Monitoring & Alerting

# Enable plugins (rabbitmq-plugins or environment variable)
rabbitmq-plugins enable rabbitmq_prometheus rabbitmq_management

# rabbitmq.conf
## Prometheus scrape port
prometheus.tcp.port = 15692

# prometheus.yml scrape config
scrape_configs:
  - job_name: rabbitmq
    static_configs:
      - targets: ['rabbitmq-host:15692']
    metrics_path: /metrics
    relabel_configs:
      - source_labels: [__address__]
        target_label: instance

# Key metrics exposed
# rabbitmq_queue_messages_ready          — messages waiting to be delivered
# rabbitmq_queue_messages_unacked_total  — delivered but not yet acked
# rabbitmq_queue_consumers               — active consumer count
# rabbitmq_channel_publish_total         — publish rate (use rate())
# rabbitmq_node_mem_used_bytes           — broker memory usage
# rabbitmq_node_disk_free_bytes          — free disk space

groups:
  - name: rabbitmq
    rules:
      # Queue growing faster than consumers can drain
      - alert: RabbitMQQueueDepthHigh
        expr: rabbitmq_queue_messages_ready > 1000
        for: 5m
        labels:
          severity: warning
        annotations:
          summary: "Queue {{ $labels.queue }} has {{ $value }} messages"

      # No consumers — messages will pile up
      - alert: RabbitMQNoConsumers
        expr: rabbitmq_queue_consumers == 0
          and rabbitmq_queue_messages_ready > 0
        for: 2m
        labels:
          severity: critical
        annotations:
          summary: "Queue {{ $labels.queue }} has no consumers!"

      # Memory watermark — broker will block publishers
      - alert: RabbitMQMemoryAlarm
        expr: rabbitmq_alarms_memory_used_watermark > 0
        for: 0m
        labels:
          severity: critical

      # High redeliver rate = consumers nacking messages repeatedly (poison pill?)
      - alert: RabbitMQHighRedeliveryRate
        expr: rate(rabbitmq_queue_messages_redelivered_total[5m]) > 10
        for: 5m
        labels:
          severity: warning

// Spring Boot: custom health indicator using Management HTTP API
@Component
public class RabbitQueueHealthIndicator implements HealthIndicator {

    private final RestTemplate rest = new RestTemplate();
    private final String mgmtUrl = "http://rabbitmq:15672/api/queues/%2F/orders.queue";

    @Override
    public Health health() {
        try {
            ResponseEntity<Map> resp = rest.withBasicAuth("guest", "guest")
                .getForEntity(mgmtUrl, Map.class);
            Map body = resp.getBody();
            int depth = (Integer) body.get("messages_ready");
            int consumers = (Integer) body.get("consumers");

            if (consumers == 0) {
                return Health.down()
                    .withDetail("reason", "No consumers")
                    .withDetail("depth", depth).build();
            }
            return Health.up()
                .withDetail("depth", depth)
                .withDetail("consumers", consumers).build();
        } catch (Exception e) {
            return Health.down(e).build();
        }
    }
}