Stockfish chess engine gets: "EngineTerminatedError: engine process died unexpectedly" on Heroku

Question

I am trying to build an AI chess bot, with a python back-end and React front-end. When I run it locally it works fine, but when deploying on Heroku for free, I get the following error message:

result = engine.play(board, chess.engine.Limit(time=0.1)) chess.engine.EngineTerminatedError: engine process died unexpectedly (exit code: 0)

The linux stockfish file works fine on Heroku bash.

This is my code:

import chess
import chess.engine
from flask import Flask
import os
import stat
import sys

app = Flask(__name__)


@app.route('/')

def index():
    board = chess.Board()
    if sys.platform == "linux":
        os.chmod("./stockfish_20011801_x64", stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH)
        engine = chess.engine.SimpleEngine.popen_uci("./stockfish_20011801_x64")
    else:
        engine = chess.engine.SimpleEngine.popen_uci("./stockfish_20011801_x64.exe")
    result = engine.play(board, chess.engine.Limit(time=3))
    board.push(result.move)
    return board.fen()

Here are part of the logs:

DEBUG:chess.engine:<UciProtocol (pid=10)>: >> uciok

DEBUG:chess.engine:<UciProtocol (pid=10)>: << ucinewgame

DEBUG:chess.engine:<UciProtocol (pid=10)>: << isready

DEBUG:chess.engine:<UciProtocol (pid=10)>: Process exited

DEBUG:chess.engine:<UciProtocol (pid=10)>: Connection lost (exit code: 0, error: None)

chess.engine.EngineTerminatedError: engine process died unexpectedly (exit code: 0)

Answer 1

When I uninstalled eventlet it did work. I tried to uninstall it because it is very similar to asyncio, which is an dependency of python-chess.