Enforce fallback values for TraceOptions namespace root; expose PrometheusSimple DoS protection params

[mgmeier]

List of changes

• Add PrometheusSimpleRun data type and field TraceConfig.tcPrometheusSimpleRun. This exposes some of the DoS protection parameters of the PrometheusSimple backend.
• The above parameters can be set via the top-level config key "TracePrometheusSimpleRun": {...}. Those values will selectively override the hardcoded ones from defaultRunParams.
• Add Cardano.Logging.Prometheus.TCPServer.runPrometheusSimpleWith to run the backend providing a custom PrometheusSimpleRun value.
• Generelly relax some of the DoS protection default values.
• Fix emptyTraceConfig to be actually empty.
• Implement the basics for the future way of providing configuration via the top-level config key "HermodTracing".
• This config key can reference an external file, or provide an object cleanly encapsulating all of Hermod's options. The option names are shortened wrt. the current top-level names.
• Support !include extension for YAML config files.
• The namespace root in "TraceOptions": { "": {...}} can now be aliased as '_root_': "TraceOptions": { "_root_": {...}}. This facilitates automations that have to treat an empty JSON string as special case.
• Module Cardano.Logging.ConfigurationParser:
  • Add readConfigurationWithFallback and readConfigurationWithFallbackAndDefault, applying fallback values to the namespace root. These will be used iff no such value was given in the file or default config, and guard against accidentally missing trace output.
  • Add mkConfiguration and readConfigurationWithFallback convenience functions that will yield a minimal viable configuration by applying fallback values to emptyTraceConfig.
  • Add readConfiguration' and readConfigurationWithFallback' which will silently provide a minimal viable config if the file can't be found.
  • Expose applyFallback for those who want to safeguard some hand-rolled config value.
  • readConfiguration and readConfigurationWithDefault will now guarantee fallback values: Notice severity, DNormal detail level and Stdout MachineFormat JSON logging.
• Add docuResultsToNamespaces to DocuGenerator to support JSON schema generation.

Furthermore, there's some general cleanup in this PR.

NB: Even though the PR introduces the new HermodTracing config format, the current cardano-node configuration cannot be represented in it, and needs to stay as-is - this would require API-breaking changes to data types. The new format targets new applications that adopt Hermod, and require a clean config interface which does not contain assumptions motivated by the cardano-node case.

[jutaro]

The parser no longer strips the "Cardano" namespace prefix from config keys, which is a compatibility regression for existing configs. The previous implementation explicitly normalized "Cardano." to "" in the base version of ConfigurationParser.hs. The new code in the PR version removes that normalization entirely. Unless every caller has already stopped using Cardano.* keys, this will make previously working namespace overrides stop matching.

[mgmeier]

Good point, and yes, this is intentional.
Internally, IOE has stopped using the Cardano.* namespace prefix for quite some time, as evidenced by https://github.com/input-output-hk/iohk-nix/blob/master/cardano-lib/generic-log-config.nix and consequently https://github.com/IntersectMBO/cardano-node/blob/master/configuration/cardano/mainnet-config.json.

External users migrating now from the legacy system won't even be tempted to use that prefix in the first place, as there's no base in the legacy tracing config to use it at all (cf. https://github.com/input-output-hk/iohk-nix/blob/master/cardano-lib/generic-log-config-legacy.nix).

Metrics is the only remaining case where this needs coverage, which is already done by the existing TraceOptionMetricsPrefix config key.

[jutaro]

Suggested change

	, "AppicationName" .= traceOptionNodeName
	, "ApplicationName" .= traceOptionNodeName

[mgmeier]

Good catch!

[jutaro]

HermodTracing: "path/to/file.yaml" does not work, even though the PR description and comments say it should. In [trace-dispatcher/src/Cardano/Logging/ConfigurationParser.hs], ExternalFile is only decoded from the entire document being a bare YAML string. But parseAsOuter at lines 65-67 assumes HermodTracing contains an object and never handles the string case. So a config like HermodTracing: "./tracing.yaml" is rejected instead of redirecting.

[mgmeier]

Indeed; thank you.
Changed the instance FromJSON ExternalFile to process an object with a top-level key "HermodTracing".
Please revisit.

[jutaro]

Looks good now