Github user zuyu commented on a diff in the pull request:
https://github.com/apache/incubator-quickstep/pull/325#discussion_r153019903
--- Diff: transaction/AdmissionControl.hpp ---
@@ -0,0 +1,83 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 QUICKSTEP_TRANSACTION_ADMISSION_CONTROL_HPP_
+#define QUICKSTEP_TRANSACTION_ADMISSION_CONTROL_HPP_
+
+#include "utility/Macros.hpp"
+#include "transaction/TransactionTable.hpp"
+
+namespace quickstep {
+namespace transaction {
+
+class AdmissionControl {
+ public:
+ /**
+ * @brief Constructor
+ * @param transaction_table A lookup table that stores information about
+ * all the running and waiting transactions.
+ */
+ AdmissionControl(TransactionTable *transaction_table) {}
+
+ virtual ~AdmissionControl() {}
+
+ /**
+ * @brief Admit a transaction to the system.
+ *
+ * @note Check the transaction's compatibility with the other running
+ * transactions. If it is compatible, let it run, otherwise put
+ * the transaction in the waiting list.
+ *
+ * @note Accesses to the transaction_table may need protection.
+ *
+ * @param tid The ID of the given transaction.
+ * @param resource_requests A vector of pairs such that each pair has a
+ * resource ID and its requested access mode.
+ * @return True if the transaction can be admitted, false if it has to
wait.
+ */
+ virtual bool admitTransaction(const transaction_id tid,
+ const std::vector<std::pair<ResourceId,
AccessMode>> &resource_requests) {
+ return false;
+ }
+
+ /**
+ * @brief Attempt to admit a waiting transaction.
+ *
+ * @note Check the transaction's compatibility with the other running
+ * transactions. If it is compatible, let it run, otherwise put
+ * the transaction in the waiting list.
+ *
+ * @note Accesses to the transaction_table may need protection.
+ *
+ * @param tid The ID of the given transaction.
+ * @return True if the transaction can be admitted, false if the
+ * transaction has to wait.
+ */
+ virtual bool admitWaitingTransaction(const transaction_id tid) {
+ return false;
+ }
--- End diff --
Optionally, I think it is better to mark these two APIs as `pure virtual`
methods.
---
