Added a CachePolicy class, which can be used to configure how aggressively the

cache should be pruned.

This will be used in an upcoming CL to help remove inactive cached data.

PiperOrigin-RevId: 280536975

Author: amablue

database/src/desktop/core/cache_policy.cc

@@ -0,0 +1,59 @@
+// Copyright 2019 Google LLC
+//
+// 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 "database/src/desktop/core/cache_policy.h"
+
+#include <cstdint>
+#include <limits>
+
+namespace firebase {
+namespace database {
+namespace internal {
+
+const uint64_t kServerUpdatesBetweenCacheSizeChecks = 1000;
+
+const uint64_t kMaxNumberOfPrunableQueriesToKeep = 1000;
+
+// 20% at a time until we're below our max.
+const double kPercentOfQueriesToPruneAtOnce = 0.2;
+
+CachePolicy::~CachePolicy() {}
+
+LRUCachePolicy::LRUCachePolicy(uint64_t max_size_bytes)
+    : max_size_bytes_(max_size_bytes) {}
+
+LRUCachePolicy::~LRUCachePolicy() {}
+
+bool LRUCachePolicy::ShouldPrune(uint64_t current_size_bytes,
+                                 uint64_t count_of_prunable_queries) const {
+  return current_size_bytes > max_size_bytes_ ||
+         count_of_prunable_queries > kMaxNumberOfPrunableQueriesToKeep;
+}
+
+bool LRUCachePolicy::ShouldCheckCacheSize(
+    uint64_t server_updates_since_last_check) const {
+  return server_updates_since_last_check > kServerUpdatesBetweenCacheSizeChecks;
+}
+
+double LRUCachePolicy::GetPercentOfQueriesToPruneAtOnce() const {
+  return kPercentOfQueriesToPruneAtOnce;
+}
+
+uint64_t LRUCachePolicy::GetMaxNumberOfQueriesToKeep() const {
+  return kMaxNumberOfPrunableQueriesToKeep;
+}
+
+}  // namespace internal
+}  // namespace database
+}  // namespace firebase

database/src/desktop/core/cache_policy.h

@@ -0,0 +1,63 @@
+// Copyright 2019 Google LLC
+//
+// 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.
+
+#ifndef FIREBASE_DATABASE_CLIENT_CPP_SRC_DESKTOP_CORE_CACHE_POLICY_H_
+#define FIREBASE_DATABASE_CLIENT_CPP_SRC_DESKTOP_CORE_CACHE_POLICY_H_
+
+#include <cstdint>
+
+namespace firebase {
+namespace database {
+namespace internal {
+
+class CachePolicy {
+ public:
+  virtual ~CachePolicy();
+
+  virtual bool ShouldPrune(uint64_t current_size_bytes,
+                           uint64_t count_of_prunable_queries) const = 0;
+
+  virtual bool ShouldCheckCacheSize(
+      uint64_t serverUpdatesSinceLastCheck) const = 0;
+
+  virtual double GetPercentOfQueriesToPruneAtOnce() const = 0;
+
+  virtual uint64_t GetMaxNumberOfQueriesToKeep() const = 0;
+};
+
+class LRUCachePolicy : public CachePolicy {
+ public:
+  explicit LRUCachePolicy(uint64_t max_size_bytes);
+
+  ~LRUCachePolicy() override;
+
+  bool ShouldPrune(uint64_t current_size_bytes,
+                   uint64_t count_of_prunable_queries) const override;
+
+  bool ShouldCheckCacheSize(
+      uint64_t server_updates_since_last_check) const override;
+
+  double GetPercentOfQueriesToPruneAtOnce() const override;
+
+  uint64_t GetMaxNumberOfQueriesToKeep() const override;
+
+ private:
+  const uint64_t max_size_bytes_;
+};
+
+}  // namespace internal
+}  // namespace database
+}  // namespace firebase
+
+#endif  // FIREBASE_DATABASE_CLIENT_CPP_SRC_DESKTOP_CORE_CACHE_POLICY_H_