Shell: add metrics about ddb messages sent/received/broadcasted

Context

Add metrics about DDB messages sent, broadcasted or received.

Grafazos dashboard integration (nomadic-labs/grafazos!39 (merged)):

Manually testing the MR

Launch a node with a given metric address:

./octez-node run --metrics-addr=localhost:12345

In another terminal, use curl to view the metrics:

curl -s http://localhost:12345/metrics |grep -v "#" |grep octez_distributed_db_message

Output example:

octez_distributed_db_message_block_header_messages{action="received"} 27830.000000
octez_distributed_db_message_block_header_messages{action="sent"} 1205.000000
octez_distributed_db_message_checkpoint_messages{action="received"} 0.000000
octez_distributed_db_message_checkpoint_messages{action="sent"} 0.000000
octez_distributed_db_message_current_branch_messages{action="received"} 6711.000000
octez_distributed_db_message_current_branch_messages{action="sent"} 3974.000000
octez_distributed_db_message_current_head_messages{action="broadcasted"} 209579.000000
octez_distributed_db_message_current_head_messages{action="received"} 14578092.000000
octez_distributed_db_message_current_head_messages{action="sent"} 132987.000000
octez_distributed_db_message_deactivate_messages{action="received"} 17.000000
octez_distributed_db_message_deactivate_messages{action="sent"} 0.000000
octez_distributed_db_message_get_block_headers_messages{action="received"} 1206.000000
octez_distributed_db_message_get_block_headers_messages{action="sent"} 27832.000000
octez_distributed_db_message_get_checkpoint_messages{action="received"} 0.000000
octez_distributed_db_message_get_checkpoint_messages{action="sent"} 0.000000
octez_distributed_db_message_get_current_branch_messages{action="received"} 3974.000000
octez_distributed_db_message_get_current_branch_messages{action="sent"} 3684.000000
octez_distributed_db_message_get_current_head_messages{action="broadcasted"} 0.000000
octez_distributed_db_message_get_current_head_messages{action="received"} 132987.000000
octez_distributed_db_message_get_current_head_messages{action="sent"} 3534.000000
octez_distributed_db_message_get_operations_for_blocks_messages{action="received"} 261981.000000
octez_distributed_db_message_get_operations_for_blocks_messages{action="sent"} 114368.000000
octez_distributed_db_message_get_operations_messages{action="received"} 23234148.000000
octez_distributed_db_message_get_operations_messages{action="sent"} 5194756.000000
octez_distributed_db_message_get_predecessor_header_messages{action="received"} 0.000000
octez_distributed_db_message_get_predecessor_header_messages{action="sent"} 0.000000
octez_distributed_db_message_get_protocol_branch_messages{action="received"} 0.000000
octez_distributed_db_message_get_protocol_branch_messages{action="sent"} 0.000000
octez_distributed_db_message_get_protocols_messages{action="received"} 2.000000
octez_distributed_db_message_get_protocols_messages{action="sent"} 0.000000
octez_distributed_db_message_operation_messages{action="received"} 6502504.000000
octez_distributed_db_message_operation_messages{action="sent"} 41559875.000000
octez_distributed_db_message_operations_for_block_messages{action="received"} 243093.000000
octez_distributed_db_message_operations_for_block_messages{action="sent"} 364083.000000
octez_distributed_db_message_predecessor_header_messages{action="received"} 0.000000
octez_distributed_db_message_predecessor_header_messages{action="sent"} 0.000000
octez_distributed_db_message_protocol_branch_messages{action="received"} 0.000000
octez_distributed_db_message_protocol_branch_messages{action="sent"} 0.000000
octez_distributed_db_message_protocol_messages{action="received"} 0.000000
octez_distributed_db_message_protocol_messages{action="sent"} 1.000000

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR