Sorry, see "attached test script" here:
from sqlalchemy import *
import logging
import threading
import time
import os
logging.basicConfig(level = logging.INFO, format =
'%(levelname)s:%(asctime)s:%(thread)d:%(message)s', filename =
"autoload_test.log")
logging.getLogger("sqlalchemy").setLevel(logging.DEBUG)
engine = create_engine("postgresql://madk@localhost/mydb", echo = False)
metadata = MetaData(bind=engine)
lock = threading.Lock()
def load_table():
while True:
try:
table = Table('mytable', metadata, autoload=True,
autoload_with=engine)
logging.info("size of columns:[%s]", len(table.columns))
except:
logging.warn("error occured", exc_info = True)
logging.info("starting")
for i in range(5):
t = threading.Thread(target = load_table)
t.daemon = False
t.start()
time.sleep(2)
os._exit(0)
On Sunday, October 25, 2015 at 3:37:55 PM UTC+8, peon ma wrote:
>
> Hello
>
> I have a problem with table reflection under multi-thread without lock.
> It works fine under single-thread or multi thread with lock protection.
>
> I got following result by the attached test script:
> single-thread or multi thread with lock protection:
> It prints some logs of create connection, query metadata etc, and then
> the table reflection returned.
> multi-thread without lock protection:
> table reflection returned before create connection and query metadata,
> without any exceptions, loggings, but got empty columns list
> and after about 20ms(metadata of this table fetched), all threads
> works fine(got correct columns list)
>
>
> I did found any related documentation about this, so I want to know:
> Is it a bug?
> Or the reflection isn't thread-safe, if so, is it thread-safe for
> reflection different tables?(see following code for example)
> with tbl1_lock:
> Table("table1", ... )
>
> with tbl2_lock:
> Table("table2", ...)
>
>
> Thanks in advance
>
>
>
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