How to monitor external resources with proxy requests and entities
What are Sensu proxy requests and entities?
Check definitions that include the
proxy_entity_name attribute will have their
results reported under this proxy entity ID instead of the agent’s entity that
emitted the result. In comparison, check definitions including the
proxy_requests attribute will trigger a check request for each entity
matched, regardless of whether that entity is a Sensu agent’s entity or a proxy
entity, and the result of each check request will be reported under the matched
entity and not the agent’s entity that emitted the result.
Why use proxy requests and entities?
Sensu proxy requests and entities allow Sensu to monitor external resources on systems or devices where a Sensu agent cannot be installed, like a network switch or a website.
Using a proxy entity to monitor a website
The purpose of this guide is to help you monitor an external resource, more specifically a website, by configuring a check with a proxy entity ID so an entity representing the website is created and the status of this website is reported under this entity and not the agent running the actual check. This guide requires a Sensu backend and a Sensu agent.
Installing a script
We will use a bash script, named
http_check.sh, to perform an HTTP
request using curl.
sudo curl https://raw.githubusercontent.com/sensu/sensu-go/60e6a68aecb0c8e0c2dc51714e08462eb81b4413/examples/checks/http_check.sh \ -o /usr/local/bin/http_check.sh && \ sudo chmod +x /usr/local/bin/http_check.sh
While this command is appropriate when running a few agents, you should consider using a configuration management tool or use Sensu assets to provide runtime dependencies to checks on bigger environments.
Creating the check
Now that our script is installed, the second step is to create a check named
check-sensuapp, which runs the command
http_check.sh https://sensu.io, at an
interval of 60 seconds, for all entities subscribed to the
subscription, using the
sensu.io proxy entity ID.
sensuctl check create check-sensuapp \ --command 'http_check.sh https://sensu.io' \ --interval 60 \ --subscriptions sensu-app \ --proxy-entity-name sensu.io
Adding the subscription
To run the the check, you’ll need an agent with the subscription
After installing an agent, open
and add the
sensu-app subscription so the subscription configuration looks like:
subscriptions: - "sensu-app"
Then restart the agent.
sudo systemctl restart sensu-agent
NOTE: For CentOS 6 and RHEL 6, use
sudo /etc/init.d/sensu-agent restart.
Validating the check
You can verify the proper behavior of this check against the proxy entity,
sensu.io, by using sensuctl. It might take a few moments, once the
check is created, for the check to be scheduled on the agent and the result
sent back to Sensu backend.
sensuctl event info sensu.io check-sensuapp
You now know how to run a simple check to verify the status of a website. From this point, here are some recommended resources:
- Read the checks reference for in-depth documentation on checks.
- Read the guide to providing runtime dependencies to checks with assets.
- Read the guide to sending alerts to Slack with handlers.