modify-metrics

name	modify-metrics
description	Telemetry and metrics patterns for the CheddarFlow project. TRIGGER when: writing or modifying telemetry events, metrics definitions, CFXMetrics modules, or monitoring-related code. Also trigger when adding :telemetry.execute or :telemetry.span calls, or working with Prometheus/Grafana metric exports. DO NOT TRIGGER when: working with code that doesn't involve observability or metrics.

Metrics & Telemetry

Uses Erlang's :telemetry with custom metric definitions published to Grafana via Prometheus.

CFXMetrics

cfx_metrics (apps/cfx_metrics/) aggregates metrics from domain-specific modules:

Module	Domain
CFXMetrics.Alerts	Alert system
CFXMetrics.DarkPoolEventsProcessor	Dark pool pipeline
CFXMetrics.FeedServers	Feed server operations
CFXMetrics.LastSymbolPricePoller	Price polling
CFXMetrics.MarketStatus	Market status changes
CFXMetrics.OptionsChainPoller	Options chain scraping
CFXMetrics.OptionChainPollScheduler	Poll scheduling
CFXMetrics.OptionsEventsProcessor	Options pipeline
CFXMetrics.SubscriptionWebhooks.Controller	Stripe webhooks
CFXMetrics.GammaExposure	Gamma exposure
CFXMetrics.RpcMetrics	Cross-node RPC
Cache.Metrics	Cache hit/miss/error (from elixir_cache)

Configuration

config :cfx_metrics, enabled?: false, exporter_opts: [enabled?: false, opts: []]  # dev/test
config :cfx_metrics, enabled?: true, exporter_opts: [enabled?: true]               # prod

Per-App Telemetry Modules

Each release app has a Telemetry module in its supervision tree: CFXWeb.Telemetry, CFXBgProcessor.Telemetry, OptionsEventsProcessor.Telemetry, DarkPoolEventsProcessor.Telemetry, OptionsFeed.Telemetry, DiscordService.Telemetry

Telemetry Event Patterns

Span-based timing:

:telemetry.span([:cfx, :feed_servers, :get_state], %{adapter: adapter}, fn ->
  result = do_work()
  {result, %{adapter: adapter}}
end)

Counter events:

:telemetry.execute([:elixir_cache, :cache, :get, :miss], %{count: 1}, %{cache_name: cache_name})

RPC metrics wrap all cross-node calls:

RpcMetrics.span_call(module, fun, node, fn ->
  :erpc.call(node, module, fun, args, timeout)
end)

Adding New Metrics

1. Define in appropriate CFXMetrics.* module
2. Add telemetry events using :telemetry.execute/3 or :telemetry.span/3
3. Ensure included in CFXMetrics.metrics/0
4. Release app Telemetry module picks up automatically

Logging

Structured logging with LogfmtEx:

config :logger, :console, format: {LogfmtEx, :format}, metadata: [:application, :client_ip, :feed_adapter]

Log aggregation via Loki in production with Grafana dashboards.