[nirvdrum]

I don't think it's that much of an edge case. If Rails and its ecosystem lead to 300ms render times without load, but your objective is 100ms, you're going to have a problem. I don't think either number here is extreme and I've encountered that sort of situation on previous projects. It's not easily solvable by throwing more machines at it, unfortunately.

[tomc1985]

If Rails and your ecosystem are pushing 300ms renders you have bigger problems on your plate

[nirvdrum]

I don't think it's uncommon. But the point is it usually has little to do with load and isn't easily solved by scaling horizontally. Sure, you might be able to gain some efficiencies with distributed caches and such, but that still requires a fair bit of effort (the developer time we're trying to minimize).

You're right though. And I managed to sidetrack myself a bit. My intention in participating in the thread was to point out that you can't always optimize for developer speed and think you can get out of it "cheaply" with more hardware. And it's not just a problem when you're big enough for it to be a good problem to have. In those cases you're going to need to find a way to make the application faster.

Maybe it's aggressive in-app caching; maybe it's sitting there analyzing application profiles; maybe it's a rewrite in another language or another framework. Our goal is to provide a fast enough runtime where you don't have to make that decision.

[tomc1985]

> the point is it usually has little to do with load and isn't easily solved by scaling horizontally.

My point exactly. Unless you're getting slammed with traffic, there's too much going on in a page load if it takes 300ms to spit out.

[nirvdrum]

If you can achieve the same rendered output much faster with a different runtime or with a rewrite or with a different framework, I don't think you're looking at a fundamental design flaw with the page. I'm happy to agree to disagree. Maybe there is too much going on with the page. But it's a common problem with Rails apps and is ideally solved without a rewrite. I think a faster runtime would be the ideal solution here.

[kuschku]

At my day job we've seen load times for pages > 5 seconds in rails. There's no way to do it faster because the data has to be dynamically generated and loaded, and that's the bottleneck.

It's not uncommon to see this in rails applications — GitLab had the same issues.

[jashmatthews]

In GitLab's case, a lot of their issues are just the classic self inflicted N+1 queries and poor planning of how to represent events in a way that could be quickly queried for display.

OTOH, the background job memory issues were completely not their fault. Glibc malloc trades high memory usage for keeping both high throughput and simplicity. With Sidekiq or puma this causes much higher memory usage than necessary. Switching to jemalloc, which they did, can reduce memory usage by 50-75%.

What does your app do that takes 5 seconds? Is this because hundreds of DB calls are required, or you need to serialize thousands of objects?

[jashmatthews]

Out of pure curiosity what took 300ms? Image composition? Huge JSON payload serialization?

[ehsanu1]

I've seen numerous big rails apps with times as long or longer, even after decent effort has been put in to optimize. Generally a case of having a lot of things on a page and rendering it all into html server-side (the classic/old rails way of doing things).

[jashmatthews]

300ms from server side rendering requires something self inflicted. Even bulk JSON endpoints should be faster than that.

27ms is the average dynamic response time for Basecamp, which is server side rendered HTML done the classic way.

I worked on a high performance Rails API serving dynamically generated map tiles and our response times were actually lower than that.

[nirvdrum]

Doesn't basecamp do a ton of caching to achieve response times like that? There are certainly techniques to get there, but how long does it take to populate the caches? That's what you're going to see out of a stock Rails app.

Self-inflicted, sure. But in my experience it's the result of picking developer-friendly tools to optimize for developer time. Erubis is much faster than HAML, but a lot of developers prefer the latter. Those sorts of decisions accumulate.

[jashmatthews]

No more than Match.com do, who run on .NET. Basecamp just uses the standard Rails caching AFAIK.

Templating just isn't the issue now that it was in the days of 1.8. HAML is slower than ERB, but usually neither have a meaningful impact on response time on modern Ruby. ERB is approaching Erubis performance now.

[ehsanu1]

I worked on a high performance Rails API serving dynamically generated map tiles and our response times were actually lower than that.

Sounds like an ideal case for fast response times honestly. I've seen rails endpoints like that aplenty. But there also exists a lot of stuff taking hundreds of ms on a cold cache, and it's the kind of thing where the same effort done in the same way using another language ecosystem would just be 10x as fast.

If you've never seen this, perhaps you've never worked with a large monolithic rails app with a few years of legacy code built up? Brand new API endpoints can be a lot faster of course.

[jashmatthews]

10x faster in, say, Go? Are you sure? Have you benchmarked it? You might be surprised.

Lets pick a weakness of Ruby: tight loops and lots of math. Take 16,000 GPS points and calculate the geographical distance to another point.

On my machine it takes 12-14ms in Ruby and 4-6ms in Go. That's only a little bit more than twice as fast! Almost certainy not worth re-writing your entire app for.

I've worked with a bunch of large, legacy Rails apps. In between a couple of Rails jobs, I worked on a large .NET app, which didn't have much better performance. One service I helped migrate from Rails to Spring/Java for an enterprisey client actually got slower overall, despite moving to the JVM.

[jashmatthews]

These are the response times for Discourse, a complex open-source Rails app. Even the slowest endpoint has an average response time of 46ms.

Percentile: repsonse time (ms) categories_admin: 50: 17 75: 18 90: 22 99: 29 home_admin: 50: 21 75: 21 90: 27 99: 40 topic_admin: 50: 17 75: 18 90: 22 99: 32 categories: 50: 35 75: 41 90: 43 99: 77 home: 50: 39 75: 46 90: 49 99: 95 topic: 50: 46 75: 52 90: 56 99: 101