Karaf and Pax Web: disabling reverse lookup

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:


org.ops4j.pax.web.config.file=${karaf.base}/etc/jetty.xml


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">
    <Arg>
      <New class="org.eclipse.jetty.server.nio.SelectChannelConnector">
        <Set name="host"><Property name="jetty.host" /></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>
      </New>
    </Arg>
  </Call>