Great idea with using mysqladmin to check the database status!

One small addition – you might probably want to add a lock file to this script, so that it can only be executed once at a time, and have it exit if the lock file already exists, otherwise you get a lot of problems if for some reason the scripts doesn’t exit, due to some socket issues, and cron executes a new copy of script every minute. :)

The problem with your initial script is that you have two separate SSH commands that create your two tunnels. That allows them to fail independently, so you can’t use one to infer the status of the other.

If you look at the original script from Brandon’s site, it forwards two ports within the same tunnel (2 -L options). Because they both are part of the same SSH, they’ll either both be up or both be down, so I can use the SSH port-forward to check on the MySQL port-forward. This way, you don’t need to create additional MySQL users.

Hope this simplifies things a bit.

The modifications now use the actual database on the remove server to prove you still have a good connection.

In order to use this, you have to create a new user on the remote db. That user should be named ’status_test’. Do NOT give the user any privileges.

> grant usage on *.* to status_test@'%' identified by 'my_bogus_password';

Now, this user can do nothing except connect to the db and check it’s status.

Here is the script :

#!/bin/bash
# Creates an SSH tunnel to allow local access to a remote mysql server.
# Call as follows : ./tunnel_setup.bsh user_name_here server_address_here remote_port_here local_port_here
# Requires ssh keys for the user running the script or the user that CRON is setup under

echo "*******************************"
echo `date`
user=$1
server=$2
remote_port=$3
local_port=$4
createTunnel() {
  /usr/bin/ssh -T -f -N -L${local_port}:127.0.0.1:${remote_port} ${user}@${server}
  if [[ $? -eq 0 ]]; then
    echo ${local_port} Tunnel to ${server} created successfully
  else
    echo An error occurred creating tunnel ${local_port} to ${server} RC was $?
  fi

}
## Run the mysqladmin status command remotely.  If it returns non-zero, then create a new connection
echo Verifying Database Connection
echo "----------------------------------"
/opt/local/bin/mysqladmin -u status_test -p my_bogus_password -h127.0.0.1 -P${local_port} status
if [[ $? -ne 0 ]]; then
  echo Creating new tunnel connection
  createTunnel
else
  echo Tunnel already exists
fi
echo "*******************************"

Then, create a cron that starts this script every X minutes. It will run the the mysqladmin status command. If the connection does not exist, the script will automatically recreate the tunnel.

Hope this helps everyone.

#!/bin/bash
# Creates an SSH tunnel to allow local access to a remote mysql server.

echo "*******************************"
echo `date`
user=$1
server=$2
remote_port=$3
local_port=$4
createTunnel() {
  /usr/bin/ssh -T -f -N -L${local_port}:127.0.0.1:${remote_port} ${user}@${server}
  if [[ $? -eq 0 ]]; then
    echo ${local_port} Tunnel to ${server} created successfully
  else
    echo An error occurred creating tunnel ${local_port} to ${server} RC was $?
  fi

  /usr/bin/ssh -T -f -N -L19922:127.0.0.1:22 ${user}@${server}
  if [[ $? -eq 0 ]]; then
    echo L19922 Tunnel to ${server} created successfully
  else
    echo An error occurred creating tunnel L19922 to ${server} RC was $?
  fi
}
## Run the 'ls' command remotely.  If it returns non-zero, then create a new connection
echo Remote Directory Listing Verifies Connection
echo "----------------------------------"
/usr/bin/ssh -p 19922 ${user}@localhost ls
if [[ $? -ne 0 ]]; then
  echo Creating new tunnel connection
  createTunnel
else
  echo Tunnel already exists
fi
echo "*******************************"

You can then cron this by calling it as follows :

./sshsetup.sh user_name_here server_address_here remote_port_here local_port_here

Thank you!