Experimental daml assistant support for metering report [DPP-816]

[simonmaxen-da]

changelog_begin
Enable experimental GRPC endpoint for metering report.
changelog_end

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[simonmaxen-da]

> daml-helper ledger metering-report --help
Usage: daml ledger metering-report ...  [--from FROM] [--to TO] [--application APP]

Available options:
    :

  --from FROM              From date of report (inclusive).
  --to TO                  To date of report (exclusive).
  --application APP        Report application identifier.

[simonmaxen-da]

> grpcurl -plaintext -d '{"from": "2022-01-19T14:00:00Z"}'  localhost:6865 com.daml.ledger.api.v1.admin.MeteringReportService.GetMeteringReport | jq
{
  "request": {
    "from": "2022-01-19T14:00:00Z"
  },
  "participantReport": {
    "participantId": "participant1",
    "toActual": "2022-01-19T14:27:01Z",
    "applicationReports": [
      {
        "applicationId": "app  1",
        "eventCount": "100"
      },
      {
        "applicationId": "app2",
        "eventCount": "200"
      }
    ]
  },
  "reportGenerationTime": "2022-01-19T14:27:01Z"
}

[simonmaxen-da]

> daml-helper ledger metering-report  --host localhost --port 6865 --from "2022-01-19T14:00:00Z" | jq
{
  "to-actual": "2022-01-19T14:27:45Z",
  "from": "2022-01-19T14:00:00Z",
  "participant": "participant1",
  "applications": [
    {
      "application": "app  1",
      "events": 100
    },
    {
      "application": "app2",
      "events": 200
    }
  ]
}

[cocreature]

Looks like it goes in the right direction, thanks!

[cocreature]

let’s move the parsing to the CLI parser instead of passing strings here

[simonmaxen-da]

Done.

[cocreature]

I’d also prefer to wrap this in the CLI parser and not pass a string in here.

[simonmaxen-da]

Done.

[cocreature]

Other flags default to a human readable output and then have a --json flag. i think it would be nice to keep that here.

[simonmaxen-da]

I would say this is a special case as the purpose of this helper is to output a report in json format as per the "Design: Ledger Metering" spec. By default the json is not pretty printed. I could add a --pretty flag to output the JSON in a more human readable format (or make pretty output the default and add a --nopretty flag) ?

[cocreature]

How about pretty print by default and add --compact-output (matching jq’s flag name) to not pretty print?

[simonmaxen-da]

Done:

DAML> daml-helper ledger metering-report --host localhost --port 6865 --from "2022-01-22T00:00:00Z" --compact-output
{"from":"2022-01-22T00:00:00Z","participant":"participant1","toActual":"2022-01-24T11:27:01.308061Z","applications":[{"application":"app1","events":100},{"application":"app2","events":200}]}

DAML> daml-helper ledger metering-report --host localhost --port 6865 --from "2022-01-22T00:00:00Z"
{
    "from": "2022-01-22T00:00:00Z",
    "participant": "participant1",
    "toActual": "2022-01-24T11:27:05.718135Z",
    "applications": [
        {
            "application": "app1",
            "events": 100
        },
        {
            "application": "app2",
            "events": 200
        }
    ]
}

[cocreature]

Nice! I suggest to address the pretty printing in this PR but apart from that looks ready to land.

[cocreature]

How about pretty print by default and add --compact-output (matching jq’s flag name) to not pretty print?

[cocreature]

Suggested change

	hPutStrLn stderr "Error: daml ledger metering can only be run via gRPC atm"
	hPutStrLn stderr "Error: daml ledger metering can only be run via gRPC at the moment"

[simonmaxen-da]

Done.

[cocreature]

Suggested change

	, "to-actual" .= timestampToIso8601 toActual
	, "to_actual" .= timestampToIso8601 toActual

Not sure if there is a specific reason for the hyphen but ime underscores are far more common in JSON encodings so I’d suggest to use that for ledger metering as well.

[simonmaxen-da]

Will update to camel case provided all are happy with the spec change.

[cocreature]

Suggested change

	++ maybeToList (fmap (("to-requested" .=) . timestampToIso8601) toRequested)
	++ maybeToList (fmap (("to_requested" .=) . timestampToIso8601) toRequested)

[simonmaxen-da]

Will update to camel case provided all are happy with the spec change.

[cocreature]

Not a huge fan of this Read instance, can we just wrap it in the ApplicationId constructor at the call site?

[simonmaxen-da]

What is wrong with it ?

[cocreature]

Read isn’t really great for general purpose parsing in general and more often than not you are better off writing parser functions. In this particular case it just accepts literally every string and wraps in in the constructor. That just seems like it’s asking for bugs. I’m not asking for validation but applying the constructor explicitly at least makes it clearer what is happening.

[simonmaxen-da]

Done.