connection pool exhausted psycopg2

Question

I have an issue with Postgresql psycopg2. I receive the error :

error in executing with exception: connection pool exhausted

My code :

from psycopg2 import pool
import pandas.io.sql as sqlio
import pandas as pd
db = pool.ThreadedConnectionPool(5, 100,host=POSTGRES['host'],
database=POSTGRES['database'],user=POSTGRES['username'],
password=POSTGRES['password'],port=POSTGRES['port'])


try:
    sql = "select * from role"  
    data = sqlio.read_sql_query(sql, db.getconn())
    return data.to_json(orient='records')
except Exception as e:
    print "error in executing with exception: ", e
    return pd.DataFrame({'empty' : []})

and this request should return only 5 rows, but i get this error.

Do you have any idea why i get this error ?

My Postgresql Database (medium instance) is deployed on a public cloud.

Thank you in advance

Answer 1

it would appear you need to return the connection back to the pool at some point, see:

http://initd.org/psycopg/docs/pool.html#psycopg2.pool.AbstractConnectionPool.putconn

i.e. something like:

sql = "select * from role"  
try:
    conn = db.getconn()
    try:
        data = sqlio.read_sql_query(sql, conn)
    finally:
        pool.putconn(conn)
    return data.to_json(orient='records')
except Exception as e:
    print "error in executing with exception: ", e
    return pd.DataFrame({'empty' : []})