chg: [user-manual] Added section about the monitoring of the system.

Author: cedricbonhomme

content/user-manual/_index.md

@@ -11,4 +11,5 @@ The Vulnerability-Lookup software is a powerful tool designed to assist security
 - [Correlations](./correlations)
 - [Email notification](./email-notification)
 - [Sightings](./sightings)
+- [System monitoring](./system-monitoring)
 - [PyVulnerabilityLookup](./pyvulnerabilitylookup)

content/user-manual/system-monitoring/index.md

@@ -0,0 +1,65 @@
+---
+title: "System monitoring" 
+description: How to check the system health 
+toc: true
+---
+
+## Presentation
+
+Vulnerability-Lookup offers multiple methods for assessing system health, including monitoring key satellite components such as sighting tools, the email notification system, and data feeders.
+
+
+## Admin Panel
+
+### Processes heartbeat signals and logs
+
+[![Processes heartbeat signals and logs](/images/user-manual/system-health/heartbeats.png)](/images/user-manual/system-health/heartbeats.png)
+
+As shown in this example, the activity of all sighting tools is centralized in the Valkey keystore and displayed in the second table (*Logs*).  
+The primary goal of the first table (*Heartbeats*) is to detect abnormal states in any of the feeders.
+
+
+### Feeders logs
+
+[![Feeders logs](/images/user-manual/system-health/feeders.png)](/images/user-manual/system-health/feeders.png)
+
+
+## API
+
+Various endpoints for checking the system health are also provided through the [API](https://vulnerability.circl.lu/api/).
+
+Examples:
+
+```bash
+$ curl https://vulnerability.circl.lu/api/system/redis_up
+true
+
+$ curl https://vulnerability.circl.lu/api/system/checkSMTP -H 'X-API-KEY: <YOUR-API-KEY>'
+true
+
+$ curl --silent https://vulnerability.circl.lu/api/system/checkProcess -H 'X-API-KEY: <YOUR-API-KEY>' | jq .
+{
+  "process_heartbeat_BlueskySight": "2025-02-19T09:28:26.490720+00:00",
+  "process_heartbeat_FediVuln": "2025-02-19T09:28:20.458222+00:00",
+  "process_heartbeat_FediVuln-Publish_bundle": "2025-02-19T09:28:24.997171+00:00",
+  "process_heartbeat_FediVuln-Publish_comment": "2025-02-19T09:28:24.429215+00:00",
+  "process_heartbeat_GistSight": "2025-02-19T09:28:20.658896+00:00",
+  "process_heartbeat_MISPSight": "2025-02-19T09:15:02.327831+00:00",
+  "process_heartbeat_NucleiVuln": "2025-02-19T09:00:02.090251+00:00",
+  "process_heartbeat_ShadowSight": "2025-02-18T10:15:02.197351+00:00",
+  "process_heartbeat_email-notification": "2025-02-19T09:28:24.820832+00:00"
+}
+```
+
+
+## Files
+
+Each feeder has a dedicated log file, stored in the ``logs/`` folder at the root of the project.
+
+The configuration files for these log files can be found in:
+
+- ``vulnerabilitylookup/feeders/*_logging.json``
+- or in ``vulnerabilitylookup/feeders/<source>/``
+
+For example: ``vulnerabilitylookup/feeders/nvd_logging.json``
+