VILLASnode/lib/hooks/limit_rate.cpp

/* Rate-limiting hook.
 *
 * Author: Steffen Vogel <post@steffenvogel.de>
 * SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University
 * SPDX-License-Identifier: Apache-2.0
 */

#include <cstring>

#include <villas/hooks/limit_rate.hpp>
#include <villas/sample.hpp>
#include <villas/timing.hpp>

namespace villas {
namespace node {

void LimitRateHook::parse(json_t *json) {
  int ret;
  json_error_t err;

  assert(state != State::STARTED);

  double rate;
  const char *m = nullptr;

  Hook::parse(json);

  ret = json_unpack_ex(json, &err, 0, "{ s: F, s?: s }", "rate", &rate, "mode",
                       &m);
  if (ret)
    throw ConfigError(json, err, "node-config-hook-limit_rate");

  if (m) {
    if (!strcmp(m, "origin"))
      mode = LIMIT_RATE_ORIGIN;
    else if (!strcmp(m, "received"))
      mode = LIMIT_RATE_RECEIVED;
    else if (!strcmp(m, "local"))
      mode = LIMIT_RATE_LOCAL;
    else
      throw ConfigError(json, "node-config-hook-limit_rate-mode",
                        "Invalid value '{}' for setting 'mode'", m);
  }

  deadtime = 1.0 / rate;

  state = State::PARSED;
}

Hook::Reason LimitRateHook::process(struct Sample *smp) {
  assert(state == State::STARTED);

  timespec next;
  switch (mode) {
  case LIMIT_RATE_LOCAL:
    next = time_now();
    break;

  case LIMIT_RATE_ORIGIN:
    next = smp->ts.origin;
    break;

  case LIMIT_RATE_RECEIVED:
    next = smp->ts.received;
    break;
  }

  if (time_delta(&last, &next) < deadtime)
    return Hook::Reason::SKIP_SAMPLE;

  last = next;

  return Reason::OK;
}

// Register hook
static char n[] = "limit_rate";
static char d[] = "Limit sending rate";
static HookPlugin<LimitRateHook, n, d,
                  (int)Hook::Flags::NODE_READ | (int)Hook::Flags::NODE_WRITE |
                      (int)Hook::Flags::PATH>
    p;

} // namespace node
} // namespace villas