ExceptionalRequestHandler.java

// Copyright 2016 Twitter. All rights reserved.
//
// 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 com.twitter.heron.scheduler.server;

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

import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;

import com.twitter.heron.proto.scheduler.Scheduler;
import com.twitter.heron.scheduler.utils.Runtime;
import com.twitter.heron.scheduler.utils.SchedulerUtils;
import com.twitter.heron.spi.common.Config;
import com.twitter.heron.spi.scheduler.IScheduler;
import com.twitter.heron.spi.utils.NetworkUtils;

/**
 * {@code HttpHandler} decorator that returns an OK response unless an exception is caught, in
 * which case a NOTOK response is returned. If the delegate throws a
 * {@code TerminateSchedulerException}, the scheduler will be terminated after the response is
 * handled.
 */
class ExceptionalRequestHandler implements HttpHandler {
  private static final Logger LOG = Logger.getLogger(ExceptionalRequestHandler.class.getName());
  private HttpHandler delegate;
  private Config runtime;
  private IScheduler scheduler;

  ExceptionalRequestHandler(HttpHandler delegate, Config runtime, IScheduler scheduler) {
    this.delegate = delegate;
    this.runtime = runtime;
    this.scheduler = scheduler;
  }

  @SuppressWarnings("IllegalCatch")
  @Override
  public void handle(HttpExchange exchange) throws IOException {

    try {
      delegate.handle(exchange);
      sendResponse(exchange, true);
    } catch (TerminateSchedulerException e) {
      sendResponse(exchange, true);

      // tell the scheduler to shutdown
      LOG.info("Request handler issuing a terminate request to scheduler");
      try {
        scheduler.close();
      } finally {
        Runtime.schedulerShutdown(runtime).terminate();
      }
    } catch (Exception e) {
      handleFailure(exchange, e);
    }
  }

  private static void handleFailure(HttpExchange exchange, Exception e) {
    LOG.log(Level.SEVERE,
        String.format("Failed to handle %s request", exchange.getRequestURI()), e);
    sendResponse(exchange, false);
  }

  private static void sendResponse(HttpExchange exchange, boolean success) {
    Scheduler.SchedulerResponse response = SchedulerUtils.constructSchedulerResponse(success);
    NetworkUtils.sendHttpResponse(exchange, response.toByteArray());
  }
}