Capture distribution of node versions seen on the network over time

[placer14]

Feature Request

In order to infer the distribution of node versions which are being used on the network, drone's lotus input plugin should periodically query lotus for the number of peers seen for each user agent and persist these values with the current timestamp.

Proposal:

Desired behavior:

Via the lotus input plugin's Gather method, capture and add the following metric once per unique version string and return error appropriately upon completion.

var versionCounts map[string]uint
versionCounts = gatherObservedVersions(api)
for version, count := range versionCounts {
    acc.AddFields("observed_node_versions",
		map[string]interface{}{
			"count": count,
		},
		map[string]string{
			"version": version,
		},
		time.Now(),
    )
}

Data can be sourced via lotus's NetPeers API.

Acceptance Criteria

• The following schema result in observed_node_versions table:
  • text column "version"
  • int column "count"
  • timestamp column "time"
• execution against lotus collects and persists data to the above schema once per configured interval

Example data output (non-prescriptive):

version	count	time
lotus-1.1.0	3	2020-12-19 22:16:03
lotus-1.2.0	4	2020-12-19 22:16:03
lotus-1.1.2	10	2020-12-19 22:16:03
lotus-1.2.2	22	2020-12-19 22:16:03
lotus-1.4.0	53	2020-12-19 22:16:03
lotus-1.2.1	58	2020-12-19 22:16:03
lotus-1.3.0	71	2020-12-19 22:16:03

Use case:

Useful for tracking node upgrades being adopted by the network.