Posts Tagged ‘HTTPS’

Improve Apache Load Balancing with mod_cluster – Apaches to Tomcats Application servers Get Better Load Balancing

Thursday, March 31st, 2016


Earlier I've blogged on How to set up Apache to to serve as a Load Balancer for 2, 3, 4  etc. Tomcat / other backend application servers with mod_proxy and mod_proxy_balancer, however though default Apache provided mod_proxy_balancer works fine most of the time, If you want a more precise and sophisticated balancing with better load distribuion you will probably want to install and use mod_cluster instead.


So what is Mod_Cluster and why use it instead of Apache proxy_balancer ?

Mod_cluster is an innovative Apache module for HTTP load balancing and proxying. It implements a communication channel between the load balancer and back-end nodes to make better load-balancing decisions and redistribute loads more evenly.

Why use mod_cluster instead of a traditional load balancer such as Apache's mod_balancer and mod_proxy or even a high-performance hardware balancer?

Thanks to its unique back-end communication channel, mod_cluster takes into account back-end servers' loads, and thus provides better and more precise load balancing tailored for JBoss and Tomcat servers. Mod_cluster also knows when an application is undeployed, and does not forward requests for its context (URL path) until its redeployment. And mod_cluster is easy to implement, use, and configure, requiring minimal configuration on the front-end Apache server and on the back-end servers.

So what is the advantage of mod_cluster vs mod proxy_balancer ?

Well here is few things that turns the scales  in favour for mod_cluster:


  •     advertises its presence via multicast so as workers can join without any configuration
  •     workers will report their available contexts
  •     mod_cluster will create proxies for these contexts automatically
  •     if you want to, you can still fine-tune this behaviour, e.g. so as .gif images are served from httpd and not from workers…
  •     most importantly: unlike pure mod_proxy or mod_jk, mod_cluster knows exactly how much load there is on each node because nodes are reporting their load back to the balancer via special messages
  •     default communication goes over AJP, you can use HTTP and HTTPS


1. How to install mod_cluster on Linux ?

You can use mod_cluster either with JBoss or Tomcat back-end servers. We'll install and configure mod_cluster with Tomcat under CentOS; using it with JBoss or on other Linux distributions is a similar process. I'll assume you already have at least one front-end Apache server and a few back-end Tomcat servers installed.

To install mod_cluster, first download the latest mod_cluster httpd binaries. Make sure to select the correct package for your hardware architecture – 32- or 64-bit.
Unpack the archive to create four new Apache module files:,,, and We won't need; it advertises the location of the load balancer through multicast packets, but we will use a static address on each back-end server.

Copy the other three .so files to the default Apache modules directory (/etc/httpd/modules/ for CentOS).
Before loading the new modules in Apache you have to remove the default proxy balancer module ( because it is not compatible with mod_cluster.

Edit the Apache configuration file (/etc/httpd/conf/httpd.conf) and remove the line


LoadModule proxy_balancer_module modules/


Create a new configuration file and give it a name such as /etc/httpd/conf.d/mod_cluster.conf. Use it to load mod_cluster's modules:




LoadModule slotmem_module modules/
LoadModule manager_module modules/
LoadModule proxy_cluster_module modules/

In the same file add the rest of the settings you'll need for mod_cluster something like:

And for permissions and Virtualhost section



        Order deny,allow
        Allow from all 192.168

    ManagerBalancerName mymodcluster

ProxyPass / balancer://mymodcluster/

The above directives create a new virtual host listening on port 9999 on the Apache server you want to use for load balancing, on which the load balancer will receive information from the back-end application servers. In this example, the virtual host is listening on IP address, and for security reasons it allows connections only from the network.
The directive ManagerBalancerName defines the name of the cluster – mymodcluster in this example. The directive EnableMCPMReceive allows the back-end servers to send updates to the load balancer. The standard ProxyPass and ProxyPassReverse directives instruct Apache to proxy all requests to the mymodcluster balancer.
That's all you need for a minimal configuration of mod_cluster on the Apache load balancer. At next server restart Apache will automatically load the file mod_cluster.conf from the /etc/httpd/conf.d directory. To learn about more options that might be useful in specific scenarios, check mod_cluster's documentation.

While you're changing Apache configuration, you should probably set the log level in Apache to debug when you're getting started with mod_cluster, so that you can trace the communication between the front- and the back-end servers and troubleshoot problems more easily. To do so, edit Apache's configuration file and add the line LogLevel debug, then restart Apache.

2. How to set up Tomcat appserver for mod_cluster ?

Mod_cluster works with Tomcat version 6, 7 and 8, to set up the Tomcat back ends you have to deploy a few JAR files and make a change in Tomcat's server.xml configuration file.
The necessary JAR files extend Tomcat's default functionality so that it can communicate with the proxy load balancer. You can download the JAR file archive by clicking on "Java bundles" on the mod_cluster download page. It will be saved under the name mod_cluster-parent-1.2.6.Final-bin.tar.gz.

Create a new directory such as /root/java_bundles and extract the files from mod_cluster-parent-1.2.6.Final-bin.tar.gz there. Inside the directory /root/java_bundlesJBossWeb-Tomcat/lib/*.jar you will find all the necessary JAR files for Tomcat, including two Tomcat version-specific JAR files – mod_cluster-container-tomcat6-1.2.6.Final.jar for Tomcat 6 and mod_cluster-container-tomcat7-1.2.6.Final.jar for Tomcat 7. Delete the one that does not correspond to your Tomcat version.

Copy all the files from /root/java_bundlesJBossWeb-Tomcat/lib/ to your Tomcat lib directory – thus if you have installed Tomcat in


run the command:


cp -rpf /root/java_bundles/JBossWeb-Tomcat/lib/* /srv/tomcat/lib/.


Then edit your Tomcat's server.xml file


After the default listeners add the following line:


<listener classname="org.jboss.modcluster.container.catalina.standalone.ModClusterListener" proxylist=""> </listener>

This instructs Tomcat to send its mod_cluster-related information to IP on TCP port 9999, which is what we set up as Apache's dedicated vhost for mod_cluster.
While that's enough for a basic mod_cluster setup, you should also configure a unique, intuitive JVM route value on each Tomcat instance so that you can easily differentiate the nodes later. To do so, edit the server.xml file and extend the Engine property to contain a jvmRoute, like this:



<engine defaulthost="localhost" jvmroute="node2" name="Catalina"></engine>

Assign a different value, such as node2, to each Tomcat instance. Then restart Tomcat so that these settings take effect.

To confirm that everything is working as expected and that the Tomcat instance connects to the load balancer, grep Tomcat's log for the string "modcluster" (case-insensitive). You should see output similar to:

Mar 29, 2016 10:05:00 AM org.jboss.modcluster.ModClusterService init
INFO: MODCLUSTER000001: Initializing mod_cluster ${project.version}
Mar 29, 2016 10:05:17 AM org.jboss.modcluster.ModClusterService connectionEstablished
INFO: MODCLUSTER000012: Catalina connector will use /

This shows that mod_cluster has been successfully initialized and that it will use the connector for, the configured IP address for the main listener.
Also check Apache's error log. You should see confirmation about the properly working back-end server:

[Tue Mar 29 10:05:00 2013] [debug] proxy_util.c(2026): proxy: ajp: has acquired connection for (
[Tue Mar 29 10:05:00 2013] [debug] proxy_util.c(2082): proxy: connecting ajp:// to
[Tue Mar 29 10:05:00 2013] [debug] proxy_util.c(2209): proxy: connected / to
[Tue Mar 29 10:05:00 2013] [debug] mod_proxy_cluster.c(1366): proxy_cluster_try_pingpong: connected to backend
[Tue Mar 29 10:05:00 2013] [debug] mod_proxy_cluster.c(1089): ajp_cping_cpong: Done
[Tue Mar 29 10:05:00 2013] [debug] proxy_util.c(2044): proxy: ajp: has released connection for (

This Apache error log shows that an AJP connection with was successfully established and confirms the working state of the node, then shows that the load balancer closed the connection after the successful attempt.

You can start testing by opening in a browser the example servlet SessionExample, which is available in a default installation of Tomcat.
Access this servlet through a browser at the URL http://balancer_address/examples/servlets/servlet/SessionExample. In your browser you should see first a session ID that contains the name of the back-end node that is serving your request – for instance, Session ID: 5D90CB3C0AA05CB5FE13121E4B23E670.node2.

Next, through the servlet's web form, create different session attributes. If you have a properly working load balancer with sticky sessions you should always (that is, until your current browser session expires) access the same node, with the previously created session attributes still available.

To test further to confirm load balancing is in place, at the same time open the same servlet from another browser. You should be redirected to another back-end server where you can conduct a similar session test.
As you can see, mod_cluster is easy to use and configure. Give it a try to address sporadic single-back-end overloads that cause overall application slowdowns.

How to use wget and curl via HTTP Proxy server / How to set a HTTPS proxy server on a bash shell on Linux

Wednesday, January 27th, 2016


I've been working a bit on a client's automation, the task is to automate process of installations of Apaches / Tomcats / JBoss and Java servers, so me and colleagues don't waste too
much time in trivial things. To complete that I've created a small repository on a Apache with a WebDav server with major versions of each general branch of Application servers and Javas.
In order to access the remote URL where the .tar.gz binaries archives reside, I had to use a proxy serve as the client runs all his network in a DMZ and all Web Port 80 and 443 HTTPS traffic inside the client network
has to pass by the network proxy.

Thus to make the downloads possible via the shell script, writting I needed to set the script to use the HTTPS proxy server. I've been using proxy earlier and I was pretty aware of the http_proxy bash shell
variable thus I tried to use this one for the Secured HTTPS proxy, however the connection was failing and thanks to colleague Anatoliy I realized the whole problem is I'm trying to use http_proxy shell variable
which has to only be used for unencrypted Proxy servers and in this case the proxy server is over SSL encrypted HTTPS protocol so instead the right variable to use is:


The https_proxy var syntax, goes like this:

export https_proxy="$proxy_url"


Once the https_proxy variable is set  UNIX's wget non interactive download tool starts using the proxy_url variable set proxy and the downloads in my script works.

Hence to make the different version application archives download work out, I've used wget like so:

 wget –no-check-certificate –timeout=5

For other BSD / HP-UX / SunOS UNIX Servers where  shells are different from Bourne Again (Bash) Shell, the http_proxy and  https_proxy variable might not be working.
In such cases if you have curl (command line tool) is available instead of wget to script downloads you can use something like:

 curl -O -1 -k –proxy

The http_proxy and https_proxy variables works perfect also on Mac OS X, default bash shell, so Mac users enjoy.
For some bash users in some kind of firewall hardened environments like in my case, its handy to permanently set a proxy to all shell activities via auto login Linux / *unix scripts .bashrc or .bash_profile that saves the inconvenience to always
set the proxy so lynx and links, elinks text console browsers does work also anytime you login to shell.

Well that's it, my script enjoys proxying traffic 🙂

Fiddler – Windows web debugging proxy for any browser – Linux web debugging applications

Thursday, May 29th, 2014

Earlier I've blogged about helpful web developer or a web hosting system administrator Web Browser plugins . Among the list of useful plugins for debugging sent / received web content on your desktop (HTTPWatchm, HTTPFox, Yslow etc.), I've found another one called Fiddler.

Telerik's Fiddler is a Browser plugin  and a Windows Desktop application to monitor HTTP and HTTPS outbound web traffic and report and provide you with various information useful for:


  • Performance Testing
  • Traffic recording
  • Security Testing
  • Web Session Manipulation
  • Encode Decode web traffic
  • Convert strings from / to Base64, Hex, DeflatedSAML etc.
  • Log all URL requests originating from all opened browsers on your Desktop
  • Decrypt / encrypt HTTPS traffic using man in the middle techniques
  • Show tuning details for accessed web pages

Fiddler is available to install and use as a desktop application (requires .NET 2) or install as a browser plugin. Perhaps the coolest  Fiddler feature from my perspective is its decrypt / encrypt in Base64 and Hex available from TextWizard menu. The tool is relatively easy to use for those who have experience in web debugging, for novice here is a video explaining tool's basics.

Fiddler doesn't have a Linux build yet but it is possible to run it also on Linux using Mono Framework and a few hacks.

A good native Linux / UNIX alternatives to Fiddler are Nettool, Charles Proxy, Paros Proxy and Web Scarab.

mod_rewrite redirect rule 80 to 443 on Apache webserver

Wednesday, April 2nd, 2014

A classic sysadmin scenario is to configure new Apache webserver with requirement to have an SSL ceriticate installed and working on port 443 and all requests coming on port 80 to be redirected to https://.
On Apache this is done with simple mod_rewrite rule:

RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}

Before applying the rule don't forget to have Apache mod_rewrite enabled usually it is not enabled on default most Linux distributions by default.
On shared hostings if you don't have access to directly modify Apache configuration but have .htaccess enabled you can add above rules also to .htaccess

Add this to respective VirtualHost configuration and restart Apache and that's it. If after configuring it for some reason it is not working debug mod_rewrite issues by enabling mod_rewrite's rewrite.log

Other useful Apache mod_rewrite redirect rule is redirect a single landing page from HTTP to HTTP

RewriteEngine On
RewriteRule ^apache-redirect-http-to-https.html$ [R=301,L]

!Note! that in case where performance is a key requirement for a website it might be better to use the standard way to redirect HTTP to HTTPS protocol in Apache through:

ServerName Redirect /

To learn more on mod_rewrite redirecting  check out this official documentation on Apache's official site.

Redirect http URL folder to https e.g. redirect (http:// to https://) with mod_rewrite – redirect port 80 to port 443 Rewrite rule

Saturday, July 17th, 2010

There is a quick way to achieve a a full url redirect from a normal unencrypted HTTP request to a SSL crypted HTTPS

This is achieved through mod_rewrite using the RedirectMatch directive.

For instance let’s say we’d like to redirect to
We simply put in our .htacess file the following rule:

Redirect permanent /blog

Of course this rule assumes that the current working directory where the .htacess file is stored is the main domain directory e.g. / .
However this kind of redirect is a way inflexible so for more complex redirect, you might want to take a look at mod rewrite’s RedirectMatch directive.

For instance if you inted to redirect all urls ( which as you see includes the string blog/somestring/asdf/etc. to ( then you might use some htaccess RedirectMatch rule like:

RedirectMatch permanent ^/blog/(.*)$$1
RedirectMatch permanent ^/blog/(.*)$$1

Hopefully your redirect from the http protocol to https protocol with mod_rewrite rule should be completed.
Also consider that the Redirect directive which by the way is an Apache directive should be faster to process requests, so everywhere you can I recommend using instead of RedirectMatch which calls the external Apache mod_rewrite and will probably be times slower.

Configuring server running both OpenSSHD and Apache to be accessed via HTTPS

Friday, December 18th, 2009

I wanted to make this machine accessible for both me and others also with a simple browser,
I was thinking about configuring this on pc-freak since some time now.
It took me a while until I found a program that does this for me, anyhow luckily I found it.
It’s called webshell and is working pretty well. Check out the home page of WebShell for download and more info on it. I’ve succesfully installed it on FreeBSD 7.2.
All that is needed for the program to operate is python 2.3 or higher and python openssl (this is optional),
however most people would desire to have the service running over SSL thus this is mandatory.
On my FreeBSD box I had to install:
the port/package py26-openssl and subversion (this is a prerequirement in order to download the source via svn)
It also necessery to modify the and change the shebang's location pointing to python
in freebsd that is:

#!/usr/local/bin/python and not #!/usr/bin/python

as in linux.
Then I copied the downloaded source to /usr/local/web-shell/webshell as well as add recordto rc.local

# echo "/usr/local/web-shell/ -d" >> /etc/rc.localThe last thing I did was manually start the daemon with:
# /usr/local/web-shell/ -d

Tadam, it's up and running accessing it is as simple as pointing the browser
to a domain name or ip on which the python service is running
Currently the running webshell for pc-freak can be accessed via