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Splunk Network Health Check

This app will monitor health of your Internet connection by pinging Google (and a few other hosts) and creating nice graphs. It is based on Splunk's official Dockerfile.

This app uses Splunk Lab, an open-source app I built to effortlessly run Splunk in a Docker container.

Quickest Installation

bash <(curl -s https://raw.githubusercontent.com/dmuth/splunk-network-health-check/master/go.sh)

Follow the on-screen instructions for configuration Splunk Network Health Check and you should be running in no time!

Less Quick Installation

Maybe you don't want to pipe some random script on the Internet into your shell, that's cool. Here are the Docker commands to run it and view the output:

docker run --name splunk-network-health-check -d --rm -p 8000:8000 \
	-v $(pwd)/splunk-data:/opt/splunk/var/lib/splunk/defaultdb \
	dmuth1/splunk-network-health-check
docker logs -f splunk-network-health-check

No matter how you install it, you can then go to http://localhost:8000/ and get graphs like these:

Data will be persisted in the splunk-data/ directory between container runs.

Default Targets

These are the default targets, but can be overridden with -e TARGETS=...:

  • google.com
  • 8.8.8.8 (Google's DNS Resolver)
  • 1.1.1.1 (CloudFlare's DNS Resolver)

I picked Google because it's a fairly well connceted site, and I picked the second two IPs so that if DNS is flaky, it won't impact either those, and those two IP addresses are owned by completely different entities.

More detailed options

  • --restart unless-stopped - Causes this container to restart if killed Docker is restarted. This is highly recommended.
  • -e "TARGETS=google.com,cnn.com,8.8.8.8,1.1.1.1" - Specify hosts to ping
  • -e ETC_HOSTS=hosts.txt - Specify a hosts file to append to /etc/hosts. Useful for when you want to give names to local devices to ping, such as cameras.
  • -e SPLUNK_PASSWORD=password - Set a non-default password. You WILL do this if you run this in a production environment.

What's Splunk?

Splunk is an amazing app that lets you monitor your logfiles and perform analytics on them. You can monitor other kinds of data, such as the output of the ping command, which is what this app does. A free copy of Splunk Enterprise can be downloaded at Splunk.com and is downloaded in the Dockerfile.

How does it work?

At its core, this app uses a script called ping.sh. This script runs a hacked version of ping to ping all targets and report on status (packets sent/packets received) every 10 seconds.

"Oh god, why did you hack ping?"

A few reasons:

  • fping sometimes returned negative RTTs, so that's not a good sign.
  • Running ping -c 10 multiple times in parallel caused N processes to be spawned every 10 seconds.
    • The performance impact wasn't terrible, but I wanted this app to be as friendly to the CPU as I could make it.
  • fping also didn't periodically report on the status of hosts that I was pinging.
  • fping also got a little weird if there was no Internet connectivity, as DNS would not resolve
    • You'd think this wouldn't be a problem when pinging IPs, but sadly, it was.

Taking all of these into account, it seemed to make the most sense to hack ping to print its status every 10 seconds and use that as the basis of the uptime graph in Splunk.

Security Concerns

Please set a password if you are deploying this on anything other than a personal device. That is done with -e SPLUNK_PASSWORD=<password>.

Development

The Easy Way

There are some helper scripts in bin/ which make the process less painful:

  • bin/dev.sh - Build an image from the Dockerfile, start it, and spawn a bash` shell
    • This is actually a wrapper for go.sh, so just follow the on-screen prompts.
    • When exited, the container will end.
  • bin/kill.sh - Stop the container and kill it.
  • bin/logs.sh - Tail the logs of the currently running container
  • bin/clean.sh - Remove splunk-data/ directory. This will remove all indexed data (pings and latency) from Splunk!
  • bin/push.sh - Push the image up to Docker Hub

Known Bugs

For reasons unclear to me, if you set up a VPN connection, this completely breaks ping in all Docker containers. Even docker run alpine ping google.com doesn't work.

The workaround is to simply restart Docker. If you started your container with --restart unless-stopped, it will start up automatically. I am unclear on if this is something that can be fixed.

FAQ

Why does the Splunk web interface run with HTTPS enabled?

Because one day, someone somewhere will install this app on a machine which faces the public Internet, and passwords will be sent over the clear. In fact, over a long enough time, the odds of this happening approach 1.

THAT is why I use HTTPS/SSL. And why you should too on your apps.

Licensing

Splunk has its own license. Please abide by it.

Credits

Additional Reading

  • Splunk Lab - A more generic Dockerized version of Splunk which I developed

Questions, comments, abuse, and offers of employment

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A Dockerized Splunk app to monitor your Internet connection

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