Category Archives: XML Appliances

Easy-to-Use Alternative to DataPower Deployment Policies

DataPower deployment policies allow for “tweaking” device and domain configuration for different environments. Let’s face it, there are always differences between environments. Sometimes, these differences are small, such as different back-end hosts, and in other cases these differences could be significant, such as different security policies.

Deployment policies do a decent job of dealing with differences between environments. Deployment policies support changing, adding and deleting configuration, so it is possible to implement fairly complex transformations.

However, dealing with deployment policies could be confusing. Deployment policy’s match rules utilize xpath, but the syntax of the rules is not pure xpath. Consider this simple deployment policy match rule:


The part before “?” looks like xpath. But what schema is this xpath based on? There is no “protocol” element in the DataPower XML management schema. The part after “?” that uses name-value parameters is even more odd. Why use this instead of proper xpath? After all, DataPower has an XML-processing engine with full xpath support, so it would certainly be more logical to rely on XML standards.

The bottom line is that while deployment policies are useful, they have limitations. They have to be developed using Deployment Policy builder in WebGUI. They can only be applied to configuration elements supported in WebGUI. For example, creating a deployment policy that updates RemoteEndpointPort of a Web Services Proxy proves to be a non-trivial task.

This is why we added support for xpath-based transformations to our DPBuddy DataPower management tool. Instead of dealing with the obscure syntax of DataPower deployment policies, developers can simply look at the configuration export file and specify an xpath expression against this file. It is also possible to specify filters based on the types and names of DataPower objects.

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DPBuddy — Tool For DataPower Administrators and Developers

We’re pleased to announce the release of our new product, DataPower Buddy (dpbuddy). “dpbuddy” a free command-line tool for automating administration, management and deployment of IBM WebSphere DataPower appliances. The tool supports export/import, file transfer, backups and many other functions.

dpbuddy is implemented as a set of custom tasks for the popular build tool, Apache Ant.

Here is a quick example of dpbuddy in action:


This Ant task will remove remote directories if they exist, reproduce the local directory tree (all folders under “services”) on the device and upload the necessary files based on the “includes” pattern.

dpbuddy is completely free; it can be downloaded from the dpbuddy product page

dpbuddy provides many cool features, including:

* Response from the device is presented in a human-readable form as opposed to raw SOAP/XML messages. dpbuddy makes it easy to understand error and status messages.

* Powerful remote “copy” command that automatically reproduces local directory tree on the device.

* Tight integration with Ant. Ant variables can be used inside deployment policies and configuration files.

* Easy-to-use alternative to deployment policies based on XPath.

* Ability to remotely “tail” device logs. It is even possible to automatically get new log messages similarly to Unix “tail -f” command. “tail” task can also check for error patterns.

* “Export” based on naming patterns. You don’t need to know types (“classes”) of DataPower objects; simply specify a regexp pattern and dpbuddy will export all objects matching this pattern.

* Support for self-signed certificates. No need to add DataPower certificates to the JDK store.

* Support for arbitrary SOMA requests. You can use Ant variables inside a request.

* Parsing of all commands on the client. In case of XML errors, DataPower returns cryptic “internal error” message. The actual error then has to be extracted from the device logs. dpbuddy on the other hand validates management XML commands on the client and displays error messages right away.

Go to dpbuddy product page to learn more.

DataPower News

I’ve long been a “fan of XML Appliances”:/is-xml-appliance-an-ultimate-esb. Looks like IBM customers like the appliance idea as well. IBM said that DataPower was one of the top-selling products and also “announced”: that “DataPower-lution”: is one of their strategic directions for 2009. Basically, more and more edge functions will be moving into the appliance. And why not use the same device for XML acceleration, load balancing, crypto acceleration, caching, perhaps even WebSEAL replacement (it’s just a fancy reverse proxy after all). We’ll see how this vision plays out.

In a related news, there is finally a “DataPower book”: and it’s 960 pages long. And this is before IBM started adding all these edge functions to the device :).

It Takes a Mental Shift to Benefit from XML Appliances

This article on techtarget is a great illustration of my point from the previous post about the importance of the proper design patterns and techniques required to be able to benefit from XML appliance capabilities.

When implementing Web services Java developers tend to think in terms of Java classes that XML documents map to. Using XSLT (or even Schema) for implementing part of their processing logic is not on their list because the common thinking is that it is too expensive to do it in Java.

With XML appliances the situation is exactly the opposite. XSLT all of a sudden becomes one of the best performing part of an application (although, I would imagine that using Java hardware acceleration such as the one provided by Azul might once again change that). This could be a serious “paradigm shift” for many developers and architects.

Another obstacle to more effective usage of appliances could simply be the lack of XSLT skills. XSLT is essentially a functional language and so it comes with a learning curve attached, especially for complex transformations. It is important to have a good knowledge of XSLT to understand what kind of work can be “outsourced” to an appliance. Not that many developers have this knowledge today, but perhaps it will change with more widespread use of XML appliances.

Improve Your Application Performance with XML Appliance

XML appliances are capable of extremely fast XML parsing and transformation (sometimes the term “wire-speed” is used). The speed is achieved by using hardware acceleration, specially written XML parsers and XSLT engines (you won’t find Xerces on these devices) and optimized operating system (usually, a trimmed-down version of Linux or BSD).

How fast are XML appliances? I’m not aware of published benchmarks; however, I did have a chance to conduct an informal performance testing of DataPower XI50 for a client and the results were quite impressive; for example we saw little to no overhead validating medium-size XML schemas.

Clearly, offloading as much XML processing as possible to an appliance could be a performance booster. So what kind of processing could be done on the device? Here are my recommendations based on the capabilities of the DataPower appliance; the situation could be slightly different with devices from other vendors.

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XML Appliances Begin Supporting Java

Layer7 announced that its appliances will support Java-based custom assertions. Details are sketchy at this point but apparently Layer7 will provide a proprietary SDK for developing assertions. This could be much more powerful mechanism than XSLT-only facilities in IBM DataPower.

So how long before appliances begin supporting JBI and SCA components? The trick here of course is to make sure that an appliance is still a robust low-maintenance device that can’t be brought down by a rogue application thread. But if Layer7 was able to figure it out for Java in general (I wonder if they use a general Sun JDK or some kind of a special JDK build), there is no reason why an appliance can’t start supporting more advanced specifications such as JBI/SCA.