How to check whether MongoDB is running from a shell script? - mongodb

Question

Here is the shell script that I am using to check MongoDB's status. checkmongo.sh through a cron job every two minutes.
#!/bin/bash
echo "shell script called"
if pgrep mongo > /dev/null
then
echo "MongoDB Running"
else
echo "Stopped .. starting MongoDB"
sudo service mongodb start
fi
Cron job is as follows :
*/2 * * * * /etc/init.d/checkmongo.sh> /etc/init.d/cronjob.log 2>&1
No matter MongoDb is running or not cronjob.log always has the content as "MongoDB Running". What am I doing wrong ? Please help. Thanks

Answer 1

Vinay,
A couple of things:
1 -- Do you want to check if MongoDB is running or do you want to check if it is responding to queries?
Your current design will only tell if there is a process whose name includes the word "mongo" running.
I would design a "canary query" that you can run with the mongo shell and use the result to determine if MongoDB is running or not. So in the rare case where MongoDB daemon might be running but not responsive you could be alerted.
2 --Your process is checking for the word "mongo", the executable for the mongoDB database is "mongod".
Your script is called "checkmongo". Every time you script runs there is a "checkmongo" process running and the if conditions will always be true. The script is detecting itself instead of the mongod process.
Change your search condition to mongod
if pgrep mongod > /dev/null

Answer 2

#!/bin/bash
mongod_status=`service mongod status`
echo "${mongod_status}"
if [[ "${mongod_status}" == *"start/running"* ]]
then
echo "MongoDB is already running."
else
sudo service mongod start
echo "Start MongoDB."
fi