Golang Docker容器未在Docker-Compose中重新启动

Question

I want to be able to restart a golang docker file on failure to connect to rabbitmq as outined here: (Docker Compose wait for container X before starting Y see answer by: svenhornberg). Unfortunately my golang container will exit but never restart and I don't know why.

Docker-compose:

version: '3.3'
services:
  mongo:
    image: 'mongo:3.4.1'
    container_name: 'datastore'
    ports:
      - '27017:27017'
  rabbitmq:
    restart: always
    tty: true
    image: rabbitmq:3.7-management-alpine
    hostname: "rabbit"
    ports:
      - "15672:15672" 
      - "5672:5672"
    labels:
      NAME: "rabbitmq"
    volumes:
      - ./rabbitmq-isolated.conf:/etc/rabbitmq/rabbitmq.config
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:15672"]
      interval: 3s
      timeout: 5s
      retries: 20
  api:
    restart: always
    tty: true
    container_name: 'api'
    build: '.'
    working_dir: /go/src/github.com/patientplatypus/project
    ports:
      - '8000:8000'
    volumes:
      - './:/go/src/github.com/patientplatypus/project'
      - './uploads:/uploads'
      - './scripts:/scripts'
      - './templates:/templates'
    depends_on:
      - "mongo"
      - "rabbitmq"

Docker file:

FROM golang:latest

WORKDIR /go/src/github.com/patientplatypus/project
COPY . .

RUN go get github.com/imroc/req
<...more go gets...>
RUN go get github.com/joho/godotenv

EXPOSE 8000

ENTRYPOINT  [ "fresh" ]

Here is my golang code:

package main

import (
    "fmt"
    "log"
    "os"
    "os/exec"
    "net/http"
)

func main() {

    fmt.Println("Golang server started")
    godotenv.Load()
    fmt.Println("now doing healthcheck on rabbit")
    exec.Command("docker-compose restart api")
    os.Exit(1)
  <...>

And here is my terminal output (golang never restarts after rabbit called):

api         | 23:23:00 app         | Golang server started
api         | 23:23:00 app         | now doing healthcheck on rabbit
rabbitmq_1  | 
rabbitmq_1  |   ##  ##
rabbitmq_1  |   ##  ##      RabbitMQ 3.7.11. Copyright (C) 2007-2019 Pivotal Software, Inc.
rabbitmq_1  |   ##########  Licensed under the MPL.  See http://www.rabbitmq.com/
rabbitmq_1  |   ######  ##
rabbitmq_1  |   ##########  Logs: <stdout>
<...more rabbit logging...>

I'm very confused on how to get this to work. What am I doing wrong?

EDIT:

The exec.Command was incorrectly implemented, however os.Exit(1), log.Fatal, and log.Panic exit the container, but the container does not restart. Still confused.

Answer 1

The Docker documentation says:

A restart policy only takes effect after a container starts successfully. In this case, starting successfully means that the container is up for at least 10 seconds and Docker has started monitoring it. This prevents a container which does not start at all from going into a restart loop.

Since the Go code you show exits basically immediately, it never meets this 10-second-minimum rule.

You can force Go to wait until the process has been alive a minimum of 10 seconds by using time.After somewhat like:

ch := time.After(10 * time.Second)
defer (func() { fmt.Println("waiting"); <-ch; fmt.Println("waited") })()

That is, create a channel that will receive an event after 10 seconds, and then actually receive it (immediately if it's happened, waiting if not) before main returns. From playing with https://play.golang.org/p/zGY5jFWbXyk, the one trick is that there needs to be some observable effect after receiving from the channel or else it doesn't actually wait.