MySQL 8.0.32
Source Code Documentation
cs::apply::Commit_order_queue Class Reference

Queue to maintain the ordered sequence of workers waiting for commit. More...

#include <commit_order_queue.h>

Classes

class  Iterator
 Iterator helper class to iterate over the Commit_order_queue following the underlying commit order. More...
 
class  Node
 Queue element, holding the needed information to manage the commit ordering. More...
 

Public Types

enum class  enum_worker_stage {
  REGISTERED , FINISHED_APPLYING , REQUESTED_GRANT , WAITED ,
  FINISHED
}
 Enumeration to represent each worker state. More...
 
using value_type = unsigned long
 
using queue_type = container::Integrals_lockfree_queue< value_type >
 
using sequence_type = unsigned long long
 

Public Member Functions

 Commit_order_queue (size_t n_workers)
 Constructor for the class, takes the number of workers and initializes the underlying static list with such size. More...
 
virtual ~Commit_order_queue ()=default
 Default destructor for the class. More...
 
Nodeoperator[] (value_type id)
 Retrieve the commit order information Node for worker identified by id. More...
 
Commit_order_queue::queue_type::enum_queue_state get_state ()
 Retrieves the error state for the current thread last executed queue operation. More...
 
bool is_empty ()
 Whether or not there are more workers to commit. More...
 
std::tuple< value_type, sequence_typepop ()
 Removes from the queue and returns the identifier of the worker that is first in-line to commit. More...
 
void push (value_type id)
 Adds to the end of the commit queue the worker identifier passed as parameter. More...
 
value_type front ()
 Retrieves the identifier of the worker that is first in-line to commit. More...
 
void clear ()
 Removes all remaining workers from the queue. More...
 
void freeze ()
 Acquires exclusivity over changes (push, pop) on the queue. More...
 
void unfreeze ()
 Releases exclusivity over changes (push, pop) on the queue. More...
 
Iterator begin ()
 Retrieves an iterator instance that points to the head of the commit queue and that will iterate over the worker Nodes that are in-line to commit, following the requested commit order. More...
 
Iterator end ()
 Retrieves an iterator instance that points to the tail of the commit queue. More...
 
std::string to_string ()
 Retrieves the textual representation of this object's underlying commit queue. More...
 

Static Public Member Functions

static sequence_type get_next_sequence_nr (sequence_type current_seq_nr)
 Returns the expected next number in the ticket sequence. More...
 

Static Public Attributes

static constexpr value_type NO_WORKER
 

Private Attributes

memory::Aligned_atomic< sequence_typem_commit_sequence_generator
 The commit sequence number counter. More...
 
std::vector< Commit_order_queue::Nodem_workers
 The list of worker Nodes, indexed by worker ID. More...
 
queue_type m_commit_queue
 The queue to hold the sequence of worker IDs waiting to commit. More...
 
lock::Shared_spin_lock m_push_pop_lock
 The lock to acquire exlusivity over changes on the queue. More...
 

Friends

std::ostream & operator<< (std::ostream &out, Commit_order_queue &to_output)
 Friend operator for writing to an std::ostream object. More...
 

Detailed Description

Queue to maintain the ordered sequence of workers waiting for commit.

The queue has a static list of elements, each one representing each worker commit information.

The management of the order by which each worker will commit is implemented using:

  • A member variable pointing to the first worker to commit, the head.
  • A member variable pointing to the last worker to commit, the tail.
  • Each queue element holds a member variable that points to the next worker to commit, the next.
  • Pushing a new element will move the tail.
  • Popping an element will move the head.

Atomics are used to make the queue thread-safe without the need for an explicit lock.

Member Typedef Documentation

◆ queue_type

◆ sequence_type

◆ value_type

Member Enumeration Documentation

◆ enum_worker_stage

Enumeration to represent each worker state.

Enumerator
REGISTERED 
FINISHED_APPLYING 
REQUESTED_GRANT 
WAITED 
FINISHED 

Constructor & Destructor Documentation

◆ Commit_order_queue()

cs::apply::Commit_order_queue::Commit_order_queue ( size_t  n_workers)

Constructor for the class, takes the number of workers and initializes the underlying static list with such size.

Parameters
n_workersThe number of workers to include in the commit order managerment.

◆ ~Commit_order_queue()

virtual cs::apply::Commit_order_queue::~Commit_order_queue ( )
virtualdefault

Default destructor for the class.

Member Function Documentation

◆ begin()

cs::apply::Commit_order_queue::Iterator cs::apply::Commit_order_queue::begin ( void  )

Retrieves an iterator instance that points to the head of the commit queue and that will iterate over the worker Nodes that are in-line to commit, following the requested commit order.

Returns
An instance of Iterator pointing to the queue's head, that iterates over the workers that are in-line to commit and following the requested commit order.

◆ clear()

void cs::apply::Commit_order_queue::clear ( )

Removes all remaining workers from the queue.

◆ end()

cs::apply::Commit_order_queue::Iterator cs::apply::Commit_order_queue::end ( void  )

Retrieves an iterator instance that points to the tail of the commit queue.

Returns
An instance of Iterator that points to the tail of the queue.

◆ freeze()

void cs::apply::Commit_order_queue::freeze ( )

Acquires exclusivity over changes (push, pop) on the queue.

◆ front()

cs::apply::Commit_order_queue::value_type cs::apply::Commit_order_queue::front ( )

Retrieves the identifier of the worker that is first in-line to commit.

Returns
The identifier of the worker that is first in-line to commit.

◆ get_next_sequence_nr()

cs::apply::Commit_order_queue::sequence_type cs::apply::Commit_order_queue::get_next_sequence_nr ( sequence_type  current_seq_nr)
static

Returns the expected next number in the ticket sequence.

Parameters
current_seq_nrThe current sequence number, for which the next should be computed.
Returns
The expected next number in the ticket sequence.

◆ get_state()

cs::apply::Commit_order_queue::queue_type::enum_queue_state cs::apply::Commit_order_queue::get_state ( )

Retrieves the error state for the current thread last executed queue operation.

Values may be:

  • SUCCESS is the operation succeeded.
  • NO_MORE_ELEMENTS if the last pop tried to access an empty queue.
  • NO_SPACE_AVAILABLE if the last push tried to push while the queue was full.
Returns
The error state for the thread's last operation on the queue.

◆ is_empty()

bool cs::apply::Commit_order_queue::is_empty ( )

Whether or not there are more workers to commit.

Returns
True if there are no more workers, false otherwise.

◆ operator[]()

cs::apply::Commit_order_queue::Node & cs::apply::Commit_order_queue::operator[] ( value_type  id)

Retrieve the commit order information Node for worker identified by id.

Parameters
idThe identifier of the worker
Returns
A reference to the commit order information Node for the given worker.

◆ pop()

std::tuple< cs::apply::Commit_order_queue::value_type, cs::apply::Commit_order_queue::sequence_type > cs::apply::Commit_order_queue::pop ( )

Removes from the queue and returns the identifier of the worker that is first in-line to commit.

If another thread is accessing the commit order sequence number and has frozen it's state, this operation will spin until the state is unfrozen.

Returns
A tuple holding the identifier of the worker that is first in-line to commit and the associated commit order sequence number.

◆ push()

void cs::apply::Commit_order_queue::push ( value_type  id)

Adds to the end of the commit queue the worker identifier passed as parameter.

Parameters
idThe identifier of the worker to add to the commit queue.

◆ to_string()

std::string cs::apply::Commit_order_queue::to_string ( )

Retrieves the textual representation of this object's underlying commit queue.

Returns
The textual representation of this object's underlying commit queue.

◆ unfreeze()

void cs::apply::Commit_order_queue::unfreeze ( )

Releases exclusivity over changes (push, pop) on the queue.

Friends And Related Function Documentation

◆ operator<<

std::ostream & operator<< ( std::ostream &  out,
Commit_order_queue to_output 
)
friend

Friend operator for writing to an std::ostream object.

See also
std::ostream::operator<<

Member Data Documentation

◆ m_commit_queue

queue_type cs::apply::Commit_order_queue::m_commit_queue
private

The queue to hold the sequence of worker IDs waiting to commit.

◆ m_commit_sequence_generator

memory::Aligned_atomic<sequence_type> cs::apply::Commit_order_queue::m_commit_sequence_generator
private
Initial value:
{
static constexpr Commit_order_queue::sequence_type SEQUENCE_NR_FROZEN
Definition: commit_order_queue.h:135

The commit sequence number counter.

◆ m_push_pop_lock

lock::Shared_spin_lock cs::apply::Commit_order_queue::m_push_pop_lock
private

The lock to acquire exlusivity over changes on the queue.

◆ m_workers

std::vector<Commit_order_queue::Node> cs::apply::Commit_order_queue::m_workers
private

The list of worker Nodes, indexed by worker ID.

◆ NO_WORKER

constexpr value_type cs::apply::Commit_order_queue::NO_WORKER
staticconstexpr
Initial value:
{
static constexpr value_type null_value
Definition: integrals_lockfree_queue.h:147

The documentation for this class was generated from the following files: