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Several quick questions on the doc + general, Please help

Hi, Dash is awesome, i try to better understand it.:
1: the suppress_callback_exceptions seems legacy since the app.validation_layout, right? Can callbacks appear before the layout/validation layout are set? eg shuffle your example ( Layout for Multi-Page App Validation from https://dash.plotly.com/urls)

# Index callbacks
@app.callback(Output('page-content', 'children'),
              [Input('url', 'pathname')])
def display_page(pathname):
    if pathname == "/page-1":
        return layout_page_1
    elif pathname == "/page-2":
        return layout_page_2
    else:
        return layout_index

# index layout
app.layout = url_bar_and_content_div

# "complete" layout
app.validation_layout = html.Div([
    url_bar_and_content_div,
    layout_index,
    layout_page_1,
    layout_page_2,
])

The doc remains silent on that:

New in Dash 1.12 You can set app.validation_layout to a “complete” layout that contains all the components you’ll use in any of the pages / sections. app.validation_layout must be a Dash component, not a function. Then set app.layout to just the index layout.

Q2: Can the id= repeat across pages eg layout_page_1 and in layout_page_2?

Q3: Raise on non visible outputs. Shouldnt this raise since the page-2-display-value is not in the current layout when the page-1-interval is active/visible/firing?

@app.callback(Output('page-2-display-value', 'children'),
              [Input('page-1-interval', 'n_intervals')])
def update_metrics(n):
    import time
    return time.time()

Q4: on run with $ gunicorn --workers=2 'dapp.main:get_server() i wonder if it is thread safe due 2 workers?

:frowning: can you please elaborate on this, any hint appreciated?