對于容器而言,最簡單的健康檢查是進程級的健康檢查,即檢驗進程是否存活。Docker Daemon會自動監(jiān)控容器中的PID1進程,如果docker run命令中指明了restart policy,可以根據(jù)策略自動重啟已結(jié)束的容器。在很多實際場景下,僅使用進程級健康檢查機制還遠遠不夠。比如,容器進程雖然依舊運行卻由于應(yīng)用死鎖無法繼續(xù)響應(yīng)用戶請求,這樣的問題是無法通過進程監(jiān)控發(fā)現(xiàn)的。
通常我們?yōu)榱朔乐谷萜鲾嚯娀虍惓jP(guān)閉后不能自動開機,我們可以加上
--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
這樣容器就可以自動重啟,但是有時候程序進入死鎖狀態(tài),或者死循環(huán)狀態(tài),應(yīng)用進程并不退出,但是該容器已經(jīng)無法提供服務(wù)了。在 1.12 以前,Docker 不會檢測到容器的這種狀態(tài),從而不會重新調(diào)度,導致可能會有部分容器已經(jīng)無法提供服務(wù)了卻還在接受用戶請求。
而自 1.12 之后,Docker 提供了 HEALTHCHECK 指令,通過該指令指定一行命令,用這行命令來判斷容器主進程的服務(wù)狀態(tài)是否還正常,從而比較真實的反應(yīng)容器實際狀態(tài)。
當在一個鏡像指定了 HEALTHCHECK 指令后,用其啟動容器,初始狀態(tài)會為 starting,在 HEALTHCHECK 指令檢查成功后變?yōu)?healthy,如果連續(xù)一定次數(shù)失敗,則會變?yōu)?unhealthy。
HEALTHCHECK 支持下列選項:
在 HEALTHCHECK [選項] CMD 后面的命令,格式和 ENTRYPOINT 一樣,分為 shell 格式,和 exec 格式。命令的返回值決定了該次健康檢查的成功與否:0:成功;1:失??;2:保留,不要使用這個值。
下面我們看下這個 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
就是增加的健康監(jiān)測配置,然后編譯后啟動,查看進程會發(fā)現(xiàn)其狀態(tài)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,會發(fā)現(xiàn)其狀態(tài)為 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
我們可以通過 inspect 查看 最近3次的狀態(tài)
[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" }
如果健康檢查連續(xù)失敗超過了重試次數(shù),狀態(tài)就會變?yōu)?(unhealthy)。
以上就是本文的全部內(nèi)容,希望對大家的學習有所幫助,也希望大家多多支持腳本之家。