I want to make a conditional cronjob - bash

Question

I have a cron job that runs every hour. It accesses an xml feed. If the xml feed is unvailable (which seems to happen once a day or so) it creates a "failure" file. This "failure" file has some metadata in it and is erased at the next hour when the script runs again and the XML feed works again.
What I want is to make a 2nd cron job that runs a few minutes after the first one, looks into the directory for a "failure" file and, if it's there, retries the 1st cron job.
I know how to set up cron jobs, I just don't know how to make scripting conditional like that. Am I going about this in entirely the wrong way?

Answer 1

Possibly. Maybe what you'd be better off doing is having the original script sleep and retry a (limited) number of times.
Sleep is a shell command and shells support looping so it could look something like:
for ((retry=0;retry<12;retry++)); do
try the thing
if [[ -e my_xlm_file ]]; then break; fi
sleep 300
# five minutes later...
done

Answer 2

As the command to run, try:
/bin/bash -c 'test -e failurefile && retrycommand -someflag -etc'
It runs retrycommand if failurefile exists

Answer 3

Why not have your set your script touch a status file when it has successfully completed. Have it run every 5 minutes, and have the first check of the script be to see if the status file is less then 60 minutes old, and if it is young, then quit, if it is old, then fetch.

Answer 4

I agree with MarkusQ that you should retry in the original job instead of creating another job to watch the first job.
Take a look at this tool to make retrying easier: https://github.com/kadwanev/retry
You can just wrap the original cron in a retry very easily and the final existence of the failure file would indicate if it failed even after the retries.

Answer 5

If somebody will need a bash script to ping an endpoint (for example, run scheduled API tasks via cron), retry it, if the response status was bad, then:
#!/bin/bash
echo "Start pinch.sh script.";
# run 5 times
for ((i=1;i<=5;i++))
do
# run curl to do a POST request to https://www.google.com
# silently flush all its output
# get the response status code as a bash variable
http_response=$(curl -o /dev/null -s -w "%{response_code}" https://www.google.com);
# check for the expected code
if [ $http_response != "200" ]
then
# process fail
echo "The pinch is Failed. Sleeping for 5 minutes."
# wait for 300 seconds, then start another iteration
sleep 300
else
# exit from the cycle
echo "The pinch is OK. Finishing."
break;
fi
done
exit 0