Docker compose服务依赖问题

背景

当前docker compose中的depends_on只能确保服务启动，但无法保证服务已正常运行。
比如mysql的启动速度较慢，如果一个java服务依赖mysql，则java服务无法正常启动。

方案

引入wait-for-it.sh，启动java服务前等待mysql服务。

wait-of-it

你可以在git上下载: wait-for-it github

#!/usr/bin/env bash
# Use this script to test if a given TCP host/port are available

WAITFORIT_cmdname=${0##*/}

echoerr() { if [[ $WAITFORIT_QUIET -ne 1 ]]; then echo "$@" 1>&2; fi }

usage()
{
    cat << USAGE >&2
Usage:
    $WAITFORIT_cmdname host:port [-s] [-t timeout] [-- command args]
    -h HOST | --host=HOST       Host or IP under test
    -p PORT | --port=PORT       TCP port under test
                                Alternatively, you specify the host and port as host:port
    -s | --strict               Only execute subcommand if the test succeeds
    -q | --quiet                Don't 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 1
}

wait_for()
{
    if [[ $WAITFORIT_TIMEOUT -gt 0 ]]; then
        echoerr "$WAITFORIT_cmdname: waiting $WAITFORIT_TIMEOUT seconds for $WAITFORIT_HOST:$WAITFORIT_PORT"
    else
        echoerr "$WAITFORIT_cmdname: waiting for $WAITFORIT_HOST:$WAITFORIT_PORT without a timeout"
    fi
    WAITFORIT_start_ts=$(date +%s)
    while :
    do
        if [[ $WAITFORIT_ISBUSY -eq 1 ]]; then
            nc -z $WAITFORIT_HOST $WAITFORIT_PORT
            WAITFORIT_result=$?
        else
            (echo -n > /dev/tcp/$WAITFORIT_HOST/$WAITFORIT_PORT) >/dev/null 2>&1
            WAITFORIT_result=$?
        fi
        if [[ $WAITFORIT_result -eq 0 ]]; then
            WAITFORIT_end_ts=$(date +%s)
            echoerr "$WAITFORIT_cmdname: $WAITFORIT_HOST:$WAITFORIT_PORT is available after $((WAITFORIT_end_ts - WAITFORIT_start_ts)) seconds"
            break
        fi
        sleep 1
    done
    return $WAITFORIT_result
}

wait_for_wrapper()
{
    # In order to support SIGINT during timeout: http://unix.stackexchange.com/a/57692
    if [[ $WAITFORIT_QUIET -eq 1 ]]; then
        timeout $WAITFORIT_BUSYTIMEFLAG $WAITFORIT_TIMEOUT $0 --quiet --child --host=$WAITFORIT_HOST --port=$WAITFORIT_PORT --timeout=$WAITFORIT_TIMEOUT &
    else
        timeout $WAITFORIT_BUSYTIMEFLAG $WAITFORIT_TIMEOUT $0 --child --host=$WAITFORIT_HOST --port=$WAITFORIT_PORT --timeout=$WAITFORIT_TIMEOUT &
    fi
    WAITFORIT_PID=$!
    trap "kill -INT -$WAITFORIT_PID" INT
    wait $WAITFORIT_PID
    WAITFORIT_RESULT=$?
    if [[ $WAITFORIT_RESULT -ne 0 ]]; then
        echoerr "$WAITFORIT_cmdname: timeout occurred after waiting $WAITFORIT_TIMEOUT seconds for $WAITFORIT_HOST:$WAITFORIT_PORT"
    fi
    return $WAITFORIT_RESULT
}

# process arguments
while [[ $# -gt 0 ]]
do
    case "$1" in
        *:* )
        WAITFORIT_hostport=(${1//:/ })
        WAITFORIT_HOST=${WAITFORIT_hostport[0]}
        WAITFORIT_PORT=${WAITFORIT_hostport[1]}
        shift 1
        ;;
        --child)
        WAITFORIT_CHILD=1
        shift 1
        ;;
        -q | --quiet)
        WAITFORIT_QUIET=1
        shift 1
        ;;
        -s | --strict)
        WAITFORIT_STRICT=1
        shift 1
        ;;
        -h)
        WAITFORIT_HOST="$2"
        if [[ $WAITFORIT_HOST == "" ]]; then break; fi
        shift 2
        ;;
        --host=*)
        WAITFORIT_HOST="${1#*=}"
        shift 1
        ;;
        -p)
        WAITFORIT_PORT="$2"
        if [[ $WAITFORIT_PORT == "" ]]; then break; fi
        shift 2
        ;;
        --port=*)
        WAITFORIT_PORT="${1#*=}"
        shift 1
        ;;
        -t)
        WAITFORIT_TIMEOUT="$2"
        if [[ $WAITFORIT_TIMEOUT == "" ]]; then break; fi
        shift 2
        ;;
        --timeout=*)
        WAITFORIT_TIMEOUT="${1#*=}"
        shift 1
        ;;
        --)
        shift
        WAITFORIT_CLI=("$@")
        break
        ;;
        --help)
        usage
        ;;
        *)
        echoerr "Unknown argument: $1"
        usage
        ;;
    esac
done

if [[ "$WAITFORIT_HOST" == "" || "$WAITFORIT_PORT" == "" ]]; then
    echoerr "Error: you need to provide a host and port to test."
    usage
fi

WAITFORIT_TIMEOUT=${WAITFORIT_TIMEOUT:-15}
WAITFORIT_STRICT=${WAITFORIT_STRICT:-0}
WAITFORIT_CHILD=${WAITFORIT_CHILD:-0}
WAITFORIT_QUIET=${WAITFORIT_QUIET:-0}

# Check to see if timeout is from busybox?
WAITFORIT_TIMEOUT_PATH=$(type -p timeout)
WAITFORIT_TIMEOUT_PATH=$(realpath $WAITFORIT_TIMEOUT_PATH 2>/dev/null || readlink -f $WAITFORIT_TIMEOUT_PATH)

WAITFORIT_BUSYTIMEFLAG=""
if [[ $WAITFORIT_TIMEOUT_PATH =~ "busybox" ]]; then
    WAITFORIT_ISBUSY=1
    # Check if busybox timeout uses -t flag
    # (recent Alpine versions don't support -t anymore)
    if timeout &>/dev/stdout | grep -q -e '-t '; then
        WAITFORIT_BUSYTIMEFLAG="-t"
    fi
else
    WAITFORIT_ISBUSY=0
fi

if [[ $WAITFORIT_CHILD -gt 0 ]]; then
    wait_for
    WAITFORIT_RESULT=$?
    exit $WAITFORIT_RESULT
else
    if [[ $WAITFORIT_TIMEOUT -gt 0 ]]; then
        wait_for_wrapper
        WAITFORIT_RESULT=$?
    else
        wait_for
        WAITFORIT_RESULT=$?
    fi
fi

if [[ $WAITFORIT_CLI != "" ]]; then
    if [[ $WAITFORIT_RESULT -ne 0 && $WAITFORIT_STRICT -eq 1 ]]; then
        echoerr "$WAITFORIT_cmdname: strict mode, refusing to execute subprocess"
        exit $WAITFORIT_RESULT
    fi
    exec "${WAITFORIT_CLI[@]}"
else
    exit $WAITFORIT_RESULT
fi

dockerfile

FROM openjdk:11
WORKDIR /usr/src/app

COPY app.jar ./app.jar

# check mysql status
COPY wait-for-it.sh ./wait-for-it.sh
COPY docker-entrypoint.sh ./docker-entrypoint.sh

RUN chmod +x wait-for-it.sh
RUN chmod +x docker-entrypoint.sh


ENTRYPOINT ["./docker-entrypoint.sh"]
CMD ["java","-jar","app.jar"]

docker compose

version: '3.4'

services:
    # service name
  mysql:
    container_name: mysql
    # 会先从镜像仓库获取，如果获取失败，则按照build的配置构建镜像，且这个名字会作为镜像名字
    image: test/mysql
    build:
      context: ./docker/mysql # dockerfile地址
      dockerfile: Dockerfile
    # 容器服务暴露的端口
    expose:
      - "3309"
    # 端口映射：宿主机暴露端口：容器端口
    ports:
      - "3309:3306"
    # 不同容器之间的服务如果需要互相访问，则需要在一个网络中
    networks:
      - test

  server1:
    container_name: server1
    image: test/server1-image
    tty: true
    expose:
      - "8080"
    build:
      context: ../server1/
      dockerfile: Dockerfile
    ports:
      - "8080:8080"
    # 允许使用宿主机的硬件
    devices:
      - '/dev:/dev'
    # 启动后执行的命令，会覆盖Dockerfile中CMD的命令
    command: ["/bin/bash", "-c", "ls"]
    networks:
      - test


# refer to https://stackoverflow.com/questions/63198731/how-to-use-wait-for-it-in-docker-compose-file
  server2:
    container_name: server2
    image: test/server2:1.0
    build:
      context: ./
      dockerfile: Dockerfile
    ports:
      - "8088:8088"
    expose:
      - "8088"
    # 服务依赖，依赖的服务启动之后才会启动本服务，docker只检查依赖服务是否为running状态，running != ready
    # 通过wait-for-it.sh等操作确保服务ready
    depends_on:
      - mysql
      - server1
    # 挂载
#    volumes:
#      - ./wait-for-it.sh:/wait-for-it.sh
#      - ./docker-entrypoint.sh:/docker-entrypoint.sh
    # 环境参数：docker-entrypoint.sh执行需要的参数
    environment:
      CUSTOMERS_HOST: mysql
      CUSTOMERS_PORT: 3306
    networks:
      - test

# 创建网络
networks:
  test:
    driver: bridge

docker entry.sh

#!/bin/sh

# Abort on any error (including if wait-for-it fails).
set -e

# Wait for the backend to be up, if we know where it is.
if [ -n "${CUSTOMERS_HOST:lv_mysql}" ]; then
  /usr/src/app/wait-for-it.sh "${CUSTOMERS_HOST:mysql}:${CUSTOMERS_PORT:-3306} -t 60"
fi

# Run the main container command.
exec "$@"

参考：https://stackoverflow.com/questions/63198731/how-to-use-wait-for-it-in-docker-compose-file