在Queue.task_done（）之后运行多线程代码

Question

In a classical "Threading/Queue"-application. I need to do further calculations in my "consumer"-function. After Queue is empty no further code is executed after urls.task_done().

I am importing market data from an JSON api and import it into my MariaDB database. On the API every item that i want to fetch has an own url, so I am creating a queue for all available urls in a function. A "consumer"-function processes the queue importing a new set of data or updating an existent entry depending on the already existing data in my database. I already tried to wrap the actual while True loop into its own function but it didn't work for me.

def create_url():
    try:
        mariadb_connection = mariadb.connect(host='host
                                             database='db',
                                             user='user',                                             
                                           password='pw')

        cursor = mariadb_connection.cursor()

        cursor.execute('SELECT type_id from tbl_items')
        item_list = cursor.fetchall()
        print("Create URL - Record retrieved successfully")

        for row in item_list:

            url = 'https://someinternet.com/type_id=' + \
                str(row[0])
            urls.put(url)

        return urls

    except mariadb.Error as error:
        mariadb_connection.rollback()  
        print("Failed retrieving itemtypes from tbl_items table 
        {}".format(error))

    finally:
        if mariadb_connection.is_connected():
            cursor.close()
            mariadb_connection.close()

def import(urls):
    list_mo_esi = []
    try:
        mariadb_connection = mariadb.connect(host='host',
                                             database='db',
                                             user='user',
                                             password='pw')

        cursor = mariadb_connection.cursor()

        while True:
            s = requests.Session()
            retries = Retry(total=5, backoff_factor=1, status_forcelist=[502, 503, 504])
            s.mount('https://', HTTPAdapter(max_retries=retries))
            jsonraw = s.get(urls.get())
            jsondata = ujson.loads(jsonraw.text)

            for row in jsondata:
                cursor.execute('SELECT order_id from tbl_mo WHERE order_id = %s',
                               (row['order_id'], ))
                exists_mo = cursor.fetchall()
                list_mo_esi.append(row['order_id'])

                if len(exists_mo) != 0:
                    print("updating order#", row['order_id'])
                    cursor.execute('UPDATE tbl_mo SET volume = %s, price = %s WHERE order_id = %s',
                                   (row['volume_remain'], row['price'], row['order_id'], ))
                    mariadb_connection.commit()
                else:
                        cursor.execute('INSERT INTO tbl_mo (type_id, order_id, ordertype,volume, price) VALUES (%s,%s,%s,%s,%s)',
                                       (row['type_id'], row['order_id'], row['is_buy_order'], row['volume_remain'], row['price'], ))
                        mariadb_connection.commit()

            urls.task_done()

    except mariadb.Error as error:
        mariadb_connection.rollback()  
        print("Failed retrieving itemtypes from tbl_items table {}".format(error))

The following finally part of my function is not executed, but should.

    finally:
        list_mo_purge = list(set(list_mo_sql)-set(list_mo_esi))
        cursor.execute('SELECT order_id FROM tbl_mo')
        list_mo_sql = cursor.fetchall()
        print(len(list_mo_esi))
        print(len(list_mo_sql))

        if mariadb_connection.is_connected():
            cursor.close()
            mariadb_connection.close()

main thread

for i in range(num_threads):
    worker = Thread(target=import_mo, args=(urls,))
    worker.setDaemon(True)
    worker.start()

create_url()

urls.join()

After all tasks are completed my worker stop executing code right after urls.task_done(). However, i have some more code after the function urls.task_done() i need to be executed for closing database connection and cleaning up my database from old entries. How can I make this "finally"-part run?

Answer 1

You are not breaking from the while.

You should do the following:

if urls.empty():
    break

Most likely your import thread gets blocked at urls.get()