Cloud export for the Raxol metrics system.

Buffers metrics and ships them over HTTP to a configured backend:

• :otlp / :signoz — OTLP/HTTP JSON to an OpenTelemetry collector (POST to the configured endpoint, default /v1/metrics). For :signoz, a configured api_key is sent as signoz-access-token.
• :datadog — the v1 series API (DD-API-KEY header, requires api_key).
• :prometheus — Prometheus Pushgateway text exposition (POST; point the endpoint at /metrics/job/<job>).

OTLP and Datadog export every recorded data point (nanosecond timestamps). Prometheus is a snapshot format (repeating a {name, labels} sample is invalid), so it exports the latest value per rendered label set.

Ingestion and flushing

Metrics enter through record/4 (or the equivalent {:metrics, type, name, value, tags} message), which Raxol.Core.Metrics.MetricsCollector.record_metric/4 forwards automatically whenever this process is running. Only numeric values are exported; non-numeric values (the collector also accepts maps) are dropped at ingestion rather than crashing the exporter at flush time.

Automatic exports — the batch-size trigger and the periodic timer — run in a monitored helper process, so a slow or unreachable collector never blocks metric ingestion, and a crash in export code cannot take the exporter down. At most one export is in flight at a time. After a failed export the batch is retained (capped at 10 batches) and the batch-size trigger backs off; the periodic timer is the retry cadence, so an outage costs one attempt per flush_interval, not one per metric.

flush_metrics/0 is the manual/synchronous path (tests, shutdown hooks): it exports in the server and returns the transport result, or {:error, :export_in_flight} if an async export is running.

HTTP transport is Req, an optional dependency; without it every export returns {:error, :http_client_unavailable}.

Crash reports redact api_key (see format_status/1).

CloudWatch is not supported: it needs SigV4 request signing, which means an AWS dependency this library does not take; it is rejected at configuration time rather than silently dropping metrics.