java - 通过 ProcessBuilder 运行时 Shell 脚本挂起

Question

我有一个 Java 程序，我正在其中触发 shell 脚本。Java 代码示例是:

 ProcessBuilder pb = new ProcessBuilder(cmdList);
        p = pb.start();
        p.waitFor();

其中 cmdList 包含执行 shell 所需的所有必要输入参数。该 shell 脚本内部有一个 for 循环，并在该循环中执行一些数据库脚本，并在文件中打印结果信息和错误日志。

下面是示例 shell 脚本代码:

#!/bin/bash

导出 PATH=/apps/PostgresPlus/as9.6/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

设置-eE

#################################################### ＃＃ 开始

TIME_ELAPSED=""TIME_ELAPSED_IN_HOURS=""SCRIPT_START_TIME_FORMATTED=日期 '+%F %T'SCRIPT_START_TIME_IN_SEC=日期 +%s

PROCESS_LOG_BASE_PATH="/data/logs/purge_log/"PROCESS_LOG="$PROCESS_LOG_BASE_PATH/purge.log"

陷阱'err=$?; logError 2>&1“清除期间发生错误。在 $LINENO: ${BASH_COMMAND} 行处退出，状态为 $err。请检查日志以获取更多信息。” >>$PROCESS_LOG'错误trap 'logError 2>&1“清除期间发生错误。由于收到外部中断而退出 shell 脚本执行。请检查日志以获取更多信息。” >>$PROCESS_LOG;陷阱 ERR' INT

横幅(){ echo “+------------------------------------------------------------ --------------------------------------------------+ ” printf "|tput 粗体[ %-40s tput sgr0|\n""$1 ] tput setaf 2 $2" echo “+------------------------------------------------------------ --------------------------------------------------+ ”}

日志错误(){ printf "[ProcessId- $$] [日期 "+%Y-%m-%d %H:%M:%S"] tput setaf 1 tput 粗体 [错误] tput setaf 1 %-40s tput sgr0\n""$@"}

日志信息(){ printf "[ProcessId- $$] [date "+%Y-%m-%d %H:%M:%S"] tput setaf 6 粗体 [INFO ] %-40s tput sgr0\n""$@"}日志警告(){ printf "[ProcessId- $$] [date "+%Y-%m-%d %H:%M:%S"] tput setaf 3 tput 粗体 [警告] %-40s tput sgr0\n""$@"}

logHint(){ printf "[ProcessId- $$] [date "+%Y-%m-%d %H:%M:%S"] tput setaf 5 tput satm %-40s tput sgr0\n""$@"}

主函数(){
横幅“$SCRIPT_START_TIME_FORMATTED”“已开始处理”|三通-a $PROCESS_LOG logInfo "在 $SCRIPT_START_TIME_FORMATTED 开始执行"|三通-a $PROCESS_LOG

set PGPASSWORD=$DB_PASSWORD
export PGPASSWORD=$DB_PASSWORD

# Call DB function for audit and category wise data purging, population of schema names
SCHEMA_NAMES_RESULT=$(psql -h $HOST_NAME -d $DB_NAME -U $DB_USER -p $DB_PORT -At -c "SELECT $COMMON_SCHEMA_NAME.purge_audit_and_populate_schema_names('$COMMON_SCHEMA_NAME', $PURGE_DATA_INTERVAL_IN_DAYS,'$SCHEMA_NAMES',$NUM_TOP_CONTRIBUTING_TENANTS)")

SCHEMA_NAMES_RESULT=$(echo "$SCHEMA_NAMES_RESULT" | sed 's/{//g; s/}//g; s/"//g' )

SCHEMA_NAMES=$(echo $SCHEMA_NAMES_RESULT | rev | cut -d"," -f2-  | rev)

#Convert comma separated string of tenants to array
SCHEMA_NAMES=($(echo "$SCHEMA_NAMES" | tr ',' '\n'))

# loop for multi schema
for element in "${SCHEMA_NAMES[@]}"
do
    logInfo "Effective tenant - $element, Script start time - $SCRIPT_START_TIME_FORMATTED" | tee -a $PROCESS_LOG

    # PGSQL call to DB function to execute purging

    logInfo "Time elapsed since script execution started - $TIME_ELAPSED" | tee -a $PROCESS_LOG
done

#logInfo "Purge completed!" | tee -a $PROCESS_LOG
logInfo "Purge execution completed successfully at `date '+%F %T'`" | tee -a $PROCESS_LOG
exit 0

}

mkdir -p $PROCESS_LOG_BASE_PATH主要“$@”

#################################################### ＃＃ 结尾

以下是我对该程序的观察。

1. 直接在 putty 上运行 shell 脚本时，它可以正确执行，没有任何错误。

2. 当通过上述 java 程序触发 shell 脚本时，我观察到以下行为。

   a.它在 for 循环中进行一定的迭代后挂起。

   b.随着我减少 shell 脚本中的日志条目数量，迭代(for 循环)数量不断增加。

   c.当我删除所有信息日志并继续仅打印错误日志时，它成功完成。

有人可以帮助确定此行为背后的原因吗？

目前，我检查了 for 循环中的迭代次数，但是当我开始接收多个错误日志时，该问题可能随时发生。

问候

库沙格拉

Answer 1

您必须使用流程流或映射 err和 out文件，以便 native 缓冲区不会填满。如果您创建线程来使用每个流，效果会更好。 hacky 单线程版本是这样的:

ProcessBuilder pb = new ProcessBuilder(cmdList);
p = pb.start();
try (InputStream in = p.getInputStream();
            InputStream err = p.getErrorStream();
            OutputStream closeOnly = p.getOutputStream()) {
    while (p.isAlive()) {                
        long skipped = 0L;
        try {
            skipped = in.skip(in.available()) 
                     + err.skip(err.available());
        } catch (IOException jdk8155808) {
           byte[] b = new byte[2048];
           int read = in.read(b, 0, Math.min(b.length, in.available());
           if (read > 0) {
               skipped += read;
           }

           read = err.read(b, 0, Math.min(b.length, err.available());
           if (read > 0) {
               skipped += read;
           }
        }

        if(skipped == 0L) {
           p.waitFor(5L, TimeUnit.MILLISECONDS);
        }
    }
} finally {
   p.destroy();
}

线程方式的工作原理如下:

public void foo() {
    class DevNull implements Runnable {
        
        private final InputStream is;
        DevNull(final InputStream is) {
            is = Objects.requireNonNull(is);
        }
        
        public void run() {
            byte[] b = new byte[64];
            try {
                while (is.read(b) >= 0);
            } catch(IOException ignore) {
            }
        }
    }

    ExecutorService e = Executors.newCachedThreadPool();
    ProcessBuilder pb = new ProcessBuilder(cmdList);
    Process p = pb.start();
    try (InputStream in = p.getInputStream();
            InputStream err = p.getErrorStream();
            OutputStream closeOnly = p.getOutputStream()) {
        e.execute(new DevNull(in));
        e.execute(new DevNull(err));
        p.waitFor();
    } finally {
        p.destroy();
        e.shutdown();
    }
}