iOS Support

[Almouro]

iOS support isn't a priority at the moment, since on average iOS devices performance is much better (and usually that translates to apps having less performance issues).

However it is still something we want to search into and implement at some point, so if you'd like to have iOS support, feel free to show it by adding a 👍 emoji to this issue.

[developerdanx]

How can we help with iOS support?

[Almouro]

Thanks for asking @developerdanx!

On iOS, we haven't investigated much a technical solution yet.

For the performance measuring part, I think one possibility would be to use xctrace (previously XCode instruments) to generate a trace file, and then manage to parse it to get an array of measures out of it

If you'd like to try your hand at a POC, I'd be happy to help out!

[developerdanx]

Yes this is feasible I think. I'll try something out and share the results 😁

[GuillaumeEgret]

Hi ! Quick update, we are also going to try to develop a POC for iOS in the next few days with @Almouro

[Almouro]

We've deployed the (crude) POC here https://github.com/bamlab/flashlight/tree/main/packages/ios-poc

We'll work to make it easier to use in the coming weeks with @GuillaumeEgret 🤞

[Almouro]

Still in progress, but @GuillaumeEgret managed to have a POC of CPU measures per thread when running a Maestro test
It's already running in the CI on this repo https://github.com/bamlab/flashlight/blob/main/.github/workflows/ios_e2e.sh

Here's an example report: https://65031abea84fdb098fb48ce4--flashlight-open-source-reports.netlify.app/report.html

Next is:

• unify API with flashlight test on Android
• consider live measures with flashlight measure
• run it on AWS for complete Lighthouse for iOS apps

[JuanRdBO]

Hey guys! Is this still ongoing? I'd love to test iOS devices as well

[alaz-aura]

+1 to see if this iOS support is still in development

[anton-patrushev]

hey everyone 👋
do you have any updates for iOS support?

cc: @Almouro

[samholmes]

+1 for this too.

How can I help contribute to this effort? I'd like to know what are the technical challenges: is it building the perf app in iOS, or is it installing it on a device (idb hurdle), or something else?

[Almouro]

Sorry it took so long for me to answer this, it's a good idea to sum up a bit where we're at at the moment!

Sadly, things are not as easy as on Android, where we can just openly read values from system files.

There are 3 elements that are part of the Flashlight philosophy for Android which are tricky to get on iOS:

• live measures with flashlight measure
• thread by thread measures
• blackbox measures (as in: no in-app setup required, can work on production apps)

We have a few approaches that we've tried but are not entirely satisfied with, (and it's also a challenge to dedicate resources to this on our side.)

1st approach: Instruments CLI

❌ Live measures
✅ Thread by thread measures
✅ Blackbox measures

On iOS, Instruments is the usual tool used for performance measures. It's in my opinion very adequate and technically ticks all the boxes above.
However, it's not necessarily easy to use and doesn't offer an easy comparison view.

Instruments however offers a CLI that we can use. Sadly, that CLI doesn't offer live measures. It's also not super easy to use, but @GuillaumeEgret did a fantastic job researching and parsing the output.

It's not totally done still, and there's still this PR open to get it merged that we need to get back to.

2nd approach: using py-ios-device

✅ Live measures
❌ No thread by thread measures
✅ Blackbox measures

Several people have already tried to do something similar and capture live measures with their own tools. One such tool is https://github.com/YueChen-C/py-ios-device. Essentially those tools can behave just like Instruments would and talk with the app to get the same data.
The way to create such a tool is basically by reverse engineering Instruments and it's not an easy task by any mean. The protocols used by Instruments to communicate with the app is reaaaally not straightforward 😅

Unfortunately thread by thread measures seem quite hard to achieve with such a tool.

We do have a POC here which should be working, although we haven't tested it in a while 😬

3rd approach: create a plugin to install in the measured app

✅ Live measures
✅ No thread by thread measures
❌ Blackbox measures

We haven't explored this approach a lot, but coming back to it might be a good idea.
The idea would be to have something similar to https://github.com/bamlab/react-native-flipper-performance-monitor

We install an SDK in your iOS app, which can get all relevant data, and communicate that data to Flashlight via websocket. We haven't explored yet what is possible, but it seems we could get out of the box live measures and thread CPU measures.

It generally seems simpler to implement and easier to maintain, however we lose the blackbox aspect:

• we need to install an SDK in the app, which shouldn't be published with the app to the appstore

On the other hand, it's much simpler to have quick feedback on what we implement, even if it's in dev mode

In general, my current point of view is I feel like maybe we should reconsider the 3rd approach to see what we can do!

Feel free to jump in the conversation and share your point of view, or just add an emoji 1️⃣, 2️⃣, 3️⃣ to notify which option you'd rather have.
If you'd like to try your hand at implementing one option, or have another idea in mind, let me know and I can help out!

I'll also try to restart that conversation with the RN community as well before the end of the month

[bvoq]

Maybe 1️⃣ together with a video recording?
We use it mostly with maestro tests at the moment.

[MalcolmTomisin]

Previously, I wouldn’t have chosen 1️⃣ as my go-to, as I loved using Flashlight for live measurements. Recently, however, I’ve started using Flashlight to create performance reports, and it’s been working well for me. I’m also leaning towards 1️⃣ now because it provides thread-by-thread and black-box measurements, which offer a more streamlined developer experience when debugging performance issues