Simple background scheduling

Every so often I come across the need for some simple code to schedule a bit of work in the background of an application. Sometimes because a service (for integration tasks, perhaps) needs to kick off processing every so often, or sometimes because some background part of a larger program needs to happen in parallel with the main execution. A common part of these requirements is that the task should run every so often, but two instances of the task should not overlap no matter how long the background processing takes.

A few times I’ve come across projects with subtly broken implementations of this requirement, so I thought I’d write down a simple approach that has worked for me. That way next time I need it, I won’t have to go digging through git repos…

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Spotting common challenges when you’re doing performance tracing

I find myself doing quite a lot of work on performance for Sitecore websites at the moment. Whenever I do a similar job for a group of clients, I start to spot patterns in the sites I’m working on – and it struck me that there are some common performance issues that can be spotted just from the overview graphs you see when you collect trace data.

So to try and help you all improve the sites you ship, here are three that I’ve come across in a few projects recently:

An experiment with automatic tests

I spent some time working with some code recently, which had some annoying habits of failing oddly in scenarios where nulls got passed into constructors. While I was trying to work around some of these issues, it struck me that tests for parameter handling for constructors are one of those annoying things that tend to make unit testing frustrating. They’re annoying boiler-plate to write if you need them, and then a constructor signature changes, you end up with a lot of make-work test changes to do.

So as an exercise in “learning something new”, wondered whether I could automate them in a reasonable way…

Chasing down a browser detection bug

A colleague of mine recently hit upon an odd issue with the Sitecore integration for the 51Degrees browser detection service. It worked fine for most of his testing, but raised an exception in some circumstances. Trying to dig into this and create a test to demonstrate the bug kept us amused for a few hours – maybe it will help you to?

Those assumptions? You should validate them…

The one thing that is true of every aspect of IT is that it is always changing. And that change means that things you were confident of in the past may no longer hold true.

I was reminded of this while sitting in the pub with some developers recently, talking about querying for items by path in Sitecore. The debate about the best way to do this raged, but a common thread of the debate was that it is often said that the fastest way to find a set of items you needed is via a ContentSearch index. That assumptions has its roots in the time when most sites were using Lucene to run queries, and for queries with more complex matching rules. But does that hold true here?

Consuming web feeds should be easier than this…

A lot of projects I’ve worked on over the years have had requirements about consuming content feed data over the internet. Whether they’re Sitecore projects or not, “we need to display the contents of an RSS Feed” is a fairly common requirement. It should be nice and simple. There are standards and schemas for feed formats like RSS and Atom, so the data should be predictable and easy to handle…

Unfortunately, back in the real world, this rarely seems to be the case. I still regularly come across feeds which don’t match the schema, or in extreme cases feeds that aren’t even well formed. Sadly some people still seem to think that string concatenation is the way to build XML…

So what are your choices for handling feed data, and how can you try and get around bad-data challenges?

Tests that cope gracefully with Airplane Mode

Have you ever needed to write code that detects if the current computer has an internet connection or not? Having recently tried this, it turns out it’s not quite as easy as I expected it would be. So since I’ve banged my head against the challenge, here’s one approach to solving the problem that you might find useful: