Expose Prometheus metrics for aggregator

[jpraynaud]

Why

We want to have Mithril aggregator expose simple metrics via a Prometheus endpoint to facilitate the monitoring by their operators.

What

When configured to do so, the Mithril aggregator should expose a Prometheus endpoint with basic metrics.

How

• Define the metrics to compute, and how to compute them:
  • certificate_detail_total_served_since_startup (Counter)
  • artifact_detail_cardano_db_total_served_since_startup (Counter)
  • artifact_detail_mithril_stake_distribution_total_served_since_startup (Counter)
  • artifact_detail_cardano_stake_distribution_total_served_since_startup (Counter)
  • artifact_detail_cardano_transaction_total_served_since_startup (Counter)
  • proof_cardano_transaction_total_proofs_served_since_startup (Counter)
  • proof_cardano_transaction_total_transactions_served_since_startup (Counter)
  • signer_registration_total_received_since_startup (Counter)
  • signature_registration_total_received_since_startup (Counter)
  • certificate_total_produced_since_startup (Counter)
  • artifact_cardano_db_total_produced_since_startup (Counter)
  • artifact_mithril_stake_distribution_total_produced_since_startup (Counter)
  • artifact_cardano_stake_distribution_total_produced_since_startup (Counter)
  • artifact_cardano_transaction_total_produced_since_startup (Counter)
  • runtime_cycle_success_since_startup (Counter)
  • runtime_cycle_total_since_startup (Counter)
• Implement a Metrics Service that records Prometheus metrics (using the macro from mithril-metric module)
• Implement a Metrics Server that exposes Prometheus metrics to an endpoint
• Optout activation of the endpoint
• Update documentation (https://mithril.network/doc/manual/developer-docs/nodes/mithril-aggregator)
• Deploy metrics endpoints for aggregator node in infra
• Assess that there is no performance degradation on HTTP routes

Later

• Record state of prometheus metrics?

Parent issue

#1481