getZxy never resolving the returned promise, program stalled (using pmtiles js module)

[amdevelopment-world]

hello, im currently using pmtiles to read a file from my local disk, using my own Source class like this `class FileSource {
constructor(filename) {
return this.initialize(filename)
}

async initialize(filename) {
this.fd = await fs.open(filename, 'r')
return this
}

getKey() {
return ''
}

async getBytes(offset, length) {
const buffer = Buffer.alloc(length)
await this.fd.read(buffer, 0, length, offset)
const arrayBuffer = buffer.buffer.slice(buffer.byteOffset, buffer.byteOffset + buffer.byteLength)
return { data: arrayBuffer }
}

close() {
return this.fd.close()
}
}

export const transformPMTiles = async (sourceFilePath, destinationFilePath, minZoom, maxZoom, onFeatures, onProgress, topLeft, bottomRight) => {
const fileSource = await new FileSource(sourceFilePath)
const reader = new PMTiles(fileSource)

....
const tile = await reader.getZxy(z, x, y)
}`

sadly, every once in a while the program just stalls, when loading tiles from the pmtiles file i found here:https://maps.protomaps.com/builds/

no exception raised, nothing, i just keep awaiting for ever, surprisingly (for js code) it doesn't happen at the same moment

im reading all tiles, from z 0 to z 15, it usually happens at z 11, BUT at a random x and y, those tiles certainly exist, im only ever fetching tiles with a valid z,x,y

so, is there native C code involved here ?

as the whole process takes a LOT of time (the stall can happen at anytime, sometimes hours after i start the script) i had to use the following technique:

i run he code from the (mac) terminal, with --inspect, then, when i see there is no longer any movement i attach the debugger

during the execution of the code i leave "breadcrumbs" in global variables that i can access despite not being in scope, thats how i know that the lest line of code executed in my script is before going into getZxy

im currently running the code, the next time it stalls, i will be able to call getZxy again, with the same parameters and step the code, to see if it fails again (i expect not, as this must be some race/timing condition)

[amdevelopment-world]

chatgpt, of all "people" recommends this work around, lets see :)

import { PMTiles, ResolvedValueCache } from 'pmtiles'

// 1. Create a "file://" Source (so PMTiles uses local disk I/O)
const source = await new FileSource(path)) (see above)

// 2. Make a cache that never shares promises and doesn’t pre-fetch
// - maxCacheEntries = 0 (no entries retained)
// - prefetch = false
const cache = new ResolvedValueCache(0, false)

// 3. Hand that cache to PMTiles
const pm = new PMTiles(source, cache)

[amdevelopment-world]

damn no, that didn't fix it :(

[amdevelopment-world]

oh well, after a few more hours of debugging i think the problem might be with node's event loop hanging, it's not getZxy that hangs by itself, but when it calls getBytes my call to fd.read(buffer, 0, length, offset) hangs i have no idea why, i'm trying with sync IO now, my code isn't doing anything concurrently, so it should just work

[amdevelopment-world]

in the end it turned out to be a bug in the cli-progress module that was calling setTimeout waay too often, sorry :)