GetMotdServiceImpl.java

// -*- mode: java; c-basic-offset: 2; -*-
// Copyright 2009-2011 Google, All Rights reserved
// Copyright 2011-2012 MIT, All rights reserved
// Released under the MIT License https://raw.github.com/mit-cml/app-inventor/master/mitlicense.txt

package com.google.appinventor.server;

import com.google.appinventor.server.flags.Flag;
import com.google.appinventor.server.storage.StorageIo;
import com.google.appinventor.server.storage.StorageIoInstanceHolder;
import com.google.appinventor.shared.rpc.GetMotdService;
import com.google.appinventor.shared.rpc.Motd;

import java.util.logging.Logger;

import com.google.appengine.api.memcache.MemcacheService;
import com.google.appengine.api.memcache.MemcacheServiceFactory;
import com.google.appengine.api.memcache.Expiration;

/**
 * Implementation of the get motd service.
 *
 * <p>Note that this service must be state-less so that it can be run on
 * multiple servers.
 *
 * @author kerr@google.com (Debby Wallach)
 */
public class GetMotdServiceImpl extends OdeRemoteServiceServlet implements GetMotdService {

  // Logging support
  private static final Logger LOG = Logger.getLogger(GetMotdServiceImpl.class.getName());

  // The value of this flag can be changed in appengine-web.xml
  private static final Flag<Integer> motdCheckIntervalSecs =
    Flag.createFlag("motd.check.interval.secs", 300);

  private final StorageIo storageIo = StorageIoInstanceHolder.INSTANCE;

  private final MemcacheService memcache = MemcacheServiceFactory.getMemcacheService();

  private final String motdcachekey = "c3c61e03-5f77-4107-8714-0d1faa3df325"; // UUID Generated by JIS

  /**
   * Gets the current Motd
   *
   * @return  the current Motd
   */
  @Override
  public Motd getMotd() {

    Motd motd = (Motd) memcache.get(motdcachekey); // Attempt to use memcache to fetch it
    if (motd != null)
      return motd;

    motd = storageIo.getCurrentMotd();
    memcache.put(motdcachekey, motd, Expiration.byDeltaSeconds(600)); // Hold it for ten minutes
    return motd;
  }

  /**
   * Returns the value, in seconds, of the motd.check.interval.secs flag.
   * 0 means don't check motd.
   */
  @Override
  public int getCheckInterval() {
    return motdCheckIntervalSecs.get();
  }
}