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Hermes gathers a big number of different metrics which are useful when trying to observe the current state of the system.

Latencies are measured as: 50, 75, 95, 99 and 99.9 percentiles. Rates are measured and averaged in a time window. There are 3 time windows measured: 1, 5 and 15 minutes.


Frontend metrics are all prefixed with producer.{hostname}. Most of the metrics are collected in both aggregated and per-topic scope.


Latency metrics are grouped into two categories:

  • ACK-leader acknowledgment level
  • ACK-all acknowledgment level

In those categories it is possible to read both broker latency and Hermes latency. Broker latency measures Kafka response times, while Hermes latency measures time span between receiving message till sending the response.


  • ack-all.latency
  • ack-all.latency.{groupName}.{topicName}
  • ack-leader.latency
  • ack-leader.latency.{groupName}.{topicName}



  • meter
  • meter.{groupName}.{topicName}

Response codes

These metrics measure global Hermes response codes. They make for good monitoring metrics, as sudden increase of 202 or 500 status codes might signal an emergency. There are no per-topic metrics for response codes. See publishing guide for the meaning of response codes.


  • http-status-codes.code201
  • http-status-codes.code202
  • http-status-codes.code408
  • http-status-codes.code500


There are three metrics related to messages:

  • parsing time which indicates how much time it took to receive the message
  • message size in bytes
  • validation latency which indicates how long did it took to validate message schema (if enabled)


  • message-size
  • message-size.{groupName}.{topicName}
  • validation-latency
  • validation-latency.{groupName}.{topicName}


These metrics indicate available buffer size for both ACK-all:

  • ack-all.buffer-total-bytes
  • ack-all.buffer-available-bytes

and ACK-leader buffers:

  • ack-leader.buffer-total-bytes
  • ack-leader.buffer-available-bytes


When using Kafka compression algorithm, these metrics show average compression rate of messages:

  • ack-all.compression-rate
  • ack-leader.compression-rate


Consumers metrics are all prefixed with consumer.{hostname}. Most of the metrics are collected in both aggregated and per-subscription scope.

Subscription metrics

Hermes publishes a lot of metrics that can be useful when reasoning about subscribers health and debugging subscribers issues:

  • latency as measured by Hermes: from the start of sending the message till receiving response; path: latency
  • output rate: effective output rate; path: meter
  • maximum output rate: current maximum output rate as calculated by Consumers rate limiter; path: output-rate
  • response statuses: rate of different response statuses sent by client (2xx, 4xx, 5xx, timeouts and other failures); path: status


With tracing enabled, it is possible to observe the tracer queue size and remaining capacity:

  • tracker.elasticsearch.queue-size
  • tracker.elasticsearch.remaining-capacity