Kafka调试入门(一)

Docker容器管理平台Rancher高可用部署——看这篇就够了

很多人对kafka消息队列应该不陌生,使用起来也比较方便。对kafka最常见的操作一般有如下几种:

  1. 启动kafka集群
  2. 创建一个名称为xxx的主题(topic)
  3. 查看已经创建好的主题
  4. 向xxx这个主题中插入一些数据
  5. 从xxx这个主题中消费一些数据
针对这几种操作,其实kafka都为大家提供了一系列方便使用的脚本,这些脚本都在bin文件夹中,主要有

 

  • bin/kafka-server-start.sh   //作用是启动kafka服务端进程
  • bin/kafka-topics.sh    //作用是创建、查看主题 
  • bin/kafka-console-producer.sh    //命令行方式的生产者
  • bin/kafka-console-consumer.sh    //命令行方式的消费者

 

下面是一些常用的操作实例:

  • 启动kafka集群:
     bin/kafka-server-start.sh config/server.properties
  • 创建一个名称是test的主体(topic)
    bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic test
  • 查看创建的主题(topic)
    bin/kafka-topics.sh --list --zookeeper localhost:2181
  • 往test这个topic中插入一些数据,用kafka-console-producer
    bin/kafka-console-producer.sh --broker-list localhost:9092 --topic test
  • 从test这个topic中消费一些数据,用kafka-console-consumer从最开头开始读取数据:
    bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic test --from-beginning  

 正文

kafka-server-start.sh执行流程分析

首先分析一下运行bin/kafka-server-start.sh config/server.properties的时候,kafka源码的执行流程。

第一步:先看看kafka-server-start.sh这个脚本,如下

 

#!/bin/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.

# 此处是判断一下执行kafka-server-start.sh 这个脚本后边的参数的个数,
# 如果小于1,那么说明没有传入server.properties这个文件的路径,
# 那就打印使用说明给用户并直接退出,不继续执行后续的脚本。
if [ $# -lt 1 ];
then
	echo "USAGE: $0 [-daemon] server.properties [--override property=value]*"
	exit 1
fi

#该脚本所在的文件夹的路径,例如:/data/kafka/bin/
base_dir=$(dirname $0)



# 检查KAFKA_LOG4J_OPTS这个变量是否已经被设置
# 如果没有,就设置为 
# -Dlog4j.configuration=file:$base_dir/../config/log4j.properties
# 其中的$base_dir会被替换为真实路径
# 假设base_dir是/data/kafka/bin/的话
# KAFKA_LOG4J_OPTS=
# "-Dlog4j.configuration=file:/data/kafka/bin/../config/log4j.properties"

if [ "x$KAFKA_LOG4J_OPTS" = "x" ]; then
    export KAFKA_LOG4J_OPTS="-Dlog4j.configuration=file:$base_dir/../config/log4j.properties"
fi


# 检查KAFKA_HEAP_OPTS这个变量是否已经被设置
# 如果没有的话,就设置为
# -Xmx1G -Xms1G
# 即 KAFKA_HEAP_OPTS="-Xmx1G -Xms1G"

if [ "x$KAFKA_HEAP_OPTS" = "x" ]; then
    export KAFKA_HEAP_OPTS="-Xmx1G -Xms1G"
fi



# EXTRA_ARGS="-name kafkaServer -loggc"
EXTRA_ARGS=${EXTRA_ARGS-'-name kafkaServer -loggc'}

# $1是执行脚本时的第一个参数,比如
# sh 1.sh a b c
# 那么$1='a'   $2='b'  $3='c'
# 所以此处是检查运行kafka-server-start.sh 这个脚本的时候,第一个参数是不是-daemon
# 假设我运行的是./kafka-server-start.sh -daemon ../conf/server.properties
# 那么就会进入下面的   -daemon)  分支
# 假设我运行的是./kafka-server-start.sh  ../conf/server.properties
# 那么就会进入到下面的   *)   分支
# -daemon  分支做的事情是 给EXTRA_ARGS这个变量再追加一个参数,
# 原来EXTRA_ARGS="-name kafkaServer -loggc",
# 追加后变成了"-daemon -name kafkaServer -loggc"

COMMAND=$1
case $COMMAND in
  -daemon)
    EXTRA_ARGS="-daemon "$EXTRA_ARGS
    shift
    ;;
  *)
    ;;
esac

#最后运行程序启动kafka server
# 可以把exec改成 echo 打印出来看看 下面的脚本都被替换成啥了
# 我本机输出了 bin/kafka-run-class.sh -name kafkaServer -loggc kafka.Kafka -deamon config/server.properties
#也就是说其实最后运行的是 bin/kafka-run-class.sh -name kafkaServer -loggc kafka.Kafka -deamon config/server.properties

exec $base_dir/kafka-run-class.sh $EXTRA_ARGS kafka.Kafka "$@"

  

兜兜转转,我们发现我执行的

bin/kafka-server-start.sh -daemon conf/server.properties

.Net Core 使用 CSRedisCore 访问 Redis 的哨兵和主从复制

最后在kafka-server-start.sh脚本里面进行一番转换之后变成了

bin/kafka-run-class.sh -name kafkaServer -loggc kafka.Kafka -deamon config/server.properties

那么接着我们就开始分析bin/kafka-run-class.sh这个脚本,还是贴一下这个脚本完整代码,再结合代码做一些解释。

 

#!/bin/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.

#如果参数的个数小于1,进入if条件
if [ $# -lt 1 ];
then
  #打印该脚本的使用方式给用户。
  echo "USAGE: $0 [-daemon] [-name servicename] [-loggc] classname [opts]"
  exit 1
fi

# 执行一下linux命令 uname -a ,看一下的结果中是不是有“CYGWIN”字符串
if [[ $(uname -a) =~ "CYGWIN" ]]; then
  #如果有的话,就把CYGWIN设置为1
  CYGWIN=1
else
  #如果没有匹配到“CYGWIN”字符串,则把CYGWIN设置为0
  CYGWIN=0
fi

# 判断一下$INCLUDE_TEST_JARS变量的值,是否为空;是的话进入if中
if [ -z "$INCLUDE_TEST_JARS" ]; then
  #把INCLUDE_TEST_JARS设置为false
  INCLUDE_TEST_JARS=false
fi

#一个用来匹配测试用的jar包的正则表达式
regex="(-(test|test-sources|src|scaladoc|javadoc)\.jar|jar.asc)$"

#一个函数,用来判断一个文件是不是测试相关的或者文档相关的。
#如果传入的文件是测试相关的,返回0
#如果传入的是与运行程序息息相关的,重要的,则返回1
should_include_file() {
  if [ "$INCLUDE_TEST_JARS" = true ]; then
    return 0
  fi
  file=$1
  if [ -z "$(echo "$file" | egrep "$regex")" ] ; then
    return 0
  else
    return 1
  fi
}

#设置base_dir为当前脚本bin文件夹的上一级目录。
#比如我的kafka-run-class.sh路径是/data/kafka2.2/bin/,那么base_dir就是/data/kafka2.2/
base_dir=$(dirname $0)/..

# 判断一下$SCALA_VERSION变量的值,是否为空;是的话进入if中
if [ -z "$SCALA_VERSION" ]; then
  #设置$SCALA_VERSION为2.13.2
  SCALA_VERSION=2.13.2
  #判断一下base_dir目录下是不是有gradle.properties文件,如果有的话,进入if逻辑块
  if [[ -f "$base_dir/gradle.properties" ]]; then
    #设置SCALA_VERSION变量为从gradle.properties中查询到的值,比如gradle.properties中可能有一行scalaVersion=2.11.1
    #那么用cut切掉等号左边的部分,剩下2.11.1。把2.11.1设置到
    SCALA_VERSION=`grep "^scalaVersion=" "$base_dir/gradle.properties" | cut -d= -f 2`
  fi
fi

# 判断一下$SCALA_BINARY_VERSION内容的长度是不是0,是则进入if
if [ -z "$SCALA_BINARY_VERSION" ]; then
  #设置SCALA_BINARY_VERSION变量的值为SCALA_VERSION的前三分之二。
  #比如SCALA_VERSION=2.11.1   那么SCALA_BINARY_VERSION=2.11
  SCALA_BINARY_VERSION=$(echo $SCALA_VERSION | cut -f 1-2 -d '.')
fi
done

#这里设置nullglob开启,这个nullglob开启之后,shell脚本或者终端中可以识别通配符*,关闭后不能用*这个通配符
shopt -s nullglob

# 判断一下$UPGRADE_KAFKA_STREAMS_TEST_VERSION变量的值,是否为空;是的话进入if中
if [ -z "$UPGRADE_KAFKA_STREAMS_TEST_VERSION" ]; then
  #依次把base_dir/core/build/文件夹下dependant-libs-${SCALA_VERSION}开头的文件夹路径 赋值给 dir变量
  for dir in "$base_dir"/core/build/dependant-libs-${SCALA_VERSION}*;
  do
    #把dir变量的内容追加到$CLASSPATH中
    CLASSPATH="$CLASSPATH:$dir/*"
  done
fi

#依次把base_dir/examples/build/libs/文件夹下kafka-examples开头,.jar结尾的文件全路径(含文件名称) 赋值给 file变量
for file in "$base_dir"/examples/build/libs/kafka-examples*.jar;
do
  #判断一下,如果should_include_file返回1,也就是说是重要的jar包,就进入到if逻辑
  if should_include_file "$file"; then
    #添加$file变量的内容到$CLASSPATH中
    CLASSPATH="$CLASSPATH":"$file"
  fi
done


# 判断一下$UPGRADE_KAFKA_STREAMS_TEST_VERSION变量的值,是否为空;是的话进入if中
if [ -z "$UPGRADE_KAFKA_STREAMS_TEST_VERSION" ]; then
  #设置clients_lib_dir为    当期脚本所在目录/../clients/build/libs
  clients_lib_dir=$(dirname $0)/../clients/build/libs
  #设置streams_lib_dir为    当期脚本所在目录/../streams/build/libs
  streams_lib_dir=$(dirname $0)/../streams/build/libs
  #设置streams_dependant_clients_lib_dir为    当期脚本所在目录/../streams/build/dependant-libs-${SCALA_VERSION}
  streams_dependant_clients_lib_dir=$(dirname $0)/../streams/build/dependant-libs-${SCALA_VERSION}
else
  #设置clients_lib_dir为    /opt/kafka-$UPGRADE_KAFKA_STREAMS_TEST_VERSION/libs
  clients_lib_dir=/opt/kafka-$UPGRADE_KAFKA_STREAMS_TEST_VERSION/libs
  #设置streams_lib_dir为    和clients_lib_dir一样
  streams_lib_dir=$clients_lib_dir
  #设置streams_dependant_clients_lib_dir为    和clients_lib_dir一样
  streams_dependant_clients_lib_dir=$streams_lib_dir
fi

#依次把$clients_lib_dir文件夹下kafka-clients开头,.jar结尾的文件全路径(含文件名称) 赋值给 file变量
for file in "$clients_lib_dir"/kafka-clients*.jar;
do
  #判断一下,如果should_include_file返回1,也就是说是重要的jar包,就进入到if逻辑
  if should_include_file "$file"; then
    #添加$file变量的内容到$CLASSPATH中
    CLASSPATH="$CLASSPATH":"$file"
  fi
done

#依次把$streams_lib_dir文件夹下kafka-streams开头,.jar结尾的文件全路径(含文件名称) 赋值给 file变量
for file in "$streams_lib_dir"/kafka-streams*.jar;
do
  #判断一下,如果should_include_file返回1,也就是说是重要的jar包,就进入到if逻辑
  if should_include_file "$file"; then
    #添加$file变量的内容到$CLASSPATH中
    CLASSPATH="$CLASSPATH":"$file"
  fi
done

# 判断一下$UPGRADE_KAFKA_STREAMS_TEST_VERSION变量的内容的长度是否为0,是则进入
if [ -z "$UPGRADE_KAFKA_STREAMS_TEST_VERSION" ]; then
  #依次把base_dir/streams/examples/build/libs/文件夹下kafka-streams-examples开头,.jar结尾的文件全路径(含文件名称) 赋值给 file变量
  for file in "$base_dir"/streams/examples/build/libs/kafka-streams-examples*.jar;
  do
    #判断一下,如果should_include_file返回1,也就是说是重要的jar包,就进入到if逻辑
    if should_include_file "$file"; then
      #添加$file变量的内容到$CLASSPATH中
      CLASSPATH="$CLASSPATH":"$file"
    fi
  done
else
  #替换$UPGRADE_KAFKA_STREAMS_TEST_VERSION中的小数点,比如$UPGRADE_KAFKA_STREAMS_TEST_VERSION=2.12.1
  #替换后变成2121
  VERSION_NO_DOTS=`echo $UPGRADE_KAFKA_STREAMS_TEST_VERSION | sed 's/\.//g'`
  #SHORT_VERSION_NO_DOTS等于VERSION_NO_DOTS剔除最后一位,比如VERSION_NO_DOTS等于2121  SHORT_VERSION_NO_DOTS等于212
  SHORT_VERSION_NO_DOTS=${VERSION_NO_DOTS:0:((${#VERSION_NO_DOTS} - 1))} # remove last char, ie, bug-fix number
  #依次把base_dir/streams/upgrade-system-tests-$SHORT_VERSION_NO_DOTS/build/libs/文件夹下
  #kafka-streams-upgrade-system-tests开头,.jar结尾的文件全路径(含文件名称) 赋值给 file变量
  for file in "$base_dir"/streams/upgrade-system-tests-$SHORT_VERSION_NO_DOTS/build/libs/kafka-streams-upgrade-system-tests*.jar;
  do
    #判断一下,如果should_include_file返回1,也就是说是重要的jar包,就进入到if逻辑
    if should_include_file "$file"; then
      #添加$file变量的内容到$CLASSPATH中
      CLASSPATH="$file":"$CLASSPATH"
    fi
  done
  #如果$SHORT_VERSION_NO_DOTS等于0100,
  if [ "$SHORT_VERSION_NO_DOTS" = "0100" ]; then
    #追加/opt/kafka-$UPGRADE_KAFKA_STREAMS_TEST_VERSION/libs/zkclient-0.8.jar到classpath
    CLASSPATH="/opt/kafka-$UPGRADE_KAFKA_STREAMS_TEST_VERSION/libs/zkclient-0.8.jar":"$CLASSPATH"
    #追加/opt/kafka-$UPGRADE_KAFKA_STREAMS_TEST_VERSION/libs/zookeeper-3.4.6.jar到classpath
    CLASSPATH="/opt/kafka-$UPGRADE_KAFKA_STREAMS_TEST_VERSION/libs/zookeeper-3.4.6.jar":"$CLASSPATH"
  fi
  #如果$SHORT_VERSION_NO_DOTS等于0101
  if [ "$SHORT_VERSION_NO_DOTS" = "0101" ]; then
    #追加/opt/kafka-$UPGRADE_KAFKA_STREAMS_TEST_VERSION/libs/zkclient-0.9.jar到classpath
    CLASSPATH="/opt/kafka-$UPGRADE_KAFKA_STREAMS_TEST_VERSION/libs/zkclient-0.9.jar":"$CLASSPATH"
    #追加/opt/kafka-$UPGRADE_KAFKA_STREAMS_TEST_VERSION/libs/zookeeper-3.4.8.jar到classpath
    CLASSPATH="/opt/kafka-$UPGRADE_KAFKA_STREAMS_TEST_VERSION/libs/zookeeper-3.4.8.jar":"$CLASSPATH"
  fi
fi

#遍历$streams_dependant_clients_lib_dir文件夹下的rocksdb开头,.jar结尾的文件
for file in "$streams_dependant_clients_lib_dir"/rocksdb*.jar;
do
  #依次添加文件到classpath中
  CLASSPATH="$CLASSPATH":"$file"
done

#遍历$streams_dependant_clients_lib_dir文件夹下的中间匹配hamcrest字符串,.jar结尾的文件
for file in "$streams_dependant_clients_lib_dir"/*hamcrest*.jar;
do
  CLASSPATH="$CLASSPATH":"$file"
done

#遍历$streams_dependant_clients_lib_dir文件夹下的kafka-tools开头,.jar结尾的文件
for file in "$base_dir"/tools/build/libs/kafka-tools*.jar;
do
  #判断一下,如果should_include_file返回1,也就是说是重要的jar包,就进入到if逻辑
  if should_include_file "$file"; then
    #添加$file变量的内容到$CLASSPATH中
    CLASSPATH="$CLASSPATH":"$file"
  fi
done

#依次把base_dir/tools/build/文件夹下dependant-libs-${SCALA_VERSION}开头的文件夹路径 赋值给 dir变量
for dir in "$base_dir"/tools/build/dependant-libs-${SCALA_VERSION}*;
do
  #添加$file变量的内容到$CLASSPATH中
  CLASSPATH="$CLASSPATH:$dir/*"
done

#依次把 "api" "transforms" "runtime" "file" "mirror" "mirror-client" "json" "tools" "basic-auth-extension" 逐个赋值给cc_pkg变量
for cc_pkg in "api" "transforms" "runtime" "file" "mirror" "mirror-client" "json" "tools" "basic-auth-extension"
do
  #遍历$base_dir/connect/${cc_pkg}/build/libs/文件夹下的connect-${cc_pkg}开头,.jar结尾的文件
  for file in "$base_dir"/connect/${cc_pkg}/build/libs/connect-${cc_pkg}*.jar;
  do
    #判断一下,如果should_include_file返回1,也就是说是重要的jar包,就进入到if逻辑
    if should_include_file "$file"; then
      #添加$file变量的内容到$CLASSPATH中
      CLASSPATH="$CLASSPATH":"$file"
    fi
  done
  #判断$base_dir/connect/${cc_pkg}/build/dependant-libs文件夹是否存在,是的话进入if
  if [ -d "$base_dir/connect/${cc_pkg}/build/dependant-libs" ] ; then
    #把base_dir/connect/${cc_pkg}/build/dependant-libs/下的所有文件都加入到classpath中去
    CLASSPATH="$CLASSPATH:$base_dir/connect/${cc_pkg}/build/dependant-libs/*"
  fi
done

# 遍历base_dir文件夹下的libs
for file in "$base_dir"/libs/*;
do
  #判断一下,如果should_include_file返回1,也就是说是重要的jar包,就进入到if逻辑
  if should_include_file "$file"; then
    #添加$file变量的内容到$CLASSPATH中
    CLASSPATH="$CLASSPATH":"$file"
  fi
done

#遍历base_dir/core/build/libs/文件夹下所有kafka_${SCALA_BINARY_VERSION}开头的文件
for file in "$base_dir"/core/build/libs/kafka_${SCALA_BINARY_VERSION}*.jar;
do
  #判断一下,如果should_include_file返回1,也就是说是重要的jar包,就进入到if逻辑
  if should_include_file "$file"; then
    #添加$file变量的内容到$CLASSPATH中
    CLASSPATH="$CLASSPATH":"$file"
  fi
done
#到此关闭nullglob,也就是说后边用不到*去匹配文件和文件夹了
shopt -u nullglob


#判断$CLASSPATH的内容长度是不是0,是则为真
if [ -z "$CLASSPATH" ] ; then
  #打印错误信息
  echo "Classpath is empty. Please build the project first e.g. by running './gradlew jar -PscalaVersion=$SCALA_VERSION'"
  #退出脚本,不再向下继续执行
  exit 1
fi

#判断$KAFKA_JMX_OPTS的内容长度是不是0,是则为真
if [ -z "$KAFKA_JMX_OPTS" ]; then
  #设置KAFKA_JMX_OPTS的值为-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.authenticate=false  -Dcom.sun.management.jmxremote.ssl=false
  KAFKA_JMX_OPTS="-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.authenticate=false  -Dcom.sun.management.jmxremote.ssl=false "
fi

#判断$JMX_PORT是不是空的,空的话就进入if块
if [  $JMX_PORT ]; then
  #设置KAFKA_JMX_OPTS的值为 $KAFKA_JMX_OPTS -Dcom.sun.management.jmxremote.port=$JMX_PORT
  KAFKA_JMX_OPTS="$KAFKA_JMX_OPTS -Dcom.sun.management.jmxremote.port=$JMX_PORT "
fi

#判断$LOG_DIR是不是空的,空的话就进入if块
if [ "x$LOG_DIR" = "x" ]; then
  #LOG_DIR=$base_dir/log
  LOG_DIR="$base_dir/logs"
fi

#判断$KAFKA_LOG4J_OPTS内容的长度是不是0,是则为真
if [ -z "$KAFKA_LOG4J_OPTS" ]; then
  #设置LOG4J_DIR为$base_dir/config/tools-log4j.properties
  LOG4J_DIR="$base_dir/config/tools-log4j.properties"
  # 如果检测到CYGWIN,那么需要转换LOG4J_DIR中的path
  (( CYGWIN )) && LOG4J_DIR=$(cygpath --path --mixed "${LOG4J_DIR}")
  #设置KAFKA_LOG4J_OPTS为 -Dlog4j.configuration=file:${LOG4J_DIR}
  KAFKA_LOG4J_OPTS="-Dlog4j.configuration=file:${LOG4J_DIR}"
else
  # 如果不存在$LOG_DIR这个文件夹,那么就创建一个文件夹
  if [ ! -d "$LOG_DIR" ]; then
    mkdir -p "$LOG_DIR"
  fi
fi

# 如果检测到CYGWIN,那么需要转换LOG_DIR中的path
(( CYGWIN )) && LOG_DIR=$(cygpath --path --mixed "${LOG_DIR}")
KAFKA_LOG4J_OPTS="-Dkafka.logs.dir=$LOG_DIR $KAFKA_LOG4J_OPTS"

# 判断$KAFKA_OPTS这个变量内容长度为0,则为真
if [ -z "$KAFKA_OPTS" ]; then
  #如果为空,设置为""
  KAFKA_OPTS=""
fi

#如果$KAFKA_DEBUG的内容为空
if [ "x$KAFKA_DEBUG" != "x" ]; then

    # 设置DEFAULT_JAVA_DEBUG_PORT变量为5005
    DEFAULT_JAVA_DEBUG_PORT="5005"

    #如果$JAVA_DEBUG_PORT的长度为0,则为真
    if [ -z "$JAVA_DEBUG_PORT" ]; then
        #设置JAVA_DEBUG_PORT为$DEFAULT_JAVA_DEBUG_PORT
        JAVA_DEBUG_PORT="$DEFAULT_JAVA_DEBUG_PORT"
    fi

    # DEFAULT_JAVA_DEBUG_OPTS设置为-agentlib:jdwp=transport=dt_socket,server=y,suspend=${DEBUG_SUSPEND_FLAG:-n},address=$JAVA_DEBUG_PORT
    DEFAULT_JAVA_DEBUG_OPTS="-agentlib:jdwp=transport=dt_socket,server=y,suspend=${DEBUG_SUSPEND_FLAG:-n},address=$JAVA_DEBUG_PORT"
    # 检查$JAVA_DEBUG_OPTS的内容是不是长度为0,是则进入if
    if [ -z "$JAVA_DEBUG_OPTS" ]; then
        #设置JAVA_DEBUG_OPTS的值等于$DEFAULT_JAVA_DEBUG_OPTS
        JAVA_DEBUG_OPTS="$DEFAULT_JAVA_DEBUG_OPTS"
    fi

    #打印 Enabling Java debug options: $JAVA_DEBUG_OPTS 到屏幕
    echo "Enabling Java debug options: $JAVA_DEBUG_OPTS"
    #设置KAFKA_OPTS的变量值为 $JAVA_DEBUG_OPTS 拼接上$KAFKA_OPTS
    KAFKA_OPTS="$JAVA_DEBUG_OPTS $KAFKA_OPTS"
fi

#判断一下使用那个JAVA_HOME
#首先判断JAVA_HOME这个变量的内容的长度是不是0,是则进入if
if [ -z "$JAVA_HOME" ]; then
  #设置JAVA变量的值为"JAVA"
  JAVA="java"
else
  #设置JAVA变量的值为$JAVA_HOME/bin/java
  JAVA="$JAVA_HOME/bin/java"
fi

#设置内存相关的参数
#首先判断一下$KAFKA_HEAP_OPTS变量内容的长度是不是0,是则进入if
if [ -z "$KAFKA_HEAP_OPTS" ]; then
  #设置KAFKA_HEAP_OPTS的值为 -Xmx256M
  KAFKA_HEAP_OPTS="-Xmx256M"
fi

# JVM性能参数
# MaxInlineLevel=15是自JDK 14以来的默认值,一旦不再支持旧版JDK,就可以删除。
#首先判断一下$KAFKA_JVM_PERFORMANCE_OPTS变量内容的长度是不是0,是则进入if
if [ -z "$KAFKA_JVM_PERFORMANCE_OPTS" ]; then
  #设置KAFKA_JVM_PERFORMANCE_OPTS的值为-server -XX:+UseG1GC -XX:MaxGCPauseMillis=20 -XX:InitiatingHeapOccupancyPercent=35 -XX:+ExplicitGCInvokesConcurrent -XX:MaxInlineLevel=15 -Djava.awt.headless=true
  KAFKA_JVM_PERFORMANCE_OPTS="-server -XX:+UseG1GC -XX:MaxGCPauseMillis=20 -XX:InitiatingHeapOccupancyPercent=35 -XX:+ExplicitGCInvokesConcurrent -XX:MaxInlineLevel=15 -Djava.awt.headless=true"
fi

#首先$#代表的是脚本后边的参数的个数
#-gt是 greater  than 的缩写,代表的意思是 大于
#判断一下参数的个数是不是大于0,是则进入
while [ $# -gt 0 ]; do
  #设置COMMAND的值为第一个参数
  COMMAND=$1
  # 判断COMMAND的内容
  case $COMMAND in
    #如果COMMAND的内容为-name
    -name)
      #设置DAEMON_NAME的值为紧随COMMAND后边的第二个参数
      DAEMON_NAME=$2
      #设置CONSOLE_OUTPUT_FILE的值为$LOG_DIR/$DAEMON_NAME.out
      CONSOLE_OUTPUT_FILE=$LOG_DIR/$DAEMON_NAME.out
      #剔除原来的前2个参数,把原来的第三个参数变为第一个参数,原来的第四个参数变为第二个参数
      shift 2
      ;;
    #如果COMMAND的内容为-loggc
    -loggc)
      #判断$KAFKA_GC_LOG_OPTS,如果$KAFKA_GC_LOG_OPTS的内容长度为0,则进入if
      if [ -z "$KAFKA_GC_LOG_OPTS" ]; then
        #GC_LOG_ENABLED的值设置为true
        GC_LOG_ENABLED="true"
      fi
      #剔除原来的1个参数,把原来的第二个参数变为第一个参数,原来的第三个参数变为第二个参数
      shift
      ;;
    #如果COMMAND的内容为-daemon
    -daemon)
      #设置DAEMON_MODE的值为true
      DAEMON_MODE="true"
      #剔除原来的1个参数,把原来的第二个参数变为第一个参数,原来的第三个参数变为第二个参数
      shift
      ;;
    *)
      break
      ;;
  esac
done

# GC相关的参数设置
#设置GC_FILE_SUFFIX的值为-gc.log
#设置GC_LOG_FILE_NAME的指为''
GC_FILE_SUFFIX='-gc.log'
GC_LOG_FILE_NAME=''
#如果GC_LOG_ENABLED的值等于true的话
if [ "x$GC_LOG_ENABLED" = "xtrue" ]; then
  #GC_LOG_FILE_NAME的值设置为$DAEMON_NAME追加$GC_FILE_SUFFIX
  GC_LOG_FILE_NAME=$DAEMON_NAME$GC_FILE_SUFFIX

  # 版本号的第一段,对于Java 9之前的版本来说是 "1"。
  # 然后变成'9', '10', ...
  # `java --version`第一行的一些例子。
  # 8 -> java版本 "1.8.0_152"
  # 9.0.4 ->java版本 "9.0.4"
  # 10 ->java版本 "10" 2018-03-20
  # 10.0.1 -> java版本 "10.0.1" 2018-04-17
  # 我们需要匹配到行尾,以防止sed打印不匹配的字符。

  #此处匹配java的主版本号,jdk1.8之前的JAVA_MAJOR_VERSION都是1
  #jdk1.8往后就变成了9,10,11等
  JAVA_MAJOR_VERSION=$("$JAVA" -version 2>&1 | sed -E -n 's/.* version "([0-9]*).*$/\1/p')
  #如果JAVA_MAJOR_VERSION的版本号大于等于9话
  if [[ "$JAVA_MAJOR_VERSION" -ge "9" ]] ; then
    #设置KAFKA_GC_LOG_OPTS的值为 -Xlog:gc*:file=$LOG_DIR/$GC_LOG_FILE_NAME:time,tags:filecount=10,filesize=102400
    KAFKA_GC_LOG_OPTS="-Xlog:gc*:file=$LOG_DIR/$GC_LOG_FILE_NAME:time,tags:filecount=10,filesize=102400"
  else
    #否则设置为-Xloggc:$LOG_DIR/$GC_LOG_FILE_NAME -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintGCTimeStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=10 -XX:GCLogFileSize=100M
    KAFKA_GC_LOG_OPTS="-Xloggc:$LOG_DIR/$GC_LOG_FILE_NAME -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintGCTimeStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=10 -XX:GCLogFileSize=100M"
  fi
fi

# 从classpath中删除可能的冒号前缀(当CLASSPATH为空白时,发生在`CLASSPATH="$CLASSPATH:$file"`这样的行)。
# 右侧使用的语法是原生的Bash字符串操作,更多细节请看下面的内容。
# http://tldp.org/LDP/abs/html/string-manipulation.html, 特别是标题为 "子串去除 "的部分。
#设置CLASSPATH的值为
CLASSPATH=${CLASSPATH#:}

#如果检测到CGYWIN,需要把CLASSPATH的值转化为windowns特有的格式
(( CYGWIN )) && CLASSPATH=$(cygpath --path --mixed "${CLASSPATH}")

#登录模式
#如果DAEMON_MODE是true的话
if [ "x$DAEMON_MODE" = "xtrue" ]; then
  #后台执行程序,并打印到"$CONSOLE_OUTPUT_FILE" 文件中
  nohup "$JAVA" $KAFKA_HEAP_OPTS $KAFKA_JVM_PERFORMANCE_OPTS $KAFKA_GC_LOG_OPTS $KAFKA_JMX_OPTS $KAFKA_LOG4J_OPTS -cp "$CLASSPATH" $KAFKA_OPTS "$@" > "$CONSOLE_OUTPUT_FILE" 2>&1 < /dev/null &
else
  #前台之前,把日志打印到前台
  exec "$JAVA" $KAFKA_HEAP_OPTS $KAFKA_JVM_PERFORMANCE_OPTS $KAFKA_GC_LOG_OPTS $KAFKA_JMX_OPTS $KAFKA_LOG4J_OPTS -cp "$CLASSPATH" $KAFKA_OPTS "$@"
fi

  

 上面对脚本进行了细致的分析,但是最重要的其实我们要分析最后几行代码,

我以bin/kafka-run-class.sh -name kafkaServer -loggc kafka.Kafka -deamon config/server.properties

为例子,最终经过这个kafka-run-class.sh脚本后,最后其实真实运行的脚本

nohup java -Xmx1G -Xms1G -server -XX:+UseG1GC -XX:MaxGCPauseMillis=20 -XX:InitiatingHeapOccupancyPercent=35 -XX:+ExplicitGCInvokesConcurrent -XX:MaxInlineLevel=15 
-Djava.awt.headless=true -Xloggc:/home/hadoop/software/kafka_2.13-2.5.1/bin/../logs/kafkaServer-gc.log 
-verbose:gc -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintGCTimeStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=10 -XX:GCLogFileSize=100M 
-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.authenticate=false  -Dcom.sun.management.jmxremote.ssl=false  
-Dkafka.logs.dir=/home/hadoop/software/kafka_2.13-2.5.1/bin/../logs 
-Dlog4j.configuration=file:./../config/log4j.properties 
-cp /home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/activation-1.1.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/aopalliance-repackaged-2.5.0.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/argparse4j-0.7.0.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/audience-annotations-0.5.0.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/commons-cli-1.4.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/commons-lang3-3.8.1.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/connect-api-2.5.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/connect-basic-auth-extension-2.5.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/connect-file-2.5.1.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/connect-json-2.5.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/connect-mirror-2.5.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/connect-mirror-client-2.5.1.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/connect-runtime-2.5.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/connect-transforms-2.5.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/hk2-api-2.5.0.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/hk2-locator-2.5.0.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/hk2-utils-2.5.0.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jackson-annotations-2.10.2.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jackson-core-2.10.2.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jackson-databind-2.10.2.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jackson-dataformat-csv-2.10.2.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jackson-datatype-jdk8-2.10.2.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jackson-jaxrs-base-2.10.2.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jackson-jaxrs-json-provider-2.10.2.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jackson-module-jaxb-annotations-2.10.2.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jackson-module-paranamer-2.10.2.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jackson-module-scala_2.13-2.10.2.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jakarta.activation-api-1.2.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jakarta.annotation-api-1.3.4.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jakarta.inject-2.5.0.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jakarta.ws.rs-api-2.1.5.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jakarta.xml.bind-api-2.3.2.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/javassist-3.22.0-CR2.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/javassist-3.26.0-GA.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/javax.servlet-api-3.1.0.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/javax.ws.rs-api-2.1.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jaxb-api-2.3.0.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jersey-client-2.28.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jersey-common-2.28.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jersey-container-servlet-2.28.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jersey-container-servlet-core-2.28.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jersey-hk2-2.28.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jersey-media-jaxb-2.28.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jersey-server-2.28.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jetty-client-9.4.24.v20191120.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jetty-continuation-9.4.24.v20191120.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jetty-http-9.4.24.v20191120.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jetty-io-9.4.24.v20191120.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jetty-security-9.4.24.v20191120.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jetty-server-9.4.24.v20191120.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jetty-servlet-9.4.24.v20191120.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jetty-servlets-9.4.24.v20191120.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jetty-util-9.4.24.v20191120.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/jopt-simple-5.0.4.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/kafka_2.13-2.5.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/kafka_2.13-2.5.1-sources.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/kafka-clients-2.5.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/kafka-log4j-appender-2.5.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/kafka-streams-2.5.1.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/kafka-streams-examples-2.5.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/kafka-streams-scala_2.13-2.5.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/kafka-streams-test-utils-2.5.1.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/kafka-tools-2.5.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/log4j-1.2.17.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/lz4-java-1.7.1.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/maven-artifact-3.6.3.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/metrics-core-2.2.0.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/netty-buffer-4.1.50.Final.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/netty-codec-4.1.50.Final.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/netty-common-4.1.50.Final.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/netty-handler-4.1.50.Final.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/netty-resolver-4.1.50.Final.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/netty-transport-4.1.50.Final.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/netty-transport-native-epoll-4.1.50.Final.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/netty-transport-native-unix-common-4.1.50.Final.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/osgi-resource-locator-1.0.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/paranamer-2.8.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/plexus-utils-3.2.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/reflections-0.9.12.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/rocksdbjni-5.18.3.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/scala-collection-compat_2.13-2.1.3.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/scala-java8-compat_2.13-0.9.0.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/scala-library-2.13.1.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/scala-logging_2.13-3.9.2.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/scala-reflect-2.13.1.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/slf4j-api-1.7.30.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/slf4j-log4j12-1.7.30.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/snappy-java-1.1.7.3.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/validation-api-2.0.1.Final.jar:
/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/zookeeper-3.5.8.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/zookeeper-jute-3.5.8.jar:/home/hadoop/software/kafka_2.13-2.5.1/bin/../libs/zstd-jni-1.4.4-7.jar  
"kafka.Kafka ../conf/server.properties" > "/home/hadoop/software/kafka_2.13-2.5.1/bin/../logs/kafkaServer.out" 2>&1 < /dev/null &

 最终发现执行的是kafka.Kafka类,传入的参数是 ../conf/server.properties,然后把日志输出到/home/hadoop/software/kafka_2.13-2.4.1/logs/kafkaServer.out文件中。

后续的文章中我们将会继续对kafka.Kafka的执行流程进行分析,本文先暂时分析shell脚本部分。

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