getMessage()
                                                        + ". See partiesserver log for stack trace");
                        return;
                }

                // in the mean time, another party may have taken the slot anyway...
                // the chances that this happens is small though.
                try {
                        RunningPartiesRepo.instance().put(running);
                } catch (NoResourcesNowException e) {
                        running.getParty().terminate();
                        tryLater(response, name);
                        return;
                }
                log.log(Level.INFO, "started " + name);
                String url = "ws://" + request.getLocalName() + ":"
                                + request.getLocalPort() + request.getContextPath() + "/party/"
                                + running.getID();
                response.getWriter().append(url);

        }

        /**
         * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
         *      response)
         */
        @Override
        protected void doPost(HttpServletRequest request,
                        HttpServletResponse response) throws ServletException, IOException {
                // TODO Auto-generated method stub
                doGet(request, response);
        }

        /**
         * Reply with 503 plus message that the caller should try later
         * 
         * @param response the response container
         * @param name     the name of the party that was attempted to launch
         * @throws IOException
         */
        private void tryLater(HttpServletResponse response, String name)
                        throws IOException {
                long time = RunningPartiesRepo.instance().estimateCleanupTime()
                                .getTime();
                log.log(Level.INFO, "There are no free slots to run the party " + name
                                + ". suggesting " + time);
                // sendError does not always work as expected, avoid it.
                response.setStatus(HttpServletResponse.SC_SERVICE_UNAVAILABLE);
                response.getWriter().append("retry later at " + time);
        }

}