/* StatusController.java
*
* Copyright 2009-2012 Comcast Interactive Media, LLC.
*
* 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 org.fishwife.jrugged.spring;
import java.io.IOException;
import java.io.OutputStream;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.fishwife.jrugged.MonitoredService;
import org.fishwife.jrugged.Status;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller;
/**
* This is a convenient {@link Controller} that can be used to implement a
* "heartbeat" URL in a web application. The <code>StatusController</code>
* has a particular {@link MonitoredService} associated with it (a common use
* case would be to inject a {@link org.fishwife.jrugged.RolledUpMonitoredService} for
* overall system health. The <code>StatusController</code> writes the
* current status out in the response body and sets an appropriate HTTP
* response code. This is useful in a load balancer setting where the load
* balancer periodically pings a pool of application servers to see if they
* are "OK" and removes them from the pool if they are not. If the
* <code>Monitorable</code> is capable of serving requests (i.e. is GREEN
* or YELLOW) then we return a 2XX response code; otherwise we return a 5XX
* response code.
*/
public class StatusController implements Controller {
private static Map<Status,Integer> responseCodeMap;
static {
responseCodeMap = new HashMap<Status,Integer>();
responseCodeMap.put(Status.FAILED, HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
responseCodeMap.put(Status.INIT, HttpServletResponse.SC_SERVICE_UNAVAILABLE);
responseCodeMap.put(Status.DOWN, HttpServletResponse.SC_SERVICE_UNAVAILABLE);
responseCodeMap.put(Status.DEGRADED, HttpServletResponse.SC_OK);
responseCodeMap.put(Status.BYPASS, HttpServletResponse.SC_OK);
responseCodeMap.put(Status.UP, HttpServletResponse.SC_OK);
}
private MonitoredService monitoredService;
public StatusController(MonitoredService monitoredService) {
this.monitoredService = monitoredService;
}
public ModelAndView handleRequest(HttpServletRequest req,
HttpServletResponse resp) throws Exception {
Status currentStatus = monitoredService.getServiceStatus().getStatus();
setResponseCode(currentStatus, resp);
setAppropriateWarningHeaders(resp, currentStatus);
setCachingHeaders(resp);
writeOutCurrentStatusInResponseBody(resp, currentStatus);
return null;
}
private void setCachingHeaders(HttpServletResponse resp) {
long now = System.currentTimeMillis();
resp.setDateHeader("Date", now);
resp.setDateHeader("Expires", now);
resp.setHeader("Cache-Control","no-cache");
}
private void setAppropriateWarningHeaders(HttpServletResponse resp,
Status currentStatus) {
if (Status.DEGRADED.equals(currentStatus)) {
resp.addHeader("Warning", "199 jrugged \"Status degraded\"");
}
}
private void writeOutCurrentStatusInResponseBody(HttpServletResponse resp,
Status currentStatus) throws IOException {
resp.setHeader("Content-Type","text/plain;charset=utf-8");
String body = currentStatus + "\n";
byte[] bytes = body.getBytes();
resp.setHeader("Content-Length", bytes.length + "");
OutputStream out = resp.getOutputStream();
out.write(bytes);
out.flush();
out.close();
}
private void setResponseCode(Status currentStatus, HttpServletResponse resp) {
if (responseCodeMap.containsKey(currentStatus)) {
resp.setStatus(responseCodeMap.get(currentStatus));
}
}
}