feat(cpp/db): add background handling

Former-commit-id: c10f382912f3cfbeb45cedc0e17d355f9e2b0bc6

cpp/src/db/db_impl.cpp

@@ -6,7 +6,9 @@ namespace vecengine {
 DBImpl::DBImpl(const Options& options_, const std::string& name_)
     : _dbname(name_),
       _env(options_.env),
-      _options(options_) {
+      _options(options_),
+      _bg_work_finish_signal(_mutex),
+      _bg_compaction_scheduled(false) {
 }
 
 Status DBImpl::add_group(const GroupOptions& options_,
@@ -17,6 +19,35 @@ Status DBImpl::add_group(const GroupOptions& options_,
 
 }
 
+void DBImpl::try_schedule_compaction() {
+    if (_bg_compaction_scheduled) return;
+    if (!_bg_error.ok()) return;
+
+    _bg_compaction_scheduled = true;
+    _env->schedule(&DBImpl::BGWork, this);
+}
+
+void DBImpl::BGWork(void* db_) {
+    reinterpret_cast<DBImpl*>(db_)->background_call();
+}
+
+void DBImpl::background_call() {
+    std::lock_guard<std::mutex> lock(_mutex);
+    assert(_bg_compaction_scheduled);
+
+    if (!_bg_error.ok()) return;
+
+    background_compaction();
+}
+
+void DBImpl::background_compaction() {
+
+}
+
+void DBImpl::compact_memory() {
+
+}
+
 /*
  *  DB
  */

cpp/src/db/db_impl.h

@@ -1,6 +1,8 @@
 #ifndef VECENGINE_DB_IMPL_H_
 #define VECENGINE_DB_IMPL_H_
 
+#include <mutex>
+#include <condition_variable>
 #include "db.h"
 
 namespace vecengine {
@@ -15,9 +17,15 @@ public:
             const std::string& group_id_,
             std::string& gid_) override;
 
+    void try_schedule_compaction();
+
     virtual ~DBImpl();
 private:
 
+    static void BGWork(void* db);
+    void background_call();
+    void background_compaction();
+
     Status meta_add_group(const std::string& group_id_);
     Status meta_add_group_file(const std::string& group_id_);
 
@@ -25,6 +33,11 @@ private:
     Env* const _env;
     const Options _options;
 
+    std::mutex _mutex;
+    std::condition_variable _bg_work_finish_signal;
+    bool _bg_compaction_scheduled;
+    Status _bg_error;
+
 }; // DBImpl
 
 } // namespace vecengine