postgres/src/include/replication/worker_internal.h

/*-------------------------------------------------------------------------
 *
 * worker_internal.h
 *	  Internal headers shared by logical replication workers.
 *
 * Portions Copyright (c) 2016-2025, PostgreSQL Global Development Group
 *
 * src/include/replication/worker_internal.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef WORKER_INTERNAL_H
#define WORKER_INTERNAL_H

#include "access/xlogdefs.h"
#include "catalog/pg_subscription.h"
#include "datatype/timestamp.h"
#include "miscadmin.h"
#include "replication/logicalrelation.h"
#include "replication/walreceiver.h"
#include "storage/buffile.h"
#include "storage/fileset.h"
#include "storage/lock.h"
#include "storage/shm_mq.h"
#include "storage/shm_toc.h"
#include "storage/spin.h"

/* Different types of worker */
typedef enum LogicalRepWorkerType
{
	WORKERTYPE_UNKNOWN = 0,
	WORKERTYPE_TABLESYNC,
	WORKERTYPE_APPLY,
	WORKERTYPE_PARALLEL_APPLY,
} LogicalRepWorkerType;

typedef struct LogicalRepWorker
{
	/* What type of worker is this? */
	LogicalRepWorkerType type;

	/* Time at which this worker was launched. */
	TimestampTz launch_time;

	/* Indicates if this slot is used or free. */
	bool		in_use;

	/* Increased every time the slot is taken by new worker. */
	uint16		generation;

	/* Pointer to proc array. NULL if not running. */
	PGPROC	   *proc;

	/* Database id to connect to. */
	Oid			dbid;

	/* User to use for connection (will be same as owner of subscription). */
	Oid			userid;

	/* Subscription id for the worker. */
	Oid			subid;

	/* Used for initial table synchronization. */
	Oid			relid;
	char		relstate;
	XLogRecPtr	relstate_lsn;
	slock_t		relmutex;

	/*
	 * Used to create the changes and subxact files for the streaming
	 * transactions.  Upon the arrival of the first streaming transaction or
	 * when the first-time leader apply worker times out while sending changes
	 * to the parallel apply worker, the fileset will be initialized, and it
	 * will be deleted when the worker exits.  Under this, separate buffiles
	 * would be created for each transaction which will be deleted after the
	 * transaction is finished.
	 */
	FileSet    *stream_fileset;

	/*
	 * PID of leader apply worker if this slot is used for a parallel apply
	 * worker, InvalidPid otherwise.
	 */
	pid_t		leader_pid;

	/* Indicates whether apply can be performed in parallel. */
	bool		parallel_apply;

	/*
	 * Changes made by this transaction and subsequent ones must be preserved.
	 * This ensures that update_deleted conflicts can be accurately detected
	 * during the apply phase of logical replication by this worker.
	 *
	 * The logical replication launcher manages an internal replication slot
	 * named "pg_conflict_detection". It asynchronously collects this ID to
	 * decide when to advance the xmin value of the slot.
	 */
	TransactionId oldest_nonremovable_xid;

	/* Stats. */
	XLogRecPtr	last_lsn;
	TimestampTz last_send_time;
	TimestampTz last_recv_time;
	XLogRecPtr	reply_lsn;
	TimestampTz reply_time;
} LogicalRepWorker;

/*
 * State of the transaction in parallel apply worker.
 *
 * The enum values must have the same order as the transaction state
 * transitions.
 */
typedef enum ParallelTransState
{
	PARALLEL_TRANS_UNKNOWN,
	PARALLEL_TRANS_STARTED,
	PARALLEL_TRANS_FINISHED,
} ParallelTransState;

/*
 * State of fileset used to communicate changes from leader to parallel
 * apply worker.
 *
 * FS_EMPTY indicates an initial state where the leader doesn't need to use
 * the file to communicate with the parallel apply worker.
 *
 * FS_SERIALIZE_IN_PROGRESS indicates that the leader is serializing changes
 * to the file.
 *
 * FS_SERIALIZE_DONE indicates that the leader has serialized all changes to
 * the file.
 *
 * FS_READY indicates that it is now ok for a parallel apply worker to
 * read the file.
 */
typedef enum PartialFileSetState
{
	FS_EMPTY,
	FS_SERIALIZE_IN_PROGRESS,
	FS_SERIALIZE_DONE,
	FS_READY,
} PartialFileSetState;

/*
 * Struct for sharing information between leader apply worker and parallel
 * apply workers.
 */
typedef struct ParallelApplyWorkerShared
{
	slock_t		mutex;

	TransactionId xid;

	/*
	 * State used to ensure commit ordering.
	 *
	 * The parallel apply worker will set it to PARALLEL_TRANS_FINISHED after
	 * handling the transaction finish commands while the apply leader will
	 * wait for it to become PARALLEL_TRANS_FINISHED before proceeding in
	 * transaction finish commands (e.g. STREAM_COMMIT/STREAM_PREPARE/
	 * STREAM_ABORT).
	 */
	ParallelTransState xact_state;

	/* Information from the corresponding LogicalRepWorker slot. */
	uint16		logicalrep_worker_generation;
	int			logicalrep_worker_slot_no;

	/*
	 * Indicates whether there are pending streaming blocks in the queue. The
	 * parallel apply worker will check it before starting to wait.
	 */
	pg_atomic_uint32 pending_stream_count;

	/*
	 * XactLastCommitEnd from the parallel apply worker. This is required by
	 * the leader worker so it can update the lsn_mappings.
	 */
	XLogRecPtr	last_commit_end;

	/*
	 * After entering PARTIAL_SERIALIZE mode, the leader apply worker will
	 * serialize changes to the file, and share the fileset with the parallel
	 * apply worker when processing the transaction finish command. Then the
	 * parallel apply worker will apply all the spooled messages.
	 *
	 * FileSet is used here instead of SharedFileSet because we need it to
	 * survive after releasing the shared memory so that the leader apply
	 * worker can re-use the same fileset for the next streaming transaction.
	 */
	PartialFileSetState fileset_state;
	FileSet		fileset;
} ParallelApplyWorkerShared;

/*
 * Information which is used to manage the parallel apply worker.
 */
typedef struct ParallelApplyWorkerInfo
{
	/*
	 * This queue is used to send changes from the leader apply worker to the
	 * parallel apply worker.
	 */
	shm_mq_handle *mq_handle;

	/*
	 * This queue is used to transfer error messages from the parallel apply
	 * worker to the leader apply worker.
	 */
	shm_mq_handle *error_mq_handle;

	dsm_segment *dsm_seg;

	/*
	 * Indicates whether the leader apply worker needs to serialize the
	 * remaining changes to a file due to timeout when attempting to send data
	 * to the parallel apply worker via shared memory.
	 */
	bool		serialize_changes;

	/*
	 * True if the worker is being used to process a parallel apply
	 * transaction. False indicates this worker is available for re-use.
	 */
	bool		in_use;

	ParallelApplyWorkerShared *shared;
} ParallelApplyWorkerInfo;

/* Main memory context for apply worker. Permanent during worker lifetime. */
extern PGDLLIMPORT MemoryContext ApplyContext;

extern PGDLLIMPORT MemoryContext ApplyMessageContext;

extern PGDLLIMPORT ErrorContextCallback *apply_error_context_stack;

extern PGDLLIMPORT ParallelApplyWorkerShared *MyParallelShared;

/* libpqreceiver connection */
extern PGDLLIMPORT struct WalReceiverConn *LogRepWorkerWalRcvConn;

/* Worker and subscription objects. */
extern PGDLLIMPORT Subscription *MySubscription;
extern PGDLLIMPORT LogicalRepWorker *MyLogicalRepWorker;

extern PGDLLIMPORT bool in_remote_transaction;

extern PGDLLIMPORT bool InitializingApplyWorker;

extern void logicalrep_worker_attach(int slot);
extern LogicalRepWorker *logicalrep_worker_find(Oid subid, Oid relid,
												bool only_running);
extern List *logicalrep_workers_find(Oid subid, bool only_running,
									 bool acquire_lock);
extern bool logicalrep_worker_launch(LogicalRepWorkerType wtype,
									 Oid dbid, Oid subid, const char *subname,
									 Oid userid, Oid relid,
									 dsm_handle subworker_dsm,
									 bool retain_dead_tuples);
extern void logicalrep_worker_stop(Oid subid, Oid relid);
extern void logicalrep_pa_worker_stop(ParallelApplyWorkerInfo *winfo);
extern void logicalrep_worker_wakeup(Oid subid, Oid relid);
extern void logicalrep_worker_wakeup_ptr(LogicalRepWorker *worker);

extern int	logicalrep_sync_worker_count(Oid subid);

extern void ReplicationOriginNameForLogicalRep(Oid suboid, Oid relid,
											   char *originname, Size szoriginname);

extern bool AllTablesyncsReady(void);
extern void UpdateTwoPhaseState(Oid suboid, char new_state);

extern void process_syncing_tables(XLogRecPtr current_lsn);
extern void invalidate_syncing_table_states(Datum arg, int cacheid,
											uint32 hashvalue);

extern void stream_start_internal(TransactionId xid, bool first_segment);
extern void stream_stop_internal(TransactionId xid);

/* Common streaming function to apply all the spooled messages */
extern void apply_spooled_messages(FileSet *stream_fileset, TransactionId xid,
								   XLogRecPtr lsn);

extern void apply_dispatch(StringInfo s);

extern void maybe_reread_subscription(void);

extern void stream_cleanup_files(Oid subid, TransactionId xid);

extern void set_stream_options(WalRcvStreamOptions *options,
							   char *slotname,
							   XLogRecPtr *origin_startpos);

extern void start_apply(XLogRecPtr origin_startpos);

extern void InitializeLogRepWorker(void);

extern void SetupApplyOrSyncWorker(int worker_slot);

extern void DisableSubscriptionAndExit(void);

extern void store_flush_position(XLogRecPtr remote_lsn, XLogRecPtr local_lsn);

/* Function for apply error callback */
extern void apply_error_callback(void *arg);
extern void set_apply_error_context_origin(char *originname);

/* Parallel apply worker setup and interactions */
extern void pa_allocate_worker(TransactionId xid);
extern ParallelApplyWorkerInfo *pa_find_worker(TransactionId xid);
extern void pa_detach_all_error_mq(void);

extern bool pa_send_data(ParallelApplyWorkerInfo *winfo, Size nbytes,
						 const void *data);
extern void pa_switch_to_partial_serialize(ParallelApplyWorkerInfo *winfo,
										   bool stream_locked);

extern void pa_set_xact_state(ParallelApplyWorkerShared *wshared,
							  ParallelTransState xact_state);
extern void pa_set_stream_apply_worker(ParallelApplyWorkerInfo *winfo);

extern void pa_start_subtrans(TransactionId current_xid,
							  TransactionId top_xid);
extern void pa_reset_subtrans(void);
extern void pa_stream_abort(LogicalRepStreamAbortData *abort_data);
extern void pa_set_fileset_state(ParallelApplyWorkerShared *wshared,
								 PartialFileSetState fileset_state);

extern void pa_lock_stream(TransactionId xid, LOCKMODE lockmode);
extern void pa_unlock_stream(TransactionId xid, LOCKMODE lockmode);

extern void pa_lock_transaction(TransactionId xid, LOCKMODE lockmode);
extern void pa_unlock_transaction(TransactionId xid, LOCKMODE lockmode);

extern void pa_decr_and_wait_stream_block(void);

extern void pa_xact_finish(ParallelApplyWorkerInfo *winfo,
						   XLogRecPtr remote_lsn);

#define isParallelApplyWorker(worker) ((worker)->in_use && \
									   (worker)->type == WORKERTYPE_PARALLEL_APPLY)
#define isTablesyncWorker(worker) ((worker)->in_use && \
								   (worker)->type == WORKERTYPE_TABLESYNC)

static inline bool
am_tablesync_worker(void)
{
	return isTablesyncWorker(MyLogicalRepWorker);
}

static inline bool
am_leader_apply_worker(void)
{
	Assert(MyLogicalRepWorker->in_use);
	return (MyLogicalRepWorker->type == WORKERTYPE_APPLY);
}

static inline bool
am_parallel_apply_worker(void)
{
	Assert(MyLogicalRepWorker->in_use);
	return isParallelApplyWorker(MyLogicalRepWorker);
}

#endif							/* WORKER_INTERNAL_H */