add_periodic_callback not working with pn.state.cache and --autoreload flag

[MarcSkovMadsen]

Panel 0.12.1

If I run the below script using panel serve script.py --autoreload --show --port=5006 does not work.

If I run the below script using panel serve script.py --port=5007 it works.

periodic_callback_not_working.mp4

import datetime

import panel as pn

pn.extension(sizing_mode="stretch_both")

ACCENT_BASE_COLOR = "#DAA520"

if not "streaming_component" in pn.state.cache:
    streaming_component = pn.pane.Markdown("hello")
    def update():
        text = f"""# Last Update: {datetime.datetime.utcnow().strftime('%H:%M:%S.%f')}"""
        print(text)
        streaming_component.object = text
    pn.state.cache["streaming_component"]=streaming_component
    periodic_callback = pn.state.add_periodic_callback(callback=update, period=500)

streaming_component=pn.state.cache["streaming_component"]


panel = pn.Row(streaming_component, height=90)

template = pn.template.FastListTemplate(
    site="Awesome Panel",
    title="add_periodic_callback",
    logo="https://panel.holoviz.org/_static/logo_stacked.png",
    header_background=ACCENT_BASE_COLOR,
    accent_base_color=ACCENT_BASE_COLOR,
    main=[panel],
).servable()

[philippjfr]

Interesting approach, but absolutely not a supported configuration. As I mentioned elsewhere add_periodic_callback adds a callback which is specific to a particular session. In this case --autoreload creates a session on launch, which is immediately cleaned up. Even without --autoreload this will break on second load of the app (or rather as soon as the initial session is cleaned up).

[philippjfr]

Once #2661 you should be able to use that instead.