gc bug fix

db/db_impl.cc

@@ -1084,7 +1084,7 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
       }
 
       if (type == kVTableIndex) {
-        if (compact->compaction->level() > config::kNumLevels - 3) {
+        if (compact->compaction->level() >= config::kNumLevels - config::kLevelMergeLevel) {
           if (compact->vtable_builder == nullptr) {
             auto fname = VTableFileName(dbname_, compact->vtb_num);
             status = env_->NewWritableFile(fname, &compact->vtb_file);
@@ -1092,16 +1092,17 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
             compact->vtable_builder = vtable_builder;
           }
           VTableIndex index;
-          VTableReader reader;
           VTableRecord record;
           VTableHandle handle;
 
           status = index.Decode(&value);
 
+          VTableReader reader(index.file_number, this->vtable_manager_);
           std::string vtb_name = VTableFileName(this->dbname_, index.file_number);
           status = reader.Open(this->options_, vtb_name);
           status = reader.Get(index.vtable_handle, &record);
 
+          reader.Close();
           vtable_manager_->AddInvalid(index.file_number);
           compact->vtable_builder->Add(record, &handle);
           VTableIndex new_index;
@@ -1259,7 +1260,6 @@ Status DBImpl::DecodeValue(std::string* value) const {
   }
   if (type == kVTableIndex) {
     VTableIndex index;
-    VTableReader reader;
     VTableRecord record;
 
     Status s = index.Decode(input);
@@ -1267,17 +1267,21 @@ Status DBImpl::DecodeValue(std::string* value) const {
       return s;
     }
 
+    VTableReader reader(index.file_number, this->vtable_manager_);
     std::string vtb_name = VTableFileName(this->dbname_, index.file_number);
     s = reader.Open(this->options_, vtb_name);
     if (!s.ok()) {
+      reader.Close();
       return s;
     }
 
     s = reader.Get(index.vtable_handle, &record);
     if (!s.ok()) {
+      reader.Close();
       return s;
     }
     *value = record.value.ToString();
+    reader.Close();
     return s;
   }
   return Status::Corruption("Unsupported value type");
@@ -1287,7 +1291,7 @@ Status DBImpl::DecodeValue(std::string* value) const {
 
 Status DBImpl::Get(const ReadOptions& options, const Slice& key,
                    std::string* value) {
-  Status s;
+  Status s = Status::TimeOutRead("");
   MutexLock l(&mutex_);
   SequenceNumber snapshot;
   if (options.snapshot != nullptr) {
@@ -1343,7 +1347,7 @@ Status DBImpl::Get(const ReadOptions& options, const Slice& key,
 
 Status DBImpl::Get(const ReadOptions& options, const Slice& key,
                    Fields* fields) {
-  Status s;
+  Status s = Status::TimeOutRead("");
   MutexLock l(&mutex_);
   SequenceNumber snapshot;
   if (options.snapshot != nullptr) {

db/dbformat.h

@@ -24,6 +24,8 @@ namespace leveldb {
 namespace config {
 static const int kNumLevels = 7;
 
+static const int kLevelMergeLevel = 2;
+
 // Level-0 compaction is started when we hit this many files.
 static const int kL0_CompactionTrigger = 4;
 

db/filename.cc

@@ -36,7 +36,7 @@ std::string TableFileName(const std::string& dbname, uint64_t number) {
 }
 
 std::string VTableFileName(const std::string& dbname, uint64_t number) {
-  assert(number > 0);
+  // assert(number > 0);
   return MakeFileName(dbname, number, "vtb");
 }
 

include/leveldb/status.h

@@ -52,6 +52,9 @@ class LEVELDB_EXPORT Status {
   static Status IOError(const Slice& msg, const Slice& msg2 = Slice()) {
     return Status(kIOError, msg, msg2);
   }
+  static Status TimeOutRead(const Slice& msg, const Slice& msg2 = Slice()) {
+    return Status(kTimeOutRead, msg, msg2);
+  }
 
   // Returns true iff the status indicates success.
   bool ok() const { return (state_ == nullptr); }
@@ -71,6 +74,8 @@ class LEVELDB_EXPORT Status {
   // Returns true iff the status indicates an InvalidArgument.
   bool IsInvalidArgument() const { return code() == kInvalidArgument; }
 
+  bool IsTimeOutReadError() const { return code() == kTimeOutRead; }
+
   // Return a string representation of this status suitable for printing.
   // Returns the string "OK" for success.
   std::string ToString() const;
@@ -82,7 +87,8 @@ class LEVELDB_EXPORT Status {
     kCorruption = 2,
     kNotSupported = 3,
     kInvalidArgument = 4,
-    kIOError = 5
+    kIOError = 5,
+    kTimeOutRead = 6
   };
 
   Code code() const {

table/vtable_manager.cc

@@ -1,5 +1,6 @@
 #include "table/vtable_manager.h"
 
+#include "db/dbformat.h"
 #include "db/filename.h"
 #include <iostream>
 #include <ostream>
@@ -13,8 +14,9 @@ namespace leveldb {
 
 struct GCInfo {
   std::string dbname;
-  std::vector<uint64_t> file_list;
+  std::set<uint64_t>* file_list;
   Env* env = nullptr;
+  VTableManager* vtable_manager = nullptr;
 };
 
 void VTableMeta::Encode(std::string* target) const {
@@ -50,7 +52,7 @@ Status VTableManager::AddInvalid(uint64_t file_num) {
 
   vtables_[file_num].invalid_num += 1;
   if (vtables_[file_num].invalid_num >= vtables_[file_num].records_num) {
-    invalid_.emplace_back(file_num);
+    invalid_.insert(file_num);
   }
 
   MaybeScheduleGarbageCollect();
@@ -127,7 +129,7 @@ Status VTableManager::LoadVTableMeta() {
       }
       AddVTable(vtable_meta);
       if (vtable_meta.invalid_num >= vtable_meta.records_num) {
-        invalid_.emplace_back(vtable_meta.number);
+        invalid_.insert(vtable_meta.number);
       }
     } else {
       return s;
@@ -139,31 +141,43 @@ Status VTableManager::LoadVTableMeta() {
 
 void VTableManager::MaybeScheduleGarbageCollect() {
   size_t size = 0;
+  auto* delete_list = new std::set<uint64_t>();
   for (auto & file_num : invalid_) {
     size += vtables_[file_num].table_size;
   }
   if (size >= gc_threshold_) {
     auto* gc_info = new GCInfo;
     gc_info->dbname = dbname_;
-    gc_info->file_list = invalid_;
+    gc_info->file_list = delete_list;
     gc_info->env = env_;
+    gc_info->vtable_manager = this;
     env_->StartThread(&VTableManager::BackgroudGC, gc_info);
-    for (auto & file_num : gc_info->file_list) {
+    // for (auto & file_num : gc_info->file_list) {
-      RemoveVTable(file_num);
+    //   RemoveVTable(file_num);
-      auto it = std::remove(invalid_.begin(), invalid_.end(), file_num);
+    //   auto it = std::remove(invalid_.begin(), invalid_.end(), file_num);
-    }
+    // }
   }
 }
 
 void VTableManager::BackgroudGC(void* gc_info) {
   auto info = reinterpret_cast<GCInfo*>(gc_info);
-  for (auto & file_num : info->file_list) {
+  for (auto & file_num : *info->file_list) {
+    // if (file_num <= 0) {continue;}
     auto fname = VTableFileName(info->dbname, file_num);
-    info->env->RemoveFile(fname);
+    if (info->vtable_manager->vtables_[file_num].ref <= 0) {
+      info->env->RemoveFile(fname);
+      info->vtable_manager->invalid_.erase(file_num);
+    }
   }
-  delete info;
 }
 
+void VTableManager::RefVTable(uint64_t file_num) {
+  vtables_[file_num].ref += 1;
+}
 
+void VTableManager::UnrefVTable(uint64_t file_num) {
+  vtables_[file_num].ref -= 1;
+}
 
 } // namespace leveldb

table/vtable_manager.h

@@ -2,6 +2,7 @@
 #define VTABLE_MANAGER_H
 
 #include <map>
+#include <set>
 
 #include "leveldb/env.h"
 #include "leveldb/slice.h"
@@ -18,6 +19,8 @@ struct VTableMeta {
 
   uint64_t table_size;
 
+  uint64_t ref = 0;
+
   void Encode(std::string* target) const;
   Status Decode(Slice* input);
 
@@ -43,6 +46,10 @@ class VTableManager {
 
     Status LoadVTableMeta();
 
+    void RefVTable(uint64_t file_num);
+
+    void UnrefVTable(uint64_t file_num);
+
     void MaybeScheduleGarbageCollect();
 
     static void BackgroudGC(void* gc_info);
@@ -51,7 +58,7 @@ class VTableManager {
     std::string dbname_;
     Env* env_;
     std::map<uint64_t, VTableMeta> vtables_;
-    std::vector<uint64_t> invalid_;
+    std::set<uint64_t> invalid_;
     size_t gc_threshold_;
 };
 

table/vtable_reader.cc

@@ -7,14 +7,23 @@
 namespace leveldb {
   Status VTableReader::Open(const Options& options, std::string fname) {
     options_ = options;
-    return options_.env->NewRandomAccessFile(fname, &file_);
+    Status s = options_.env->NewRandomAccessFile(fname, &file_);
+    if (manager_ != nullptr) {
+      manager_->RefVTable(fnum_);
+    }
+    return s;
   }
 
   Status VTableReader::Get(const VTableHandle& handle,
                            VTableRecord* record) const {
     auto buf = new char[handle.size];
     Slice input;
-    Status s = file_->Read(handle.offset, handle.size, &input, buf);
+    Status s;
+    if (file_ != nullptr) {
+      s = file_->Read(handle.offset, handle.size, &input, buf);
+    } else {
+      s = Status::TimeOutRead("Get for another time");
+    }
 
     if (!s.ok()) {
       return s;
@@ -35,5 +44,11 @@ namespace leveldb {
     return s;
   }
 
+  void VTableReader::Close() {
+    file_ = nullptr;
+    if (manager_ != nullptr) {
+      manager_->UnrefVTable(fnum_);
+    }
+  }
 
 } // namespace leveldb

table/vtable_reader.h

@@ -11,18 +11,29 @@
 #include "util/coding.h"
 
 #include "vtable_format.h"
+#include "vtable_manager.h"
 
 namespace leveldb {
 
 class VTableReader {
   public:
+    VTableReader() = default;
+
+    VTableReader(uint64_t fnum, VTableManager *manager) :
+      fnum_(fnum),
+      manager_(manager) {};
+
     Status Open(const Options& options, std::string fname);
 
     Status Get(const VTableHandle& handle,
                VTableRecord* record) const ;
+
+    void Close();
   private:
     Options options_;
+    uint64_t fnum_;
     RandomAccessFile* file_{nullptr};
+    VTableManager* manager_{nullptr};
 };
 
 } // namespace leveldb