zkServer.sh 分析

#!/usr/bin/env bash# Licensed to the Apache Software Foundation (ASF) under one or more# contributor license agreements.  See the NOTICE file distributed with# this work for additional information regarding copyright ownership.# The ASF licenses this file to You 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.## If this scripted is run out of /usr/bin or some other system bin directory# it should be linked to and not copied. Things like java jar files are found# relative to the canonical path of this script.## use POSTIX interface, symlink is followed automatically#获取脚本名称，$0是shell本身的文件名ZOOBIN="${BASH_SOURCE-$0}"#dirname命令去除文件名中的非目录部分，仅显示与目录有关的内容ZOOBIN="$(dirname "${ZOOBIN}")"ZOOBINDIR="$(cd "${ZOOBIN}"; pwd)"#优先执行libexec下的zkEnv.shif [ -e "$ZOOBIN/../libexec/zkEnv.sh" ]; then  . "$ZOOBINDIR/../libexec/zkEnv.sh"else  . "$ZOOBINDIR/zkEnv.sh"fi# See the following page for extensive details on setting# up the JVM to accept JMX remote management:# http://java.sun.com/javase/6/docs/technotes/guides/management/agent.html# by default we allow local JMX connectionsif [ "x$JMXLOCALONLY" = "x" ]then    JMXLOCALONLY=falsefi#&2是stderrif [ "x$JMXDISABLE" = "x" ] || [ "$JMXDISABLE" = 'false' ]then  echo "ZooKeeper JMX enabled by default" >&2  #如果没有指定jmx端口  if [ "x$JMXPORT" = "x" ]  then    # for some reason these two options are necessary on jdk6 on Ubuntu    #   accord to the docs they are not necessary, but otw jconsole cannot    #   do a local attach    ZOOMAIN="-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.local.only=$JMXLOCALONLY org.apache.zookeeper.server.quorum.QuorumPeerMain"  else    if [ "x$JMXAUTH" = "x" ]    then      JMXAUTH=false    fi    if [ "x$JMXSSL" = "x" ]    then      JMXSSL=false    fi    if [ "x$JMXLOG4J" = "x" ]    then      JMXLOG4J=true    fi    echo "ZooKeeper remote JMX Port set to $JMXPORT" >&2    echo "ZooKeeper remote JMX authenticate set to $JMXAUTH" >&2    echo "ZooKeeper remote JMX ssl set to $JMXSSL" >&2    echo "ZooKeeper remote JMX log4j set to $JMXLOG4J" >&2    ZOOMAIN="-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=$JMXPORT -Dcom.sun.management.jmxremote.authenticate=$JMXAUTH -Dcom.sun.management.jmxremote.ssl=$JMXSSL -Dzookeeper.jmx.log4j.disable=$JMXLOG4J org.apache.zookeeper.server.quorum.QuorumPeerMain"  fielse    echo "JMX disabled by user request" >&2    ZOOMAIN="org.apache.zookeeper.server.quorum.QuorumPeerMain"fiif [ "x$SERVER_JVMFLAGS"  != "x" ]then    JVMFLAGS="$SERVER_JVMFLAGS $JVMFLAGS"fi#添加到shell的第2个参数if [ "x$2" != "x" ]then    ZOOCFG="$ZOOCFGDIR/$2"fi# if we give a more complicated path to the config, don't screw around in $ZOOCFGDIRif [ "x$(dirname "$ZOOCFG")" != "x$ZOOCFGDIR" ]then    ZOOCFG="$2"fi#针对cygwin做特殊设置if $cygwinthen    ZOOCFG=`cygpath -wp "$ZOOCFG"`    # cygwin has a "kill" in the shell itself, gets confused    KILL=/bin/killelse    KILL=killfiecho "Using config: $ZOOCFG" >&2#针对solaris系统做特殊设置case "$OSTYPE" in*solaris*)  GREP=/usr/xpg4/bin/grep  ;;*)  GREP=grep  ;;esac#如果ZOOPIDFILE为空串if [ -z "$ZOOPIDFILE" ]; then    ZOO_DATADIR="$($GREP "^[[:space:]]*dataDir" "$ZOOCFG" | sed -e 's/.*=//')"    #如果$ZOO_DATADIR不存在或不是一个目录    if [ ! -d "$ZOO_DATADIR" ]; then        mkdir -p "$ZOO_DATADIR"    fi    ZOOPIDFILE="$ZOO_DATADIR/zookeeper_server.pid"else    # ensure it exists, otw stop will fail    mkdir -p "$(dirname "$ZOOPIDFILE")"fi#如果ZOO_LOG_DIR不存在，或者不可写if [ ! -w "$ZOO_LOG_DIR" ] ; thenmkdir -p "$ZOO_LOG_DIR"fi_ZOO_DAEMON_OUT="$ZOO_LOG_DIR/zookeeper.out"#判断第一个参数case $1 in#起动zookeeperstart)    #-n表示不换行输出    echo  -n "Starting zookeeper ... "    #判断这个server是否已在运行    if [ -f "$ZOOPIDFILE" ]; then      if kill -0 `cat "$ZOOPIDFILE"` > /dev/null 2>&1; then         echo $command already running as process `cat "$ZOOPIDFILE"`.          exit 0      fi    fi    #核心的起动语句    nohup "$JAVA" "-Dzookeeper.log.dir=${ZOO_LOG_DIR}" "-Dzookeeper.root.logger=${ZOO_LOG4J_PROP}" \    -cp "$CLASSPATH" $JVMFLAGS $ZOOMAIN "$ZOOCFG" > "$_ZOO_DAEMON_OUT" 2>&1 < /dev/null &    #如果返回值为0    if [ $? -eq 0 ]    then      case "$OSTYPE" in      *solaris*)        /bin/echo "${!}\\c" > "$ZOOPIDFILE"        ;;      #其它操作系统，把进程id写入文件中      *)        /bin/echo -n $! > "$ZOOPIDFILE"         ;;      esac      #输出起动成功与否的信息      if [ $? -eq 0 ];      then        sleep 1        echo STARTED      else        echo FAILED TO WRITE PID        exit 1      fi    else      echo SERVER DID NOT START      exit 1    fi    ;;#这种启动会把日志显示在控制台上start-foreground)    ZOO_CMD=(exec "$JAVA")    if [ "${ZOO_NOEXEC}" != "" ]; then      ZOO_CMD=("$JAVA")    fi    "${ZOO_CMD[@]}" "-Dzookeeper.log.dir=${ZOO_LOG_DIR}" "-Dzookeeper.root.logger=${ZOO_LOG4J_PROP}" \    -cp "$CLASSPATH" $JVMFLAGS $ZOOMAIN "$ZOOCFG"    ;;#输出启动串print-cmd)    echo "\"$JAVA\" -Dzookeeper.log.dir=\"${ZOO_LOG_DIR}\" -Dzookeeper.root.logger=\"${ZOO_LOG4J_PROP}\" -cp \"$CLASSPATH\" $JVMFLAGS $ZOOMAIN \"$ZOOCFG\" > \"$_ZOO_DAEMON_OUT\" 2>&1 < /dev/null"    ;;#停止Zookeeper服务器stop)    echo -n "Stopping zookeeper ... "    if [ ! -f "$ZOOPIDFILE" ]    then      echo "no zookeeper to stop (could not find file $ZOOPIDFILE)"    else      $KILL -9 $(cat "$ZOOPIDFILE")      rm "$ZOOPIDFILE"      echo STOPPED    fi    exit 0    ;;#执行UpgradeMainupgrade)    shift    echo "upgrading the servers to 3.*"    #$@是传给脚本的所有参数的列表    "$JAVA" "-Dzookeeper.log.dir=${ZOO_LOG_DIR}" "-Dzookeeper.root.logger=${ZOO_LOG4J_PROP}" \    -cp "$CLASSPATH" $JVMFLAGS org.apache.zookeeper.server.upgrade.UpgradeMain ${@}    echo "Upgrading ... "    ;;#重启Zookeeper Serverrestart)    shift    "$0" stop ${@}    sleep 3    "$0" start ${@}    ;;#查看Zookeeper server的状态status)    # -q is necessary on some versions of linux where nc returns too quickly, and no stat result is output    clientPortAddress=`$GREP "^[[:space:]]*clientPortAddress[^[:alpha:]]" "$ZOOCFG" | sed -e 's/.*=//'`    if ! [ $clientPortAddress ]    thenclientPortAddress="localhost"    fi    clientPort=`$GREP "^[[:space:]]*clientPort[^[:alpha:]]" "$ZOOCFG" | sed -e 's/.*=//'`    STAT=`"$JAVA" "-Dzookeeper.log.dir=${ZOO_LOG_DIR}" "-Dzookeeper.root.logger=${ZOO_LOG4J_PROP}" \             -cp "$CLASSPATH" $JVMFLAGS org.apache.zookeeper.client.FourLetterWordMain \             $clientPortAddress $clientPort srvr 2> /dev/null    \          | $GREP Mode`    if [ "x$STAT" = "x" ]    then        echo "Error contacting service. It is probably not running."        exit 1    else        echo $STAT        exit 0    fi    ;;*)    echo "Usage: $0 {start|start-foreground|stop|restart|status|upgrade|print-cmd}" >&2esac