thread local for tailing iterator

Summary:
replace the super version acquisision in tailing itrator with thread
local

Test Plan: will post results

Reviewers: igor, haobo, sdong, yhchiang, dhruba

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17757

db/column_family.cc

@@ -270,6 +270,10 @@ ColumnFamilyData::~ColumnFamilyData() {
   }
 }
 
+const EnvOptions* ColumnFamilyData::soptions() const {
+  return &(column_family_set_->storage_options_);
+}
+
 void ColumnFamilyData::SetCurrent(Version* current) {
   current_ = current;
   need_slowdown_for_num_level0_files_ =

db/column_family.h

@@ -168,6 +168,7 @@ class ColumnFamilyData {
 
   // thread-safe
   const Options* options() const { return &options_; }
+  const EnvOptions* soptions() const;
 
   InternalStats* internal_stats() { return internal_stats_.get(); }
 

db/db_impl.cc

@@ -3238,45 +3238,6 @@ Iterator* DBImpl::TEST_NewInternalIterator(ColumnFamilyHandle* column_family) {
   return NewInternalIterator(roptions, cfd, super_version);
 }
 
-std::pair<Iterator*, Iterator*> DBImpl::GetTailingIteratorPair(
-    const ReadOptions& options, ColumnFamilyData* cfd,
-    uint64_t* superversion_number) {
-
-  mutex_.Lock();
-  SuperVersion* super_version = cfd->GetSuperVersion()->Ref();
-  if (superversion_number != nullptr) {
-    *superversion_number = cfd->GetSuperVersionNumber();
-  }
-  mutex_.Unlock();
-
-  Iterator* mutable_iter = super_version->mem->NewIterator(options);
-  // create a DBIter that only uses memtable content; see NewIterator()
-  mutable_iter =
-      NewDBIterator(&dbname_, env_, *cfd->options(), cfd->user_comparator(),
-                    mutable_iter, kMaxSequenceNumber);
-
-  std::vector<Iterator*> list;
-  super_version->imm->AddIterators(options, &list);
-  super_version->current->AddIterators(options, storage_options_, &list);
-  Iterator* immutable_iter =
-      NewMergingIterator(&cfd->internal_comparator(), &list[0], list.size());
-
-  // create a DBIter that only uses memtable content; see NewIterator()
-  immutable_iter =
-      NewDBIterator(&dbname_, env_, *cfd->options(), cfd->user_comparator(),
-                    immutable_iter, kMaxSequenceNumber);
-
-  // register cleanups
-  mutable_iter->RegisterCleanup(CleanupIteratorState,
-    new IterState(this, &mutex_, super_version), nullptr);
-
-  // bump the ref one more time since it will be Unref'ed twice
-  immutable_iter->RegisterCleanup(CleanupIteratorState,
-    new IterState(this, &mutex_, super_version->Ref()), nullptr);
-
-  return std::make_pair(mutable_iter, immutable_iter);
-}
-
 int64_t DBImpl::TEST_MaxNextLevelOverlappingBytes(
     ColumnFamilyHandle* column_family) {
   ColumnFamilyData* cfd;
@@ -3628,7 +3589,7 @@ Iterator* DBImpl::NewIterator(const ReadOptions& options,
 
   Iterator* iter;
   if (options.tailing) {
-    iter = new TailingIterator(this, options, cfd);
+    iter = new TailingIterator(env_, this, options, cfd);
   } else {
     SequenceNumber latest_snapshot = versions_->LastSequence();
     SuperVersion* sv = nullptr;
@@ -3640,7 +3601,7 @@ Iterator* DBImpl::NewIterator(const ReadOptions& options,
         options.snapshot != nullptr
             ? reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_
             : latest_snapshot;
-    iter = NewDBIterator(&dbname_, env_, *cfd->options(),
+    iter = NewDBIterator(env_, *cfd->options(),
                          cfd->user_comparator(), iter, snapshot);
   }
 
@@ -3682,7 +3643,7 @@ Status DBImpl::NewIterators(
   if (options.tailing) {
     for (auto cfh : column_families) {
       auto cfd = reinterpret_cast<ColumnFamilyHandleImpl*>(cfh)->cfd();
-      iterators->push_back(new TailingIterator(this, options, cfd));
+      iterators->push_back(new TailingIterator(env_, this, options, cfd));
     }
   } else {
     for (size_t i = 0; i < column_families.size(); ++i) {
@@ -3695,7 +3656,7 @@ Status DBImpl::NewIterators(
               : latest_snapshot;
 
       auto iter = NewInternalIterator(options, cfd, super_versions[i]);
-      iter = NewDBIterator(&dbname_, env_, *cfd->options(),
+      iter = NewDBIterator(env_, *cfd->options(),
                            cfd->user_comparator(), iter, snapshot);
       iterators->push_back(iter);
     }

db/db_impl.h

@@ -409,14 +409,6 @@ class DBImpl : public DB {
   // hold the data set.
   Status ReFitLevel(ColumnFamilyData* cfd, int level, int target_level = -1);
 
-  // Returns a pair of iterators (mutable-only and immutable-only) used
-  // internally by TailingIterator and stores cfd->GetSuperVersionNumber() in
-  // *superversion_number. These iterators are always up-to-date, i.e. can
-  // be used to read new data.
-  std::pair<Iterator*, Iterator*> GetTailingIteratorPair(
-      const ReadOptions& options, ColumnFamilyData* cfd,
-      uint64_t* superversion_number);
-
   // table_cache_ provides its own synchronization
   std::shared_ptr<Cache> table_cache_;
 

db/db_impl_readonly.cc

@@ -80,7 +80,7 @@ Iterator* DBImplReadOnly::NewIterator(const ReadOptions& options,
   SequenceNumber latest_snapshot = versions_->LastSequence();
   Iterator* internal_iter = NewInternalIterator(options, cfd, super_version);
   return NewDBIterator(
-      &dbname_, env_, *cfd->options(), cfd->user_comparator(), internal_iter,
+      env_, *cfd->options(), cfd->user_comparator(), internal_iter,
       (options.snapshot != nullptr
            ? reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_
            : latest_snapshot));

db/db_iter.cc

@@ -57,10 +57,9 @@ class DBIter: public Iterator {
     kReverse
   };
 
-  DBIter(const std::string* dbname, Env* env, const Options& options,
+  DBIter(Env* env, const Options& options,
          const Comparator* cmp, Iterator* iter, SequenceNumber s)
-      : dbname_(dbname),
-        env_(env),
+      : env_(env),
         logger_(options.info_log.get()),
         user_comparator_(cmp),
         user_merge_operator_(options.merge_operator.get()),
@@ -117,7 +116,6 @@ class DBIter: public Iterator {
     }
   }
 
-  const std::string* const dbname_;
   Env* const env_;
   Logger* logger_;
   const Comparator* const user_comparator_;
@@ -467,13 +465,12 @@ void DBIter::SeekToLast() {
 }  // anonymous namespace
 
 Iterator* NewDBIterator(
-    const std::string* dbname,
     Env* env,
     const Options& options,
     const Comparator *user_key_comparator,
     Iterator* internal_iter,
     const SequenceNumber& sequence) {
-  return new DBIter(dbname, env, options, user_key_comparator,
+  return new DBIter(env, options, user_key_comparator,
                     internal_iter, sequence);
 }
 

db/db_iter.h

@@ -18,7 +18,6 @@ namespace rocksdb {
 // "*internal_iter") that were live at the specified "sequence" number
 // into appropriate user keys.
 extern Iterator* NewDBIterator(
-    const std::string* dbname,
     Env* env,
     const Options& options,
     const Comparator *user_key_comparator,

db/tailing_iter.cc

@@ -7,22 +7,31 @@
 
 #include <string>
 #include <utility>
+#include <vector>
 #include "db/db_impl.h"
+#include "db/db_iter.h"
 #include "db/column_family.h"
+#include "rocksdb/env.h"
 #include "rocksdb/slice.h"
 #include "rocksdb/slice_transform.h"
+#include "table/merger.h"
 
 namespace rocksdb {
 
-TailingIterator::TailingIterator(DBImpl* db, const ReadOptions& options,
-                                 ColumnFamilyData* cfd)
-    : db_(db),
-      options_(options),
+TailingIterator::TailingIterator(Env* const env, DBImpl* db,
+    const ReadOptions& read_options, ColumnFamilyData* cfd)
+    : env_(env),
+      db_(db),
+      read_options_(read_options),
       cfd_(cfd),
-      version_number_(0),
+      super_version_(nullptr),
       current_(nullptr),
       status_(Status::InvalidArgument("Seek() not called on this iterator")) {}
 
+TailingIterator::~TailingIterator() {
+  Cleanup();
+}
+
 bool TailingIterator::Valid() const {
   return current_ != nullptr;
 }
@@ -60,7 +69,7 @@ void TailingIterator::Seek(const Slice& target) {
   const Comparator* cmp = cfd_->user_comparator();
   if (!is_prev_set_ || cmp->Compare(prev_key_, target) >= !is_prev_inclusive_ ||
       (immutable_->Valid() && cmp->Compare(target, immutable_->key()) > 0) ||
-      (options_.prefix_seek && !IsSamePrefix(target))) {
+      (read_options_.prefix_seek && !IsSamePrefix(target))) {
     SeekImmutable(target);
   }
 
@@ -122,14 +131,45 @@ void TailingIterator::SeekToLast() {
   status_ = Status::NotSupported("This iterator doesn't support SeekToLast()");
 }
 
-void TailingIterator::CreateIterators() {
-  std::pair<Iterator*, Iterator*> iters =
-      db_->GetTailingIteratorPair(options_, cfd_, &version_number_);
+void TailingIterator::Cleanup() {
+  // Release old super version if necessary
+  mutable_.reset();
+  immutable_.reset();
+  if (super_version_ != nullptr && super_version_->Unref()) {
+    DBImpl::DeletionState deletion_state;
+    db_->mutex_.Lock();
+    super_version_->Cleanup();
+    db_->FindObsoleteFiles(deletion_state, false, true);
+    db_->mutex_.Unlock();
+    delete super_version_;
+    if (deletion_state.HaveSomethingToDelete()) {
+      db_->PurgeObsoleteFiles(deletion_state);
+    }
+  }
+}
 
-  assert(iters.first && iters.second);
+void TailingIterator::CreateIterators() {
+  Cleanup();
+  super_version_= cfd_->GetReferencedSuperVersion(&(db_->mutex_));
+
+  Iterator* mutable_iter = super_version_->mem->NewIterator(read_options_);
+  // create a DBIter that only uses memtable content; see NewIterator()
+  mutable_.reset(
+      NewDBIterator(env_, *cfd_->options(), cfd_->user_comparator(),
+                    mutable_iter, kMaxSequenceNumber));
+
+  std::vector<Iterator*> list;
+  super_version_->imm->AddIterators(read_options_, &list);
+  super_version_->current->AddIterators(
+      read_options_, *cfd_->soptions(), &list);
+  Iterator* immutable_iter =
+      NewMergingIterator(&cfd_->internal_comparator(), &list[0], list.size());
+
+  // create a DBIter that only uses memtable content; see NewIterator()
+  immutable_.reset(
+      NewDBIterator(env_, *cfd_->options(), cfd_->user_comparator(),
+                    immutable_iter, kMaxSequenceNumber));
 
-  mutable_.reset(iters.first);
-  immutable_.reset(iters.second);
   current_ = nullptr;
   is_prev_set_ = false;
 }
@@ -154,8 +194,8 @@ void TailingIterator::UpdateCurrent() {
 }
 
 bool TailingIterator::IsCurrentVersion() const {
-  return mutable_ != nullptr && immutable_ != nullptr &&
-         version_number_ == cfd_->GetSuperVersionNumber();
+  return super_version_ != nullptr &&
+         super_version_->version_number == cfd_->GetSuperVersionNumber();
 }
 
 bool TailingIterator::IsSamePrefix(const Slice& target) const {

db/tailing_iter.h

@@ -13,6 +13,8 @@
 namespace rocksdb {
 
 class DBImpl;
+class Env;
+class SuperVersion;
 class ColumnFamilyData;
 
 /**
@@ -25,9 +27,9 @@ class ColumnFamilyData;
  */
 class TailingIterator : public Iterator {
  public:
-  TailingIterator(DBImpl* db, const ReadOptions& options,
+  TailingIterator(Env* const env, DBImpl* db, const ReadOptions& read_options,
                   ColumnFamilyData* cfd);
-  virtual ~TailingIterator() {}
+  virtual ~TailingIterator();
 
   virtual bool Valid() const override;
   virtual void SeekToFirst() override;
@@ -40,10 +42,13 @@ class TailingIterator : public Iterator {
   virtual Status status() const override;
 
  private:
+  void Cleanup();
+
+  Env* const env_;
   DBImpl* const db_;
-  const ReadOptions options_;
+  const ReadOptions read_options_;
   ColumnFamilyData* const cfd_;
-  uint64_t version_number_;
+  SuperVersion* super_version_;
 
   // TailingIterator merges the contents of the two iterators below (one using
   // mutable memtable contents only, other over SSTs and immutable memtables).