Deli is a Haskell DSL which allows you to model a system, and then run simulations to understand performance. Deli borrows from queueing theory, and allows us to model and understand how work is performed with a limited set of resources. Deli can be used to model everything from elevator scheduling, thread and disk schedulers in operating systems, to how to design checkout lines at a grocery store.
To model your system, Deli gives you a concurrency and message passing API similar to the Go programming language, and allows you to model input into your system either statistically, or from a production log (like a CSV file).
Once you have modeled your system and its inputs, you run Deli, which runs as quickly as it can, simulating wall-clock time, and then returns with statistics about how your system performed.
Before digging in further, let's start with why you should not use Deli.
- It may take longer to learn to use Deli than to fix your problem another way
- Uses Deli requires a small but existent knowledge of the Haskell programming language
- Using Deli doesn't obviate the need to understand basic statistics and the distribution of your input data
- Deli currently is light on documentation, we hope that the community can assist here
Deli was built to explore improvements to GitHub's webhook infrastructure, where the HTTP response time distribution can vary dramatically when a single popular webhook target is unavailable.
The initial design goals were sketched out as follows:
- Easily test new algorithms
- Run several orders of magnitude faster than “real time”. Ideally constrained only by CPU, not wall-clock whatsoever.
- Run deterministically (given the same RNG seed/state)
Deli is a Haskell library and DSL, implemented as a discrete event simulation. It presents a CSP concurrency API which is used to model systems.
If you'd like to start using Deli, head over to our user guide.