Go Backend unable to connect to postgres instance - postgresql

Question

I have a postgres instance installed on a cluster and I am able to exec into the pod and work with the DB. I have a simple Go application to interact with the Postgres, The program runs as intended, the following is the connection string of my Go application:
db, err = sql.Open("postgres", "postgres://santosh:dts123#localhost:5432/bookstore?")
But, when I containerze the application and run it or add it to a pod, the pod stays in CrashLoopBackOff and it is unable to connect to the Postgres and when I try to exec into the container or run the container, I am getting the following result:
santosh#frontend*$:k logs -n frontend-api bookstore-frontend-7c68888df6-7nsx4 -c bookstore
panic: dial tcp [::1]:5432: connect: connection refused
goroutine 1 [running]:
main.main()
/home/main.go:41 +0x2d2
I have a service infront of the postgres pod:
apiVersion: v1
kind: Service
metadata:
name: postgres
namespace: database
labels:
app: postgres
spec:
type: NodePort
ports:
- port: 5432
selector:
app: bookstore
In the backend depployment, I have routed the POSTGRES_HOST as the FQDN of the service with port postgres.database.svc:5432 in the configMap, the configmap and deployment is as follows:
apiVersion: v1
kind: ConfigMap
metadata:
name: frontend-cm
namespace: frontend-api
data:
dbHost: postgres.database:5432
dbName: bookstore
sslMode: disable
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: bookstore-frontend
name: bookstore-frontend
namespace: frontend-api
spec:
replicas: 1
selector:
matchLabels:
app: bookstore-frontend
strategy: {}
template:
metadata:
labels:
app: bookstore-frontend
spec:
containers:
- image: docker.io/santoshdts/bookstore:build-1
name: bookstore
ports:
- name: http
containerPort: 8080
env:
- name: POSTGRES_SSLMODE
valueFrom:
configMapKeyRef:
name: frontend-cm
key: sslMode
- name: POSTGRES_HOST
valueFrom:
configMapKeyRef:
name: frontend-cm
key: dbHost
- name: POSTGRES_DB
valueFrom:
configMapKeyRef:
name: frontend-cm
key: dbName
- name: POSTGRES_USER
valueFrom:
secretKeyRef:
name: frontend-secret
key: dbUser
- name: POSTGRES_PASSWORD
valueFrom:
secretKeyRef:
name: frontend-secret
key: dbPassword
resources: {}
status: {}
Is this issue related to some misconfiguration in the env variables? I have some data in the DB, so the backend is trying to connect to an existing DB. Hence, the env names I've used like POSTGRES_* is valid for this workflow or I need to specify the variales as PG* format as explained here?
Or my backend Go application needs some amendment?
can someone please help me on this.
Thank you!
I've tried installing the wbitt/network-multitool to debug the connections and when I try to NSLookup the svc, I get:
/ # nslookup postgres.database.svc
Server: 10.96.0.10
Address: 10.96.0.10#53
Name: postgres.database.svc.cluster.local
Address: 10.96.11.156
and when I curl the postgres instance, I get the empty response:
/ # curl postgres.database.svc:5432
curl: (52) Empty reply from server
The logs aren't helping much,as the container is in CrashLoopBackOff. The postgres pod logs are as below:
santosh#frontend*$:k logs -n database postgres-75fb5c858d-pswdn
PostgreSQL Database directory appears to contain a database; Skipping initialization
2022-11-22 06:23:08.306 UTC [1] LOG: starting PostgreSQL 15.1 (Debian 15.1-1.pgdg110+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 10.2.1-6) 10.2.1 20210110, 64-bit
2022-11-22 06:23:08.306 UTC [1] LOG: listening on IPv4 address "0.0.0.0", port 5432
2022-11-22 06:23:08.306 UTC [1] LOG: listening on IPv6 address "::", port 5432
2022-11-22 06:23:08.308 UTC [1] LOG: listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
2022-11-22 06:23:08.312 UTC [34] LOG: database system was shut down at 2022-11-21 19:25:23 UTC
2022-11-22 06:23:08.336 UTC [1] LOG: database system is ready to accept connections
2022-11-22 06:28:08.412 UTC [32] LOG: checkpoint starting: time
2022-11-22 06:28:08.521 UTC [32] LOG: checkpoint complete: wrote 4 buffers (0.0%); 0 WAL file(s) added, 0 removed, 0 recycled; write=0.103 s, sync=0.002 s, total=0.109 s; sync files=3, longest=0.001 s, average=0.001 s; distance=0 kB, estimate=0 kB
2022-11-22 06:39:44.421 UTC [88] LOG: invalid length of startup packet
2022-11-22 07:15:46.705 UTC [197] LOG: invalid length of startup packet
2022-11-22 07:19:31.744 UTC [225] LOG: invalid length of startup packet
2022-11-22 07:32:01.716 UTC [263] LOG: invalid length of startup packet
2022-11-22 07:32:12.053 UTC [265] LOG: invalid length of startup packet
2022-11-22 08:12:27.927 UTC [386] LOG: invalid length of startup packet
2022-11-22 08:47:25.072 UTC [492] LOG: invalid length of startup packet

Answer 1

I finally resloved my issue. The problem was with my connection string in the Go application. I replaced the dbhost parameter from localhost to the fqdn of the service, in my case it was: postgres.database.svc.cluster.local.