Bash linux 强制多个实例等待运行 sqlplus 命令完成

Question

我有一个 bash 脚本，可以同时允许多个运行实例。但是，有一个到 Oracle 数据库的 sqlplus 连接来检索值。如果多个 bash 脚本实例同时获取此值，它们可能会检索到相同的值，因为当第一个实例仍在处理时，第二个实例已经在验证 'old data'.

我只能想到两个选项，一个是用PIDFILE锁定函数。缺点是如果用户在删除 pid 文件之前中止操作，则会导致问题。另一个是基于声明用 ps -ef | grep 'scriptname' | wc -l 计数的最大进程来锁定整个脚本。但这会锁定整个脚本，而不仅仅是数据库部分。

那么还有其他选择吗？这个与数据库的 sqlplus 连接是否有可能以某种方式捕获，以便我可以在其中一个实例执行此函数时暂停多个运行实例？

Answer 1

您可以在 tmp 文件中使用唯一值（/tmp/pidfile 对于本例），并在脚本中止或完成时重置它。

更新：这看起来很可靠，请参阅底部的测试。

#!/bin/bash


bashpid="$$"                     # Records PID of script.  Unused so far
pidfile=/tmp/pidfile             # pidfile var
pidlimit=2                       # pidlimit

cleanup () {                     # cleanup operations
        exit
    }

pidreset () {                    # trap operations (if reqd)
        pkill -a -P "$bashpid"
        kill -9 0
    }

trap "pidreset" SIGINT           # trap (if reqd)


countpid () {                    # This is the true PID count, only called
                                 # Once allowed in the database block
                                 # This includes self instance

     ps aux | grep "$(basename [=10=])" | grep -v grep > $pidfile

}

countloop () {                   # This counts PID while waiting for a spot
                                 # (-1 decrement since self is included but 
                                 # not yet granted access to database block)
    echo "(( ("$(ps aux | grep "$(basename [=10=])" | grep -v grep | wc -l )") - 1))" | bc > $pidfile

}
databasecall () {                # The database script calls

    touch $pidfile
    pidcount="$(cat $pidfile | wc -l)"
    until [[ "$pidcount" -le "$pidlimit" ]]; do
        echo "too many processes"
        countloop 
        pidcount="$(cat $pidfile | wc -l)"
        sleep 5
    done

    #   ================  Start of Database access Code ================
    #   Go ahead and do database stuff
    #   Write this script into the pidfile incrementing its count also

    countpid 
    pidcount="$(cat $pidfile | wc -l)"
    echo "We're in"
    echo "Scriptcount: $pidcount (Including this one)"
    sleep 5
    cleanup
    # return / whatever
    #   ================  End of Database access Code ================

}



echo "Main script block"          # Main script outside of Database block
sleep .1


databasecall                      # Call database function


cleanup                           # Call to housekeeping

测试

它工作正常但稳定在运行比 pidlimit 多一个，虽然我不确定这是在哪里发生的或者它是否是我的测试场景。

bash>echo "imrunning & sleep .5 ; imrunning & sleep .5 ; imrunning & sleep .5 ; imrunning & sleep .5 ; imrunning" > /tmp/initrunning ; chmod +x /tmp/initrunning
bash>/tmp/./initrunning 
Main script block
We're in
Scriptcount:        1 (Including this one)
Main script block
We're in
Scriptcount:        2 (Including this one)
Main script block
too many processes
Main script block
too many processes
Main script block
too many processes
We're in
Scriptcount:        3 (Including this one)
We're in
Scriptcount:        3 (Including this one)
We're in
Scriptcount:        3 (Including this one)
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Bash linux 强制多个实例等待运行 sqlplus 命令完成

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Bash linux 强制多个实例等待 运行 sqlplus 命令完成

Bash linux force multiple instances to wait for running sqlplus command to finish

linux

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Bash linux 强制多个实例等待运行 sqlplus 命令完成