Lab_team_2

Lab Pre Requisite

• Maven 3.0.x

• YSlow Plugin installed on your favorite browser ( chrome, firefox)

• Google PageSpeed extension for Chrome or Firefox

Lab Agenda

The application

Initial Architecture

Add Expire Headers

Use Apache Httpd as a Caching Proxy

Use Varnish Caching Proxy

Use Amazon CloudFront CDN

1. Connect to your Cokctail App

Connect to your application http://xfr-cocktail-2.elasticbeanstalk.com/cocktail/.

2. Download Cocktail App

Get the Cocktail App on Github (download it or clone it) : https://github.com/xebia-france/workshop-web-caching-cocktail

3. Build Cocktail App

Build the application with Maven

mvn package

4. Create your CDN Distribution with Amazon CloudFront

Note: as the creation of a CDN distribution takes several minutes with Amazon CloudFront, we create it at the beginning of the lab and we will use it later.

1. Connect to Amazon AWS Console: https://xebia-france.signin.aws.amazon.com/console

2. Open Services > CloudFront tab

   

3. Click on Create Distribution

   

4. Select Download delivery method

   

5. Enter Origin Domain Name: xfr-cocktail-2.elasticbeanstalk.com and Origin Protocol Policy: Match Viewer

   

6. Keep default cache behaviors

   

7. Keep default Distribution details

   

8. Review your configuration

   

9. Verify that your distribution is being created

   

Congratulations, you have created your CDN Distribution!

Note: Don't wait for the completion of this creation, go to the next exercice.

5. Find Web Caching Issues with YSlow

Analyse with YSlow the web page http://xfr-cocktail-2.elasticbeanstalk.com/cocktail/.

During this lab, we will focus on two YSlow recommandations:

• Add Expires Headers

  

• Use a Content Delivery Network (CDN)

  

6. Add Expires Headers

See docs:

• W3C > RFC 2616 - Hypertext Transfer Protocol - HTTP/1.1 > 14 Header Field Definitions > Cache-Control
• YSlow > Best Practices for Speeding Up Your Web Site > Add an Expires or a Cache-Control Header

Info: Adding Expires Headers programmatically according to the business logic

This step is purely informational, the next exercise is 'Adding Expires Headers With a Servlet Filter'.

You can define the caching policy according to the business logic. For example, an RSS feed could be cached for 5 minutes.

Java - Spring MVC Sample

See CocktailManager.java.

Behavior

1. Query the /rss URL:

    curl -v http://xfr-cocktail-2.elasticbeanstalk.com/rss
   

2. Look at the Cache-Control and Expires header in the response

    < HTTP/1.1 200 OK
    < Cache-Control: public, max-age=300
    < Content-Language: en-US
    < Content-Type: application/rss+xml;charset=ISO-8859-1
    < Date: Wed, 06 Jun 2012 18:40:16 GMT
    < Expires: Wed, 06 Jun 2012 18:45:16 GMT
    < Server: Apache-Coyote/1.1
    < transfer-encoding: chunked
    < Connection: keep-alive
   

Adding Expires Headers With a Servlet Filter

Docs available at Google Code - Xebia France > ExpiresFilter.

1. Modify src/main/webapp/WEB-INF/web.xml(source) to add an ExpiresFilter:

     	<filter>
    	   <filter-name>ExpiresFilter</filter-name>
    	   <filter-class>fr.xebia.servlet.filter.ExpiresFilter</filter-class>
    	   <init-param>
    	      <param-name>ExpiresByType image</param-name>
    	      <param-value>access plus 1 year</param-value>
    	   </init-param>
    	   <init-param>
    	      <param-name>ExpiresByType text/css</param-name>
    	      <param-value>access plus 1 year</param-value>
    	   </init-param>
    	   <init-param>
    	      <param-name>ExpiresByType application/javascript</param-name>
    	      <param-value>access plus 1 year</param-value>
    	   </init-param>
    	</filter>
    	...
    	<filter-mapping>
    	   <filter-name>ExpiresFilter</filter-name>
    	   <url-pattern>/*</url-pattern>
    	   <dispatcher>REQUEST</dispatcher>
    	</filter-mapping>
   

2. Repackage your application

    mvn package
   

3. Deploy the new version named of your application on your Amazon Elastic Beanstalk environment xfr-cocktail-2 with Version Label: 1.1.0-team-2

   1. Connect to https://console.aws.amazon.com/elasticbeanstalk/home?region=eu-west-1

   2. Select your environment xfr-cocktail-2 and click on Deploy a Different Version:

   ![Beanstalk Update Version 1](beanstalk-update-version-1.png)
   

   1. Select Upload and deploy a new version and enter Version Label: 1.1.0-team-2

   ![Beanstalk Update Version 2](beanstalk-update-version-2.png)
   

   1. Click on Deploy Version and wait for the deployment

   2. Verify with YSlow that your expiration headers appeared: http://xfr-cocktail-2.elasticbeanstalk.com/cocktail/

Cheat sheet: deploy version `1.1.0` if you have a problem deploying your own patched version.

Congratulations!!! You fixed the first YSlow recommandation to add Expires Headers

Adding Expires Headers with Apache Httpd mod_expires

This step is purely informational, the next exercise is 'Add a Caching Proxy with Apache mod_cache in front of the Tomcat Server'.

Apache > HTTP Server > Documentation > Version 2.2 > Modules > mod_expires

Sample of of httpd.conf

ExpiresByType image "access plus 1 year"
ExpiresByType text/css "access plus 1 year"
ExpiresByType text/javascript "access plus 1 year"

7. Add a Caching Proxy with Apache mod_cache in front of the Tomcat Server

Enable mod_proxy between Apache and Tomcat

Apache > HTTP Server > Documentation > Version 2.2 > Modules > mod_proxy

1. Download the web-caching-workshop.pem SSH private key

    cd
    mkdir .aws
    cd .aws
    wget http://xfr-workshop-caching.s3-website-eu-west-1.amazonaws.com/web-caching-workshop.pem
    chmod 400 web-caching-workshop.pem
    echo "Certificate 'web-caching-workshop.pem' installed under `pwd`"
   

2. Connect to your proxy server www-cocktail-2.aws.xebiatechevent.info

    ssh -i web-caching-workshop.pem [email protected]
   

3. Configure Apache mod_proxy

   1. Create a conf.d/cocktail.conf configuration fragment to configure mod_proxy

       sudo vi /etc/httpd/conf.d/cocktail.conf
      

   2. Add a ProxyPass directive in cocktail.conf

       # connect Apache to Tomcat
       ProxyPass / http://xfr-cocktail-2.elasticbeanstalk.com/
      

4. Restart Apache

    sudo service httpd restart
   

5. Verify opening in your browser http://www-cocktail-2.aws.xebiatechevent.info/cocktail/

WARNING: a production ready `mod_proxy` configuration is more complex.

Enable mod_cache

See Apache > HTTP Server > Documentation > Version 2.2 > Modules > mod_cache

1. Connect to your proxy server www-cocktail-2.aws.xebiatechevent.info

    ssh -i web-caching-workshop.pem [email protected]
   

2. Enabled mod_disk_cache in httpd.conf

   1. Edit httpd.conf

       sudo vi /etc/httpd/conf/httpd.conf
      

   2. Unncoment

       <IfModule mod_disk_cache.c>
           CacheEnable disk /
           CacheRoot "/var/cache/mod_proxy"
       </IfModule>
      

3. Restart Apache

    sudo service httpd restart
   

4. Verify that the Httpd Server successfully restarted opening in your browser http://www-cocktail-2.aws.xebiatechevent.info/cocktail/

WARNING: a production ready `mod_disk_cache` configuration is more complex, you must schedule a disk cleaner (TODO add hyperlink to disk cleaner).

Check response caching with Apache Httpd mod_cache

Apache Httpd 2.2 does not add a X-Cache-Detail header to the HTTP response in order to ease debugging of page caching.

This X-Cache-Detail header has been introduced in Apache Httpd 2.4 with the CacheDetailHeader directive.

As of Apache 2.2, you can check that a resource has been served by mod_cache rather than by Tomcat checking the existence of the Age header.

Query twice the URL to load the resource in the caching resource.

curl -v http://www-cocktail-2.aws.xebiatechevent.info/css/bootstrap.min.css | more
curl -v http://www-cocktail-2.aws.xebiatechevent.info/css/bootstrap.min.css | more

Sample of response without caching

< HTTP/1.1 200 OK
< Date: Mon, 28 May 2012 13:57:24 GMT
< Server: Apache-Coyote/1.1                        <==== RESPONSE GENERATED BY TOMCAT
< Cache-Control: max-age=86400
< Content-Type: text/css
< Expires: Tue, 29 May 2012 13:57:24 GMT
< Last-Modified: Sun, 01 Apr 2012 14:07:28 GMT
< Content-Length: 81150
< Connection: close

Sample of response with caching

< HTTP/1.1 200 OK
< Date: Mon, 28 May 2012 13:43:18 GMT
< Server: Apache/2.2.22 (Amazon)                   <==== RESPONSE GENERATED BY APACHE HTTPD
< Last-Modified: Sun, 01 Apr 2012 14:07:28 GMT
< Cache-Control: max-age=86400
< Expires: Tue, 29 May 2012 13:08:40 GMT
< Age: 222									       <==== 'Age': DURATION IN CACHE IN SECS
< Content-Length: 81150
< Connection: close
< Content-Type: text/css

W3C > RFC 2616 - Hypertext Transfer Protocol - HTTP/1.1 > 14 Header Field Definitions > Age

The Age response-header field conveys the sender's estimate of the amount of time since the response (or its revalidation) was generated at the origin server. A cached response is "fresh" if its age does not exceed its freshness lifetime.

8. Configure Varnish

• Varnish 3.0 Documentation

Connect via SSH to the varnish server

ssh -i web-caching-workshop.pem [email protected]

Setup Backend server

1. Edit default.vcl and setup your backend server:

    sudo vi /etc/varnish/default.vcl
   

2. Update backend default:

    backend default {
        .host = "xfr-cocktail-2.elasticbeanstalk.com";
        .port = "80";
    }
   

3. Restart Varnish:

    sudo service varnish restart
   

4. Verify that the Httpd Server successfully restarted opening in your browser http://www-cocktail-2.aws.xebiatechevent.info:6081/cocktail/

Add X-Cache and X-Cacheable header

By default Varnish does not inform us about its execution, let's set up some configuration to keep informed about cache usage per request. X-Cache header will get HIT when resource was found in cache or MISS if not in cache.

1. Edit default.vcl

    sudo vi /etc/varnish/default.vcl
   

2. Add vcl_fetch and vcl_deliver routines in default.vcl (after backend default directive):

    sub vcl_fetch {
    
        # Varnish determined the object was not cacheable
        if (!beresp.cacheable) {
            set beresp.http.X-Cacheable = "NO:Not Cacheable";
    
        # You are respecting the Cache-Control=private header from the backend
        } elsif (beresp.http.Cache-Control ~ "private") {
            set beresp.http.X-Cacheable = "NO:Cache-Control=private";
            return(pass);
        
        # You are extending the lifetime of the object artificially
        }  else {
            set beresp.http.X-Cacheable = "YES";
        }
        
        # ....
        
        return(deliver);
    }
    
    sub vcl_deliver {
        if (obj.hits > 0) {
            set resp.http.X-Cache = "HIT";
        } else {
            set resp.http.X-Cache = "MISS";
        }
    }
   

3. Restart Varnish:

    sudo service varnish restart
   

4. Verify the existence of the

    curl -v http://www-cocktail-2.aws.xebiatechevent.info:6081/css/bootstrap.min.css | more
   

Now you should see the X-Cache header indicating wether the cache hit or miss, X-Cacheable will display wether the resource was cacheable or not and why.

Sample of response without caching

< HTTP/1.1 200 OK
< Cache-Control: max-age=31536000
< Content-Type: text/css
< Expires: Mon, 03 Jun 2013 23:13:44 GMT
< Last-Modified: Sun, 01 Apr 2012 14:07:28 GMT
< Server: Apache-Coyote/1.1
< X-Cacheable: YES                                <==== CACHEABLE BY VARNISH
< Content-Length: 81150
< Date: Sun, 03 Jun 2012 23:13:44 GMT
< X-Varnish: 758000267
< Age: 0
< Via: 1.1 varnish
< Connection: keep-alive
< X-Cache: MISS                                    <==== VARNISH MISS

Sample of response with caching

< HTTP/1.1 200 OK
< Cache-Control: max-age=31536000
< Content-Type: text/css
< Expires: Mon, 03 Jun 2013 23:13:44 GMT
< Last-Modified: Sun, 01 Apr 2012 14:07:28 GMT
< Server: Apache-Coyote/1.1                       <==== VARNISH DOESN'T MODIFY THE SERVER HEADER
< X-Cacheable: YES                                <==== CACHEABLE BY VARNISH
< Content-Length: 81150
< Date: Sun, 03 Jun 2012 23:14:10 GMT
< X-Varnish: 758000268 758000267
< Age: 27
< Via: 1.1 varnish
< Connection: keep-alive
< X-Cache: HIT                                    <==== VARNISH HIT

Note about Varnish default behaviour

By default Varnish consider requests with Cookie and response with Set-Cookie not cacheable and just pass the request as a simple reverse proxy to the backend. A solution is to force Varnish to cache resources even though there is one or more Cookie header present in request.

Add vcl_recv routine in /etc/varnish/default.vcl:

sub vcl_recv {
    if (req.restarts == 0) {
        if (req.http.x-forwarded-for) {
            set req.http.X-Forwarded-For =
                req.http.X-Forwarded-For + ", " + client.ip;
        } else {
            set req.http.X-Forwarded-For = client.ip;
        }
    }
    if (req.request != "GET" &&
      req.request != "HEAD" &&
      req.request != "PUT" &&
      req.request != "POST" &&
      req.request != "TRACE" &&
      req.request != "OPTIONS" &&
      req.request != "DELETE") {
        /* Non-RFC2616 or CONNECT which is weird. */
        return (pipe);
    }
    if (req.request != "GET" && req.request != "HEAD") {
        /* We only deal with GET and HEAD by default */
        return (pass);
    }
    if (req.http.Authorization) {
        /* Not cacheable by default */
        return (pass);
    }
     /* Now let's use the cache */
    return (lookup);
}

Restart Varnish and check access:

sudo service varnish restart


curl -v http://www-cocktail-2.aws.xebiatechevent.info:6081/css/bootstrap.min.css | more

With this setup, Varnish will cache resources even if a session Cookie is present in the request.

Configure Backend probe

Backend probes will monitor backend health wich allows to use grace mode to keep delivering resources while backend server is down.

Update the backend default directive in default.vcl:

backend default {
    .host = "xfr-cocktail-clc.elasticbeanstalk.com";
    .port = "80";
    .probe = {
        .url = "/";
        .timeout = 0.3 s;
        .window = 8;
        .threshold = 3;
        .initial = 3;
    }
}

Add req.grace timeout in vcl_recv and vcl_fetch routines /etc/varnish/default.vcl:

sub vcl_recv {
    # ....
    set req.grace = 120m;
    # ....
}
sub vcl_fetch {
    # ....
    set beresp.grace = 120m;
    # ....
}

Now if the backend goes down, Varnish will keep resources and deliver them during grace timeout.

9. Use Amazon CloudFront as a CDN to Deliver the Cacheable Content

Verify the behavior of the CloudFront Distribution

1. Go to CloudFront tab

   

2. Get the base URL of your distribution

   The hostname of the distribution looks like d1mm4v4zybjqbh.cloudfront.net

   

3. Open the cocktail app in your browser via the CloudFront distribution URL (something like http://d1mm4v4zybjqbh.cloudfront.net/)

   

Look at the integration of the CDN URL in the application

Here is a technique to use switchable CDN URLs in your application. Other techniques exist.

Look at the use of ${cdnUrl} in view.jsp (source):

<link rel="shortcut icon" href="${cdnUrl}${pageContext.request.contextPath}/img/favicon.ico">
... 
<link href="${cdnUrl}${pageContext.request.contextPath}/css/bootstrap.min.css" media="screen" rel="stylesheet" type="text/css" />
...
<script src="${cdnUrl}${pageContext.request.contextPath}/js/bootstrap.min.js" type="text/javascript"></script>

And the injection of cdn_url System Property as cdnUrl variable in JSP Expression Language in spring-mvc-servlet.xml (source)

<!-- source 'cdn_url' from the system-properties -->
<context:property-placeholder system-properties-mode="OVERRIDE" />

<!-- inject 'cdn_url' as "cdnUrl" in JSP EL variables -->
<bean class="org.springframework.web.context.support.ServletContextAttributeExporter">
    <property name="attributes">
        <map>
            <entry key="cdnUrl" value="${cdn_url:}/>
        </map>
    </property>
</bean>

Declare cdn_url System Property

1. Edit the configuration of your Amazon Beanstalk Tomcat Environment

   

2. Add a JVM Command Line Options: -Dcdn_url=http://...FIXME....cloudfront.net and click on Apply Changes

   

3. Once your application is restarted, reopen in your browser http://xfr-cocktail-2.elasticbeanstalk.com/

4. Verify in the HTML source code that the CloudFront CDN Distribution servers

   

10. CONCLUSION

You learned in this workshop how to:

• Add expiration headers to a Java web application
• Use Apache Httpd as a Caching Proxy
• Configure Varnish Caching Proxy
• Use the Content Delivery Network Amazon CloudFront
• Integrate CDN based URLs in a web application