Installing Apache Karaf as a service

When we install Apache Karaf, we'll want it to operate as a system service on our host platform (just like Windows or Linux). In this recipe, we'll set up Karaf to start when your system boots up.

Getting ready

The ingredients of this recipe include the Apache Karaf distribution kit, access to JDK, and a source code editor. The sample wrapper configuration for this recipe is available at https://github.com/jgoodyear/ApacheKarafCookbook/tree/master/chapter1/chapter1-recipe7.

How to do it…

1. The first step is installing the service wrapper feature. Apache Karaf utilizes a service wrapper feature to handle gathering and deploying of the required resources for your host operating environment. We begin its installation by invoking the following command:

   karaf@root()>feature:install service-wrapper
   

   The service wrapper feature URL is included in Karaf by default; so, no additional step is required to make it available.

2. The next step is installing the wrapper service. Now, we must instruct the wrapper to configure and install the appropriate service scripts and resources for us. Consider the following command:

   karaf@root()>wrapper:install –s AUTO_START –n Karaf3 –D "Apache Karaf Cookbook"
   

   The preceding wrapper:install command invocation includes three flags: -s for the start type, -n for the service name, and –D for the service description. The start type can be one of two options: AUTO_START, to automatically start the service on boot, and DEMAND_START, to start only when manually invoked. The service name is used as an identifier in the host's service registry. The description provides system administrators with a brief description of your Karaf installation. After executing the install command, the Karaf console will display the libraries, scripts, and configuration files that the wrapper generates. You'll now need to exit Karaf to continue the service installation.

3. The final step is integrating it in to the host operating system. This step will require administrator level permissions to execute the generated Karaf service wrapper installation scripts.

   The following command installs the service natively into Windows:

   C:> C:\Path\To\apache-karaf-3.0.0\bin\Karaf3-service.bat install
   

   The following net commands allow an administrator to start or stop the Karaf service:

   C:> net start "Karaf3"
   C:> net stop "Karaf3"
   

   Linux integration will vary based on distribution. The following commands will work on Debian- or Ubuntu-based systems:

   jgoodyear@ubuntu1204:~$ ln –s /Path/To/apache-karaf-3.0.0/bin/Karaf3-service /etc/init.d
   jgoodyear@ubuntu1204:~$ update-rc.d Karaf3-service defaults
   jgoodyear@ubuntu1204:~$ /etc/init.d/Karaf3-service start
   jgoodyear@ubuntu1204:~$ /etc/init.d/Karaf3-service stop
   

   The first command creates a symbolic link from the service script in Karaf's bin folder to the init.d directory and then updates the startup scripts to include the Karaf service to automatically start during boot. The remaining two commands can be used to manually start or stop the Karaf service.

How it works…

The wrapper service feature integrates Karaf into the host operating system's service mechanism. This means that on a Windows- or Linux-based system, Karaf will avail of the available fault, crash, processing freeze, out of memory, or similar event detections and automatically attempt to restart Karaf.

See also

• The Setting up Apache Karaf for high availability recipe