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What is the Java Service Wrapper?

What is the Java Service Wrapper?

Note from the Wrapper team.

NOTE MEG

The Java Service Wrapper continues to be actively developed. Each new version is the culmination of a great deal of time and energy in development, testing, documentation and user support.

While the Wrapper is being used within a number of open sourced projects, by far the majority of our user base is directly or indirectly making use of the Wrapper to support commercial applications and or commercial infrastructure.

We urge all of our users to please review the value that the Wrapper is providing to your organization. The Wrapper team develops and maintains the Wrapper on a volunteer basis, but the time and effort involved is real.

Please help us to keep the Wrapper project alive, free, and growing, by showing your appreciation and support for the project with a donation to the team.

We would also like to thank all of our users for the ongoing feedback which has helped us to continuously improve the Wrapper over time.

Sincerely,

The Java Service Wrapper team.

Quick Start

As with any application, reading through the documentation the best way to get started. But realizing the desire to get your feet wet quickly, you should glance over this page to get a feel for what the Wrapper can do.

Then to get up and running , at a minimum you will need to read over the Integration Page. There you will be presented with 3 integration methods. From the overviews, choose the one that best meets your needs and then proceed to read over the page dedicated to that integration method.

The Wrapper provides a very large feature set. At some point it is suggested that you look over the full properties list to get a feel for the full power of the Java Service Wrapper.

If you run into problems or have any questions, the preferred method for getting help is posting a message to the wrapper-user mailing list.

Introduction

The Java Service Wrapper is an application which has evolved out of a desire to solve a number of problems common to many Java applications:

- Run as a Windows Service or Unix Daemon
- Application Reliability
- Standard, Out of the Box Scripting
- On Demand Restarts
- Flexible Configuration
- Ease Application Installations
- Logging

| Run as a Windows Service or UNIX Daemon
The Wrapper makes it possible to install a Java Application as a Windows NT Service. The scripts provided with the Wrapper also make it very easy to install those same Java Applications as daemon processes on UNIX systems. The Wrapper correctly handles user log outs under Windows, service dependencies, and the ability to run services which interact with the desktop.

| Application Reliability

Application Reliability. As the use of Java expands, applications have been written to provide a variety of mission critical services. These services must be able to provide a high level of reliability. In an ideal world, only software which is 100% bug free will ever be released and installed. However, history has shown this not to be the case. Almost every application suffers from quality issues at one point or another during their life-cycle. Applications hang, crash, run out of memory or suffer from any number of problems. Where possible, problems are fixed quickly without significant service outages. There are times, however, when fixing a problem can be prohibitively expensive or impossible to solve in a short time period.

The Wrapper monitors a JVM process and automatically restarts it if it that the JVM has crashed or hung. This process takes just a few seconds once the Wrapper has decided there is a problem. There is also a way to configure the Wrapper to monitor the console output of a JVM and react to certain strings by restarting or shutting down the JVM.

While these features will not make every problem go away, they will help you to sleep easier knowing that if there is a problem, the Wrapper will be there to keep things up and running until you can get into the office to check the logs. Say goodbye to that pager!! (Or as so as not to date myself, that cel phone!)

| Standard, Out of the Box Scripting

Write once run everywhere configuration. Java has been marketed as a "Write Once, Run Everywhere" programming language. While this is true for many aspects of an application, the developer is often plagued with having to write complicated, platform specific scripts which are tasked with building up class paths and collecting other system information necessary to launch an application.

The Java Service Wrapper helps to relieve the developer of this task by providing a set of scripts for a wide range of platforms that can be used as is to launch almost any Java Application controlled by the Wrapper.

The Wrapper moves all JVM configuration into a platform independent configuration file. See the integration examples for details.

| On Demand Restarts

The Wrapper provides a way for a Java Application to request that its own JVM be restarted. This can be useful in a number of cases. Applications may wish to restart after having had their configuration files modified. Or the application may simply need to be restarted to avoid problems with a memory or resource leak of some kind.

JVM restarts can be triggered from within the JVM by making a call to `WrapperManager.restart()`. See the Javadocs for more details.

There are also more passive ways to trigger restarts. The Wrapper has the ability to monitor console output and trigger shutdowns or restarts whenever certain text is detected.

The Wrapper can also be configured to either restart another JVM instance or shudown normally depending on the exit code returned by a JVM.

| Flexible Configuration

The Wrapper provides a wide range of configuration properties which can be used to configure the JVM in any way possible from the command line. The Wrapper configuration file also provides a number of properties to allow you configure things like logging and how the Wrapper is installed as a service.

See the Configuration Properties section for details on what is possible. Be sure you have read over the integration section before jumping into the configuration file.

| Ease Application Installations
By using the Wrapper's standard scripts, and relative paths in the configuration file, it is usually possible to create an application which requires no further installation than simply expanding an archive file into a directory of the user's choice.

| Logging

While the Wrapper does not attempt to, nor should it, replace any of the great logging tools available, it does provide a number of properties to configure how stdout and stderr output to the JVM console is handled. This output can be logged to any combination of the console, a file, or the Event Log (Windows) or syslog (UNIX).

Logging the output to the JVM console can be critical to tracking down problems with an application. Without the Wrapper, when a JVM is being run as a service under Windows, or as a daemon under UNIX, the console output would normally be lost. The Wrapper makes sure that all console output is logged.

Java-based logging tools are only capable of logging output generated from within the JVM. If the JVM crashes or prints out low level messages such as thread dumps, there is normally no way to log it. The Wrapper logs all console output from the JVM process regardless of its source meaning that a record of any crash will survive even after the Wrapper has restarted the JVM.

See the Logging Configuration section for further details.

Supported JVMs

The Wrapper is known to work with the Sun, IBM, Blackdown and BEA WebLogic JRockit JVMs without any problems. If you get a chance to test any other JVMs, please be sure and let us know the results.

NOTE MEG |  | The Wrapper can be used with 1.2.x versions however some functions are disabled due to this version of Java's lack of support for shutdown hooks. Shutdown hooks were implemented with the 1.3.0 release of Java.

Supported Platforms

Binary distributions are provided for the following list of platforms and are available on the download page.

Only OS versions which are known to work have been listed. If you have had successful or unsuccessful results running on other OS versions, please post a comment below and it will be added to the list.

It should be fairly easy to build the Wrapper from source on additional UNIX platforms. Please let us know and we will update the list.

- `aix` - AIX

- `freebsd` - FreeBSD

- `hpux`, `hpux64` - HP-UX, 32 and 64-bit versions.

- `irix` - SGI Irix

- `linux` - Linux kernels; 2.2.x 2.4.x, 2.6.x. Known to work with Debian and Red Hat, but should work with any distribution. Currently supported on both 32 and 64-bit x86, and 64-bit ppc systems.

- `macosx` - Macintosh OS X.

- `osf1` - DEC OSF1.

- `solaris` - Sun OS, Solaris 7, 8, 9 and 10. Currently supported on both 32 and 64-bit sparc, and x86 systems.

- `win32` - Windows NT, 2000, XP, and 2003.

  Also known to run on Windows 98 and ME, however due the lack of support for services in the OS, the Wrapper can only be run in console mode.

by Leif Mortenson

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