From d2545cbf7f7dfae4b1d01c299ed0e17d71664439 Mon Sep 17 00:00:00 2001

From: Hiram Chirino <hiram@hiramchirino.com>

Date: Tue, 30 Oct 2012 16:56:52 -0400

Subject: [PATCH 5/6] Added a DB:SuspendCompations() and DB:ResumeCompactions()

 methods. Fixes issue #184

https://code.google.com/p/leveldb/issues/detail?id=184

---

 db/db_impl.cc        | 36 ++++++++++++++++++++++++++++++++++++

 db/db_impl.h         |  9 +++++++++

 db/db_test.cc        |  4 ++++

 include/leveldb/db.h |  6 ++++++

 4 files changed, 55 insertions(+)

diff --git a/db/db_impl.cc b/db/db_impl.cc

index 395d317..593a5b5 100644

--- a/db/db_impl.cc

+++ b/db/db_impl.cc

@@ -124,6 +124,9 @@ DBImpl::DBImpl(const Options& options, const std::string& dbname)

       dbname_(dbname),

       db_lock_(NULL),

       shutting_down_(NULL),

+      suspend_cv(&suspend_mutex),

+      suspend_count(0),

+      suspended(false),

       bg_cv_(&mutex_),

       mem_(new MemTable(internal_comparator_)),

       imm_(NULL),

@@ -1398,6 +1401,39 @@ void DBImpl::GetApproximateSizes(

   }

 }

+void DBImpl::SuspendCompactions() {

+  MutexLock l(& suspend_mutex);

+  env_->Schedule(&SuspendWork, this);

+  suspend_count++;

+  while( !suspended ) {

+    suspend_cv.Wait();

+  }  

+}

+void DBImpl::SuspendWork(void* db) {

+  reinterpret_cast<DBImpl*>(db)->SuspendCallback();

+}

+void DBImpl::SuspendCallback() {

+    MutexLock l(&suspend_mutex);

+    Log(options_.info_log, "Compactions suspended");

+    suspended = true;

+    suspend_cv.SignalAll();

+    while( suspend_count > 0 ) {

+        suspend_cv.Wait();

+    }

+    suspended = false;

+    suspend_cv.SignalAll();

+    Log(options_.info_log, "Compactions resumed");

+}

+void DBImpl::ResumeCompactions() {

+    MutexLock l(&suspend_mutex);

+    suspend_count--;

+    suspend_cv.SignalAll();

+    while( suspended ) {

+      suspend_cv.Wait();

+    }  

+}

+

+

 // Default implementations of convenience methods that subclasses of DB

 // can call if they wish

 Status DB::Put(const WriteOptions& opt, const Slice& key, const Slice& value) {

diff --git a/db/db_impl.h b/db/db_impl.h

index 3c8d711..9f3949c 100644

--- a/db/db_impl.h

+++ b/db/db_impl.h

@@ -41,6 +41,8 @@ class DBImpl : public DB {

   virtual bool GetProperty(const Slice& property, std::string* value);

   virtual void GetApproximateSizes(const Range* range, int n, uint64_t* sizes);

   virtual void CompactRange(const Slice* begin, const Slice* end);

+  virtual void SuspendCompactions();

+  virtual void ResumeCompactions();

   // Extra methods (for testing) that are not in the public DB interface

@@ -125,6 +127,13 @@ class DBImpl : public DB {

   // Lock over the persistent DB state.  Non-NULL iff successfully acquired.

   FileLock* db_lock_;

+  port::Mutex suspend_mutex;

+  port::CondVar suspend_cv;

+  int suspend_count;

+  bool suspended;

+  static void SuspendWork(void* db);

+  void SuspendCallback();

+

   // State below is protected by mutex_

   port::Mutex mutex_;

   port::AtomicPointer shutting_down_;

diff --git a/db/db_test.cc b/db/db_test.cc

index 49aae04..782be38 100644

--- a/db/db_test.cc

+++ b/db/db_test.cc

@@ -1801,6 +1801,10 @@ class ModelDB: public DB {

   explicit ModelDB(const Options& options): options_(options) { }

   ~ModelDB() { }

+  

+  virtual void SuspendCompactions() {}

+  virtual void ResumeCompactions() {}

+  

   virtual Status Put(const WriteOptions& o, const Slice& k, const Slice& v) {

     return DB::Put(o, k, v);

   }

diff --git a/include/leveldb/db.h b/include/leveldb/db.h

index da8b11a..089707c 100644

--- a/include/leveldb/db.h

+++ b/include/leveldb/db.h

@@ -140,6 +140,12 @@ class DB {

   //    db->CompactRange(NULL, NULL);

   virtual void CompactRange(const Slice* begin, const Slice* end) = 0;

+  // Suspends the background compaction thread.  This methods

+  // returns once suspended.

+  virtual void SuspendCompactions() = 0;

+  // Resumes a suspended background compation thread.

+  virtual void ResumeCompactions() = 0;

+

  private:

   // No copying allowed

   DB(const DB&);

-- 

1.8.3.1