LiveRebel FAQ

This will startup the UI for LiveRebel and you can access this via opening your browser at the URL printed or by navigating to http://localhost:9001.

The Command Center will guide you through the initial configuration:

1. Configure the LiveRebel agents to run on each of your servers
2. Add liverebel.xml to your applications

After that you can easily manage the deployed application versions using the Command Center Web UI, command-line interface or the REST API.

1. Add a liverebel.xml into the EAR root directory containing the application name and version. E.g.

<application>
  <name>com.mycompany:MyBigApp</name>
  <version>2.3</version>
</application>

2. Provide each module with a liverebel.xml only including the module name. (No version, it would be ignored.) E.g.

   <application>
     <name>com.mycompany:MyWebModule</name>
   </application>

   Each JAR module must contain a liverebel.xml in its root directory.
   Eech WAR module must contain a liverebel.xml under WEB-INF/classes.

3. Provide each WEB-INF/lib JAR file you want to be managed by LiveRebel with a liverebel.xml only including the library name. (No version, it would be ignored.) E.g.

   <application>
     <name>com.mycompany:MyLibrary</name>
   </application>

   This is only required for libraries you want to update using LiveRebel. A liverebel.xml goes to the root directory of a JAR file.

1. Add a liverebel.xml under WEB-INF/classes containing the application name and version. E.g.

<application>
  <name>com.mycompany:MyWebApp</name>
  <version>2.3</version>
</application>

2. Provide each WEB-INF/lib JAR file you want to be managed by LiveRebel with a liverebel.xml only including the library name. (No version, it would be ignored.) E.g.

   <application>
     <name>com.mycompany:MyLibrary</name>
   </application>

   This is only required for libraries you want to update using LiveRebel. A liverebel.xml goes to the root directory of a JAR file.

Add a liverebel.xml into its root directory containing the application name and version. E.g.

<application>
  <name>com.mycompany:MyLibrary</name>
  <version>2.3</version>
</application>

Running bin\lr-cli.cmd help will show the help screen for the command-line utility. To connect to the LiveRebel Command Center the CLI utility needs the authentication token you can get from https://localhost:9001/profile/index or corresponding page in your installation.

The following type of changes to classes are unsupported:

• Replacing the superclass
• Implementing a new interface

Because LiveRebel cannot create new state the following types of changes may have undesired effect:

• Adding new instance field or renaming an existing one will cause existing objects to have it initialized to null
• Changing constructors will only have effect on objects created after the update
• Generally changes to various initializers will not take effect on existing objects

However LIveRebel does support new static fields and changes to enums.

LiveRebel supports changes to framework/server configuration with plugins. You can see the support provided from LiveRebel features page.

To use it add the following fragments to your pom.xml:

<repositories>
...
  <repository>
    <id>zt-repo</id>
    <url>http://repos.zeroturnaround.com/nexus/content/groups/zt-public/</url>
    <releases>
      <checksumPolicy>ignore</checksumPolicy>
    </releases>
    <snapshots>
      <enabled>false</enabled>
    </snapshots>
  </repository>
...
</repositories>
 
<plugins>
...
  <plugin>
    <groupId>com.zeroturnaround</groupId>
    <artifactId>lr-diff-maven</artifactId>
    <executions>
      <execution>
        <id>compare</id>
        <phase>verify</phase>
        <goals>
          <goal>compare</goal>
        </goals>
      </execution>
    </executions>
    <configuration>
      <compareWith>/path/to/old-version.jar</compareWith>
    </configuration>
  </plugin>
...
</plugins>

Just point the to the archive of the old version.
Notice that both the current archive and the old version must contain valid liverebel.xml files.

By default the comparison results will be printed to the standard output.
To redirect it to a file add

my-diff.log

under the .

The task is bundled with LiveRebel distribution (lib/lr-diff-ant.jar).
To use it add the following fragment to your build.xml:

<taskdef name="compare" classname="com.zeroturnaround.liverebel.diffant.CompareTask">
  <classpath>
    <pathelement location="/path/to/lr-diff-ant.jar" />
  </classpath>
</taskdef>
 
<compare file="/path/to/new-version.jar" with="/path/to/old-version.jar" />

Notice that both archives must contain valid liverebel.xml files.

By default the comparsion results will be printed to the standard output.
To redirect it to a file add output="my-diff.log" parameter.

1. Build the application archive (WAR or EAR) of the new version. It has to include a liverebel.xml with the version of the application. NOTE: this step is not necessary if you are downgrading the application to a previously updated version.
2. Upload the application archive to LiveRebel Command Center. NOTE: this step is not necessary if you are downgrading the application to a previously updated version.
3. Select the version you want to switch to and press “Prepare update”. LiveRebel will compare this version to the one currently active and display all incompatibilities and warnings.
4. Review the version compatibility and press “Update”. LiveRebel Command Center will send the update out to all managed servers. Once all uploads are complete the update will be activated. LiveRebel will pause incoming requests and wait until all requests in-progress complete before activating the update and resuming the new requests. If you also selected the Pause option, LiveRebel will pause all new requests until you press Resume, allowing you to run database or environment updates while user requests are paused.

Although the instructions are given for the Command Center Web UI, the same steps are possible using our CLI utility and REST API.

LiveRebel runtime performance overhead is under 3%, as measured by SpecJVM2008. The tests were run on an Amazon Large Instance (7.5 GB memory, 4 EC2 Compute Units, 64-bit platform, I/O Performance: High). For running the tests with LiveRebel lr-agent.jar was enabled and a liverebel.xml file was added to the SPECjvm2008.jar.

If you did not change the version number of the new archive LiveRebel detects the change but cannot distinguish two versions in the Command Center as the version number is still the same. You will see a message in the standard output of your container,

LiveRebel: Could not manage versions of Your-Application (/../webapps/your-application):
Deployed application is changed without updating the version (1.0).
Please update the version in deployed liverebel.xml and redeploy.

The new version will be used but LiveRebel remains disabled for this application. There is a message in the LiveRebel Command Center also. You need to update the version number and redeploy the application. After that the new version will be picked up by LiveRebel and it will show up in the Command Center.

Now you have a correct installation of the Tomcat. To install Tomcat with LiveRebel as a service, you need to download lr-agent-installer.jar from your LiveRebel Command Center and run it in your %CATALINA_HOME%. It will create a %CATALINA_HOME%\lr-agent directory and configure Tomcat to run with LiveRebel.

Start Command Prompt (cmd.exe) as an administrator (right-click -> Run as Administrator) and navigate to %CATALINA_HOME%\lr-agent directory.

Now to install Tomcat with LiveRebel as Windows service run:
bin\service.cmd install [optional_service_name], where [optional_service_name] is the name for your service (default is “tomcat” + version number, e.g. “tomcat6″ in case of Tomcat 6.x).

Also, if you want to remove a service, run:
bin\service.cmd remove service_name, where service name is a name of the service to remove.

You can start and stop this service from Windows SCM (Service Control Manager). Service startup type is “auto”, which means it will start when Windows starts.

To install the service run (with the admin rights):
%LIVEREBEL_HOME%/bin/lr-as-service.cmd install [service_name]
where [service_name] is the desired service name.

Also, if you have 64 bit OS and want to use 32 bit java, specify the 32bit flag, as in:
%LIVEREBEL_HOME%/bin/lr-as-service.cmd 32bit install [service_name]

To remove the service run (also with the admin rights):
%LIVEREBEL_HOME%/bin/lr-as-service.cmd uninstall [service_name]