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/*
* include/framework/scheduling/Version.h
*
* Copyright (C) 2023-2024 Douglas B. Rumbaugh <drumbaugh@psu.edu>
*
* Distributed under the Modified BSD License.
*
*/
#pragma once
#include <mutex>
#include "framework/structure/BufferView.h"
#include "framework/structure/ExtensionStructure.h"
#include "framework/structure/MutableBuffer.h"
namespace de {
template <ShardInterface ShardType, QueryInterface<ShardType> QueryType>
class Version {
private:
typedef typename ShardType::RECORD RecordType;
typedef MutableBuffer<RecordType> Buffer;
typedef ExtensionStructure<ShardType, QueryType> Structure;
typedef BufferView<RecordType> BufView;
public:
Version(size_t number = 0)
: m_buffer(nullptr), m_structure(nullptr), m_active_merge(false),
m_epoch_number(number), m_buffer_head(0) {}
Version(size_t number, Structure *structure, Buffer *buff, size_t head)
: m_buffer(buff), m_structure(structure), m_active_merge(false),
m_epoch_number(number), m_buffer_head(head) {
structure->take_reference();
}
~Version() {
if (m_structure) {
m_structure->release_reference();
}
if (m_structure->get_reference_count() == 0) {
delete m_structure;
}
}
/*
* Versions are *not* copyable or movable. Only one can exist, and all users
* of it work with pointers
*/
Version(const Version &) = delete;
Version(Version &&) = delete;
Version &operator=(const Version &) = delete;
Version &operator=(Version &&) = delete;
size_t get_epoch_number() const { return m_epoch_number; }
const Structure *get_structure() const { return m_structure.get(); }
Structure *get_mutable_structure() { return m_structure.get(); }
BufView get_buffer() const { return m_buffer->get_buffer_view(m_buffer_head); }
/*
* Returns a new Version object that is a copy of this one. The new object
* will also contain a copy of the m_structure, rather than a reference to
* the same one. The epoch number of the new epoch will be set to the
* provided argument.
*/
Version *clone(size_t number) {
std::unique_lock<std::mutex> m_buffer_lock;
auto epoch = new Version(number);
epoch->m_buffer = m_buffer;
epoch->m_buffer_head = m_buffer_head;
if (m_structure) {
epoch->m_structure = m_structure->copy();
/* the copy routine returns a structure with 0 references */
epoch->m_structure->take_reference();
}
return epoch;
}
/*
* Check if a merge can be started from this Version. At present, without
* concurrent merging, this simply checks if there is currently a scheduled
* merge based on this Version. If there is, returns false. If there isn't,
* return true and set a flag indicating that there is an active merge.
*/
bool prepare_reconstruction() {
auto old = m_active_merge.load();
if (old) {
return false;
}
// FIXME: this needs cleaned up
while (!m_active_merge.compare_exchange_strong(old, true)) {
old = m_active_merge.load();
if (old) {
return false;
}
}
return true;
}
bool advance_buffer_head(size_t head) {
m_buffer_head = head;
return m_buffer->advance_head(m_buffer_head);
}
private:
Buffer *m_buffer;
std::unique_ptr<Structure> m_structure;
std::mutex m_buffer_lock;
std::atomic<bool> m_active_merge;
/*
* The number of currently active jobs
* (queries/merges) operating on this
* epoch. An epoch can only be retired
* when this number is 0.
*/
size_t m_epoch_number;
size_t m_buffer_head;
};
} // namespace de
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