CODEWITHSUNDEEP
bashcpusnmpsnmp-trap
Miguel7799
Miguel7799

Reputation: 33

Limit execution number of bash script triggered by snmp trap

When a trap arrives to my system I execute a bash script automatically. Problem is sometimes a lot of traps arrive simultaneously making a lot executions of the script and generating system cpu pikes Do you know how could avoid that situation? I thought some mechanism that only executes a determined scripts and the rest waiting like a FIFO queue but I don’t know if that is possible

Thanks

Upvotes: 0

Views: 60

Answers (1)

Ljm Dullaart
Ljm Dullaart

Reputation: 4989

It is a possible solution that would prevent multiple executions of a script at the same time.

First, you would define a fifo:

mkfifo /some/directory/fifo

Then, you would create a script that reads the fifo:

#!/bin/bash
tail -f /some/directory/fifo | while read line ; do
    process "$line"
done

When a trap arrives, you execute the following script:

#!/bin/bash
echo "something from the trap" > /some/directory/fifo

The script that posts the message on the fifo is lightweight and would therefore produce less of a spike than the whole processing. The processing is now serialized, so only one processing script runs at a given time. You can also nice the processing to give it even less impact.

The echo should be atomic enough to prevent interleaved lines most of the time.

Another option is to use a lock to prevent multiple copies to execute at the same time. That would look like:

#!/bin/bash
me=$$
echo $me>>lockfile
lockedby=$(head -1 lockfile)
while [ "$me" != "$lockedby" ] ; do
    sleep 1
    echo $me>>lockfile
    lockedby=$(head -1 lockfile)
done

process the trap

rm -f lockfile

Upvotes: 1

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