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by F-W-M
112 days ago
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How do you structure your program to do this? I had huge success writing a trading system where everything went through the same `on_event(Inputs) -> Outputs` function of the core and a thin shell was translating everything to inputs and the outputs to actions. I actually had a handful of these components communicating via message passing. This worked rather well as most of the input is async messages anyway, but building anything else this way feels very tiresome. |
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Usually two methods `onMessage(long timeNow, byte[] buf)` and `onTimer(long timeNow, int timerId)`.
All output sinks and a scheduler need to be passed in on construction of the application.
Then you can record all inputs to a file. Outputs don’t need to be recorded because the inputs can be replayed but it is useful for easier analysis when bugs happen.
I have even worked on systems where there were tools that you could paste recorded input and outputs to and they code generated the source code for a unit test. Super useful for reproducing issues quickly.
But you are spot on in that there is an overhead. For example, if you want to open a TCP socket and then read and write to it, you need to create a separate service and serialise all the inputs and outputs in a way that can be recorded and replayed.