Docker-compose Postgres connection refused - postgresql

Question

I'm running Postgres DB with pg-admin and GO on the docker-compose.
Problem: I can connect from pg-admin to Postgres. But cannot establish a connection from Go.
I tried different combinations of authentication string but it does not work. String format same as here https://github.com/karlkeefer/pngr - but different container name - database
(ERROR) Connection URl:
backend_1 | 2021/08/08 14:24:40 DB connection: database://main:fugZwypczB94m0LP7CcH#postgres:5432/temp_db?sslmode=disable
backend_1 | 2021/08/08 14:24:40 Unalble to open DB connection: dial tcp 127.0.0.1:5432: connect: connection refused
(URI generation same as here https://github.com/karlkeefer/pngr)
Docker:
version: '3.8'
services:
backend:
restart: always
build:
context: backend
target: dev
volumes:
- ./backend:/root
ports:
- "5000:5000"
env_file: .env
depends_on:
- database
database:
build: database
restart: always
environment:
POSTGRES_DB: ${POSTGRES_DB}
POSTGRES_USER: ${POSTGRES_USER}
POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
PGDATA: /var/lib/postgresql/data
volumes:
- ./database/data:/var/lib/postgresql/data
- ./logs/databse:/var/log/postgresql
- ./database/migrations:/docker-entrypoint-initdb.d/migrations
ports:
- "5432:5432"
database-admin:
image: dpage/pgadmin4:5.5
restart: always
environment:
PGADMIN_DEFAULT_EMAIL: ${PG_ADMIN_EMAIL}
PGADMIN_DEFAULT_PASSWORD: ${PG_ADMIN_PASSWORD}
PGADMIN_LISTEN_PORT: 80
ports:
- "8080:80"
volumes:
- ./database/admin:/var/lib/pgadmin
links:
- "database:pgsql-server"
depends_on:
- database
volumes:
database:
database-admin:
Environment:
POSTGRES_HOST=postgres
POSTGRES_PORT=5432
POSTGRES_DB=temp_db
POSTGRES_USER=main
POSTGRES_PASSWORD=fugZwypczB94m0LP7CcH
PG_ADMIN_EMAIL=admin#temp.com
PG_ADMIN_PASSWORD=ayzi2ta8f1TnX3vKQSN1
PG_ADMIN_PORT=80
GO Code:
db, err = sqlx.Open("postgres", str)
str
func buildConnectionString() string {
user := os.Getenv("POSTGRES_USER")
pass := os.Getenv("POSTGRES_PASSWORD")
if user == "" || pass == "" {
log.Fatalln("You must include POSTGRES_USER and POSTGRES_PASSWORD environment variables")
}
host := os.Getenv("POSTGRES_HOST")
port := os.Getenv("POSTGRES_PORT")
dbname := os.Getenv("POSTGRES_DB")
if host == "" || port == "" || dbname == "" {
log.Fatalln("You must include POSTGRES_HOST, POSTGRES_PORT, and POSTGRES_DB environment variables")
}
str := fmt.Sprintf("database://%s:%s#%s:%s/%s?sslmode=disable", user, pass, host, port, dbname)
log.Println("DB connection: " + str)
return str
}
Thanks in advance!

Answer 1

You reference the database hostname as postgres (POSTGRES_HOST=postgres) which is fine, but the container/service name is database.
Either change the name in your compose.yaml from database to postgres or add an explicit hostname field:
database:
build: database
restart: always
hostname: postgres # <- add this
You may also want to add a dedicated network for multiple container services to talk to one another (or prevent others from). To do this, add this to each service your want to use a specific network e.g.
database:
# ...
networks:
- mynet
backend:
# ...
networks:
- mynet
and define the network at the end of your compose.yaml
networks:
mynet:
name: my-shared-db-network