Check out my new course Learn you some Lambda best practice for great good! and learn the best practices for performance, cost, security, resilience, observability and scalability.
Whilst searching for an elegant solution to apply string interning across a large number of classes (we’re talking about hundreds of classes here..) it dawned on me that I can achieve this with ease using PostSharp’s LocationInterceptionAspect. All I needed was something along the lines of:
You can apply this attribute to a class or even a whole assembly and it’ll ensure every piece of string constructed is interned, including string properties and fields defined by its subclass, which is exactly what I was after.
For example, take this trivial piece of code:
If you inspect the compiled code for the Base class in ILSpy you will see something along the lines of:
notice how the setter for BaseStringProperty has been modified to invoke the OnSetValue method defined in our aspect above as opposed to the setter method. In this case, it’ll call the String.Intern method to retrieve a reference to an interned instance of the string and set the property to that reference.
For more details on PostSharp’s interception aspects, I recommend reading Dustin Davis’s excellent posts on the topic:
As we’ve specified the multicast inheritance behaviour to multicast the attribute to members of the children of the original element, the string properties defined in both A and B classes are also subject to the same string interning treatment without us having to explicitly apply the InternAttribute on them:
If you look at the generated C# code for the discriminated union type, the internal MyDuType.CaseB type would look something like the following:
notice how the two internal item1 and item2 properties’s setter methods have been modified in much the same way as the C# examples above? The public Item1 and Item2 properties are read-only and get their values from the internal properties instead.
Indeed, when a new instance of the CaseB type is constructed, it is the internal properties whose values are initialized:
Finally, let’s look at the record type, which interestingly also defines a non-string field:
because we have specified that the InternAttribute should only be applied to properties or fields of type string (via the CompileTimeValidate method which is executed as part of the post-compilation weaving process as opposed to runtime), so the internal representation of the Age field is left unaltered.
The Name field, however, being of string type, was subject to the same transformation as all our other examples.
I hope this little attribute can prove to be useful to you too, it has certainly saved me from an unbearable amount of grunt work!
I specialise in rapidly transitioning teams to serverless and building production-ready services on AWS.
Are you struggling with serverless or need guidance on best practices? Do you want someone to review your architecture and help you avoid costly mistakes down the line? Whatever the case, I’m here to help.
Check out my new course, Learn you some Lambda best practice for great good! In this course, you will learn best practices for working with AWS Lambda in terms of performance, cost, security, scalability, resilience and observability. Enrol now and enjoy a special preorder price of £9.99 (~$13).
Are you working with Serverless and looking for expert training to level-up your skills? Or are you looking for a solid foundation to start from? Look no further, register for my Production-Ready Serverless workshop to learn how to build production-grade Serverless applications!
Here is a complete list of all my posts on serverless and AWS Lambda. In the meantime, here are a few of my most popular blog posts.
- Lambda optimization tip – enable HTTP keep-alive
- You are thinking about serverless costs all wrong
- Many faced threats to Serverless security
- We can do better than percentile latencies
- I’m afraid you’re thinking about AWS Lambda cold starts all wrong
- Yubl’s road to Serverless
- AWS Lambda – should you have few monolithic functions or many single-purposed functions?
- AWS Lambda – compare coldstart time with different languages, memory and code sizes
- Guys, we’re doing pagination wrong