AEM Cloud Service - Invalidate Dispatcher and Purge Fastly CDN Cache using API

Goal

A simple servlet /bin/eaem/cache/invalidate for operations team to Invalidate Dispatcher and Purge Fastly CDN cache on demand for a page...

Clear CDN Cache

1) Page served from CDN Cache (Response Header - x-cache: HIT)

2) Purge the Page in cache by executing API request added in servlet /bin/eaem/cache/invalidate. Required in payload, Fastly Purge Key can be requested from the support...

https://author-p10961-e880305.adobeaemcloud.com/bin/eaem/cache/invalidate?type=CDN&publishHost=publish-p10961-e878563.adobeaemcloud.com&purgeKey=32e62d78xxxxxxxxxxxxxxxxx9c9xxxxxxxxxxx922&path=/content/eaem-svg-stream-clear-cache/us/en/dispatcher-and-cdn.html

3) After Purge, request to the page returns x-cache: MISS, meaning the response was served from dispatcher...

3) Page purge using a POSTMAN request..

Clear Dispatcher Cache

1) Page served from Dispatcher Cache

2) Request executed for purging page cache in dispatcher...

https://author-p10961-e880305.adobeaemcloud.com/bin/eaem/cache/invalidate?type=DISPATCHER&path=/content/eaem-svg-stream-clear-cache/us/en/dispatcher

3) Dispatcher INVALIDATE call logged in author distribution logs...

https://author-p10961-e880305.adobeaemcloud.com/ui#/aem/libs/granite/distribution/content/distribution-agent.html?agentName=publish

4) Further requests to the page first log [actionmiss] at dispatcher (requesting the page from publisher) and later log [actionhit] (served from dispatcher)

Solution

1) Add a servlet with path /bin/eaem/cache/invalidate with necessary API to execute purge cache requests to Dispatcher and CDN...

package apps.eaem.assets.core.servlets;

import org.apache.commons.lang3.StringUtils;
import org.apache.http.HttpHost;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.message.BasicHttpRequest;
import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.SlingHttpServletResponse;
import org.apache.sling.api.resource.ResourceResolver;
import org.apache.sling.api.servlets.SlingSafeMethodsServlet;
import org.apache.sling.distribution.*;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.component.annotations.Reference;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.servlet.Servlet;
import javax.servlet.ServletException;
import java.io.IOException;
import java.io.PrintWriter;

@Component(
        name = "Experience AEM Invalidate Cache Servlet",
        immediate = true,
        service = Servlet.class,
        property = {
                "sling.servlet.methods=GET",
                "sling.servlet.paths=/bin/eaem/cache/invalidate"
        }
)
public class InvalidateCacheServlet extends SlingSafeMethodsServlet {
    private static final Logger LOGGER = LoggerFactory.getLogger(InvalidateCacheServlet.class);

    private static final String PUBLISH_AGENT = "publish";

    @Reference
    private Distributor distributor;

    @Override
    protected void doGet(SlingHttpServletRequest request, SlingHttpServletResponse response)
            throws ServletException, IOException {
        try{
            String path = request.getParameter("path");
            String type = request.getParameter("type");

            if(StringUtils.isEmpty(type)){
                type = "BOTH";
            }

            PrintWriter writer = response.getWriter();

            if(StringUtils.isEmpty(path)){
                writer.println("---->Empty Path, nothing to invalidate");
                return;
            }

            ResourceResolver resolver = request.getResourceResolver();

            if("DISPATCHER".equals(type)){
                writer.println("---->DISPATCHER CLEAR CACHE VIA SERVLET : " + path + "\n");
                clearDispatcherCache(resolver, path, writer);
            }else if("CDN".equals(type)){
                writer.println("---->CDN CLEAR CACHE VIA SERVLET : " + path + "\n");
                clearCDNCache(path, writer, request);
            }else{
                LOGGER.info("---->DISPATCHER AND CDN CLEAR CACHE VIA SERVLET : " + path);
                clearDispatcherCache(resolver, path, writer);
                clearCDNCache(path, writer, request) ;
            }
        }catch(Exception e){
            throw new ServletException("Error", e);
        }
    }

    private void clearDispatcherCache(ResourceResolver resolver, String path, PrintWriter writer ){
        DistributionRequest distributionRequest = new SimpleDistributionRequest(DistributionRequestType.INVALIDATE, false, path);

        DistributionResponse dResponse = distributor.distribute(PUBLISH_AGENT, resolver, distributionRequest);

        if(!dResponse.isSuccessful()){
            writer.println("Error Dispatcher Clear : " + dResponse.getDistributionInfo().getId() + " - " + dResponse.getMessage());
        }else{
            writer.println("Success Dispatcher Cache cleared successfully for - " + path + ", " + dResponse.getMessage());
        }
    }

    private void clearCDNCache(String path, PrintWriter writer, SlingHttpServletRequest request ) throws Exception{
        String CDN_PUBLISH_HOST = request.getParameter("publishHost");
        String PURGE_KEY = request.getParameter("purgeKey");
        String METHOD_PURGE = "PURGE";

        HttpHost host = new HttpHost(CDN_PUBLISH_HOST,443,"https");
        HttpClient httpclient = HttpClientBuilder.create().build();

        BasicHttpRequest purgeRequest = new BasicHttpRequest(METHOD_PURGE, path);
        purgeRequest.addHeader("x-aem-purge-key", PURGE_KEY);

        HttpResponse cdnResponse = httpclient.execute(host, purgeRequest);
        writer.println("Success : " + cdnResponse.getStatusLine());
    }
}

2) For testing purposes two pages were created, using the following configuration in dispatcher\src\conf.d\available_vhosts\eaem.vhost, page dispatcher.html is only cached on Dispatcher and page dispatcher-and-cdn.html is cached on both Dispatcher and CDN

   <LocationMatch "/content/eaem-svg-stream-clear-cache/us/en/dispatcher-and-cdn.html">
    Header add X-EAEM-TEST "eaem-disp-cdn-01-04"
   </LocationMatch>

   <LocationMatch "/content/eaem-svg-stream-clear-cache/us/en/dispatcher.html">
       Header add X-EAEM-TEST "eaem-disp-01-04"
       Header unset Surrogate-Control
       Header always set Surrogate-Control "no-store, no-cache"
   </LocationMatch>