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David Fowler 🇧🇧💉

@davidfowl

29 Apr

Super happy to ship Azure Web Pub Sub! A new azure service for doing pure websockets + HTTP triggering!
azure.microsoft.com/en-us/blog/eas… #azure #websockets

How is it different from SignalR you ask? Well internally it's built on the same underlying tech but the big difference is that there's no client requirement or protocol requirement, BYOWL (bring your own websocket library).

The mainline scenarios are also focused on severless so we can handle your long running websocket connections and trigger HTTP calls to any backend. It can be azure functions or any addressable HTTP endpoint!

Read 12 tweets

David Fowler 🇧🇧💉

@davidfowl

14 Feb

The transition to asynchronous code changes a lot of the basics we're used to. There's usually much more concurrency in these systems and that becomes more challenging to diagnose when things go wrong. #dotnet #aspnetcore

The threads are usually switching between lots of concurrent operations as various IO operations complete. Here's an example of visualizing lots of concurrent operations happening in the parallel tasks window. The right is parallel stacks. Async stacks vs OS thread stacks.

Essentially the async logical stacks are linked lists of objects stored on the heap. There may not be any code executing if a request is waiting on IO for example.

Read 5 tweets

David Fowler 🇧🇧💉

@davidfowl

12 Feb

Goodbye beautiful Barbados

4 months I got to spend time with friends and family. We went on cruises, and had lots of beach days. The kids learned how to swim at the beach. They got to live with grandparents for 3 of those 4 months. Got to spend my birthday here for the first time in over 10 years.

Got to experience what it would be like to work remotely from Barbados. Started a relationship between Microsoft and the UWI (University of the West Indies). Joined a WhatsApp group of coders of Barbados and am doing what I can to make them love .NET 🤣.

Read 6 tweets

David Fowler 🇧🇧💉

@davidfowl

10 Feb

.NET APIs you didn't know existed. StringBuilder.GetChunks docs.microsoft.com/en-us/dotnet/a…. You can use this API to get access to the internal buffer of the StringBuilder instead of turning it into a String. #dotnet

StringSplitOptions.TrimEntries docs.microsoft.com/en-us/dotnet/a…. Ever split a string and didn't want to trim each entry? Me too, now you can use this enum to do it!

Writing Type.IsAssignableFrom always feel backwards, so we added Type.IsAssignableTo docs.microsoft.com/en-us/dotnet/a….

Read 7 tweets

David Fowler 🇧🇧💉

@davidfowl

5 Feb

There are some common issues I see when people use ConcurrentDictionary:
- Dealing with the fact that GetOrAdd executes the creation callback more than once. This means if you create something expensive, it'll happen more than once. (this is documented) #dotnet

- If you create a disposable object in your factory and it gets called multiple times, the created objects will never be disposed.
- Making sure asynchronous factories and are called once. (making all callers wait on the same value).

Here's a contrived example of the resource leak. The code runs a couple of concurrent operations and uses GetOrAdd to cache a FileStream. This will call File.OpenRead potentially multiple times which will result in opening a handle to the resource and not disposing it.

Read 8 tweets

David Fowler 🇧🇧💉

@davidfowl

11 Jan

Week 2 of analyzing how goroutines pause and resume and how the networking stack and other subsystems interact with the primitives exposed by the runtime.

One of the things I appreciate about C# is how many low level features are directly exposed to users. #golang #dotnet

In golang, it's not possible for you to implement pausing and resuming of goroutines other than by using the primitives go offers, channels, network IO, timers (sleep). This is fine for most applications but comes with additional overhead.

I also learned that go's GC doesn't move pointers and therefore there's no way to pin memory when working with C interop. There's no equivalent to passing around a GCHandle in go, just don't pass things with managed pointers to C.

Read 5 tweets

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