metrics.hpp

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// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License

#ifndef __PROCESS_METRICS_METRICS_HPP__
#define __PROCESS_METRICS_METRICS_HPP__

#include <map>
#include <string>
#include <vector>

#include <process/dispatch.hpp>
#include <process/future.hpp>
#include <process/limiter.hpp>
#include <process/owned.hpp>
#include <process/process.hpp>

#include <process/metrics/metric.hpp>

#include <stout/nothing.hpp>
#include <stout/option.hpp>

namespace process {
namespace metrics {
namespace internal {

class MetricsProcess : public Process<MetricsProcess>
{
public:
  static MetricsProcess* create(const Option<std::string>& authenticationRealm);

  Future<Nothing> add(Owned<Metric> metric);

  Future<Nothing> remove(const std::string& name);

  Future<std::map<std::string, double>> snapshot(
      const Option<Duration>& timeout);

protected:
  void initialize() override;

private:
  static std::string help();

  MetricsProcess(
      const Option<Owned<RateLimiter>>& _limiter,
      const Option<std::string>& _authenticationRealm)
    : ProcessBase("metrics"),
      limiter(_limiter),
      authenticationRealm(_authenticationRealm)
  {}

  // Non-copyable, non-assignable.
  MetricsProcess(const MetricsProcess&);
  MetricsProcess& operator=(const MetricsProcess&);

  Future<http::Response> _snapshot(
      const http::Request& request,
      const Option<http::authentication::Principal>&);

  // TODO(bmahler): Make this static once we can move
  // capture with C++14.
  Future<std::map<std::string, double>> __snapshot(
      const Option<Duration>& timeout,
      std::vector<std::string>&& keys,
      std::vector<Future<double>>&& metrics,
      std::vector<Option<Statistics<double>>>&& statistics);

  // The Owned<Metric> is an explicit copy of the Metric passed to 'add'.
  std::map<std::string, Owned<Metric>> metrics;

  // Used to rate limit the snapshot endpoint.
  Option<Owned<RateLimiter>> limiter;

  // The authentication realm that metrics HTTP endpoints are installed into.
  const Option<std::string> authenticationRealm;
};


// Global metrics process. Defined in process.cpp.
extern PID<MetricsProcess> metrics;

}  // namespace internal {


template <typename T>
Future<Nothing> add(const T& metric)
{
  // The metrics process is instantiated in `process::initialize`.
  process::initialize();

  // There is an explicit copy in this call to ensure we end up owning
  // the last copy of a Metric when we remove it.
  return dispatch(
      internal::metrics,
      &internal::MetricsProcess::add,
      Owned<Metric>(new T(metric)));
}


inline Future<Nothing> remove(const Metric& metric)
{
  // The metrics process is instantiated in `process::initialize`.
  process::initialize();

  return dispatch(
      internal::metrics,
      &internal::MetricsProcess::remove,
      metric.name());
}


inline Future<std::map<std::string, double>> snapshot(
    const Option<Duration>& timeout)
{
  // The metrics process is instantiated in `process::initialize`.
  process::initialize();

  return dispatch(
      internal::metrics,
      &internal::MetricsProcess::snapshot,
      timeout);
}

}  // namespace metrics {
}  // namespace process {

#endif // __PROCESS_METRICS_METRICS_HPP__