Is it normal for `kobweb run` to lock up a whole thread(100% util) ?

# kobweb

[hamyn]

Is it normal for kobweb run to lock up a whole thread(100% util) ?

[David Herman]

Try running ./gradlew kobwebStart -t instead and compare, same result?

It's probably expected, especially the first time you run it. Compiling is hard, use all the CPU you can!

[hamyn]

Yup, Webpack of course uses a lot when recompiling but dev server is always utilizing 100% of some thread even on IDLE

[hamyn]

i don't remember ktor being this cpu heavy, what am I missing ?

[David Herman]

Ah, it's 100% utilized after everything started and the server is running? That's very strange

[hamyn]

Yes

[hamyn]

I've set the log level to ALL and used it a bit, now I'm analyzing the log file

[David Herman]

Thanks

[David Herman]

The server should be pretty quiet

[David Herman]

It does read the state of a file every 300ms (and then sleeps)

[David Herman]

That's the only thing I do custom besides just letting ktor do its own thing

[hamyn]

I've got 150 hits on "FAILURE ..." and almost all of them are "Selector didn't match" @/api with same child element but it ends with @ /{...}/

[David Herman]

I can look into that, but 150 hits shouldn't cause 100% thread utiliziation

[hamyn]

I'll try running it on a different project, let's see

[David Herman]

Appreciate it

[David Herman]

You can try with kobweb create app , kobweb create examples/clock, and/or kobweb create examples/jb/counter?

[hamyn]

Okay will do

[David Herman]

The last one (examples/jb/counter) is about as simple as a Kobweb project can get

[hamyn]

trying with that one then

[hamyn]

Same, nothing weird in the log file

[David Herman]

What's your OS?

[hamyn]

Linux

[David Herman]

I'll see if I can repro

[David Herman]

Does ./gradlew kobwebStart -t also throttle your thread?

[hamyn]

yes

[hamyn]

Might it be jdk related ? I'm using 11-*-jbr

[David Herman]

So maybe I should check my assumption. You're saying I'm locking a thread, but not necessarily locking up a CPU?

[David Herman]

My code does work by running in an infinite while loop that sleeps... and then when it gets a signal that the server can shut down, it exits the loop, shuts down ktor, and exits main

[hamyn]

No not the whole CPU but always one of the threads when idling is at 100%, it changes to a different thread from time to time(~4,5 seconds)

[David Herman]

suspend fun main: https://github.com/varabyte/kobweb/blob/a13d9696e813b483f4b00028a74f4d12555451ed/b[…]erver/src/main/kotlin/com/varabyte/kobweb/server/Application.kt

while loop:
https://github.com/varabyte/kobweb/blob/a13d9696e813b483f4b00028a74f4d12555451ed/b[…]erver/src/main/kotlin/com/varabyte/kobweb/server/Application.kt

[hamyn]

Thread changing is probably by the OS scheduler but idk

[David Herman]

Maybe the way I wrote that code is not thread friendly

[David Herman]

So yes, I'm seeing a thread pegged at 100%. It says the command associated with the thread is logback-1

[hamyn]

yup

[hamyn]

I was just going to mention that

[David Herman]

I do configure logging a bit. Let me see if that's related.

[David Herman]

Although it is dinnertime here, so it will be an hour or two

[hamyn]

No problem, thanks for helping out

[David Herman]

Sure. I was totally unaware so thanks for reporting.

[hamyn]

Meanwhile I will look into it too, maybe this yet-to-be-a-junior will spot something )

[David Herman]

Sure, no pressure! The things I'm asking myself are...
1. Is this ktor? Can I repro it in normal ktor projects? Or is it something in my code?
2. Is this related to my specific version of ktor? Does upgrading fix it?
3. (After seeing the logback thread name) Is this related to how I'm configuring logback?
4. How bad is this really? Is this actually resulting in significant performance degradation that people would notice without using profiling tools?

[hamyn]

Can I dm you ?

[hamyn]

It's probably not ktor related

[David Herman]

If you want to play with code itself, you can sync kobweb git clone <https://github.com/varabyte/kobweb> , go into playground/site, and run kobweb run in there. That way, you can actually change code under backend/server/ , quit, and rerun, to see if things are still happening.

[David Herman]

Can I dm you ?

Absolutely!

[hamyn]

I've already been debugging the server