Class: PrometheusExporter::Server::WebServer

Inherits:
Object
  • Object
show all
Defined in:
lib/prometheus_exporter/server/web_server.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(port:, collector: nil) ⇒ WebServer

Returns a new instance of WebServer.



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# File 'lib/prometheus_exporter/server/web_server.rb', line 12

def initialize(port: , collector: nil)

  @server = WEBrick::HTTPServer.new(
    Port: port,
    AccessLog: [],
    Logger: WEBrick::Log.new("/dev/null")
  )

  @collector = collector || Collector.new
  @port = port

  @server.mount_proc '/' do |req, res|
    res['ContentType'] = 'text/plain; charset=utf-8'
    if req.path == '/metrics'
      res.status = 200
      if req.header["accept-encoding"].to_s.include?("gzip")
        sio = StringIO.new
        collected_metrics = metrics
        begin
          writer = Zlib::GzipWriter.new(sio)
          writer.write(collected_metrics)
        ensure
          writer.close
        end
        res.body = sio.string
        res.header["content-encoding"] = "gzip"
      else
        res.body = metrics
      end
    elsif req.path == '/send-metrics'
      handle_metrics(req, res)
    else
      res.status = 404
      res.body = "Not Found! The Prometheus Discourse plugin only listens on /metrics and /send-metrics"
    end
  end
end

Instance Attribute Details

#collector ⇒ Object (readonly)

Returns the value of attribute collector.



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# File 'lib/prometheus_exporter/server/web_server.rb', line 10

def collector
  @collector
end

Instance Method Details

#add_gauge(name, help, value) ⇒ Object 



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# File 'lib/prometheus_exporter/server/web_server.rb', line 115

def add_gauge(name, help, value)
  gauge = PrometheusExporter::Metric::Gauge.new(name, help)
  gauge.observe(value)
  @metrics << gauge
end

#get_rss ⇒ Object 



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# File 'lib/prometheus_exporter/server/web_server.rb', line 110

def get_rss
  @pagesize ||= `getconf PAGESIZE`.to_i rescue 4096
  File.read("/proc/#{pid}/statm").split(' ')[1].to_i * @pagesize rescue 0
end

#handle_metrics(req, res) ⇒ Object 



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# File 'lib/prometheus_exporter/server/web_server.rb', line 50

def handle_metrics(req, res)
  req.body do |block|
    begin
      @collector.process(JSON.parse(block))
    rescue => e
      res.body = "Bad Metrics #{e}"
      res.status = e.respond_to?(:status_code) ? e.status_code : 500
      return
    end
  end

  res.body = "OK"
  res.status = 200
end

#metrics ⇒ Object 



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# File 'lib/prometheus_exporter/server/web_server.rb', line 79

def metrics
  metric_text = nil
  begin
    Timeout::timeout(2) do
      metric_text = @collector.prometheus_metrics_text
    end
  rescue Timeout::Error
    # we timed out ... bummer
    STDERR.puts "Generating Prometheus metrics text timed out"
  end

  @metrics = []

  add_gauge(
    "collector_working",
    "Is the master process collector able to collect metrics",
    metric_text && metric_text.length > 0 ? 1 : 0
  )

  add_gauge(
    "collector_rss",
    "total memory used by collector process",
    get_rss
  )

  <<~TEXT
  #{@metrics.map(&:to_prometheus_text).join("\n\n")}
  #{metric_text}
  TEXT
end

#start ⇒ Object 



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# File 'lib/prometheus_exporter/server/web_server.rb', line 65

def start
  @runner ||= Thread.start do
    begin
      @server.start
    rescue => e
      STDERR.puts "Failed to start prometheus collector web on port #{@port}: #{e}"
    end
  end
end

#stop ⇒ Object 



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# File 'lib/prometheus_exporter/server/web_server.rb', line 75

def stop
  @server.shutdown
end