Class: PrometheusExporter::Middleware

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

Constant Summary collapse

MethodProfiler =
PrometheusExporter::Instrumentation::MethodProfiler

Instance Method Summary collapse

Constructor Details

#initialize(app, config = { instrument: :alias_method, client: nil }) ⇒ Middleware

Returns a new instance of Middleware.


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# File 'lib/prometheus_exporter/middleware.rb', line 9

def initialize(app, config = { instrument: :alias_method, client: nil })
  @app = app
  @client = config[:client] || PrometheusExporter::Client.default

  if config[:instrument]
    if defined? Redis::Client
      MethodProfiler.patch(Redis::Client, [
        :call, :call_pipeline
      ], :redis, instrument: config[:instrument])
    end
    if defined? PG::Connection
      MethodProfiler.patch(PG::Connection, [
        :exec, :async_exec, :exec_prepared, :send_query_prepared, :query
      ], :sql, instrument: config[:instrument])
    end
    if defined? Mysql2::Client
      MethodProfiler.patch(Mysql2::Client, [:query], :sql, instrument: config[:instrument])
      MethodProfiler.patch(Mysql2::Statement, [:execute], :sql, instrument: config[:instrument])
      MethodProfiler.patch(Mysql2::Result, [:each], :sql, instrument: config[:instrument])
    end
  end
end

Instance Method Details

#call(env) ⇒ Object


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# File 'lib/prometheus_exporter/middleware.rb', line 32

def call(env)
  queue_time = measure_queue_time(env)

  MethodProfiler.start
  result = @app.call(env)
  info = MethodProfiler.stop

  result
ensure
  status = (result && result[0]) || -1
  obj = {
    type: "web",
    timings: info,
    queue_time: queue_time,
    status: status,
    default_labels: default_labels(env, result)
  }
  labels = custom_labels(env)
  if labels
    obj = obj.merge(custom_labels: labels)
  end

  @client.send_json(obj)
end

#custom_labels(env) ⇒ Object

allows subclasses to add custom labels based on env


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# File 'lib/prometheus_exporter/middleware.rb', line 77

def custom_labels(env)
  nil
end

#default_labels(env, result) ⇒ Object


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# File 'lib/prometheus_exporter/middleware.rb', line 57

def default_labels(env, result)
  params = env["action_dispatch.request.parameters"]
  action = controller = nil
  if params
    action = params["action"]
    controller = params["controller"]
  elsif (cors = env["rack.cors"]) && cors.respond_to?(:preflight?) && cors.preflight?
    # if the Rack CORS Middleware identifies the request as a preflight request,
    # the stack doesn't get to the point where controllers/actions are defined
    action = "preflight"
    controller = "preflight"
  end

  {
    action: action || "other",
    controller: controller || "other"
  }
end