HealthCheckShallow.java

/**
 * Copyright 2012 Comcast Corporation
 * 
 * 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.comcast.cmb.common.controller;

import javax.servlet.AsyncContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.comcast.cmb.common.model.CMBPolicy;
import com.comcast.cmb.common.model.User;
import com.comcast.cmb.common.persistence.AbstractDurablePersistence;
import com.comcast.cmb.common.persistence.DurablePersistenceFactory;
import com.comcast.cmb.common.persistence.PersistenceFactory;
import com.comcast.cmb.common.util.CMBProperties;
import com.comcast.cqs.controller.CQSAction;

/**
 * Provide a basic health-check URL for load-balancers to hit to monitor whether service is up and version
 * @author aseem
 */
public class HealthCheckShallow extends CQSAction {

    public HealthCheckShallow() {
        super("HealthCheck");
    }

    @Override
    public boolean isActionAllowed(User user, HttpServletRequest request, String service, CMBPolicy policy) throws Exception {
    	return true;
    }
    
    @Override
    public boolean isAuthRequired() {
        return false;
    }

    @Override
    public boolean doAction(User user, AsyncContext asyncContext) throws Exception {     
    	
        HttpServletResponse response = (HttpServletResponse)asyncContext.getResponse();
        
    	boolean healthy = true;
    	
        StringBuffer sb = new StringBuffer("");
        
        sb.append("<HealthCheckResponse>\n");
        sb.append("\t<Version>" + CMBControllerServlet.VERSION + "</Version>\n");
        
        if (CMBProperties.getInstance().getCQSServiceEnabled()) {
	        try {
	        	
	        	if (PersistenceFactory.getCQSMessagePersistence().isAlive()) {
	        		sb.append("\t<Redis>OK</Redis>\n");
	        	} else {
	        		sb.append("\t<Redis>All shards down.</Redis>\n");
	        		healthy = false;
	        	}
	        	
	        } catch (Exception ex) {
	    		sb.append("\t<Redis>Cache unavailable: "+ex.getMessage()+"</Redis>\n");
	    		healthy = false;
	        }
        }
        
        try {
        	
        	AbstractDurablePersistence cassandra = DurablePersistenceFactory.getInstance();
        	
        	if (cassandra.isAlive()) {
        		sb.append("\t<Cassandra>OK</Cassandra>\n");
        	} else {
        		sb.append("\t<Cassandra>Ring unavailable.</Cassandra>\n");
        		healthy = false;
        	}
        	
        } catch (Exception ex) {
    		sb.append("\t<Cassandra>Ring unavailable: "+ex.getMessage()+"</Cassandra>\n");
    		healthy = false;
        }
        
        // for now do not include cns worker availability in health check 
        
        /*if (CMBProperties.getInstance().getCNSServiceEnabled()) {

        	try {
        	
	        	List<CNSWorkerStats> statsList = CNSGetWorkerStatsAction.getWorkerStats();
	        	
	        	if (statsList.size() == 0) {
	        		sb.append("\t<CNSWorkers>Zero workers available.</CNSWorkers>\n");
	        		healthy = false;
	        	} else {
	        		int activeCount = 0;
	        		int overloadedCount = 0;
	    			long now = System.currentTimeMillis();
	        		for (CNSWorkerStats stats : statsList) {
	        			if (now-stats.getConsumerTimestamp()<5*60*1000 || now-stats.getProducerTimestamp()<5*60*1000) {
		        			if (stats.isConsumerOverloaded()) {
		        				overloadedCount++;
		        				healthy = false;
		        			} else {
		        				activeCount++;
		        			}
	        			}
	        		}
	        		if (activeCount >= 1 && overloadedCount == 0) {
	        			sb.append("\t<CNSWorkers>OK</CNSWorkers>\n");
	        		} else {
	        			sb.append("\t<CNSWorkers>"+activeCount+" active workers, "+overloadedCount+" overladed workers.</CNSWorkers>\n");
	        		}
	        		if (activeCount == 0) {
	        			healthy = false;
	        		}
	        	}
	        	
	        } catch (Exception ex) {
	    		sb.append("\t<CNSWorkers>Unknown state: "+ex.getMessage()+"</CNSWorkers>\n");
	    		healthy = false;
	        }
        }*/

        sb.append("</HealthCheckResponse>");
        
    	if (healthy) {
    		response.setStatus(HttpServletResponse.SC_OK);
    	} else {
    		response.setStatus(HttpServletResponse.SC_SERVICE_UNAVAILABLE);
    	}
    	
    	writeResponse(sb.toString(), response);
        
        return true;
    }
}