Function txn_queue_cont

plugins/experimental/rate_limit/txn_limiter.cc:70–108

}

static int
txn_queue_cont(TSCont cont, TSEvent /* event ATS_UNUSED */, void * /* edata ATS_UNUSED */)
{
  auto     *limiter = static_cast<TxnRateLimiter *>(TSContDataGet(cont));
  QueueTime now     = std::chrono::system_clock::now(); // Only do this once per "loop"

  // Try to enable some queued txns (if any) if there are slots available
  while (limiter->size() > 0 && limiter->reserve() != ReserveStatus::FULL) { // Can't be UNLIMITED here
    auto [txnp, contp, start_time]  = limiter->pop();
    std::chrono::milliseconds delay = std::chrono::duration_cast<std::chrono::milliseconds>(now - start_time);

    delayHeader(txnp, limiter->header(), delay);
    Dbg(dbg_ctl, "Enabling queued txn after %ldms", static_cast<long>(delay.count()));
    // Since this was a delayed transaction, we need to add the TXN_CLOSE hook to free the slot when done
    TSHttpTxnHookAdd(txnp, TS_HTTP_TXN_CLOSE_HOOK, contp);
    limiter->incrementMetric(RATE_LIMITER_METRIC_RESUMED);
    TSHttpTxnReenable(txnp, TS_EVENT_HTTP_CONTINUE);
  }

  // Kill any queued txns if they are too old
  if (limiter->size() > 0 && limiter->max_age() > std::chrono::milliseconds::zero()) {
    now = std::chrono::system_clock::now(); // Update the "now", for some extra accuracy

    while (limiter->size() > 0 && limiter->hasOldEntity(now)) {
      // The oldest object on the queue is too old on the queue, so "kill" it.
      auto [txnp, contp, start_time] = limiter->pop();
      std::chrono::milliseconds age  = std::chrono::duration_cast<std::chrono::milliseconds>(now - start_time);

      delayHeader(txnp, limiter->header(), age);
      Dbg(dbg_ctl, "Queued TXN is too old (%ldms), erroring out", static_cast<long>(age.count()));
      TSHttpTxnStatusSet(txnp, static_cast<TSHttpStatus>(limiter->error()));
      TSHttpTxnHookAdd(txnp, TS_HTTP_SEND_RESPONSE_HDR_HOOK, contp);
      limiter->incrementMetric(RATE_LIMITER_METRIC_EXPIRED);
      TSHttpTxnReenable(txnp, TS_EVENT_HTTP_ERROR);
    }
  }

  return TS_EVENT_NONE;
}

///////////////////////////////////////////////////////////////////////////////
// Parse the configurations for the TXN limiter.