Failed to connect to cloud SQL using proxy despite following the documentation - doctrine-orm

Question

I'm using doctrine ORM with Symfony, the PHP framework. I'm getting bizarre behaviour when trying to connect to cloud SQL using GKE.
I'm able to get a connection to the DB via doctrine on command line, for example php bin/console doctrine:database:create is successful and I can see a connection opened in the proxy pod logs.
But when I try and connect to the DB via doctrine in my application I run into this error without fail:
An exception occurred in driver: SQLSTATE[HY000] [2002] php_network_getaddresses: getaddrinfo failed: Name or service not known
I have been trying to get my head around this but it doesn't make sense, why would I be able to connect via command line but not in my application?
I followed the documentation here for setting up a db connection using cloud proxy. This is my Kubernetes deployment:
---
apiVersion: "extensions/v1beta1"
kind: "Deployment"
metadata:
name: "riptides-api"
namespace: "default"
labels:
app: "riptides-api"
microservice: "riptides"
spec:
replicas: 3
selector:
matchLabels:
app: "riptides-api"
microservice: "riptides"
template:
metadata:
labels:
app: "riptides-api"
microservice: "riptides"
spec:
containers:
- name: "api-sha256"
image: "eu.gcr.io/riptides/api#sha256:ce0ead9d1dd04d7bfc129998eca6efb58cb779f4f3e41dcc3681c9aac1156867"
env:
- name: DB_HOST
value: 127.0.0.1:3306
- name: DB_USER
valueFrom:
secretKeyRef:
name: riptides-mysql-user-skye
key: user
- name: DB_PASSWORD
valueFrom:
secretKeyRef:
name: riptides-mysql-user-skye
key: password
- name: DB_NAME
value: riptides
lifecycle:
postStart:
exec:
command: ["/bin/bash", "-c", "php bin/console doctrine:migrations:migrate -n"]
volumeMounts:
- name: keys
mountPath: "/app/config/jwt"
readOnly: true
- name: cloudsql-proxy
image: gcr.io/cloudsql-docker/gce-proxy:1.11
command: ["/cloud_sql_proxy",
"-instances=riptides:europe-west4:riptides-sql=tcp:3306",
"-credential_file=/secrets/cloudsql/credentials.json"]
# [START cloudsql_security_context]
securityContext:
runAsUser: 2 # non-root user
allowPrivilegeEscalation: false
# [END cloudsql_security_context]
volumeMounts:
- name: riptides-mysql-service-account
mountPath: /secrets/cloudsql
readOnly: true
volumes:
- name: keys
secret:
secretName: riptides-api-keys
items:
- key: private.pem
path: private.pem
- key: public.pem
path: public.pem
- name: riptides-mysql-service-account
secret:
secretName: riptides-mysql-service-account
---
apiVersion: "autoscaling/v2beta1"
kind: "HorizontalPodAutoscaler"
metadata:
name: "riptides-api-hpa"
namespace: "default"
labels:
app: "riptides-api"
microservice: "riptides"
spec:
scaleTargetRef:
kind: "Deployment"
name: "riptides-api"
apiVersion: "apps/v1beta1"
minReplicas: 1
maxReplicas: 5
metrics:
- type: "Resource"
resource:
name: "cpu"
targetAverageUtilization: 70
If anyone has any suggestions I'd be forever greatful

Answer 1

It doesn't look like anything is wrong with your k8s yaml, but more likely in how you are connecting using Symfony. According to the documentation here, Symfony expect the DB URI to be passed in through an environment variable called "DATABASE_URL". See the following example:
# customize this line!
DATABASE_URL="postgres://db_user:db_password#127.0.0.1:5432/db_name"

Answer 2

This was happening because doctrine was using default values instead of the (should be overriding) environment variables I had set up in my deployment. I changed the environment variable names to be different to the default ones and it works