未定义名称“ conn”：NameError

Question

I want to store my aws iot mqtt messages into my postgresql. To do so, I have already connected my local posrtgresql to the amazon RDS instance. Now, I need to create a connection between amazon lambda calculus and then send the data to the postgresql database. But whenever, I am testing my lambda calculus, it was giving me "name 'conn' is not defined: NameError" error. Here, is my python code in aws lambda. I have also included the psycopg2 library to my project.

import sys
import logging
import rds_config
import psycopg2
#rds settings
rds_host  = "myhost"
name = "username"
password = "username_password"
db_name = "dbname"

logger = logging.getLogger()
logger.setLevel(logging.INFO)

try:
    conn = psycopg2.connect(host=rds_host, user=name, password=password, 
           dbname=db_name, connect_timeout=5)
except:
     logger.error("ERROR: Unexpected error: Could not connect to postgreSQL 
          instance.")

logger.info("SUCCESS: Connection to RDS postgreSQL instance succeeded")
def handler(event, context):
"""
This function fetches content from postgreSQL RDS instance
"""
item_count = 0
with conn.cursor() as cur: 
    cur.execute('insert into awsiotdata (serialnumber, dateandtime, clicktype, batteryvoltage) values(serialNumber, datetime.datetime.utcnow(), clickType, batteryVoltage)')
    conn.commit()
    cur.execute("select * from awsiotdata")
    for row in cur:
        item_count += 1
        logger.info(row)
        #print(row)


return "Added %d items from RDS PostgreSQL table" %(item_count)

Answer 1

You are hiding a true error message. Exception handling patter for Python looks like this :

try:
    conn = psycopg2.connect(host=rds_host,
                            user=name,
                            password=password,
                            database=db_name)
except Exception as e:
    print(e)

This way you will see the real error message:

invalid dsn: invalid connection option "passwd"

Edit #1:

"Timeout" means that lambda can't connect because of "Security group rules" for RDS instance. Please keep in mind that even public RDS instance by default have inbound restriction by IP (ie it is posible to connect from PC but it is imposible to connect from AWS Lambda).