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Debian – Can not connect Postgres with Golang API and docker-compose

When I run docker-compose up postgres service start successful. However my Golang API can not connect to my postgres service. I tried manually without docker and it works. Golang Connection string looks like this host=db port=5432 user=%s dbname=%s password=%s sslmode=disable. But when I restart my container, it works.

docker-compose

    FROM golang:1.22
    WORKDIR /app
    COPY . .
    RUN go install

Dockerfile

    version: "3.7"
    services:
      gobank:
        build: .
        container_name: gobank
        env_file:
          - .env
        ports:
          - 3000:3000
        command: make run
        extra_hosts:
          - "host.docker.internal:host-gateway"
    
      db:
        image: postgres:16
        container_name: postgres
        environment:
          - POSTGRES_PASSWORD=postgres
          - POSTGRES_USER=postgres
          - POSTGRES_DB=gobank
        ports:
          - 5432:5432
        extra_hosts:
          - "host.docker.internal:host-gateway"
PostgresLog
    postgres  | 2024-07-12 22:51:24.133 UTC [1] LOG:  starting PostgreSQL 16.3 (Debian 16.3-1.pgdg120+1) on aarch64-unknown-linux-gnu, compiled by gcc (Debian 12.2.0-14) 12.2.0, 64-bit
    postgres  | 2024-07-12 22:51:24.133 UTC [1] LOG:  listening on IPv4 address "0.0.0.0", port 5432
    postgres  | 2024-07-12 22:51:24.133 UTC [1] LOG:  listening on IPv6 address "::", port 5432
    postgres  | 2024-07-12 22:51:24.135 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
    postgres  | 2024-07-12 22:51:24.138 UTC [64] LOG:  database system was shut down at 2024-07-12 22:51:24 UTC
GolangLog
    gobank    | 2024/07/12 22:51:23 there was an error: dial tcp 172.18.0.2:5432: connect: connection refused
    gobank    | make: *** [Makefile:14: run] Error 1
    postgres  | performing post-bootstrap initialization ... ok
    gobank exited with code 2
    postgres  | syncing data to disk ... ok
Tags:

2

Answers


  1. 0

    Your Go program tried to connect to the database before it was ready. To make Docker wait until Postgres is ready before starting your Go program, you need to add a healthcheck to the db container, like this:

    healthcheck:
  test: ["CMD", "pg_isready", "-U", "postgres", "-d", "gobank"]
  interval: 10s
  timeout: 5s
  retries: 10

    Then, you need to make the Go program depend on the healthcheck like so:

    depends_on:
  db:
    condition: service_healthy
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  2. 0

    You can add:

    depends_on:
  - db

    and as a measure add a health check inside golang in the form of a endless for loop which basically pings the DB.

    go func() {
    for {
        err := cnx.Cnx.Ping()
        if err == nil {
            log.Info("DB Health Check Success")
        } else {
            log.Warn("DB Health Check Failed")
        }
        time.Sleep(time.Hour * 3)
    }
}()
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