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# Background Tasks / Executor
# Use q.exec() to execute background functions using a thread-pool or process-pool.
# #background_tasks #executor
# ---
import time
import random
import concurrent.futures
from h2o_wave import main, app, Q, ui
def blocking_function(secs) -> str:
time.sleep(secs) # Blocks!
return f'Done waiting for {secs} seconds!'
@app('/demo')
async def serve(q: Q):
if q.args.start:
q.page['form'] = ui.form_card(box='1 1 6 2', items=[ui.progress('Running...')])
await q.page.save()
seconds = random.randint(1, 6)
# DON'T DO THIS!
# This will make your app unresponsive for some time:
# message = blocking_function(seconds)
# Do this instead:
with concurrent.futures.ThreadPoolExecutor() as pool:
message = await q.exec(pool, blocking_function, seconds)
# You can also pass a ProcessPoolExecutor, like this:
# with concurrent.futures.ProcessPoolExecutor() as pool:
# message = await q.exec(pool, blocking_function, seconds)
q.page['form'] = ui.form_card(box='1 1 6 1', items=[ui.message_bar('info', message)])
await q.page.save()
else:
q.page['form'] = ui.form_card(box='1 1 2 1', items=[ui.button(name='start', label='Start')])
await q.page.save()
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