nacos/nacos-server:v2.1.2-slim analysis

今天，我们来简要解析一下nacos的nacos/nacos-server:v2.1.2-slim镜像版本做了哪些事。

1、Dockerfile.Slim

我们在nacos官网的Quick Start for Nacos Docker页面可以找了解到github名称为nacos-group/nacos-docker的项目是nacos官方用于维护nacos docker镜像的地方，进入项目主页，我们找到2.12对应的版本，下载源码文件，具体链接如下：

• Source code(zip)
• Source code(tar.gz)

这里，我们以Source code(tar.gz)为例来介绍，下载以后，我们得到一个名称为nacos-docker-2.1.2.tar.gz的文件，解压得到一个名称为nacos-docker-2.1.2的目录，目录结构如下所示:

lwk@qwfys:~/Downloads/.tmp/.nacos$ tree nacos-docker-2.1.2
nacos-docker-2.1.2
├── build
│   ├── bin
│   │   └── docker-startup.sh
│   ├── conf
│   │   └── application.properties
│   ├── Dockerfile
│   └── Dockerfile.Slim
├── changlog
├── env
│   ├── mysql.env
│   ├── nacos-embedded.env
│   ├── nacos-hostname.env
│   ├── nacos-ip.env
│   └── nacos-standlone-mysql.env
├── example
│   ├── cluster-embedded.yaml
│   ├── cluster-hostname.yaml
│   ├── cluster-ip.yaml
│   ├── image
│   │   └── mysql
│   │       ├── 5.7
│   │       │   └── Dockerfile
│   │       └── 8
│   │           └── Dockerfile
│   ├── prometheus
│   │   ├── prometheus-cluster.yaml
│   │   └── prometheus-standalone.yaml
│   ├── standalone-derby.yaml
│   ├── standalone-mysql-5.7.yaml
│   └── standalone-mysql-8.yaml
├── README.md
└── README_ZH.md

10 directories, 22 files
lwk@qwfys:~/Downloads/.tmp/.nacos$ 

我们找到文件build/Dockerfile.Slim，该文件维护了nacos的slim版本的docker镜像所完成的主要工作，内容如下：

FROM amd64/buildpack-deps:buster-curl as installer

ARG NACOS_VERSION=2.1.1
ARG HOT_FIX_FLAG=""

RUN set -x \
    && curl -SL --output /var/tmp/nacos-server.tar.gz https://github.com/alibaba/nacos/releases/download/${NACOS_VERSION}${HOT_FIX_FLAG}/nacos-server-${NACOS_VERSION}.tar.gz \
    && tar -xzvf /var/tmp/nacos-server.tar.gz -C /home \
    && rm -rf /var/tmp/nacos-server.tar.gz /home/nacos/bin/* /home/nacos/conf/*.properties /home/nacos/conf/*.example /home/nacos/conf/nacos-mysql.sql

FROM openjdk:8-jre-slim

# set environment
ENV MODE="cluster" \
    PREFER_HOST_MODE="ip"\
    BASE_DIR="/home/nacos" \
    CLASSPATH=".:/home/nacos/conf:$CLASSPATH" \
    CLUSTER_CONF="/home/nacos/conf/cluster.conf" \
    FUNCTION_MODE="all" \
    NACOS_USER="nacos" \
    JAVA="/usr/local/openjdk-8/bin/java" \
    JVM_XMS="1g" \
    JVM_XMX="1g" \
    JVM_XMN="512m" \
    JVM_MS="128m" \
    JVM_MMS="320m" \
    NACOS_DEBUG="n" \
    TOMCAT_ACCESSLOG_ENABLED="false" \
    TZ="Asia/Shanghai"

WORKDIR $BASE_DIR

# copy nacos bin
COPY --from=installer ["/home/nacos", "/home/nacos"]

ADD bin/docker-startup.sh bin/docker-startup.sh
ADD conf/application.properties conf/application.properties

# set startup log dir
RUN mkdir -p logs \
    && cd logs \
    && touch start.out \
    && ln -sf /dev/stdout start.out \
    && ln -sf /dev/stderr start.out
RUN chmod +x bin/docker-startup.sh

EXPOSE 8848
ENTRYPOINT ["bin/docker-startup.sh"]

我们可以看到，docker镜像构建的时候，会从nacos github官网找对应的版本，这里会下载到一个名称为nacos-server-2.1.2.tar.gz的文件，解压到/home目录，解压完成以后，清理掉以下几组文件：

• /home/nacos/bin/*
• /home/nacos/conf/*.properties
• /home/nacos/conf/*.example
• /home/nacos/conf/nacos-mysql.sql

构建的时候，以openjdk:8-jre-slim为母板构建。

• 设置好北京时间对应的时区
• 将/home/nacos复制到镜像中的目录/home中
• 将nacos-docker-2.1.2/build/bin复制到/home/nacos/bin中去
• 将nacos-docker-2.1.2/build/conf复制到/home/naocs/conf中去

最后设置容器中的文件/home/nacos/bin/docker-startup.sh为容器启动后要执行的初始化命令。

2、docker-startup.sh

文件docker-startup.sh主要用于设置nacos启动过程中java如何启动naocs进程，具体内容如下：

#!/bin/bash
# Copyright 1999-2018 Alibaba Group Holding Ltd.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
set -x
export CUSTOM_SEARCH_NAMES="application"
export CUSTOM_SEARCH_LOCATIONS=file:${BASE_DIR}/conf/
export MEMBER_LIST=""
PLUGINS_DIR="/home/nacos/plugins/peer-finder"
function print_servers() {
  if [[ ! -f "${CLUSTER_CONF}" ]]; then
    echo "" >"$CLUSTER_CONF"
    for server in ${NACOS_SERVERS}; do
      echo "$server" >>"$CLUSTER_CONF"
    done
  else
    bash $PLUGINS_DIR/plugin.sh
    sleep 30
  fi
}
#===========================================================================================
# JVM Configuration
#===========================================================================================
if [[ "${MODE}" == "standalone" ]]; then

  JAVA_OPT="${JAVA_OPT} -Xms${JVM_XMS} -Xmx${JVM_XMX} -Xmn${JVM_XMN}"
  JAVA_OPT="${JAVA_OPT} -Dnacos.standalone=true"
else
  if [[ "${EMBEDDED_STORAGE}" == "embedded" ]]; then
    JAVA_OPT="${JAVA_OPT} -DembeddedStorage=true"
  fi
  JAVA_OPT="${JAVA_OPT} -server -Xms${JVM_XMS} -Xmx${JVM_XMX} -Xmn${JVM_XMN} -XX:MetaspaceSize=${JVM_MS} -XX:MaxMetaspaceSize=${JVM_MMS}"
  if [[ "${NACOS_DEBUG}" == "y" ]]; then
    JAVA_OPT="${JAVA_OPT} -Xdebug -Xrunjdwp:transport=dt_socket,address=9555,server=y,suspend=n"
  fi
  JAVA_OPT="${JAVA_OPT} -XX:-OmitStackTraceInFastThrow -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=${BASE_DIR}/logs/java_heapdump.hprof"
  JAVA_OPT="${JAVA_OPT} -XX:-UseLargePages"
  print_servers
fi

#===========================================================================================
# Setting system properties
#===========================================================================================
# set  mode that Nacos Server function of split
if [[ "${FUNCTION_MODE}" == "config" ]]; then
  JAVA_OPT="${JAVA_OPT} -Dnacos.functionMode=config"
elif [[ "${FUNCTION_MODE}" == "naming" ]]; then
  JAVA_OPT="${JAVA_OPT} -Dnacos.functionMode=naming"
fi
# set nacos server ip
if [[ ! -z "${NACOS_SERVER_IP}" ]]; then
  JAVA_OPT="${JAVA_OPT} -Dnacos.server.ip=${NACOS_SERVER_IP}"
fi

if [[ ! -z "${USE_ONLY_SITE_INTERFACES}" ]]; then
  JAVA_OPT="${JAVA_OPT} -Dnacos.inetutils.use-only-site-local-interfaces=${USE_ONLY_SITE_INTERFACES}"
fi

if [[ ! -z "${PREFERRED_NETWORKS}" ]]; then
  JAVA_OPT="${JAVA_OPT} -Dnacos.inetutils.preferred-networks=${PREFERRED_NETWORKS}"
fi

if [[ ! -z "${IGNORED_INTERFACES}" ]]; then
  JAVA_OPT="${JAVA_OPT} -Dnacos.inetutils.ignored-interfaces=${IGNORED_INTERFACES}"
fi

### If turn on auth system:
if [[ ! -z "${NACOS_AUTH_ENABLE}" ]]; then
  JAVA_OPT="${JAVA_OPT} -Dnacos.core.auth.enabled=${NACOS_AUTH_ENABLE}"
fi

if [[ "${PREFER_HOST_MODE}" == "hostname" ]]; then
  JAVA_OPT="${JAVA_OPT} -Dnacos.preferHostnameOverIp=true"
fi
JAVA_OPT="${JAVA_OPT} -Dnacos.member.list=${MEMBER_LIST}"

JAVA_MAJOR_VERSION=$($JAVA -version 2>&1 | sed -E -n 's/.* version "([0-9]*).*$/\1/p')
if [[ "$JAVA_MAJOR_VERSION" -ge "9" ]]; then
  JAVA_OPT="${JAVA_OPT} -cp .:${BASE_DIR}/plugins/cmdb/*.jar:${BASE_DIR}/plugins/mysql/*.jar"
  JAVA_OPT="${JAVA_OPT} -Xlog:gc*:file=${BASE_DIR}/logs/nacos_gc.log:time,tags:filecount=10,filesize=102400"
else
  JAVA_OPT="${JAVA_OPT} -Djava.ext.dirs=${JAVA_HOME}/jre/lib/ext:${JAVA_HOME}/lib/ext:${BASE_DIR}/plugins/health:${BASE_DIR}/plugins/cmdb:${BASE_DIR}/plugins/mysql"
  JAVA_OPT="${JAVA_OPT} -Xloggc:${BASE_DIR}/logs/nacos_gc.log -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintGCTimeStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=10 -XX:GCLogFileSize=100M"
fi

JAVA_OPT="${JAVA_OPT} -Dnacos.home=${BASE_DIR}"
JAVA_OPT="${JAVA_OPT} -jar ${BASE_DIR}/target/nacos-server.jar"
JAVA_OPT="${JAVA_OPT} ${JAVA_OPT_EXT}"
JAVA_OPT="${JAVA_OPT} --spring.config.additional-location=${CUSTOM_SEARCH_LOCATIONS}"
JAVA_OPT="${JAVA_OPT} --spring.config.name=${CUSTOM_SEARCH_NAMES}"
JAVA_OPT="${JAVA_OPT} --logging.config=${BASE_DIR}/conf/nacos-logback.xml"
JAVA_OPT="${JAVA_OPT} --server.max-http-header-size=524288"

echo "Nacos is starting, you can docker logs your container"
exec $JAVA ${JAVA_OPT}

我们看到，像java堆内存大小这些，这里都已经做了参数化配置。

如果我们要以debug方式启动，这里也做了参数化配置，不过启动后，debug端口号为9555。

环境变量CUSTOM_SEARCH_NAMES、CUSTOM_SEARCH_LOCATIONS可以指定新的nacos 配置文件的名称及路径。

3、application.properties

文件nacos-docker-2.1.2/build/conf/application.properties重写了nacos github项目中给到的默认配置文件，主要用于将部分配置项以环境变量的方式暴露了出来，方便我们从外部控制nacos启动过程中的相关细节，具体内容如下:

# spring
server.servlet.contextPath=${SERVER_SERVLET_CONTEXTPATH:/nacos}
server.contextPath=/nacos
server.port=${NACOS_APPLICATION_PORT:8848}
server.tomcat.accesslog.max-days=30
server.tomcat.accesslog.pattern=%h %l %u %t "%r" %s %b %D %{User-Agent}i %{Request-Source}i
spring.datasource.platform=${SPRING_DATASOURCE_PLATFORM:""}
nacos.cmdb.dumpTaskInterval=3600
nacos.cmdb.eventTaskInterval=10
nacos.cmdb.labelTaskInterval=300
nacos.cmdb.loadDataAtStart=false
db.num=${MYSQL_DATABASE_NUM:1}
db.url.0=jdbc:mysql://${MYSQL_SERVICE_HOST}:${MYSQL_SERVICE_PORT:3306}/${MYSQL_SERVICE_DB_NAME}?${MYSQL_SERVICE_DB_PARAM:characterEncoding=utf8&connectTimeout=1000&socketTimeout=3000&autoReconnect=true&useSSL=false}
db.url.1=jdbc:mysql://${MYSQL_SERVICE_HOST}:${MYSQL_SERVICE_PORT:3306}/${MYSQL_SERVICE_DB_NAME}?${MYSQL_SERVICE_DB_PARAM:characterEncoding=utf8&connectTimeout=1000&socketTimeout=3000&autoReconnect=true&useSSL=false}
db.user=${MYSQL_SERVICE_USER}
db.password=${MYSQL_SERVICE_PASSWORD}
### The auth system to use, currently only 'nacos' and 'ldap' is supported:
nacos.core.auth.system.type=${NACOS_AUTH_SYSTEM_TYPE:nacos}
### worked when nacos.core.auth.system.type=nacos
### The token expiration in seconds:
nacos.core.auth.plugin.nacos.token.expire.seconds=${NACOS_AUTH_TOKEN_EXPIRE_SECONDS:18000}
### The default token:
nacos.core.auth.plugin.nacos.token.secret.key=${NACOS_AUTH_TOKEN:SecretKey012345678901234567890123456789012345678901234567890123456789}
### Turn on/off caching of auth information. By turning on this switch, the update of auth information would have a 15 seconds delay.
nacos.core.auth.caching.enabled=${NACOS_AUTH_CACHE_ENABLE:false}
nacos.core.auth.enable.userAgentAuthWhite=${NACOS_AUTH_USER_AGENT_AUTH_WHITE_ENABLE:false}
nacos.core.auth.server.identity.key=${NACOS_AUTH_IDENTITY_KEY:serverIdentity}
nacos.core.auth.server.identity.value=${NACOS_AUTH_IDENTITY_VALUE:security}
server.tomcat.accesslog.enabled=${TOMCAT_ACCESSLOG_ENABLED:false}
# default current work dir
server.tomcat.basedir=file:.
## spring security config
### turn off security
nacos.security.ignore.urls=${NACOS_SECURITY_IGNORE_URLS:/,/error,/**/*.css,/**/*.js,/**/*.html,/**/*.map,/**/*.svg,/**/*.png,/**/*.ico,/console-fe/public/**,/v1/auth/**,/v1/console/health/**,/actuator/**,/v1/console/server/**}
# metrics for elastic search
management.metrics.export.elastic.enabled=false
management.metrics.export.influx.enabled=false
nacos.naming.distro.taskDispatchThreadCount=10
nacos.naming.distro.taskDispatchPeriod=200
nacos.naming.distro.batchSyncKeyCount=1000
nacos.naming.distro.initDataRatio=0.9
nacos.naming.distro.syncRetryDelay=5000
nacos.naming.data.warmup=true

我们看到，这里关于数据源类型部分，没有给到默认值，如果大家要用到mysql，需要通过环境变量SPRING_DATASOURCE_PLATFORM指定为mysql。

Summary

源码分析，要点是抓住主干把整个业务逻辑理顺，然后在必要时候去仔细研讨细节，这样就可以做到功半事倍、四两拨千斤的效果，否则一头扎进细节中会把自己搞得晕头转向，理不出头绪。