Posts Tagged: ‘pax-web’

Karaf and Pax Web: disabling reverse lookup

September 29, 2013 Posted by jbonofre

Karaf can be a full WebContainer just by installing the war feature:

features:install war

The war feature will install Pax Web and Jetty web server. You can configure Pax Web using a configuration file etc/org.ops4j.pax.web.cfg. In this configuration, you can define a Jetty configuration file (like jetty.xml) using the following property:


Now, using the etc/jetty.xml, you have a complete access to the Jetty configuration, especially, you can define the Connector configuration.

In the “default” connector (bound to port 8181 by default), you can set “advanced” configuration.

An interesting configuration is the reverse lookup. Depending of your network, the DNS resolution may not work. By default, Jetty will try to do reverse DNS resolution, and if you can’t use a DNS server on the machine, you may encounter “bad response time”, because you will have to wait the timeout for each DNS lookup.
So, in that case, it makes sense to disable the reverse lookup. You can disable reverse lookup per Jetty connector, using the etc/jetty.xml and adding the resolveNames option on the connector:

  <Call name="addConnector">
      <New class="org.eclipse.jetty.server.nio.SelectChannelConnector">
        <Set name="host"><Property name="" /></Set>
        <Set name="port"><Property name="jetty.port" default="8040"/></Set>
        <Set name="maxIdleTime">300000</Set>
        <Set name="Acceptors">2</Set>
        <Set name="statsOn">false</Set>
        <Set name="confidentialPort">8443</Set>
        <Set name="lowResourcesConnections">20000</Set>
        <Set name="lowResourcesMaxIdleTime">5000</Set>
        <Set name="resolveNames">false</Set>

Load balancing with Apache Karaf Cellar, and mod_proxy_balancer

February 3, 2013 Posted by jbonofre

Thanks to Cellar, you can deploy your applications, CXF services, Camel routes, … on several Karaf nodes.

When you use Cellar with web applications, or CXF/HTTP endpoints, a “classic” need is to load balance the HTTP requests on the Karaf nodes.

You have different ways to do that:
– using Camel Load Balancer EIP: it’s an interesting EIP, working with any kind of endpoints. However, it requires to have a Karaf running the Load Balancer routes, so it’s not always possible depending of the user security policy (for instance, putting it in DMZ or so)
– using hardware appliances like F5, Juniper, Cisco: it’s a very good solution, “classic” solution in network teams. However, it requires expensive hardwares, not easy to buy and setup for test or “small” solution.
– using Apache httpd with mod_proxy_balancer: it’s the solution that I’m going to detail. It’s a very stable solution, powerful and easy to setup. And it costs nothing 😉

For instance, you have three Karaf nodes, exposing the following services and the hostname:

We want to load balance those three nodes.

On a dedicated server (it could be installed on one hosting Karaf), we just install Apache httpd:

# on Debian/Ubuntu system
aptitude install apache2

# on RHEL/CentOS/Fedora system
yum install httpd
# enable network connect on httpd
/usr/sbin/setsebool -P httpd_can_network_connect 1

Apache httpd comes with mod_proxy, mod_proxy_http, and mod_proxy_balancer modules. Just check if those modules are loaded in the main httpd.conf.

You can now create a new configuration for your load balancer (directly in the main httpd.conf or by creating a conf file in etc/httpd/conf.d):

<Proxy balancer://mycluster>
ProxyPass /services balancer://mycluster

The load balancer will proxy the /services requests to the different Karaf nodes.

By default, the mod_proxy_balancer module uses a byrequests algorithm: all nodes will receive the same number of requests.
You can switch to bytraffic (using the lbmethod=bytraffic in the proxy configuration): in that case, all nodes will receive the same amount of traffic (by KB).

The mod_proxy_balancer module is able to support session “affinity” if your application needs it.
When a request is proxied to some back-end, then all following requests from the same user should be proxied to the same back-end.
For instance, you can use the cookie in header to define the session affinity:

<Proxy balancer://mycluster>
  BalancerMember route=1
  BalancerMember route=2
ProxySet stickysession=ROUTEID
ProxyPass /myapp balancer://mycluster

The mod_proxy_balancer module also provide a web manager allowing you to see if your Karaf nodes are up or not, the number of requests received by each node, and the current lbmethod in use.

To enable this balancer manager, you just have to add a dedicated handler:

<Location /balancer-manager>
  SetHandler balancer-manager
  Order allow,deny
  Allow from all

Point your browser to http://host/balancer-manager and you will see the manager page.

You can find more information about mod_proxy_balancer here:

Apache httpd with mod_proxy_balancer is an easy and good HTTP load balancer solution in front of Karaf and Cellar.

Multiple HTTP connectors in Apache Karaf

February 3, 2013 Posted by jbonofre

Installing the http feature in Karaf leverages Pax Web to embed a Jetty webcontainer.

By default, Karaf create a Jetty connector on the 8181 http port (and 8443 for https). You can change this port number by providing etc/org.ops4j.pax.web.cfg file.

But, you can also create new connector in the embedded Jetty.

You may see several advantages for multiple connectors:

  • you can isolate a set of applications, CXF services, Camel routes on a dedicated port number
  • you can setup a different configuration for each connector. For instance, you can create two SSL connectors, each with a different keystore, truststore, …

You can find etc/jetty.xml configuration file where you can create custom Jetty configuration.

NB: if you want to have both etc/org.ops4j.pax.web.cfg and etc/jetty.xmll, don’t forget to reference jetty.xml in org.ops4j.pax.web.cfg using the org.ops4j.pax.web.config.file property pointing to the jetty.xml, for instance:

# in etc/org.ops4j.pax.web.cfg

To configure a new connector, you can add a addConnector call in this configuration. For instance, we can create a new connector on 9191 http port number (and 9443 https port number):

  <Call name="addConnector">
      <New class="org.eclipse.jetty.server.nio.SelectChannelConnector">
        <Set name="host"></Set>
        <Set name="port">9191</Set>
        <Set name="maxIdleTime">300000</Set>
        <Set name="Acceptors">1</Set>
        <Set name="statsOn">false</Set>
        <Set name="confidentialPort">9443</Set>
        <Set name="name">myConnector</Set>

Now, Karaf will listen on 8181 and 9191 (for http), 8443 and 9443 (for https).

You can also define a connector dedicated to https with dedicated configuration for this connection, especially keystore, truststore, and client authentication:

  <Call name="addConnector">
      <New class="org.eclipse.jetty.server.ssl.SslSelectChannelConnector">
        <Set name="port">9443</Set>
        <Set name="maxIdleTime">30000</Set>
        <Set name="keystore">./etc/keystore</Set>
        <Set name="password">password</Set>
        <Set name="keyPassword">password</Set>

By default, the web application will be bind on all connectors. If you want that your web application use a specific connector, you have to define it in the MANIFEST using the following properties:

Web-Connectors: myConnector
Web-VirtualHosts: localhost

If you use CXF services or Camel routes, if you use a connetor hostname and port number in the endpoint, it will use the corresponding connector.

For instance, the following CXF endpoint of a Camel route will use myConnector:

  <cxf:cxfEndpoint id="cxfEndpoint" address="http://localhost:9191/services/myservice" wsdlUrl="..."/>

Karaf allows you a fine grained Jetty configuration. Karaf becomes a real complete WebContainer, with custom configuration on several connectors. It’s especially interesting for SSL connector where each connector can have a dedicated keystore and truststore, and client authentication configuration.

Overview on Apache Karaf, Pax Web, and Camel archetypes

December 19, 2011 Posted by jbonofre

In my previous blog post, I introduced the Karaf Maven plugins.
The Karaf Maven plugins are really helpful, starting from an existing POM.

If you can write this POM by hand (it’s my favorite way ;)), we also provide several archetypes which create and pre-configure a Maven project for you.

Karaf Archetypes

The next Karaf release (2.2.5) provides a set of new archetypes:

Assembly Archetype

The karaf-assembly-archetype create a Maven project which create a custom Karaf distribution.

It allows you to create your own Karaf distribution. The project downloads a Karaf standard distribution (in tar.gz and zip formats), unpack it, and create a new distribution.

The easiest way to use it is to use the interactive mode:

mvn archetype:generate -DarchetypeGroupId=org.apache.karaf.archetypes -DarchetypeArtifactId=karaf-assembly-archetype -DarchetypeVersion=2.2.5-SNAPSHOT

Bundle Archetype

If basically a bundle is a jar file with some special statement in the MANIFEST, the easiest way to create a bundle is to use the Felix maven-bundle-plugin.

Karaf provides an archetype which prepare a Maven project and provide a bundle Activator (a special callback class when the bundle start/stop).

To generate this project, simply type:

mvn archetype:generate -DarchetypeGroupId=org.apache.karaf.archetypes -DarchetypeArtifactId=karaf-bundle-archetype -DarchetypeVersion=2.2.5-SNAPSHOT

NB: I think that this archetype should be in Felix (as the same level as maven-bundle-plugin), I will propose a donation to the Felix community.

Blueprint Archetype

Blueprint is IoC approach applied to OSGi (it comes from Spring DM in fact). It allows you to avoid to write bundle Activator, ServiceTracker, etc.

Karaf provides a karaf-blueprint-archetype which prepare a Maven project including the maven-bundle-plugin, and a blueprint descriptor with a sample of OSGi service definition:

mvn archetype:generate -DarchetypeGroupId=org.apache.karaf.archetypes -DarchetypeArtifactId=karaf-blueprint-archetype -DarchetypeVersion=2.2.5-SNAPSHOT

NB: I think that this archetype should be in Aries (as it’s the blueprint implementation used in Karaf), I will propose a donation to the Aries community.

Feature Archetype

In Karaf, a feature is an application descriptor, defining all bundles, configurations/configuration files, others features. This features descriptor could be generated by hand (it’s my favorite way, and I guess the recommended one), we also provide a archetype which prepare a project to generate features file regarding the POM dependencies:

mvn archetype:generate -DarchetypeGroupId=org.apache.karaf.archetypes -DarchetypeArtifactId=karaf-feature-archetype -DarchetypeVersion=2.2.5-SNAPSHOT

Kar Archetype

We saw in my previous post a new goal of the features-maven-plugin to create a kar file starting from a features XML. A KAR file is a zip file containing the features XML and all its dependencies.

We also provide an archetype to prepare a Maven project containing a features XML and generate a KAR file:

mvn archetype:generate -DarchetypeGroupId=org.apache.karaf.archetypes -DarchetypeArtifactId=karaf-kar-archetype -DarchetypeVersion=2.2.5-SNAPSHOT

Pax-Web Archetypes

We also add several archetypes in Pax Web to deal with the web bundle. Charles talk about wab-gwt archetype in his last blog entry (, but I added also two others.

Web Bundle Archetype

The Web Bundle Archetype create a “special” bundle containing web resources and statements. It creates a Maven project with webapp resources and WebApp Context in the POM:

mvn archetype:generate -DarchetypeGroupId=org.ops4j.pax.web.archetypes -DarchetypeArtifactId=wab-archetype -DarchetypeVersion=1.1.2-SNAPSHOT

War Archetype

We also provide an archetype to create a Maven project which generate a standard war (that you can deploy “outside” of OSGi) but including OSGi statements in the MANIFEST (which allows you to use OSGi values):

mvn archetype:generate -DarchetypeGroupId=org.ops4j.pax.web.archetypes -DarchetypeArtifactId=war-archetype -DarchetypeVersion=1.1.2-SNAPSHOT

Camel Archetypes

Camel also provides a set of very useful archetypes, especially:

  • camel-archetype-blueprint to generate a Maven project with a blueprint XML in which you can define your routes
  • camel-archetype-component providing a template to create your own Camel component
  • camel-archetype-dataformat providing a template to create your own Camel data format
  • camel-archetype-java providing a template with a class in which you can define your routes
  • camel-archetype-spring to generate a Maven project with a Spring XML in which you can define your routes

For instance, to create a Camel blueprint Maven project, simply type:

mvn archetype:generate -DarchetypeGroupId=org.apache.camel.archetypes -DarchetypeArtifactId=camel-archetype-blueprint -DarchetypeVersion=2.9-SNAPSHOT