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usagemon.cpp

/***************************************************************
 *
 * Copyright (C) 1990-2007, Condor Team, Computer Sciences Department,
 * University of Wisconsin-Madison, WI.
 * 
 * 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.
 *
 ***************************************************************/


#include "condor_common.h"
#include "condor_debug.h"
#include "usagemon.h"

UsageMonitor::~UsageMonitor()
{
      for (UsageRec *rec = first, *next = NULL; rec; rec = next) {
            next = rec->next;
            delete rec;
      }
}

int
UsageMonitor::Request(double units)
{
      UsageRec *rec;

      if (interval == 0) return -1;

      time_t current_time = time(NULL);

      // clean up any old records at the head of the history list
      for (rec = first; rec && rec->timestamp < current_time - interval;
             first = rec->next, delete rec, rec = first);
      if (first == NULL) last = NULL;

      // special case: units > max_units -- reserve larger window of time
      if (units > max_units) {
            dprintf(D_FULLDEBUG, "usagemon: %.0f > %.0f (units > max_units) "
                        "special case\n", units, max_units);
            // wait until our history clears
            if (last) {
                  int wait_time = last->timestamp + interval - current_time;
                  dprintf(D_FULLDEBUG, "usagemon: request for %.0f must wait %d "
                              "seconds\n", units, wait_time);
                  return wait_time;
            }
            // okay, history is clear, so grant request
            // set time forward to reserve larger window
            time_t forward_time = current_time +
                  (int)(((units/max_units)-1)*interval);
            dprintf(D_FULLDEBUG, "usagemon: request for %.0f forwarded dated by "
                        "%ld seconds\n",  units, (long)(forward_time - current_time));
            // add new history record (list is empty!)
            rec = new UsageRec(units, forward_time);
            first = last = rec;
            return 0;
      }

      // first, find usage in the past interval seconds
      double usage_this_interval = 0.0;
      for (rec = first; rec; rec = rec->next) {
            usage_this_interval += rec->units;
      }

      dprintf(D_FULLDEBUG, "usagemon: request=%.0f, history=%.0f, max=%.0f\n",
                  units, usage_this_interval, max_units);

      // then, check to see if this request will overflow the maximum
      double overflow = usage_this_interval + units - max_units;
      if (overflow <= 0.0) {        // request granted
            // add new history record to the end of the list
            if (last && last->timestamp == current_time) {
                  last->units += units;
            } else {
                  rec = new UsageRec(units, current_time);
                  if (last) {
                        last->next = rec;
                        last = rec;
                  } else {
                        first = last = rec;
                  }
            }
            return 0;
      }

      // if this request would overflow, find how many seconds it will take for
      // the necessary records to expire before we will allow this request
      usage_this_interval = 0;
      for (rec = first; rec; rec = rec->next) {
            usage_this_interval += rec->units;
            if (usage_this_interval > overflow) {
                  int wait_time = rec->timestamp + interval - current_time;
                  dprintf(D_FULLDEBUG, "usagemon: request for %.0f must wait %d "
                              "seconds\n", units, wait_time);
                  return wait_time;
            }
      }

      return -1;                          // should never get here
}

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