K2.net 2003 development best practices...

I've spent some time with some of the top K2.net UK consultants recently. The topic of K2.net 2003 workflow development best practices came up (again) and I thought I'll share some here. Best practices are subjective, so feel free to share your own opinions.

Datafields: You'll by now have noticed the three check boxes at the bottom of the screen when creating a datafield in the K2.net Studio. Don't ignore them! 'Keep Audit Trail' will result in the K2 server making a copy of the datafield every time its value change. This option should not be checked by default. Only enable this for datafields that needs to be audited (for tracking or compliance reasons). 'Data On Demand' means that the value of the datafield is only loaded when its accessed and not when the process instance is created. A ProcessInstance object is created (and all the non-data on demand datafields are loaded) whenever a worklist item or server item is loaded. Only leave this option unchecked for datafields that you will access often to make sure they are readily available. For datafields that are large or datafields that are not often accessed, ticking this option will create a small delay when accessing them, but will greatly improve the performance of loading a worklist item or server item.

Worklist performance: This is where most clients experience bottlenecks in performance and its very often due to a bad design. Consider the best practise for datafields to improve access to a worklist. Secondly, don't load a users full worklist if its not required. Use the WorklistCriteria object when loading the worklist in order to paginate and optimally filter the result.

Connections: The rule of 'acquire late, release early' for any resources that your application use applies to the K2.net Connection object as well. In plain English this means, open the connection to the K2 server as late as possible and close it as soon as you are done (except if you need to keep holding onto the connection to improve multiple transactions that follow each other). When you are done, close the connection, don't be lazy and just conveniently forget about it. The Connection object itself might be a managed object in .NET but the resource you are consuming, the actual connection to the K2 server, is not. Same goes for SQL connections, files handles, etc. Because the K2 Connection object does not implement IDisposable (and even if it did, (repeat after me) you must still close the connection), I normally use this simple pattern to ensure that my connection is closed:

K2ROM.Connection con;
try
{
con = new K2ROM.Connection();
con.Open();
// use it here
}
catch (Exception ex)
{
// handle exception here
}
finally
{
if (con != null) con.Close();
}

Error Handling: Things go wrong, bottom line. You must build exception handling into your process. Exception handling can be added as low as event and line rule level, up to a general exception handler for the process. Build exception handling that can work around the error in line with the business process. As a last resort, allow the exception to be bubbled up to the K2 server.

Code location: Although there has been massive improvements in the code editor in K2.net Studio, consider a better, re-usable and more maintainable architecture by writing your code in VS.NET and building a referenced assembly. You can pass any event sensitive context object from your process into your assembly by setting a reference to the K2ROM and KO libraries in your assembly.

Log file performance: Once your solution has been tested and rolled out, disable the log file output of the K2.net server in the Service Manager - if its not needed. Depending on the amount of activity on your server, writing a log file can impact on the server's performance.

Process data v.s. external data: K2.net 2003 is a great workflow engine, its a bad data store. You don't store your MP3 files in your email client, so don't store your application data in your process. Store only in the process data that's related to the workflow. If your workflow processes a document, keep the document in its own store (network share, SharePoint, etc.) and work with a reference to the document in your process. If your workflow processes a customer, store the customer record in a database and work with the id in the process. Ask yourself the question, 'who is the owner of this data'. If its not K2, don't store it in K2.

Large destination rules: Few developers realise that the K2 server creates an instance of an Activity for each destination in the destination rule. This means that an Activity with a hundred destinations will result in the K2 server creating a 100 instances of the Activity in the transaction database. A service pack 3 feature allows you to limit this to one instance and should be considered where performance is important and multiple Activity instances (i.e. Activity datafields) are not required.

Debugging: By running the K2 server in interactive mode, you can view the real time log output of the server. Write plenty of trace information in your process - this does not only help tracking development bugs, but will help to assist finding the audit and source of an issue that surface during production.

I'll keep building this list as I stumble across issues.