Issue with utemplate - silent death of process

[JohannesMaierhofer]

Hi, I have some issues with the reliability of using the utemplate rendering. The thing is: 1 out of 10 times it works, and the next call could again silently crash the application. Observing the webbrowser, the rendered template always loads, but the referenced static files are often not loaded, or only loaded partially. Working with send_file, all the static files load perfectly well.

Pressing "stop" in Thonny unveils the following message:

GET /dataviewer 200

───────────────────────────────────────────────────
Traceback (most recent call last):
  File "<stdin>", line 123, in <module>
  File "microdot/microdot.py", line 1281, in run
  File "asyncio/core.py", line 1, in run
  File "asyncio/core.py", line 1, in run_until_complete
  File "asyncio/core.py", line 1, in wait_io_event
KeyboardInterrupt: 

Here are some code-snippets:

app = Microdot()
Response.default_content_type = 'text/html'

@app.route('/dataviewer', methods=['GET'])
async def dataviewer(request):
    filename = request.args['filename']
    if filename and filename.endswith('.json'):
        return Template('dataview.html').generate(filename=filename)
    else:
        return 'File not found', 404

@app.route('/static/<path:path>')
async def static(request, path):
    if '..' in path:
        # directory traversal is not allowed
        return 'Not found', 404
    return send_file('static/' + path)

if __name__ == '__main__':
    app.run(port=80, debug=True)

...     
<link type="text/css" rel="stylesheet" href="static/index.css">
      <script type="text/javascript" src="static/chart.umd.js"></script>
      <script type="text/javascript" src="static/WebAppDataView.js"></script>
...

Any help or comment is appreciated.

[miguelgrinberg]

The only thing that comes to mind is if you may be using templates that require more RAM than what you have in your device to compile. I'm honestly not familiar with the internals of utemplate, which isn't my project. Does the problem occur if you run your application on the Unix port of MicroPython, for example? It would be interesting to know.

[JohannesMaierhofer]

sorry, it is the send_file('static/' + path) which crashes randomly after Template('dataview.html').generate(filename=filename) is called once.

[miguelgrinberg]

Crashes how? Please include the stack trace of the crash.

[JohannesMaierhofer]

I prepared a minimal working example, which shows my issue with minimal code and super small files. I tried with Micropython on ESP32S3 v 1.21, 1.22, 1.23. everywhere the same behavior.
firmwareMinimalExample.zip

[miguelgrinberg]

I don't know what I'm supposed to look for in this example. It runs fine for me. What error(s) are you getting?

[JohannesMaierhofer]

Sorry I bothered you. It seems I have a general issue with the filesystem and therefore the files are/were not served. It is not an issue of microdot!