multiprocessing.Process fetch_trade: 'luno' object has no attribute 'publicGetTickers'

Hi I’m trying to spawn a process for each of a number of exchanges, and testing with a single one for now, just to get the Multiprocessing working. However, it is failing.

import ccxt
import multiprocessing

if __name__ == '__main__':
    exchange_class = getattr(ccxt, 'luno')
    exchange = exchange_class()
    a_process = multiprocessing.Process(target=exchange.fetch_trades, args=('BTC/ZAR', 1553983200000))
    a_process.start()

fails with

AttributeError: 'luno' object has no attribute 'publicGetTickers'

Any way to fix this? If not, any alternatives?

Environment info:

• OS: Win 10, 64 bit
• Programming Language version: Python 3.7.2
• CCXT version: 1.18.398
• Exchange: luno
• Method: fetch_trades(), via multiprocessing.Process()

[kroitor]

@ErnstDinkelmann

Can you confirm that the above will not break your rate-limiting (or other stuff) since only one instance of any class used at any one time?

The above code doesn’t use the rate-limiter, it is off by default and has to be enabled as described in the Manual: https://github.com/ccxt/ccxt/wiki/Manual#rate-limit

If you’re creating one process per exchange, i’d suggest that you rather pass the exchange name to the process, and create the exchange instance inside the worker subprocess:

def worker_function(exchange_id, *args):
    exchange = getattr(ccxt, exchange_id)({'enableRateLimit': True})
    result = exchange.fetch_trades(*args)
    print(result)

if __name__ == '__main__':
    lst_processes = []
    for exchange_id in lst_exchangeids:
        lst_processes.append(multiprocessing.Process(target=worker_function, args=(exchange_id, 'BTC/USD', 1553983200000)))

    for one_process in lst_processes:
        one_process.start()

Does that work for you? (pardon, didn’t have the time to actually test it throughly yet)

[ErnstDinkelmann]

Yes, aware of default being false, sorry, just removed that code in the example.

I’m happy with the solution provided.

I guess some further thinking would be required if one wants to fetch trade data with multiple processes, and at the same time execute trades on one or more of the exchanges. I guess this would require rate-limiting to be implemented in the application to be safe.

You are welcome to close this issue. Thank you both.