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Comment by KaiserPro | Hacker News Reader

what the OP describes is caching.

Each lambda has some state which, if one is sensible can be used to cache things. Having a db connection cached is perfectly sensible, assuming there is some retry logic.

Making an API around RDS its just a boat load of tech debt, when its trivial to cache a connection object. Not only that, it will add latency, especially as the goto API fabric of choice is http. So a 20ms call(worst case) can easily balloon upto 80ms (average)

its now possible to have SSM secrets referenced directly in lambda environment variables, so I don't see the need for the complications of doing it yourself.

Lambda is just cgi-bin, for the 21st century. There is nothing magic to it.

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Caching the db connection may not work depending on your DB driver. A possible scenario is:

* Cold start, connection is established.

* Code runs and returns.

* Lambda stops the process entirely but retains the container.

* DB detects the socket is closed and kills the connection.

* Warm start.

* Code runs and fails because the connection is invalid.

The OP commenter said that the cache would have to contain retry logic, which in your sceanrio would trigger and then initiate a new connection object.

Yeah, I should have been clearer, it's not that it can't be done, it's just a bit messier than it seems at first blush.

The issue is that actions taken by stateful clients can't always be retried.

You can detect these kinds of errors, but it's klugey because these drivers generally assume that sockets dying is relatively uncommon, and it's painful to test this behavior when FaaS doesn't give you direct control over it.

So you typically wind up either with a proxy, or you decorate any handlers to refresh the connection ahead of time to make sure you have a fresh object.

I agree with you that it's messy and an anti-pattern to try to implement something like this in lambda.

After they fix VPC cold starts (the ENI issue) I hope we get Lambda lifecycle events. onDestroyed, onFrozen, onThawed, etc. You kind of get onCreated now if you put the code into global scope but that's gross

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