浅谈Docker-compose中的depends_on顺序的问题解决

使用depends_on进行容器排序时并不能完美的解决容器之间的依赖问题，原因是因为 depends_on只能保证容器进入到 运行状态而不是完全状态（不知道怎么描述了）。

网上已经列出来了解决方法，使用 wait-for-it或者 wait-for，在启动时对需要优先启动的容器进行访问，当可以访问成功时在启动，但是都不够详细，甚至很多都是同样的内容，（这里吐槽一下环境真乱）。

可能我比较笨，花了一天才解决，在这里记录下来。

我使用的是 wait-for ，wait-for-it.sh我测试的时候了出现了保错所以没用。

正文：

需求是要将一个 打包好的 ar文件注册到nacos中，但是nacos启动较慢，就需要进行顺序的设置。

将需要的 jar文件删除到虚拟机或服务器。接下来编写 dockerfile和docker-compose

from openjdk:8-jre	// 基于 openjdk 
copy wait-for .		// 将 wait-for 拷贝到虚拟机中
run apt-get update	// 更新源，
run apt-get install netcat -y // 安装 netcat， wait-for 需要使用到
workdir /app				// 设置落脚点
add course.jar course.jar	// 将 jar 文件 添加到 虚拟机中
expose 8002					// 需要暴露的端口

我的配置是以图片为准的，代码块中的是为了更好的理解 ，想来应该没有差别。

docker-compose

version: '3.0'
services:
  nacos:
    image: nacos/nacos-server:1.1.4
    container_name: nacos
    ports:
      - "8848:8848"
    environment:
      mode: standalone   # nacos 单节点运行

  course:
    build: /root/
    container_name: course
    ports:
      - "18002:18002"
    depends_on:
      - nacos
    command: ["sh","wait-for","nacos:8848","--","java","-jar","course.jar"]

这里就不做过多的解释了，与平常相差不大。

我之前查找到的帖子中，没有贴出dockerfile文件在这里最重要的就是，将 wait-for文件拷贝到虚拟机中，因为在 docker-compose中配置的command所使用的 文件是容器中的，如果你没有拷贝那么将找不到文件。然后是 apt-get update和 apt-get install netcat -y则是安装 wait-for运行的环境

我的wait-for代码，26行为超时时间，刚开始是15，但是时间太短了 容器超时我就设置为了 60，这是我唯一跟原来不一样的地方,之后就可以测试运行了

#!/bin/sh

# the mit license (mit)
#
# copyright (c) 2017 eficode oy
#
# permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "software"), to deal
# in the software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the software, and to permit persons to whom the software is
# furnished to do so, subject to the following conditions:
#
# the above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the software.
#
# the software is provided "as is", without warranty of any kind, express or
# implied, including but not limited to the warranties of merchantability,
# fitness for a particular purpose and noninfringement. in no event shall the
# authors or copyright holders be liable for any claim, damages or other
# liability, whether in an action of contract, tort or otherwise, arising from,
# out of or in connection with the software or the use or other dealings in the
# software.

set -- "$@" -- "$timeout" "$quiet" "$protocol" "$host" "$port" "$result"
timeout=60
quiet=0
# the protocol to make the request with, either "tcp" or "http"
protocol="tcp"

echoerr() {
  if [ "$quiet" -ne 1 ]; then printf "%s\n" "$*" 1>&2; fi
}

usage() {
  exitcode="$1"
  cat << usage >&2
usage:
  $0 host:port|url [-t timeout] [-- command args]
  -q | --quiet                        do not output any status messages
  -t timeout | --timeout=timeout      timeout in seconds, zero for no timeout
  -- command args                     execute command with args after the test finishes
usage
  exit "$exitcode"
}

wait_for() {
  case "$protocol" in
    tcp)
      if ! command -v nc >/dev/null; then
        echoerr 'nc command is missing!'
        exit 1
      fi
      ;;
    wget)
      if ! command -v wget >/dev/null; then
        echoerr 'wget command is missing!'
        exit 1
      fi
      ;;
  esac

  while :; do
    case "$protocol" in
      tcp) 
        nc -w 1 -z "$host" "$port" > /dev/null 2>&1
        ;;
      http)
        wget --timeout=1 -q "$host" -o /dev/null > /dev/null 2>&1 
        ;;
      *)
        echoerr "unknown protocol '$protocol'"
        exit 1
        ;;
    esac

    result=$?
        
    if [ $result -eq 0 ] ; then
      if [ $# -gt 7 ] ; then
        for result in $(seq $(($# - 7))); do
          result=$1
          shift
          set -- "$@" "$result"
        done

        timeout=$2 quiet=$3 protocol=$4 host=$5 port=$6 result=$7
        shift 7
        exec "$@"
      fi
      exit 0
    fi

    if [ "$timeout" -le 0 ]; then
      break
    fi
    timeout=$((timeout - 1))

    sleep 1
  done
  echo "operation timed out" >&2
  exit 1
}

while :; do
  case "$1" in
    http://*|https://*)
    host="$1"
    protocol="http"
    shift 1
    ;;
    *:* )
    host=$(printf "%s\n" "$1"| cut -d : -f 1)
    port=$(printf "%s\n" "$1"| cut -d : -f 2)
    shift 1
    ;;
    -q | --quiet)
    quiet=1
    shift 1
    ;;
    -q-*)
    quiet=0
    echoerr "unknown option: $1"
    usage 1
    ;;
    -q*)
    quiet=1
    result=$1
    shift 1
    set -- -"${result#-q}" "$@"
    ;;
    -t | --timeout)
    timeout="$2"
    shift 2
    ;;
    -t*)
    timeout="${1#-t}"
    shift 1
    ;;
    --timeout=*)
    timeout="${1#*=}"
    shift 1
    ;;
    --)
    shift
    break
    ;;
    --help)
    usage 0
    ;;
    -*)
    quiet=0
    echoerr "unknown option: $1"
    usage 1
    ;;
    *)
    quiet=0
    echoerr "unknown argument: $1"
    usage 1
    ;;
  esac
done

if ! [ "$timeout" -ge 0 ] 2>/dev/null; then
  echoerr "error: invalid timeout '$timeout'"
  usage 3
fi

case "$protocol" in
  tcp)
    if [ "$host" = "" ] || [ "$port" = "" ]; then
      echoerr "error: you need to provide a host and port to test."
      usage 2
    fi
  ;;
  http)
    if [ "$host" = "" ]; then
      echoerr "error: you need to provide a host to test."
      usage 2
    fi
  ;;
esac

wait_for "$@"

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