Erik Hansen erikhansen

Opening and closing an SSH tunnel in a shell script the smart way

I recently had the following problem:

From an unattended shell script (called by Jenkins), run a command-line tool that accesses the MySQL database on another host.
That tool doesn't know that the database is on another host, plus the MySQL port on that host is firewalled and not accessible from other machines.

We didn't want to open the MySQL port to the network, but it's possible to SSH from the Jenkins machine to the MySQL machine. So, basically you would do something like

ssh -L 3306:localhost:3306 remotehost

	# clear the entire cache
	varnishadm "ban req.url ~ /"

	# monitor varnish log with multiple patterns
	varnishlog \| grep 'eqURL\\|Age:\\|VCL_call\\|TTL\\|Expires:\\|Cache-Control:'

	# Use a query with varnishlog to watch requests from a specific IP
	varnishlog -q 'ReqHeader:X-User-IP eq "1.2.3.4" or BereqHeader:X-User-IP eq "1.2.3.4"'

	# Monitor PURGE requests hitting Varnish

	#!/bin/bash
	set -euo pipefail

	FRONT_URL="${FRONT_URL:-https://app.exampleproject.test/}"

	echo "==> [$(date +%H:%M:%S)] waiting on readiness"
	ELAPSED_SECONDS=0
	while : ; do
	ELAPSED_SECONDS=$(echo ${ELAPSED_SECONDS}+2 \| bc)
	RESPONSE_CODE=$(curl -sI "${FRONT_URL}" 2>/dev/null \| head -n1 \| awk '{print $2}')