Not able to connect app engine to cloud sql for mysql instance

Question

sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2003, "Can't connect to MySQL server on 'localhost' ([Errno 2] No such file or directory)") (Background on this error at: http://sqlalche.me/e/e3q8)

Its been long time i am stuck at this error , I am trying to connect my app engine python code to a cloud sql for mysql instance. This is the first time i am working with google cloud.below is the code i have written 1. in app.yaml

runtime:
    python37
vpc_access_connector:
    name: "projects/projectnameandcode/locations/location name/connectors/connector name"

2.requirements.txt

sqlalchemy
pymysql

3. in main.py

   import pymysql

   db = sqlalchemy.create_engine(

   sqlalchemy.engine.url.URL(
       drivername="mysql+pymysql",
       username="username",
       password=password,
       database="databasename",
       query={"unix_socket": "/cloudsql/{}".format("instance name")},
   ),
   

   ) a= db.connect()

why am i facing this problem ? My Iam roles are owner or admin.

Answer 1

App Engine standard enviroments do not support connecting to the Cloud SQL instance using TCP. Your code should not try to access the instance using an IP address (such as 127.0.0.1 or 172.17.0.1) unless you have configured Serverless VPC Access.

From your question I understand that you are using vpc_access_connector. Therefore I assume that you configured Serverless VPC Access.

The code used in main.py is for connecting to Cloud SQL instance's using unix domain socket and not TCP.

EDIT:

CONNECTING FROM APP ENGINE TO CLOUD SQL USING TCP AND UNIX DOMAIN SOCKETS

1.Create a new project

gcloud projects create con-ae-to-sql
gcloud config set project con-ae-to-sql
gcloud projects describe con-ae-to-sql

2.Enable billing on you project: https://cloud.google.com/billing/docs/how-to/modify-project

3.Run the following gcloud command to enable App Engine and create the associated application resources

gcloud app create -region europe-west2
gcloud app describe
#Remember the location of you App Engine aplication, because we will create all our resources on the same region

4.Set the compute project-info metadata:

 gcloud compute project-info describe --project con-ae-to-sql
 #Enable the Api, and you can check that default-region,google-compute-default-zone are not set. Set the metadata.
 gcloud compute project-info add-metadata --metadata google-compute-default-region=europe-west2,google-compute-default-zone=europe-west2-b

5.Enable Service Networking Api:

gcloud services list --available
gcloud services enable servicenetworking.googleapis.com

6.Create 2 cloud sql instances, (one with internall ip and one with public ip)- https://cloud.google.com/sql/docs/mysql/create-instance:

6.a Cloud Sql Instance with external ip:

#Create the sql instance in the same region as App Engine Application
gcloud --project=con-ae-to-sql beta sql instances create database-external --region=europe-west2
#Set the password for the "root@%" MySQL user:
gcloud sql users set-password root --host=% --instance database-external --password root 
#Create a user
gcloud sql users create user_name --host=% --instance=database-external  --password=user_password
#Create a database
gcloud sql databases create user_database --instance=database-external
gcloud sql databases list --instance=database-external

6.b Cloud Sql Instance with internal ip:

i.#Create a private connection to Google so that the VM instances in the default VPC network can use private services access to reach Google services that support it.

gcloud compute addresses create google-managed-services-my-network     --global  --purpose=VPC_PEERING --prefix-length=16  --description="peering range for Google"  --network=default --project=con-ae-to-sql
gcloud services vpc-peerings connect --service=servicenetworking.googleapis.com --ranges=google-managed-services-my-network  --network=default  --project=con-ae-to-sql
#Check whether the operation was successful.
gcloud services vpc-peerings operations describe     --name=operations/pssn.dacc3510-ebc6-40bd-a07b-8c79c1f4fa9a
#Listing private connections
gcloud services vpc-peerings list --network=default --project=con-ae-to-sql
 
ii.Create the instance:

gcloud --project=con-ae-to-sql beta sql instances create database-ipinternal --network=default --no-assign-ip  --region=europe-west2
#Set the password for the "root@%" MySQL user:
gcloud sql users set-password root --host=% --instance database-ipinternal --password root
#Create a user
gcloud sql users create user_name --host=% --instance=database-ipinternal  --password=user_password
#Create a database
gcloud sql databases create user_database --instance=database-ipinternal
gcloud sql databases list --instance=database-ipinternal 


gcloud sql instances list
gcloud sql instances describe database-external
gcloud sql instances describe database-ipinternal
#Remember the instances connectionName

OK, so we have two mysql instances, we will connect from App Engine Standard to database-ipinternal using Serverless Access and TCP, from App Engine Standard to database-external using unix domain socket, from App Engine Flex to database-ipinternal using TCP, and from App Engine Flex to database-external using unix domain socket.

7.Enable the Cloud SQL Admin API

gcloud services list --available
gcloud services enable sqladmin.googleapis.com

8.At this time App Engine standard enviroments do not support connecting to the Cloud SQL instance using TCP. Your code should not try to access the instance using an IP address (such as 127.0.0.1 or 172.17.0.1) unless you have configured Serverless VPC Access.So let's configure Serverless VPC Access.

8.a Ensure the Serverless VPC Access API is enabled for your project:

gcloud services enable vpcaccess.googleapis.com

8.b Create a connector:

gcloud compute networks vpc-access connectors create serverless-connector --network default --region europe-west2 --range 10.10.0.0/28
#Verify that your connector is in the READY state before using it
gcloud compute networks vpc-access connectors describe serverless-connector --region europe-west2

9.App Engine uses a service account to authorize your connections to Cloud SQL. This service account must have the correct IAM permissions to successfully connect. Unless otherwise configured, the default service account is in the format service-PROJECT_NUMBER@gae-api-prod.google.com.iam.gserviceaccount.com. Ensure that the service account for your service has the following IAM roles: Cloud SQL Client, and for connecting from App Engine Standard to Cloud Sql on internal ip we need also the role Compute Network User.

gcloud iam service-accounts list
gcloud projects add-iam-policy-binding con-ae-to-sql --member serviceAccount:con-ae-to-sql@appspot.gserviceaccount.com --role roles/cloudsql.client
gcloud projects add-iam-policy-binding con-ae-to-sql --member serviceAccount:con-ae-to-sql@appspot.gserviceaccount.com --role roles/compute.networkUser

Now that I configured the set up

1. Connect from App Engine Standard to Cloud Sql using Tcp and unix domanin socket

cd app-engine-standard/
ls
#app.yaml  main.py requirements.txt

cat requirements.txt
Flask==1.1.1
sqlalchemy
pymysql
uwsgi==2.0.18

cat app.yaml
runtime: python37
entrypoint: uwsgi --http-socket :8080 --wsgi-file main.py --callable app --master --processes 1 --threads 2
vpc_access_connector:
    name: "projects/con-ae-to-sql/locations/europe-west2/connectors/serverless-connector" 



cat main.py

from flask import Flask
import pymysql
from sqlalchemy import create_engine

# If `entrypoint` is not defined in app.yaml, App Engine will look for an app
# called `app` in `main.py`.
app = Flask(__name__)

@app.route('/')
def hello():
    engine_tcp = create_engine('mysql+pymysql://user_name:user_password@internal-ip-of-database-ipinternal:3306')
    existing_databases_tcp = engine_tcp.execute("SHOW DATABASES;")
    con_tcp = "Connecting from APP Engine Standard to Cloud SQL using TCP: databases => " + str([d[0] for d in existing_databases_tcp]).strip('[]') + "\n"
    engine_unix_socket = create_engine('mysql+pymysql://user_name:user_password@/user_database?unix_socket=/cloudsql/con-ae-to-sql:europe-west2:database-external')
    existing_databases_unix_socket = engine_unix_socket.execute("SHOW DATABASES;")
    con_unix_socket = "Connecting from APP Engine Standard to Cloud SQL using Unix Sockets: tables in sys database:  => " + str([d[0] for d in existing_databases_unix_socket]).strip('[]') + "\n"
    return con_tcp + con_unix_socket



gcloud app deploy -q
gcloud app browse
#Go to https://con-ae-to-sql.appspot.com
#Connecting from APP Engine Standard to Cloud SQL using TCP: databases => 'information_schema', 'user_database', 'mysql', 'performance_schema', 'sys' Connecting from APP Engine Standard to Cloud SQL using Unix Sockets: tables in sys database: => 'information_schema', 'user_database', 'mysql', 'performance_schema', 'sys'

SUCCESS!

2.Connect from App Engine Flex to Cloud Sql using Tcp and unix domanin socket

cd app-engine-flex/
ls
#app.yaml  main.py requirements.txt

cat requirements.txt
Flask==1.1.1
gunicorn==19.9.0
sqlalchemy
pymysql

cat app.yaml
runtime: python
env: flex
entrypoint: gunicorn -b :$PORT main:app
runtime_config:
  python_version: 3
#Using TCP and unix sockets domain
beta_settings:
 cloud_sql_instances: con-ae-to-sql:europe-west2:database-ipinternal=tcp:3306,con-ae-to-sql:europe-west2:database-external
manual_scaling:
  instances: 1
resources:
  cpu: 1
  memory_gb: 0.5
  disk_size_gb: 10


cat main.py

from flask import Flask
import pymysql
from sqlalchemy import create_engine

app = Flask(__name__)

@app.route('/')
def hello():
    engine_tcp = create_engine('mysql+pymysql://user_name:user_password@internal-ip-of-database-ipinternal:3306')
    existing_databases_tcp = engine_tcp.execute("SHOW DATABASES;")
    con_tcp = "Connecting from APP Engine Flex to Cloud SQL using TCP: databases => " + str([d[0] for d in existing_databases_tcp]).strip('[]') + "\n"

    engine_unix_socket = create_engine('mysql+pymysql://user_name:user_password@/user_database?unix_socket=/cloudsql/con-ae-to-sql:europe-west2:database-external')
    existing_databases_unix_socket = engine_unix_socket.execute("SHOW DATABASES;")
    con_unix_socket = "Connecting from APP Engine Flex to Cloud SQL using Unix Sockets: tables in sys database:  => " + str([d[0] for d in existing_databases_unix_socket]).strip('[]') + "\n"
    return con_tcp + con_unix_socket


gcloud app deploy -q
gcloud app browse
#Go to https://con-ae-to-sql.appspot.com
#Connecting from APP Engine Flex to Cloud SQL using TCP: databases => 'information_schema', 'marian', 'mysql', 'performance_schema', 'sys' Connecting from APP Engine Flex to Cloud SQL using Unix Sockets: tables in sys database: => 'information_schema', 'marian', 'mysql', 'performance_schema', 'sys'

SUCCESS!

Answer 2

Take a quick look at the Connecting to Cloud SQL from App Engine documentation, and make sure you have followed all of the steps correctly. Specifically, make sure of the following:

1. The instance has a public IP
2. The Cloud SQL Admin API is enabled
3. The service account has the Cloud SQL IAM permissions