通常我们为了防止容器断电或异常关闭后不能自动开机,我们可以加上
--restart=always
例如
[root@aliyun ~]# docker run --restart=always -d --name blog -d -v /www:/www -v /wwwlogs:/var/log/wwwlogs -p 65423:65422 -p 80:80 -p 443:443 677
7714a84063ee6d405c80b891254bba0e5930f5d271c5ad76cfd6e2f0058d8056
这样容器就可以自动重启,但是有时候程序进入死锁状态,或者死循环状态,应用进程并不退出,但是该容器已经无法提供服务了。在 1.12 以前,Docker 不会检测到容器的这种状态,从而不会重新调度,导致可能会有部分容器已经无法提供服务了却还在接受用户请求。
而自 1.12 之后,Docker 提供了 HEALTHCHECK 指令,通过该指令指定一行命令,用这行命令来判断容器主进程的服务状态是否还正常,从而比较真实的反应容器实际状态。
当在一个镜像指定了 HEALTHCHECK 指令后,用其启动容器,初始状态会为 starting,在 HEALTHCHECK 指令检查成功后变为 healthy,如果连续一定次数失败,则会变为 unhealthy。
HEALTHCHECK 支持下列选项:
- –interval=<间隔>:两次健康检查的间隔,默认为 30 秒;
- –timeout=<时长>:健康检查命令运行超时时间,如果超过这个时间,本次健康检查就被视为失败,默认 30 秒;
- –retries=<次数>:当连续失败指定次数后,则将容器状态视为 unhealthy,默认 3 次。
和 CMD, ENTRYPOINT 一样,HEALTHCHECK 只可以出现一次,如果写了多个,只有最后一个生效。
在 HEALTHCHECK [选项] CMD 后面的命令,格式和 ENTRYPOINT 一样,分为 shell 格式,和 exec 格式。命令的返回值决定了该次健康检查的成功与否:0:成功;1:失败;2:保留,不要使用这个值。
下面我们看下这个 dockerfile 文件
FROM centos
LABEL maintainer "awen Email: <hi@awen.me>"
WORKDIR /opt/
COPY CentOS7-Base-163.repo /etc/yum.repos.d/CentOS-Base.repo
COPY nginx /etc/init.d/nginx
ENV NGINX_V=1.13.5 \
OPENSSL_V=1.0.2l \
PCRE_V=8.41 \
ZLIB_V=1.2.11
RUN yum -y update \
&& yum -y install openssh-server openssl gcc gcc-c++ pcre-devel openssl-devel zlib-devel wget make perl tar net-tools \
&& wget -c -4 https://nginx.org/download/nginx-$NGINX_V.tar.gz \
&& wget -c -4 https://www.openssl.org/source/openssl-$OPENSSL_V.tar.gz \
&& wget -c -4 ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre-$PCRE_V.tar.gz \
&& wget -c -4 http://zlib.net/zlib-$ZLIB_V.tar.gz \
&& groupadd -r www && useradd -r -g www www \
&& tar zxvf zlib-$ZLIB_V.tar.gz \
&& cd zlib-$ZLIB_V \
&& ./configure \
&& make \
&& make install \
&& cd /opt \
&& tar zxvf pcre-$PCRE_V.tar.gz \
&& cd pcre-$PCRE_V \
&& ./configure \
&& make \
&& make install \
&& cd /opt \
&& tar zxvf openssl-$OPENSSL_V.tar.gz \
&& tar zxvf nginx-$NGINX_V.tar.gz \
&& cd nginx-$NGINX_V \
&& ./configure --prefix=/usr/local/nginx --user=www --group=www --with-pcre=/opt/pcre-$PCRE_V --with-http_ssl_module --with-zlib=/opt/zlib-$ZLIB_V --with-openssl=/opt/openssl-$OPENSSL_V --with-http_v2_module --with-http_ssl_module \
&& make \
&& make install \
&& rm -rf /opt/* \
&& mkdir -p /usr/local/nginx/ssl \
&& mkdir -p /usr/local/nginx/conf/vhost \
&& mkdir -p /var/log/wwwlogs/ \
&& mkdir -p /www/ \
&& ssh-keygen -t rsa -f /etc/ssh/ssh_host_rsa_key -N '' \
&& ssh-keygen -t dsa -f /etc/ssh/ssh_host_dsa_key -N '' \
&& ssh-keygen -t ecdsa -f /etc/ssh/ssh_host_ecdsa_key -N '' \
&& ssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key -N '' \
&& echo "RSAAuthentication yes" >> /etc/ssh/sshd_config \
&& echo "PubkeyAuthentication yes" >> /etc/ssh/sshd_config \
&& sed -i "s/PasswordAuthentication yes/PasswordAuthentication no/g" /etc/ssh/sshd_config \
&& sed -i "s/UsePAM yes/UsePAM no/g" /etc/ssh/sshd_config \
&& sed -i "s/#Port 22/Port 65422/g" /etc/ssh/sshd_config \
&& yum clean all \
&& mkdir /var/run/sshd \
&& chmod +x /etc/init.d/nginx \
&& rm -rf /root/*.cfg \
&& echo "Asia/Shanghai" > /etc/localtime
COPY ssl/* /usr/local/nginx/ssl/
COPY vhost/* /usr/local/nginx/conf/vhost/
COPY nginx.conf /usr/local/nginx/conf/
COPY ssh/* /root/.ssh/
VOLUME ["/www","/var/log/wwwlogs","/usr/local/nginx/ssl","/usr/local/nginx/conf/vhost"]
EXPOSE 65422 80 443
HEALTHCHECK CMD curl -fs http://localhost/ || exit 1
ENTRYPOINT /etc/init.d/nginx start && chown -R www:www /var/log/wwwlogs/ && /usr/sbin/sshd -D
其中
HEALTHCHECK CMD curl -fs http://localhost/ || exit 1
就是增加的健康监测配置,然后编译后启动,查看进程会发现其状态是 starting
[root@aliyun ~]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
7714a84063ee 677 "/bin/sh -c '/etc/ini" 3 seconds ago Up 2 seconds (health: starting) 0.0.0.0:80->80/tcp, 0.0.0.0:443->443/tcp, 0.0.0.0:65423->65422/tcp blog
稍等查看,会发现其状态为 healthy
[root@aliyun ~]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
7714a84063ee 677 "/bin/sh -c '/etc/ini" About a minute ago Up About a minute (healthy) 0.0.0.0:80->80/tcp, 0.0.0.0:443->443/tcp, 0.0.0.0:65423->65422/tcp blog
我们可以通过 inspect 查看 最近3次的状态
[root@aliyun ~]# docker inspect --format '{{json .State.Health}}' blog | python -m json.tool
{
"FailingStreak": 0,
"Log": [
{
"End": "2017-10-11T11:15:27.516562686+08:00",
"ExitCode": 0,
"Output": "<html>\r\n<head><title>301 Moved Permanently</title></head>\r\n<body bgcolor=\"white\">\r\n<center><h1>301 Moved Permanently</h1></center>\r\n<hr><center>nginx</center>\r\n</body>\r\n</html>\r\n",
"Start": "2017-10-11T11:15:27.470554485+08:00"
},
{
"End": "2017-10-11T11:15:57.563377729+08:00",
"ExitCode": 0,
"Output": "<html>\r\n<head><title>301 Moved Permanently</title></head>\r\n<body bgcolor=\"white\">\r\n<center><h1>301 Moved Permanently</h1></center>\r\n<hr><center>nginx</center>\r\n</body>\r\n</html>\r\n",
"Start": "2017-10-11T11:15:57.516690754+08:00"
},
{
"End": "2017-10-11T11:16:27.609685416+08:00",
"ExitCode": 0,
"Output": "<html>\r\n<head><title>301 Moved Permanently</title></head>\r\n<body bgcolor=\"white\">\r\n<center><h1>301 Moved Permanently</h1></center>\r\n<hr><center>nginx</center>\r\n</body>\r\n</html>\r\n",
"Start": "2017-10-11T11:16:27.563533362+08:00"
},
{
"End": "2017-10-11T11:16:57.654441173+08:00",
"ExitCode": 0,
"Output": "<html>\r\n<head><title>301 Moved Permanently</title></head>\r\n<body bgcolor=\"white\">\r\n<center><h1>301 Moved Permanently</h1></center>\r\n<hr><center>nginx</center>\r\n</body>\r\n</html>\r\n",
"Start": "2017-10-11T11:16:57.609810588+08:00"
},
{
"End": "2017-10-11T11:17:27.701113019+08:00",
"ExitCode": 0,
"Output": "<html>\r\n<head><title>301 Moved Permanently</title></head>\r\n<body bgcolor=\"white\">\r\n<center><h1>301 Moved Permanently</h1></center>\r\n<hr><center>nginx</center>\r\n</body>\r\n</html>\r\n",
"Start": "2017-10-11T11:17:27.654580727+08:00"
}
],
"Status": "healthy"
}
如果健康检查连续失败超过了重试次数,状态就会变为 (unhealthy)。