A Dockerized Splunk app to monitor your Internet connection
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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.

Quickest Installation

curl -s https://raw.githubusercontent.com/dmuth/splunk-network-health-check/master/bin/run.sh | bash

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 \
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
  • (Google's DNS Resolver)
  • (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" - Specify hosts to ping
  • -e TZ=EST5EDT - Specify the timezone of the container (UTC by default)
  • -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>.


The Easy Way

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

  • bin/attach.sh - Spin up a bash shell in a running instance
  • bin/dev.sh [ target [ target [ ... ] ] ] - Build an image from the Dockerfile, start it up, and run an interactive bash shell.
    • Any targets that are specified are pinged in addition to the defaults
    • When exited, the container will end.
    • Network data will persist in splunk-data/ off the project root.
    • Set the SPLUNK_PORT environment variable to listen on a port other than 8000 on the Docker host
  • bin/kill.sh - Stop the container and kill it.
  • bin/logs.sh - Tail the logs of the currently running container
  • bin/push.sh - Push the image up to Docker Hub
  • bin/run.sh [ target [ target [ ... ] ] ] - Pull the laetst copy of the image and create a container named splunk-network-health-check.
    • Any targets that are specified are pinged in addition to the defaults
    • Network data will persist in splunk-data/ off the project root.
    • This container will be started with --restart unless-stopped, so if Docker is restarted, so will this container.
    • Set the SPLUNK_PORT environment variable to listen on a port other than 8000 on the Docker host

The overall process for running the above should be:

  • bin/dev.sh
  • If you edited something in the app, look in local/ and move changed files to default/.
  • Run bin/dev.sh again so the changes are added to the Docker image and make sure the container works to your satisfaction.
  • Run bin/push.sh to upload the changes to Docker Hub
  • Run bin/run.sh to run the properly named version (it won't be pulled unless it was deleted)

The Medium Way (with Docker Compose)

  • docker-compose build
  • docker-compose up -d
  • You can view progress with docker-compose logs

The Hard Way

Here's how to do development:

docker build . -t splunk-network-health-check && \
	docker run --rm --name splunk-network-health-check \
	-e TZ=EST5EDT -ti -p 8000:8000 \
	-v $(pwd)/splunk-data:/opt/splunk/var/lib/splunk/defaultdb \
	-v $(pwd):/mnt \
	--privileged \
docker tag splunk-network-health-check dmuth1/splunk-network-health-check
docker push dmuth1/splunk-network-health-check

--privileged is specified so that /opt/splunk/etc/apps/Network-Monitor/bin/icmp_loop.sh can be run inside of the container for testing.

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.

Additional Reading

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

Questions, comments, abuse, and offers of employment