Prometheus Provider

The prometheus.Provider implements invoker.MetricProvider using Prometheus client libraries.

Setup

import eventprom "github.com/isaquesb/go-event-bus/prometheus"

provider := eventprom.NewProvider("myapp")

The namespace is prepended to all metric names: myapp_eventbus_invoker_calls_total.

Options

// Custom registerer (useful for testing)
provider := eventprom.NewProvider("myapp",
    eventprom.WithRegisterer(customRegistry),
)

How It Works

The provider dynamically creates and caches Prometheus metrics (counters, histograms, gauges) based on the metric names and labels provided by invokers. Metrics are created on first use and reused thereafter.

Metric Names

All invokers emit metrics with the eventbus_ prefix:

Core Metrics

Metric	Type	Labels	Source
eventbus_invoker_calls_total	Counter	event, handler, result	Metrics invoker
eventbus_invoker_latency_seconds	Histogram	event, handler, result	Metrics invoker

Retry Metrics

Metric	Type	Labels	Source
eventbus_retry_attempt_total	Counter	handler	Retry invoker
eventbus_retry_success_total	Counter	handler	Retry invoker
eventbus_retry_terminal_total	Counter	handler	Retry invoker
eventbus_retry_exhausted_total	Counter	handler	Retry invoker
eventbus_retry_backoff_ms	Histogram	handler	Retry invoker

Circuit Breaker Metrics

Metric	Type	Labels	Source
eventbus_circuit_state	Gauge	handler	Circuit breaker
eventbus_circuit_open_total	Counter	handler	Circuit breaker
eventbus_circuit_half_open_total	Counter	handler	Circuit breaker
eventbus_circuit_blocked_total	Counter	handler	Circuit breaker

Rate Limit Metrics

Metric	Type	Labels	Source
eventbus_ratelimit_allowed_total	Counter	handler	Rate limiter
eventbus_ratelimit_blocked_total	Counter	handler	Rate limiter
eventbus_ratelimit_error_total	Counter	handler	Rate limiter

Idempotency Metrics

Metric	Type	Labels	Source
eventbus_idempotency_duplicate_total	Counter	handler, reason	Idempotency
eventbus_idempotency_lock_acquired_total	Counter	handler	Idempotency
eventbus_idempotency_executed_total	Counter	handler	Idempotency
eventbus_idempotency_processing_stale_total	Counter	handler	Idempotency
eventbus_idempotency_error_total	Counter	handler, stage	Idempotency

DLQ Metrics

Metric	Type	Labels	Source
eventbus_dlq_published_total	Counter	handler	DLQ invoker
eventbus_dlq_publish_error_total	Counter	handler	DLQ invoker

Histogram Buckets

The eventbus_invoker_latency_seconds histogram uses custom buckets optimized for event processing:

0.001, 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10

All other histograms use Prometheus default buckets.