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MySQL Connection Pool Doesn't Seem to Work · Issue #564 · encode/databases · GitHub
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MySQL Connection Pool Doesn't Seem to Work #564

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Open
MySQL Connection Pool Doesn't Seem to Work#564
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bugSomething isn't working

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@Vastxiao
Vastxiao
opened on Jul 14, 2023

I am experiencing an issue with the MySQL connection pool. I have been testing the following code:

DATABASE_URL = "mysql+aiomysql://root:root192.168.62.195:3306/test?charset=utf8mb4"

# Additional database URL parameters can also be passed in the Database constructor
database = Database(DATABASE_URL, min_size=3, max_size=10, charset="utf8mb4")

async def exec_sql(exec_func, sql: str, tid):
    while True:
        try:
            start_time = time.time()
            result = await exec_func(sql)
            logger.info(f'task({tid}|{start_time:.0f}|{time.time() - start_time:.3f}) {exec_func} {sql} {result}')
        except MySQLError as err:
            logger.error(f'task({tid}){exec_func} {sql} {err}')

async def main():
    await database.connect()

    async with asyncio.TaskGroup() as tg:
        for tid in range(1, 100000):
            tg.create_task(exec_sql(database.fetch_all, 'show tables', tid))
            tg.create_task(exec_sql(database.fetch_one, 'select * from tbl_sms_record', tid))
            tg.create_task(exec_sql(database.fetch_val, 'select * from tbl_sms_record', tid))

    await database.disconnect()

asyncio.run(main())

During concurrency testing, I noticed that only one TCP connection is being utilized for executing queries, while the other two initial connections remain idle.

MySQL process list output:

mysql> show processlist;
+-----+-----------------+---------------------+--------+---------+----------+----------------------------+------------------------------+
| Id  | User            | Host                | db     | Command | Time     | State                      | Info                         |
+-----+-----------------+---------------------+--------+---------+----------+----------------------------+------------------------------+
|  99 | root            | 192.168.51.70:59810 | db_sms | Sleep   |       46 |                            | NULL                         |
| 100 | root            | 192.168.51.70:59826 | db_sms | Query   |        0 | waiting for handler commit | select * from tbl_sms_record |
| 101 | root            | 192.168.51.70:59832 | db_sms | Sleep   |       46 |                            | NULL                         |
+-----+-----------------+---------------------+--------+---------+----------+----------------------------+------------------------------+

TCP Connections:

State        Recv-Q   Send-Q           Local Address:Port                  Peer Address:Port    Process
ESTAB 0      0      [::ffff:10.0.0.161]:3306  [::ffff:192.168.51.70]:37426 users:(("mysqld",pid=542638,fd=39))
ESTAB 0      1400   [::ffff:10.0.0.161]:3306  [::ffff:192.168.51.70]:37412 users:(("mysqld",pid=542638,fd=38))
ESTAB 0      0      [::ffff:10.0.0.161]:3306  [::ffff:192.168.51.70]:37408 users:(("mysqld",pid=542638,fd=37))

I expected that with 100,000 concurrent tasks, more connections would be utilized. Is this an issue with my code or the databases library?

Activity

  1. Vastxiao commented on Jul 15, 2023

    @Vastxiao
    Vastxiao
    on Jul 15, 2023
    Author

    yeah, it's an issue with databases library

    test the working code:

    import aiomysql
import asyncio


async def create_pool():
    pool = await aiomysql.create_pool(
        host='192.168.62.195',
        port=3306,
        user='root',
        password='xiao',
        db='db_sms',
        minsize=3,
        maxsize=10
    )
    return pool


async def execute_query(pool, query):
    while True:
        async with pool.acquire() as conn:
            async with conn.cursor() as cur:
                await cur.execute(query)
                result = await cur.fetchall()
                # return result
                print(result)


async def run_concurrent_queries(pool, num_queries):
    tasks = []
    query = "select * from tbl_sms_record"

    async with asyncio.TaskGroup() as tg:
        for tid in range(num_queries):
            # tg.create_task(exec_sql(database.fetch_all, 'show tables', tid))
            tg.create_task(execute_query(pool, query))


async def main():
    pool = await create_pool()
    num_queries = 100000
    await run_concurrent_queries(pool, num_queries)
    pool.close()
    await pool.wait_closed()


asyncio.run(main())

    TCP Connections:

    ESTAB 0      1400   [::ffff:10.0.0.161]:3306  [::ffff:192.168.50.139]:53520 users:(("mysqld",pid=542638,fd=37))                        
ESTAB 0      1400   [::ffff:10.0.0.161]:3306  [::ffff:192.168.50.139]:53560 users:(("mysqld",pid=542638,fd=42))                        
ESTAB 0      1400   [::ffff:10.0.0.161]:3306  [::ffff:192.168.50.139]:53574 users:(("mysqld",pid=542638,fd=45))                        
ESTAB 0      1400   [::ffff:10.0.0.161]:3306  [::ffff:192.168.50.139]:53530 users:(("mysqld",pid=542638,fd=38))                        
ESTAB 0      1400   [::ffff:10.0.0.161]:3306  [::ffff:192.168.50.139]:53564 users:(("mysqld",pid=542638,fd=44))                        
ESTAB 0      1400   [::ffff:10.0.0.161]:3306  [::ffff:192.168.50.139]:53548 users:(("mysqld",pid=542638,fd=41))                        
ESTAB 0      1400   [::ffff:10.0.0.161]:3306  [::ffff:192.168.50.139]:53510 users:(("mysqld",pid=542638,fd=23))                        
ESTAB 0      1400   [::ffff:10.0.0.161]:3306  [::ffff:192.168.50.139]:53538 users:(("mysqld",pid=542638,fd=39))                        
ESTAB 0      1400   [::ffff:10.0.0.161]:3306  [::ffff:192.168.50.139]:53562 users:(("mysqld",pid=542638,fd=43))                        
ESTAB 0      1400   [::ffff:10.0.0.161]:3306  [::ffff:192.168.50.139]:53590 users:(("mysqld",pid=542638,fd=46))

    and qps to 1k
    databases just qps 600

  2. zanieb commented on Jul 15, 2023

    @zanieb
    zanieb
    on Jul 15, 2023
    Contributor

    Thanks for the report! Let me know if you determine the cause — there's not a lot of activity from people that would know the reason off the top of their head.

  3. zanieb
    added
    bugSomething isn't working
    on Jul 15, 2023

  4. Priyansh2 commented on Jul 15, 2023

    @Priyansh2
    Priyansh2
    on Jul 15, 2023

    @Vastxiao which library works for making async database connection which supports connection pooling, raw SQL execution ?

  5. sungeer commented on Oct 30, 2024

    @sungeer
    sungeer
    on Oct 30, 2024

    @Vastxiao which library works for making async database connection which supports connection pooling, raw SQL execution ?

    aiomysql comes with asynchronous connection pooling, native sql support

  6. Vastxiao commented on Oct 31, 2024

    @Vastxiao
    Vastxiao
    on Oct 31, 2024
    Author

    @zanieb I don't know the reason for databases, but I created asmysql as a replacement.
    https://github.com/vastxiao/asmysql

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