# Sensu Integration
[Sensu](https://sensu.io/) is a tool that functions as an observability pipeline which delivers monitoring as code on any cloud.
## In ilert: Create a Sensu alert source
1. Go to **Alert sources** --> **Alert sources** and click on **Create new alert source**
2. Search for **Sensu** in the search field, click on the Sensu tile and click on **Next**.
3. Give your alert source a name, optionally assign teams and click **Next**.
4. Select an **escalation policy** by creating a new one or assigning an existing one.
5. Select you [Alert grouping](https://docs.ilert.com/alerting/configure-alerting/alert-sources#alert-grouping) preference and click **Continue setup**. You may click **Do not group alerts** for now and change it later.
6. The next page show additional settings such as customer alert templates or notification prioritiy. Click on **Finish setup** for now.
7. On the final page, an API key and / or webhook URL will be generated that you will need later in this guide.
## In Sensu
1. Add Sensu ilert Handler
```
sensuctl asset add iLert/sensu-ilert
```
2. Make sure that the asset was added to your Sensu backend. Run:
```
sensuctl asset info iLert/sensu-ilert
```
3. In the following command, replace **\** with your ilert API key.
Then run the updated command:
```
sensuctl handler create ilert \
--type pipe \
--runtime-assets iLert/sensu-ilert \
--command "sensu-ilert -t "
```
4. Make sure that your handler was added by retrieving the complete handler definition in YAML or JSON format:
```
sensuctl handler info ilert --format yaml
```
5. Trigger an event. You can try it with the **file\_exists** check and an ilert handler workflow in place - remove a file to cause Sensu to send a non-OK event.
You can refer to the next section for more instructions.
## Triggering an event
### Add system subscription to entity
1. Find your entity name:
```
sensuctl entity list
```
2. The `ID` in the response is the name of your entity and replace `` with the name of your entity in the `sensuctl` command below. Then run the command to add the `system` subscription to your entity:
```
sensuctl entity update
```
3. For `Entity Class`, press enter.
4. For `Subscriptions`, type `system` and press enter.
5. Confirm both `sensu-backend` and `sensu-agent` are running. You can use `docker ps` if you are running both from docker.
### Add the `file_exists` check
1. Before you can add the check, you need to add the Nagios Foundation asset to your Sensu configuration:
```
sensuctl asset add ncr-devops-platform/nagiosfoundationCopy
```
2. To confirm that the asset was added to your Sensu backend, run:
```
sensuctl asset info ncr-devops-platform/nagiosfoundationCopy
```
3. The check command includes the path for the file that the check will look for on your system, `/tmp/my-file.txt`. For this guide, you’ll add `/tmp/my-file.txt` as a temporary file:
```
touch /tmp/my-file.txt
```
4. You should see `=== ncr-devops-platform/nagiosfoundation` followed by a list of available builds for the asset. Now that you’ve added the Nagios Foundation dynamic runtime asset, you can add its `file_exists` check to your Sensu backend. Use sensuctl to add the check:
```
sensuctl check create file_exists \
--command "check_file_exists --pattern /tmp/my-file.txt" \
--subscriptions system \
--handlers ilert \
--interval 10 \
--runtime-assets ncr-devops-platform/nagiosfoundationCopy
```
5. To confirm that the check was added to your Sensu backend and view the check definition in YAML or JSON format,
```
sensuctl check info file_exists --format yaml
```
### Trigger a `file_exists` check
1. Remove the file `/tmp/my-file.txt`:
```
rm /tmp/my-file.txtCopy
```
2. This will make sure the file is **not** there for Sensu to find the next time the `file_exists` check runs. After about 10 seconds, Sensu will detect that `my-file.txt` is missing and reflect that in an event. To view the event with `sensuctl`, run:
```
sensuctl event listCopy
```
3. The response should show that the file removal resulted in a *CRITICAL (2)* event:
```
Entity Check Output Status Silenced Timestamp UUID
────────────── ───────────── ──────────────────────────────────────────────────────────────────────── ──────── ────────── ─────────────────────────────── ──────────────────────────────────────
host01 file_exists CheckFileExists CRITICAL - 0 files matched pattern /tmp/my-file.txt 2 false 2021-03-15 19:28:21 +0000 UTC 1b4266ae-7200-4728-a0n4-2f50f7a56613Copy
```
4. Open the Sensu web UI to see the events the `file_exists` check is generating. Visit , and log in as the admin user (created during initialization when you installed the Sensu backend). The failing check’s events will be listed on the **Events** page.
5. The Alert should be created on the Sensu Alert Source on ilert's side as well
6. To complete your workflow, restore the file that you removed so Sensu sends a resolution to ilert:
```
touch /tmp/my-file.txt
```
---
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