context-managed resource on module level

user_2401309 0
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I am looking for a pattern where I have multiple functions that need access to a resource that is context-managed.

In particular, I am using fastAPI and want to re-use aiopg (async psycopg2) connections.

This is the basic layout:

@app.get("/hello")
def hello():
    async with aiopg.connect(...) as conn:
        async with conn.cursor(...):
            return cursor.execute(...)

Now I want to avoid a connection per route. I could think of an object outside, and in the route I either access the conn property or await creation (and store back) and then just use the with on the cursor() method.

class Pg():
    async def conn(self):
        if not self._conn:
            self._conn = await aiopg.connect(...)
        return self._conn

myPg = Pg()

@app.get("/hello")
def hello():
    conn = await myPg.conn()
    async with conn.cursor(...):
        return cursor.execute(...)

However, I then would lose the ability to automatically close the connection.

I think that I miss something really obvious here and hope that someone could guide me how to implement this properly.

Thanks!

fastapi python
1 Answers

aiopg provides a Pool class that can manage connections.

just create a pool instance at the module level:

pool = await aiopg.create_pool('<your connection string>')

Then you can use the Pool.acquire context-manager to get a connection:

async with pool.acquire() as conn:
    ...

If connections already exist in the pool, they will be re-used.

user_26963550
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