Create API endpoint for Prometheus (api/prometheus/metrics)

[ishantiw]

Description

Prometheus supports three value types, counter, gauge and histogram. It accepts a specific format of data.
List of parameters for Prometheus

Below is the text format that is accepted by Prometheus and including parameters that are good candidates to be included in the response.

avg_number_of_times_block_received: get averageReceivedBlock from #5295
avg_number_of_times_transaction_received: get averageReceivedTransactions from #5884
node_height: await channel.invoke('app:getNodeInfo')
finalized_height: await channel.invoke('app:getNodeInfo')
unconfirmed_transactions: await channel.invoke('app:getNodeInfo')
connected_peers: await channel.invoke('app:getConnectedPeers')
disconnected_peers: await channel.invoke('app:getDisconnectedPeers')
number_of_fork_events: get the count from the counter from #5886

# HELP Block propagation
# TYPE avg_number_of_times_block_received gauge
avg_number_of_times_block_received 18

# HELP Transaction propagation
# TYPE avg_number_of_times_transaction_received gauge
avg_number_of_times_transaction_received 42

# HELP Node height
# TYPE node_height gauge
node_height 126688

# HELP Finalised height
# TYPE finalized_height gauge
finalized_height 42

# HELP Unconfirmed transactions
# TYPE unconfirmed_transactions gauge
unconfirmed_transactions 2

# HELP Connected peers // This can be broken down into outgoing and incoming peers
# TYPE connected_peers gauge
connected_peers 85

# HELP Disconnected peers
# TYPE disconnected_peers gauge
disconnected_peers 1234

# HELP Number of fork events
# TYPE number_of_fork_events gauge
number_of_fork_events 23

Motivation

To provide data that is compatible with Prometheus that can be used to visualize or to have network wide view of nodes during alpha testing based on some key parameters.

Acceptance Criteria

• Add unit test to check if the above values are exposed
• Check if the above values are responded by registering to the framework

Additional Information

Related issues: #5216