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/*
* Copyright (c) 2023 AtLarge Research
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package org.opendc.web.server.service;
import jakarta.enterprise.context.ApplicationScoped;
import jakarta.persistence.EntityExistsException;
import java.time.Duration;
import java.time.LocalDate;
import java.time.temporal.TemporalAdjusters;
import org.eclipse.microprofile.config.inject.ConfigProperty;
import org.opendc.web.server.model.UserAccounting;
/**
* Service to track the simulation budget of users.
*/
@ApplicationScoped
public final class UserAccountingService {
/**
* The default simulation budget for new users.
*/
private final Duration simulationBudget;
/**
* Construct a {@link UserAccountingService} instance.
*
* @param simulationBudget The default simulation budget for new users.
*/
public UserAccountingService(
@ConfigProperty(name = "opendc.accounting.simulation-budget", defaultValue = "2000m")
Duration simulationBudget) {
this.simulationBudget = simulationBudget;
}
/**
* Return the {@link org.opendc.web.proto.user.UserAccounting} object for the user with the
* specified <code>userId</code>. If the object does not exist in the database, a default value is constructed.
*/
public org.opendc.web.proto.user.UserAccounting getAccounting(String userId) {
UserAccounting accounting = UserAccounting.findByUser(userId);
if (accounting != null) {
return new org.opendc.web.proto.user.UserAccounting(
accounting.periodEnd, accounting.simulationTime, accounting.simulationTimeBudget);
}
return new org.opendc.web.proto.user.UserAccounting(
getNextAccountingPeriod(LocalDate.now()), 0, (int) simulationBudget.toSeconds());
}
/**
* Determine whether the user with <code>userId</code> has any remaining simulation budget.
*
* @param userId The unique identifier of the user.
* @return <code>true</code> when the user still has budget left, <code>false</code> otherwise.
*/
public boolean hasSimulationBudget(String userId) {
UserAccounting accounting = UserAccounting.findByUser(userId);
if (accounting == null) {
return true;
}
return accounting.hasSimulationBudget();
}
/**
* Consume <code>seconds</code> from the simulation budget of the user with <code>userId</code>.
*
* @param userId The unique identifier of the user.
* @param seconds The seconds to consume from the simulation budget.
* @return <code>true</code> if the user has consumed his full budget or <code>false</code> if there is still budget
* remaining.
*/
public boolean consumeSimulationBudget(String userId, int seconds) {
LocalDate today = LocalDate.now();
LocalDate nextAccountingPeriod = getNextAccountingPeriod(today);
// We need to be careful to prevent conflicts in case of concurrency
// 1. First, we try to create the accounting object if it does not exist yet. This may fail if another instance
// creates the object concurrently.
// 2. Second, we check if the budget needs to be reset and try this atomically.
// 3. Finally, we atomically consume the budget from the object
// This is repeated three times in case there is a conflict
for (int i = 0; i < 3; i++) {
UserAccounting accounting = UserAccounting.findByUser(userId);
if (accounting == null) {
try {
UserAccounting newAccounting = UserAccounting.create(
userId, nextAccountingPeriod, (int) simulationBudget.toSeconds(), seconds);
return !newAccounting.hasSimulationBudget();
} catch (EntityExistsException e) {
// Conflict due to concurrency; retry
}
} else {
boolean success;
if (!today.isBefore(accounting.periodEnd)) {
success = accounting.resetBudget(nextAccountingPeriod, seconds);
} else {
success = accounting.consumeBudget(seconds);
}
if (success) {
return !accounting.hasSimulationBudget();
}
}
}
throw new IllegalStateException("Failed to allocate consume budget due to conflict");
}
/**
* Helper method to find next accounting period.
*/
private static LocalDate getNextAccountingPeriod(LocalDate today) {
return today.with(TemporalAdjusters.firstDayOfNextMonth());
}
}
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