Module: Hyperion::PrometheusExporter

Defined in:
lib/hyperion/prometheus_exporter.rb

Overview

Renders Hyperion.stats as Prometheus text exposition format (v0.0.4). Mounted by AdminMiddleware on GET /-/metrics; the returned content-type is ‘text/plain; version=0.0.4; charset=utf-8`.

Mapping rules:

  • keys listed in KNOWN_METRICS get their canonical name + curated HELP/TYPE

  • keys matching ‘responses_<3-digit>` are grouped under a single `hyperion_responses_status_total` family with a `status` label

  • any other key is auto-exported as ‘hyperion_<key>` with a generic HELP line, so newly-added counters surface in Prometheus without code changes here (the curated-name path is just nicer presentation, not gating)

Output ordering is deterministic for stable scrape diffs:

  • known metrics in KNOWN_METRICS declaration order

  • status codes ascending

  • other keys alphabetically

Constant Summary collapse

KNOWN_METRICS = 
{
  requests: { name: 'hyperion_requests_total',
              help: 'Total HTTP requests handled',
              type: 'counter' },
  bytes_read: { name: 'hyperion_bytes_read_total',
                help: 'Total bytes read from request sockets',
                type: 'counter' },
  bytes_written: { name: 'hyperion_bytes_written_total',
                   help: 'Total bytes written to response sockets',
                   type: 'counter' },
  rejected_connections: { name: 'hyperion_rejected_connections_total',
                          help: 'Connections rejected due to backpressure (max_pending)',
                          type: 'counter' },
  sendfile_responses: { name: 'hyperion_sendfile_responses_total',
                        help: 'Responses sent via plain-TCP sendfile(2) zero-copy path',
                        type: 'counter' },
  tls_zerobuf_responses: { name: 'hyperion_tls_zerobuf_responses_total',
                           help: 'Responses sent via TLS IO.copy_stream (avoids userspace String build, but TLS encryption forces copy)',
                           type: 'counter' }
}.freeze
STATUS_KEY_PATTERN = 
/\Aresponses_(\d{3})\z/
STATUS_FAMILY_NAME = 
'hyperion_responses_status_total'
STATUS_FAMILY_HELP = 
'Responses by HTTP status code'

Class Method Summary collapse

Class Method Details

.render(stats) ⇒ Object 



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# File 'lib/hyperion/prometheus_exporter.rb', line 49

def render(stats)
  buf = +''
  grouped_status = {}
  other = {}
  known = {}

  stats.each do |key, value|
    if (match = key.to_s.match(STATUS_KEY_PATTERN))
      grouped_status[match[1]] = value
    elsif KNOWN_METRICS.key?(key)
      known[key] = value
    else
      other[key] = value
    end
  end

  # Known metrics first, in declaration order — gives the scrape a stable,
  # human-friendly preamble regardless of hash insertion order.
  KNOWN_METRICS.each do |key, meta|
    next unless known.key?(key)

    append_metric(buf, meta[:name], meta[:help], meta[:type], known[key])
  end

  unless grouped_status.empty?
    buf << "# HELP #{STATUS_FAMILY_NAME} #{STATUS_FAMILY_HELP}\n"
    buf << "# TYPE #{STATUS_FAMILY_NAME} counter\n"
    grouped_status.sort.each do |status, value|
      buf << %(#{STATUS_FAMILY_NAME}{status="#{status}"} #{value}\n)
    end
  end

  other.sort_by { |k, _| k.to_s }.each do |key, value|
    name = "hyperion_#{key}"
    append_metric(buf, name, 'Hyperion internal counter (auto-exported)', 'counter', value)
  end

  buf
end