dis-web-mount-check

Once a minute, checks for the expected apps in the web-mount boxes and reports any change of state to slack.

Getting started

• Run make debug to run application on http://localhost:24310
• Run make help to see full list of make targets

Dependencies

• No further dependencies other than those defined in go.mod

Configuration

Environment variable	Default	Description
NOMAD_ENDPOINT	http://localhost:4646	The endpoint of the Nomad API
NOMAD_TOKEN		The ACL token used to authorise HTTP requests
NOMAD_CA_CERT		The path to the CA cert file
NOMAD_TLS_SKIP_VERIFY	false	When using TLS to nomad, skip checking certs
BIND_ADDR	:24310	The listen address to bind to
HEALTHCHECK_INTERVAL	10s	The time between calling healthcheck endpoints for check subsystems
HEALTHCHECK_CRITICAL_TIMEOUT	60s	The time taken for the health changes from warning state to critical due to subsystem check failures
GRACEFUL_SHUTDOWN_TIMEOUT	5s	Time time to wait when gracefully shutting down before closing
APPS_TO_CHECK	[]string{"app1", "app2", etc }	List of apps expected on each web-mount box
SLACK_ENABLED	false	Whether to send a slack message on failed checks
SLACK_TEST	false	Used to force alerts at app startup to confirm slack comm's working
SLACK_API_TOKEN	"get from env"	A valid slack api token (suppressed from logs)
SLACK_USER_NAME	"Spread Check"	User name to be used for slack messages
SLACK_ALARM_CHANNEL	"#sandbox-alarm"	Slack channel to send alarm messages to
SLACK_ALARM_EMOJI	":x:"	Emoji to use for alarm messages, a red cross
SLACK_OK_EMOJI	":white_check_mark:"	Emoji to use for alarm messages, a white tick in a green box

A valid Slack token with chat:write and chat:write.customize permissions is required if Slack notification is to be enabled.

Healthcheck

The /health endpoint returns the current status of the service. Dependent services are health checked on an interval defined by the HEALTHCHECK_INTERVAL environment variable.

On a development machine, a request to the health check endpoint can be made by:

curl localhost:24300/health

How to test the dis-web-mount-check in the environment (outside of concourse)

You will need to get the secrets: NOMAD_TOKEN and SLACK_API_TOKEN from vault.

Set up your AWS access to Sandbox in the usual way.

Make any changes you want to the app for testing ...

If this app is already running via nomad and concourse, stop it in nomad and pause its pipeline in concourse.

Then run:

make buildamd64
make pushamd64

Then log into web 3 box in sandbox:

dp ssh sandbox web 3

Then:

cd test

Then do:

export NOMAD_TLS_SKIP_VERIFY=true
export NOMAD_ENDPOINT=https://localhost:4646
export SLACK_ENABLED=true

Then run the following two lines with a SPACE at the start of the line to not save the secret in bash history:

 export NOMAD_TOKEN=<from vault for the app>
 export SLACK_API_TOKEN=<from vault for the app>

Then run the app with:

./dis-web-mount-check

Remember to use CTRL-C to stop the application after your tests.

You will also have to stop the application before doing any make pushamd64 of any new builds to test.

If this app was already running via nomad and concourse, unpause its pipeline in concourse and start it in nomad.

Contributing

See CONTRIBUTING for details.

License

Copyright © 2025, Office for National Statistics (https://www.ons.gov.uk)

Released under MIT license, see LICENSE for details.