Scientist: A Ruby library for carefully refactoring critical paths
1–10 of 17 posts
Re: Scientist: A Ruby library for carefully refactoring critical paths
#2This is fantastic! Do folks do this manually in other languages or are there proven packages folks use?
Re: Scientist: A Ruby library for carefully refactoring critical paths
#3This is pretty cool, but in my experience critical path code generally has side effects and most code is not idempotent. That is to say it may not be safe or feasible to run the old and new code in parallel, without some special considerations. Think bidding on a auction item or transferring a bank balance.
Re: Scientist: A Ruby library for carefully refactoring critical paths
#4This is fantastic! Do folks do this manually in other languages or are there proven packages folks use?
There is a list of packages in other languages at the bottom of the README.
Re: Scientist: A Ruby library for carefully refactoring critical paths
#5This is pretty cool, but in my experience critical path code generally has side effects and most code is not idempotent. That is to say it may not be safe or feasible to run the old and new code in parallel, without some special considerations. Think bidding on a auction item or transferring a bank balance.
Sure but IMO most code can and should be structured to decouple the side effect from the logic that is being replaced.
Example in the transferring a bank balance, you have some storage DB you interact with, but that is an abstraction and when you run the dry run of the new code you can have an implementation that just does verification on the data from the real implementation.
Anyways, it does take discipline and effort, but you can still safely make changes in this manner.
Re: Scientist: A Ruby library for carefully refactoring critical paths
#6I’ve used this gem to remove a Rails Model that was heavily tangled and used in production. It had a bit of a learning curve, such as seeing how errors get handled in try {} blocks, but really nice otherwise when doing the equivalent of open heart surgery.
Re: Scientist: A Ruby library for carefully refactoring critical paths
#7We've used this extensively at my work and it has been great. As someone else pointed out it's a bit tricky if the code isn't idempotent. We used this as part of a data migration project and for writing we ran the experiment 100% of the time and read back the result to check it was correct - a bit of a performance impact but nothing that was noticeable. One super useful extension we've made to the gem is to have it update Prometheus metrics so you can easily see how often your experiment is showing that the candidate is different from the control.
Re: Scientist: A Ruby library for carefully refactoring critical paths
#8previously: https://news.ycombinator.com/item?id=21489877 (178 pt, 19 comments)
Re: Scientist: A Ruby library for carefully refactoring critical paths
#9Dear lazyweb, is there a similar library for python? :)
Re: Scientist: A Ruby library for carefully refactoring critical paths
#10This is pretty cool, but in my experience critical path code generally has side effects and most code is not idempotent. That is to say it may not be safe or feasible to run the old and new code in parallel, without some special considerations. Think bidding on a auction item or transferring a bank balance.
I would imagine that applications that use a relational database could use transactions to reduce the impact of non-idempotent code.