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Comment by nvahalik | Hacker News Reader

When doing web development I will occasionally connect my local code base to a remote SQL server via SSH.

This adds enough latency to be noticeable and I’ve found pages that were “OK” in prod that were unbearable in my local environment. Most of the time it was N+1 queries. Sometimes it was a cache that wasn’t working as intended. Sometimes it simply was a feature that “looked cool” but offered no value.

I’m not sure if there is a proxy that would do this locally but I’ve found it invaluable.

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I'm a big fan of Toxiproxy for these kinds of things:

https://github.com/Shopify/toxiproxy

I do networked game development on Windows and I've found the clumsy program to be very valuable to simulate adverse network conditions. You can set it up to simulate arbitrary network latency, packet loss and so forth.

https://jagt.github.io/clumsy/

You can use the tc command from the netem package for those wondering how to achieve this on Linux. https://man7.org/linux/man-pages/man8/tc-netem.8.html

I've used `tc` about three times in the last 15 years. Every time I have to relearn it.

+1 for clumsy On Windows I've also used Heavy Load, Netlimiter for more fine-grained control and Microsoft's Driver Verifier.

This looks interesting. I'll check it out, thank you!

I’m not sure if you’re saying the latency was introduced in client <-> server hops or server <-> db hops, but chrome dev tools (I’m sure all browsers too) can simulate different network conditions with a few clicks! Useful for something similar to what you’ve said, but in the end I think you meant server <-> db latency is what you want to inject

This was the first thing I thought of. Dev Tools in any browser have a boatload of great stuff like this.

> I’m not sure if there is a proxy that would do this locally but I’ve found it invaluable.

If you're on Linux, you can use iptables to randomly drop a fraction of packets to simulate bad connections - even for localhost. The TCP retransmits will induce a tunable latency. You have to be careful with this on a remote host or you may find yourself locked out, unless you can reboot out of band

On FreeBSD I have used https://man.freebsd.org/cgi/man.cgi?dummynet for this exact thing.

macOS has embedded feature that allows slowing down network calls. Similar to the IP/netfilter suite Linux has. PF handles most of the magic behind the scenes.

Even better because there is an UI to configure it. You just need to download Xcode additional tools package, there is a NetworkConditioner.prefpane inside. Install that and various settings will show up in the regular System Settings/Preferences...

I do this with a Makefile that calls “kubectl port-forward.”

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