Document Prometheus metrics and Grafana Dahsboard for signer

[jpraynaud]

Why

Some SPO asked for explanation about the Prometheus metrics and Grafana dashboard for the Mithril signer node.

What

Add some explanation about the metrics in the signer node in the documentation.

How

• Explain the metrics exposed by the Prometheus endpoint in the Activate Prometheus endpoint
• Describe the metrics aggregated in the Grafana dashboard template page

[dlachaume]

This is a proposal to expand the description of the Grafana dashboard template page:

---

We recommend configuring the dashboard to retrieve data over a meaningful period (e.g., 24 hours or a week).

Below is a detailed table outlining the metrics for better understanding and monitoring of the Mithril signer node:

Metrics	Description
Signer Registration Last Epoch	The epoch during which the last signer registration occurred
Signer Registration Success	Number of successful signer registrations
Signer Registration Errors	Number of errors that occurred during signer registrations
Signature Registration Last Epoch	The epoch during which the last signature registration occurred
Signature Registration Success	Number of successful signature registrations
Signature Registration Errors	Number of errors that occurred during signature registrations
State Machine Cycles	Total number of state machine cycles
State Machine Cycles Success	Number of state machine cycles that ended successfully
State Machine Cycles Errors	Number of state machine cycles that ended due to an error

It is not concerning to have an error rate not exceeding 1% on the State Machine Cycles.

Feel free to reach out to us on the Discord channel for questions and/or help.