[Python] Run a Python web server (Quart) with Chaquopy without blocking the main android...

This is not exactly a bug i assume but nothing in the rather short documentation or from online searches could help me. I am trying to build an android app that runs a Quart app in background with Chaquopy and a web view to display it full screen. The problem is i can't find a way to run Chaquopy without blocking the main thread which is kind of pointless, no matter what i try there is an error!

Here's why i can't figure it out:

• Running a web server in Chaquopy is a blocking long-running operation which blocks the android thread execution therefore the UI even if the UI is in a thread. So Chaquopy cannot run in the main android thread.
• Some part of Quart (seems to be asyncio) requires it to run in the main thread of the main interpreter.

So is it simply impossible to run a python web server and a webview in the same android app?

Running Chaquopy in the activity like such blocks the main thread and the UI (webview) stops working:

class MainActivity : AppCompatActivity() {

private val tag: String = "MainActivity" // Define a tag for your logs
private lateinit var webView: WebView

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
Log.i(tag, "Starting server");
if (! Python.isStarted()) {
Python.start(AndroidPlatform(this))
}
// Run the Python server
try {
val py = Python.getInstance()
py.getModule("app").callAttr("run")
} catch (e: Exception) {
Log.e(tag, "Error starting Python server: ${e.message}")
}

webView = findViewById(R.id.webview)
webView.webViewClient = WebViewClient()
webView.settings.javaScriptEnabled = true
webView.loadUrl("http://localhost:5000")
}

}


I tried running Chaquopy in an android thread as such:

class MainActivity : AppCompatActivity() {

private val tag: String = "MainActivity" // Define a tag for your logs
private lateinit var webView: WebView

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
Log.i(tag, "Starting server");
if (! Python.isStarted()) {
Python.start(AndroidPlatform(this))
}
// Run the Python server in a background thread
Thread {
try {
val py = Python.getInstance()
py.getModule("app").callAttr("run")
} catch (e: Exception) {
Log.e(tag, "Error starting Python server: ${e.message}")
}
}.start()
webView = findViewById(R.id.webview)
webView.webViewClient = WebViewClient()
webView.settings.javaScriptEnabled = true
webView.loadUrl("http://localhost:5000")
}

}


Which give me this error from the activity:

Error starting Python server: RuntimeError: set_wakeup_fd only works in main thread of the main interpreter


I tried running the server in a Python thread like this:

import threading
from quart import Quart

app = Quart(__name__)


@app.route('/')
async def hello():
return 'hello'

def run():
# Create a new thread
thread = threading.Thread(target=app.run, args=("1",))
# Start the thread
thread.start()
# Optionally, wait for the thread to finish
thread.join()


Which give me this error in logcat through python.stderr:

Exception in thread Thread-1 (run):
Traceback (most recent call last):
File "stdlib/asyncio/unix_events.py", line 105, in add_signal_handler
ValueError: set_wakeup_fd only works in main thread of the main interpreter


I tried running Chaquopy in a coroutine:

class MainActivity : AppCompatActivity() {

private val tag: String = "MainActivity" // Define a tag for your logs
private lateinit var webView: WebView

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
Log.i(tag, "Starting server");
if (! Python.isStarted()) {
Python.start(AndroidPlatform(this))
}
// Launch a coroutine to run Python code
CoroutineScope(Dispatchers.IO).launch {
runPythonCode()
}
// Run the Python server in a background thread
Thread {

}.start()
webView = findViewById(R.id.webview)
webView.webViewClient = WebViewClient()
webView.settings.javaScriptEnabled = true
webView.loadUrl("http://localhost:5000")
}

private suspend fun runPythonCode() {
// Switch to the main thread to update UI if needed
withContext(Dispatchers.Main) {
try {
val py = Python.getInstance()
py.getModule("app").callAttr("run")
} catch (e: Exception) {
Log.e(tag, "Error starting Python server: ${e.message}")
}
}
}

}


Which does start the server but still blocks the main android thread and cause this error:

ANR in com.example.chatterbot (com.example.chatterbot/.MainActivity)
PID: 12527
Reason: Input dispatching timed out (7aa0a25 com.example.chatterbot/com.example.chatterbot.MainActivity (server) is not responding. Waited 10007ms for FocusEvent(hasFocus=true))
Parent: com.example.chatterbot/.MainActivity
ErrorId: f902fe3a-f5fa-40be-907d-fab77be9f0ca
Frozen: s[false] g[false]
Load: 26.58 / 26.37 / 26.93
------ Current CPU Core Info ------
- offline :
- online : 0-7
0 1 2 3 4 5 6 7
------------------------------------------------------------------------------------------------------------------
scaling_cur_freq 2301000 2301000 2301000 2301000 501000 501000 501000 501000
scaling_governor schedutil schedutil schedutil schedutil schedutil schedutil schedutil schedutil
scaling_max_freq 2301000 2301000 2301000 2301000 1800000 1800000 1800000 1800000 ------------------------------------------------------------------------------------------------------------------
----- Output from /proc/pressure/memory -----
some avg10=1.41 avg60=1.40 avg300=1.01 total=8666562438
full avg10=1.10 avg60=0.93 avg300=0.64 total=5116135829
----- End output from /proc/pressure/memory -----
CPU usage from 0ms to 12700ms later (2024-09-13 18:29:29.762 to 2024-09-13 18:29:42.462):
52% 3492/system_server: 33% user + 19% kernel / faults: 57585 minor 80 major
14% 157/kswapd0: 0% user + 14% kernel
0.2% 1040/media.swcodec: 0% user + 0.1% kernel / faults: 27482 minor 79 major
5.9% 12527/com.example.chatterbot: 3.4% user + 2.4% kernel / faults: 26634 minor 11 major
4.9% 307/exe_cq/0: 0% user + 4.9% kernel
0% 995/media.extractor: 0% user + 0% kernel / faults: 6019 minor 28 major
3% 4187/com.sec.imsservice: 1.5% user + 1.4% kernel / faults: 8117 minor 179 major
2.9% 3843/com.android.systemui: 1.8% user + 1.1% kernel / faults: 9067 minor 33 major
2.6% 3805/com.android.phone: 1.6% user + 1% kernel / faults: 7118 minor 41 major
2.5% 1023/android.hardware.sensors@2.0-service-mediatek: 0.7% user + 1.8% kernel / faults: 132 minor
2.5% 25148/adbd: 0.8% user + 1.6% kernel / faults: 152 minor
2.3% 3253/lmkd: 0.5% user + 1.8% kernel
2.2% 5150/com.sec.android.sdhms: 1% user + 1.1% kernel / faults: 5288 minor 71 major
2% 1699/main_thread: 0% user + 2% kernel
1.8% 1700/hif_thread: 0% user + 1.8% kernel
1.7% 26185/com.menny.android.anysoftkeyboard: 1% user + 0.7% kernel / faults: 5768 minor 73 major
0% 1022/media.codec: 0% user + 0% kernel / faults: 3617 minor 18 major
1.5% 481/logd: 0.3% user + 1.1% kernel / faults: 90 minor
1.4% 559/android.system.suspend@1.0-service: 0% user + 1.4% kernel / faults: 201 minor
1.4% 3846/com.android.networkstack.process: 0.6% user + 0.8% kernel / faults: 5223 minor 27 major
1.4% 9013/kworker/u16:2-events_unbound: 0% user + 1.4% kernel
1.4% 7357/process-tracker: 0.1% user + 1.2% kernel / faults: 66 minor
1.3% 21881/kworker/u16:5-pvr_misr: 0% user + 1.3% kernel
1.2% 4170/com.sec.sve: 0.5% user + 0.7% kernel / faults: 4977 minor 44 major
1.2% 32560/com.google.android.webview:sandboxed_process0rg.chromium.content.app.SandboxedProcessService0:0: 0.9% user + 0.3% kernel / faults: 4390 minor 4 major
1.1% 802/surfaceflinger: 0.5% user + 0.6% kernel / faults: 1328 minor 5 major
1% 4206/com.android.se: 0.5% user + 0.4% kernel / faults: 4264 minor 33 major
0.9% 1701/rx_thread: 0% user + 0.9% kernel
0.9% 11542/com.google.android.gms: 0.3% user + 0.5% kernel / faults: 2885 minor 29 major
0.8% 7899/logcat: 0.3% user + 0.5% kernel / faults: 45 minor
0.7% 215/chre_kthread: 0% user + 0.7% kernel
0.7% 327/ipi_cpu_dvfs_rt: 0% user + 0.7% kernel
0.7% 12389/com.google.android.webview:sandboxed_process0rg.chromium.content.app.SandboxedProcessService0:0: 0.6% user + 0.1% kernel / faults: 1593 minor


I don't know what to try next and can't find much online, is running a webserver in Chaquopy whthout blocking the UI impossible?

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