Python

Stateless server keeps no state information

Using a stateless file server, the client must,specify complete file names in each request specify location for reading or writing re-authenticate for each request

Pros

easily recover from failure
server implementation remains

gunicorn will check which process isn't busy running a callback and send the new callback request to that process

a few processes can balance the requests of 10s or 100s of concurrent user

import dash
import dash_html_components as html
import dash_core_components as dcc

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash(__name__, external_stylesheets=external_stylesheets)

server = app.server

app.layout = html.Div([
    html.Div(dcc.Input(id='input-on-submit', type='text')),
    html.Button('Submit', id='submit-val', n_clicks=0),
    html.Div(id='container-button-basic',
             children='Enter a value and press submit')
])


@app.callback(
    dash.dependencies.Output('container-button-basic', 'children'),
    [dash.dependencies.Input('submit-val', 'n_clicks')],
    [dash.dependencies.State('input-on-submit', 'value')])
def update_output(c, v):
    return 'The input value was "{}" and the button has been clicked {} times'.format(
        v,
        c
    )


if __name__ == '__main__':
    app.run_server(debug=True)

gunicorn app:server --workers 8

/* index.htm */
<!DOCTYPE html>
<html>
<body>

<iframe src="http://localhost:8000" width=700 height=600>

</body>
</html>

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