Implemented first version of sharded archive queues.

Updated locking of ObjetOps in order to allow locking of sub-objects.
Make cta-objectstore-dump-object lockfree.

objectstore/ArchiveQueue.hpp

@@ -51,7 +51,14 @@ public:
   
   // Commit with sanity checks (override from ObjectOps
   void commit();
+private:
+  // Validates all summaries are in accordance with each other.
+  bool checkMapsAndShardsCoherency();
   
+  // Rebuild from shards if something goes wrong.
+  void rebuild();
+  
+public:
   // Set/get tape pool
   void setTapePool(const std::string & name);
   std::string getTapePool();
@@ -65,17 +72,25 @@ public:
     const cta::common::dataStructures::MountPolicy policy;
     time_t startTime;
   };
-  void addJobsAndCommit(std::list<JobToAdd> & jobsToAdd);
+  /** Add the jobs to the queue. 
+   * The lock will be used to mark the shards as locked (the lock is the same for 
+   * the main object and the shard, the is no shared access.
+   * As we potentially have to create new shard(s), we need access to the agent 
+   * reference (to generate a non-colliding object name).
+   * We will also log the shard creation (hence the context)
+   */ 
+  void addJobsAndCommit(std::list<JobToAdd> & jobsToAdd, AgentReference & agentReference, log::LogContext & lc);
   /// This version will check for existence of the job in the queue before
   // returns the count and sizes of actually added jobs (if any).
   struct AdditionSummary {
     uint64_t files = 0;
     uint64_t bytes = 0;
   };
-  AdditionSummary addJobsIfNecessaryAndCommit(std::list<JobToAdd> & jobsToAdd);
+  AdditionSummary addJobsIfNecessaryAndCommit(std::list<JobToAdd> & jobsToAdd,
+    AgentReference & agentReference, log::LogContext & lc);
   
   struct JobsSummary {
-    uint64_t files;
+    uint64_t jobs;
     uint64_t bytes;
     time_t oldestJobStartTime;
     uint64_t priority;
@@ -84,7 +99,7 @@ public:
   };
   JobsSummary getJobsSummary();
   
-  void removeJobsAndCommit(const std::list<std::string> & requestsToRemove);
+  void removeJobsAndCommit(const std::list<std::string> & jobsToRemove);
   struct JobDump {
     uint64_t size;
     std::string address;
@@ -111,6 +126,13 @@ public:
     cta::catalogue::Catalogue & catalogue) override;
   
   std::string dump();
+  
+  // The shard size. From experience, 100k is where we start to see performance difference,
+  // but nothing prevents us from using a smaller size.
+  // The performance will be roughly flat until the queue size reaches the square of this limit
+  // (meaning the queue object updates start to take too much time).
+  // with this current value of 25k, the performance should be roughly flat until 25k^2=625M.
+  static const uint64_t c_maxShardSize = 25000;
 };
   
 }}

objectstore/ArchiveQueueShard.cpp

+
+/*
+ * The CERN Tape Archive (CTA) project
+ * Copyright (C) 2015  CERN
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "ArchiveQueueShard.hpp"
+
+
+namespace cta { namespace objectstore {
+
+ArchiveQueueShard::ArchiveQueueShard(Backend& os):
+  ObjectOps<serializers::ArchiveQueueShard, serializers::ArchiveQueueShard_t>(os) { }
+
+ArchiveQueueShard::ArchiveQueueShard(const std::string& address, Backend& os):
+  ObjectOps<serializers::ArchiveQueueShard, serializers::ArchiveQueueShard_t>(os, address) { }
+
+void ArchiveQueueShard::rebuild() {
+  checkPayloadWritable();
+  uint64_t totalSize=0;
+  for (auto j: m_payload.archivejobs()) {
+    totalSize += j.size();
+  }
+  m_payload.set_archivejobstotalsize(totalSize);
+}
+
+void ArchiveQueueShard::garbageCollect(const std::string& presumedOwner, AgentReference& agentReference, log::LogContext& lc, cta::catalogue::Catalogue& catalogue) {
+  throw exception::Exception("In ArchiveQueueShard::garbageCollect(): garbage collection should not be necessary for this type of object.");
+}
+
+ArchiveQueue::CandidateJobList ArchiveQueueShard::getCandidateJobList(uint64_t maxBytes, uint64_t maxFiles, std::set<std::string> archiveRequestsToSkip) {
+  checkPayloadReadable();
+  ArchiveQueue::CandidateJobList ret;
+  ret.remainingBytesAfterCandidates = m_payload.archivejobstotalsize();
+  ret.remainingFilesAfterCandidates = m_payload.archivejobs_size();
+  for (auto & j: m_payload.archivejobs()) {
+    if (!archiveRequestsToSkip.count(j.address())) {
+      ret.candidates.push_back({j.size(), j.address(), (uint16_t)j.copynb()});
+      ret.candidateBytes += j.size();
+      ret.candidateFiles ++;
+    }
+    ret.remainingBytesAfterCandidates -= j.size();
+    ret.remainingFilesAfterCandidates--;
+    if (ret.candidateBytes >= maxBytes || ret.candidateFiles >= maxFiles) break;
+  }
+  return ret;
+}
+
+auto ArchiveQueueShard::removeJobs(const std::list<std::string>& jobsToRemove) -> RemovalResult {
+  checkPayloadWritable();
+  RemovalResult ret;
+  uint64_t totalSize = m_payload.archivejobstotalsize();
+  auto * jl=m_payload.mutable_archivejobs();
+  for (auto &rrt: jobsToRemove) {
+    bool found = false;
+    do {
+      found = false;
+      // Push the found entry all the way to the end.
+      for (size_t i=0; i<(size_t)jl->size(); i++) {
+        if (jl->Get(i).address() == rrt) {
+          found = true;
+          const auto & j = jl->Get(i);
+          ret.removedJobs.emplace_back(JobInfo());
+          ret.removedJobs.back().address = j.address();
+          ret.removedJobs.back().copyNb = j.copynb();
+          ret.removedJobs.back().maxDrivesAllowed = j.maxdrivesallowed();
+          ret.removedJobs.back().minArchiveRequestAge = j.minarchiverequestage();
+          ret.removedJobs.back().priority = j.priority();
+          ret.removedJobs.back().size = j.size();
+          ret.removedJobs.back().startTime = j.starttime();
+          ret.bytesRemoved += j.size();
+          totalSize -= j.size();
+          ret.jobsRemoved++;
+          m_payload.set_archivejobstotalsize(m_payload.archivejobstotalsize() - j.size());
+          while (i+1 < (size_t)jl->size()) {
+            jl->SwapElements(i, i+1);
+            i++;
+          }
+          break;
+        }
+      }
+      // and remove it
+      if (found)
+        jl->RemoveLast();
+    } while (found);
+  }
+  ret.bytesAfter = totalSize;
+  ret.jobsAfter = m_payload.archivejobs_size();
+  return ret;
+}
+
+void ArchiveQueueShard::initialize(const std::string& owner) {
+  ObjectOps<serializers::ArchiveQueueShard, serializers::ArchiveQueueShard_t>::initialize();
+  setOwner(owner);
+  setBackupOwner(owner);
+  m_payload.set_archivejobstotalsize(0);
+  m_payloadInterpreted=true;
+}
+
+auto ArchiveQueueShard::dumpJobs() -> std::list<JobInfo> { 
+  checkPayloadReadable();
+  std::list<JobInfo> ret;
+  for (auto &j: m_payload.archivejobs()) {
+    ret.emplace_back(JobInfo{j.size(), j.address(), (uint16_t)j.copynb(), j.priority(), 
+        j.minarchiverequestage(), j.maxdrivesallowed(), (time_t)j.starttime()});
+  }
+  return ret;
+}
+
+auto ArchiveQueueShard::getJobsSummary() -> JobsSummary {
+  checkPayloadReadable();
+  JobsSummary ret;
+  ret.bytes = m_payload.archivejobstotalsize();
+  return ret;
+}
+
+uint64_t ArchiveQueueShard::addJob(ArchiveQueue::JobToAdd& jobToAdd) {
+  checkPayloadWritable();
+  auto * j = m_payload.mutable_archivejobs()->Add();
+  j->set_address(jobToAdd.archiveRequestAddress);
+  j->set_size(jobToAdd.fileSize);
+  j->set_fileid(jobToAdd.archiveFileId);
+  j->set_copynb(jobToAdd.job.copyNb);
+  j->set_maxdrivesallowed(jobToAdd.policy.maxDrivesAllowed);
+  j->set_priority(jobToAdd.policy.archivePriority);
+  j->set_minarchiverequestage(jobToAdd.policy.archiveMinRequestAge);
+  j->set_starttime(jobToAdd.startTime);
+  m_payload.set_archivejobstotalsize(m_payload.archivejobstotalsize()+jobToAdd.fileSize);
+  return m_payload.archivejobs_size();
+}
+
+
+
+
+}}
\ No newline at end of file

objectstore/ArchiveQueueShard.hpp

+/*
+ * The CERN Tape Archive (CTA) project
+ * Copyright (C) 2015  CERN
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "ArchiveQueue.hpp"
+
+namespace cta { namespace objectstore {
+  
+class ArchiveQueueShard: public ObjectOps<serializers::ArchiveQueueShard, serializers::ArchiveQueueShard_t>  {
+public:
+  // Constructor with undefined address
+  ArchiveQueueShard(Backend & os);
+  
+  // Constructor
+  ArchiveQueueShard(const std::string & address, Backend & os);
+  
+  // Forbid/hide base initializer
+  void initialize() = delete;
+  
+  // Initializer
+  void initialize(const std::string & owner);
+  
+  void garbageCollect(const std::string& presumedOwner, AgentReference& agentReference, log::LogContext& lc, cta::catalogue::Catalogue& catalogue) override;
+
+  struct JobInfo {
+    uint64_t size;
+    std::string address;
+    uint16_t copyNb;
+    uint64_t priority;
+    uint64_t minArchiveRequestAge;
+    uint64_t maxDrivesAllowed;
+    time_t startTime;
+  };
+  std::list<JobInfo> dumpJobs();
+  
+  struct JobsSummary {
+    uint64_t jobs;
+    uint64_t bytes;
+  };
+  JobsSummary getJobsSummary();
+  
+  /**
+   * adds job, returns new size
+   */
+  uint64_t addJob(ArchiveQueue::JobToAdd & jobToAdd);
+  
+  
+  struct RemovalResult {
+    uint64_t jobsRemoved = 0;
+    uint64_t jobsAfter = 0;
+    uint64_t bytesRemoved = 0;
+    uint64_t bytesAfter = 0;
+    std::list<JobInfo> removedJobs;
+  };
+  /**
+   * Removes jobs from shard (and from the to remove list). Returns list of removed jobs.
+   */
+  RemovalResult removeJobs(const std::list<std::string> & jobsToRemove);
+  
+  ArchiveQueue::CandidateJobList getCandidateJobList(uint64_t maxBytes, uint64_t maxFiles, std::set<std::string> archiveRequestsToSkip);
+  
+  /** Re compute summaries in case they do not match the array content. */
+  void rebuild();
+  
+};
+
+}} // namespace cta::objectstore
\ No newline at end of file

objectstore/ArchiveRequest.cpp

@@ -318,7 +318,7 @@ void ArchiveRequest::garbageCollect(const std::string &presumedOwner, AgentRefer
         std::list<ArchiveQueue::JobToAdd> jta;
         jta.push_back({jd, getAddressIfSet(), getArchiveFile().archiveFileID,
           getArchiveFile().fileSize, getMountPolicy(), getEntryLog().time});
-        aq.addJobsIfNecessaryAndCommit(jta);
+        aq.addJobsIfNecessaryAndCommit(jta, agentReference, lc);
         auto queueUpdateTime = t.secs(utils::Timer::resetCounter);
         j->set_owner(aq.getAddressIfSet());
         j->set_status(serializers::AJS_PendingMount);

objectstore/CMakeLists.txt

@@ -51,6 +51,7 @@ SET_SOURCE_FILES_PROPERTIES(${CTAProtoDependants}
 include_directories (${PROTOBUF3_INCLUDE_DIRS})
 add_library (ctaobjectstore SHARED
   ${CTAProtoSources}
+  ObjectOps.cpp
   RootEntry.cpp
   Agent.cpp
   AgentHeartbeatThread.cpp
@@ -58,6 +59,7 @@ add_library (ctaobjectstore SHARED
   AgentRegister.cpp
   AgentWatchdog.cpp
   ArchiveQueue.cpp
+  ArchiveQueueShard.cpp
   RetrieveQueue.cpp
   ArchiveRequest.cpp
   RetrieveRequest.cpp

objectstore/GarbageCollector.cpp

@@ -380,7 +380,7 @@ void GarbageCollector::cleanupDeadAgent(const std::string & address, log::LogCon
     Helpers::getLockedAndFetchedQueue<ArchiveQueue>(aq, aql, m_ourAgentReference, tapepool.first, lc);
     queueLockFetchTime = t.secs(utils::Timer::resetCounter);
     auto jobsSummary=aq.getJobsSummary();
-    filesBefore=jobsSummary.files;
+    filesBefore=jobsSummary.jobs;
     bytesBefore=jobsSummary.bytes;
     // We have the queue. We will loop on the requests, add them to the queue. We will launch their updates 
     // after committing the queue.
@@ -394,7 +394,7 @@ void GarbageCollector::cleanupDeadAgent(const std::string & address, log::LogCon
         }
       }
     }
-    auto addedJobs = aq.addJobsIfNecessaryAndCommit(jtal);
+    auto addedJobs = aq.addJobsIfNecessaryAndCommit(jtal, m_ourAgentReference, lc);
     queueProcessAndCommitTime = t.secs(utils::Timer::resetCounter);
     // If we have an unexpected failure, we will re-run the individual garbage collection. Before that, 
     // we will NOT remove the object from agent's ownership. This variable is declared a bit ahead so
@@ -492,7 +492,7 @@ void GarbageCollector::cleanupDeadAgent(const std::string & address, log::LogCon
             .add("bytesDequeuedAfterErrors", bytesDequeued)
             .add("filesBefore", filesBefore)
             .add("bytesBefore", bytesBefore)
-            .add("filesAfter", jobsSummary.files)
+            .add("filesAfter", jobsSummary.jobs)
             .add("bytesAfter", jobsSummary.bytes)
             .add("queueLockFetchTime", queueLockFetchTime)
             .add("queueProcessAndCommitTime", queueProcessAndCommitTime)

objectstore/GarbageCollectorTest.cpp

@@ -387,7 +387,7 @@ TEST(ObjectStore, GarbageCollectorArchiveRequest) {
       policy.maxDrivesAllowed = 1;
       std::list <cta::objectstore::ArchiveQueue::JobToAdd> jta;
       jta.push_back({jd, ar.getAddressIfSet(), ar.getArchiveFile().archiveFileID, 1000U+pass, policy, time(NULL)});
-      aq.addJobsAndCommit(jta);
+      aq.addJobsAndCommit(jta, agentRef, lc);
     }
     if (pass < 4) { pass++; continue; }
     // TODO: partially migrated or selected
@@ -406,7 +406,7 @@ TEST(ObjectStore, GarbageCollectorArchiveRequest) {
       policy.maxDrivesAllowed = 1;
       std::list <cta::objectstore::ArchiveQueue::JobToAdd> jta;
       jta.push_back({jd, ar.getAddressIfSet(), ar.getArchiveFile().archiveFileID, 1000+pass, policy, time(NULL)});
-      aq.addJobsAndCommit(jta);
+      aq.addJobsAndCommit(jta, agentRef, lc);
     }
     if (pass < 5) { pass++; continue; }
     // - Still marked a not owned but referenced in the agent
@@ -439,8 +439,8 @@ TEST(ObjectStore, GarbageCollectorArchiveRequest) {
     auto d1=aq1.dumpJobs();
     // We expect all jobs with sizes 1002-1005 inclusive to be connected to
     // their respective tape pools.
-    ASSERT_EQ(5, aq0.getJobsSummary().files);
-    ASSERT_EQ(5, aq1.getJobsSummary().files);
+    ASSERT_EQ(5, aq0.getJobsSummary().jobs);
+    ASSERT_EQ(5, aq1.getJobsSummary().jobs);
   }
   // Unregister gc's agent
   cta::objectstore::ScopedExclusiveLock gcal(gcAgent);

objectstore/GenericObject.cpp

@@ -148,18 +148,17 @@ namespace {
   using cta::objectstore::GenericObject;
   using cta::objectstore::ScopedExclusiveLock;
   template <class C>
-  std::string dumpWithType(GenericObject * gop, ScopedSharedLock& lock) {
+  std::string dumpWithType(GenericObject * gop) {
     C typedObject(*gop);
-    lock.transfer(typedObject);
+    ScopedLock::transfer(*gop, typedObject);
     std::string ret = typedObject.dump();
     // Release the lock now as if we let the caller do, it will point
     // to the then-removed typedObject.
-    lock.release();
     return ret;
   }
 }
 
-std::string GenericObject::dump(ScopedSharedLock& lock) {
+std::string GenericObject::dump() {
   checkHeaderReadable();
   google::protobuf::util::JsonPrintOptions options;
   options.add_whitespace = true;
@@ -169,31 +168,31 @@ std::string GenericObject::dump(ScopedSharedLock& lock) {
   google::protobuf::util::MessageToJsonString(m_header, &headerDump, options);
   switch(m_header.type()) {
     case serializers::RootEntry_t:
-      bodyDump = dumpWithType<RootEntry>(this, lock);
+      bodyDump = dumpWithType<RootEntry>(this);
       break;
     case serializers::AgentRegister_t:
-      bodyDump = dumpWithType<AgentRegister>(this, lock);
+      bodyDump = dumpWithType<AgentRegister>(this);
       break;
     case serializers::Agent_t:
-      bodyDump = dumpWithType<Agent>(this, lock);
+      bodyDump = dumpWithType<Agent>(this);
       break;
     case serializers::DriveRegister_t:
-      bodyDump = dumpWithType<DriveRegister>(this, lock);
+      bodyDump = dumpWithType<DriveRegister>(this);
       break;
     case serializers::ArchiveQueue_t:
-      bodyDump = dumpWithType<cta::objectstore::ArchiveQueue>(this, lock);
+      bodyDump = dumpWithType<cta::objectstore::ArchiveQueue>(this);
       break;
     case serializers::RetrieveQueue_t:
-      bodyDump = dumpWithType<cta::objectstore::RetrieveQueue>(this, lock);
+      bodyDump = dumpWithType<cta::objectstore::RetrieveQueue>(this);
       break;
     case serializers::ArchiveRequest_t:
-      bodyDump = dumpWithType<ArchiveRequest>(this, lock);
+      bodyDump = dumpWithType<ArchiveRequest>(this);
       break;
     case serializers::RetrieveRequest_t:
-      bodyDump = dumpWithType<RetrieveRequest>(this, lock);
+      bodyDump = dumpWithType<RetrieveRequest>(this);
       break;
     case serializers::SchedulerGlobalLock_t:
-      bodyDump = dumpWithType<SchedulerGlobalLock>(this, lock);
+      bodyDump = dumpWithType<SchedulerGlobalLock>(this);
       break;
     default:
       std::stringstream err;

objectstore/GenericObject.hpp

@@ -78,7 +78,7 @@ public:
    *
    * @param lock reference to the generic object's lock
    */
-  std::string dump(ScopedSharedLock & lock);
+  std::string dump();
   
   CTA_GENERATE_EXCEPTION_CLASS(UnsupportedType);
   

objectstore/ObjectOps.cpp

+/*
+ * The CERN Tape Archive (CTA) project
+ * Copyright (C) 2015  CERN
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "ObjectOps.hpp"
+
+namespace cta { namespace objectstore {
+
+ObjectOpsBase::~ObjectOpsBase()  {
+  if (m_lockForSubObject) m_lockForSubObject->dereferenceSubObject(*this);
+}
+
+}} 
\ No newline at end of file

objectstore/ObjectOps.hpp

@@ -30,6 +30,8 @@
 namespace cta { namespace objectstore {
 
 class AgentReference;
+class ScopedLock;
+class ScopedExclusiveLock;
 
 class ObjectOpsBase {
   friend class ScopedLock;
@@ -42,6 +44,8 @@ protected:
     m_headerInterpreted(false), m_payloadInterpreted(false),
     m_existingObject(false), m_locksCount(0),
     m_locksForWriteCount(0) {}
+  
+  virtual ~ObjectOpsBase();
 public:
   CTA_GENERATE_EXCEPTION_CLASS(AddressNotSet);
   CTA_GENERATE_EXCEPTION_CLASS(NotLocked);  
@@ -82,6 +86,8 @@ protected:
   void checkWritable() {
     if (m_existingObject && !m_locksForWriteCount)
       throw NotLocked("In ObjectOps::checkWritable: object not locked for write");
+    if (m_existingObject && !m_exclusiveLock && !m_lockForSubObject)
+      throw exception::Exception("In ObjectOps::checkWritable: missing reference to exclusive lock");
   }
   
   void checkReadable() {
@@ -163,6 +169,12 @@ protected:
   int m_locksCount;
   int m_locksForWriteCount;
   bool m_noLock = false;
+  // When locked exclusively, we will keep a reference to the lock,
+  // so we can propagate it to sub objects with minimal passing through.
+  ScopedExclusiveLock * m_exclusiveLock = nullptr;
+  // When being locked as a sub object, we will keep a reference to the lock
+  // we are provided with. Likewise, the lock will update ourselves when released.
+  ScopedLock * m_lockForSubObject = nullptr;
 };
 
 class ScopedLock {
@@ -176,6 +188,39 @@ public:
     return m_locked;
   }
   
+  /**
+   * Virtual function (implemented differently in shared and exclusive locks),
+   * marking the object as locked.
+   * @param objectOps pointer to the ObjectOpsBase.
+   */
+  virtual void setObjectLocked(ObjectOpsBase * objectOps) = 0;
+  
+  /**
+   * Virtual function (implemented differently in shared and exclusive locks),
+   * marking the object as unlocked.
+   * @param objectOps pointer to the ObjectOpsBase.
+   */
+  virtual void setObjectUnlocked(ObjectOpsBase * objectOps) = 0;
+  
+  /**
+   * Expand the scope of the current lock to a sub object, which will also be covered
+   * by this lock. This will allow the sub object to benefit from the same protection
+   * from lack of proper locking. This feature is to be used with sharded objects.
+   */
+  void includeSubObject(ObjectOpsBase & subObject) {
+    // To propagate a lock, we should have one to begin with.
+    checkLocked();
+    ObjectOpsBase * oob = & subObject;
+    // Validate the sub object is defined.
+    checkObjectAndAddressSet(oob);
+    // Propagate the lock to the sub object (this is lock type dependant).
+    setObjectLocked(oob);
+    // Reference ourselves to the sub object so it can declare it destruction to us.
+    oob->m_lockForSubObject = this;
+    // Add a reference to the object.
+    m_subObjectsOps.push_back(oob);
+  }
+  
   /** Move the locked object reference to a new one. This is done when the locked
    * object is a GenericObject and the caller instantiated a derived object from
    * it. The lock follows the move.
@@ -183,20 +228,38 @@ public:
    * use case).
    * New object's locks are moved from the old one (referenced in the lock)
    */
-  void transfer(ObjectOpsBase & newObject) {
-    decltype(m_objectOps) oldObj(m_objectOps);
-    m_objectOps = & newObject;
+  static void transfer(ObjectOpsBase & oldObject, ObjectOpsBase & newObject) {
     // Transfer the locks from old to new object
-    m_objectOps->m_locksCount = oldObj->m_locksCount;
-    m_objectOps->m_locksForWriteCount = oldObj->m_locksForWriteCount;
+    newObject.m_locksCount = oldObject.m_locksCount;
+    newObject.m_locksForWriteCount = oldObject.m_locksForWriteCount;
+    newObject.m_exclusiveLock = oldObject.m_exclusiveLock;
+    newObject.m_lockForSubObject = oldObject.m_lockForSubObject;
+    newObject.m_noLock = oldObject.m_noLock;
     // The old object is not considered locked anymore and should be
     // discarded. A previous call the the new object's constructor should
-    oldObj->m_locksCount =  0;
-    oldObj->m_locksForWriteCount = 0;
+    oldObject.m_locksCount =  0;
+    oldObject.m_locksForWriteCount = 0;
+    oldObject.m_exclusiveLock = nullptr;
+    oldObject.m_lockForSubObject = nullptr;
+    oldObject.m_noLock=false;
+  }
+  
+  /**
+   * 
+   * @param subObject
+   */
+  
+  /**
+   * Dereference a sub object at destruction time
+   * @param subObject
+   */
+  void dereferenceSubObject(ObjectOpsBase & subObject) {
+    m_subObjectsOps.remove(&subObject);
   }
   
   virtual ~ScopedLock() {
-    releaseIfNeeded();
+    // Each child class will have to call releaseIfNeeded() in their own destructor
+    // as it relies on pure virtual members of this base class.