Function CronBackgroundWorker

src/backend/task/pg_cron.c:1762–1833

* Background worker logic. */

 * Background worker logic.
 */
void
CronBackgroundWorker(Datum main_arg)
{
	dsm_segment *seg;
	shm_toc *toc;
	char *database;
	char *username;
	char *command;
	shm_mq *mq;
	shm_mq_handle *responseq;

	/* handle SIGTERM like regular backend */
	pqsignal(SIGTERM, die);
	BackgroundWorkerUnblockSignals();

	/* Set up a memory context and resource owner. */
	Assert(CurrentResourceOwner == NULL);
	CurrentResourceOwner = ResourceOwnerCreate(NULL, "pg_cron");
	CurrentMemoryContext = AllocSetContextCreate(TopMemoryContext,
												 "pg_cron worker",
												 ALLOCSET_DEFAULT_MINSIZE,
												 ALLOCSET_DEFAULT_INITSIZE,
												 ALLOCSET_DEFAULT_MAXSIZE);

	/* Set up a dynamic shared memory segment. */
	seg = dsm_attach(DatumGetUInt32(main_arg));
	if (seg == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("unable to map dynamic shared memory segment")));
	toc = shm_toc_attach(PG_CRON_MAGIC, dsm_segment_address(seg));
	if (toc == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
			   errmsg("bad magic number in dynamic shared memory segment")));

	database = shm_toc_lookup(toc, PG_CRON_KEY_DATABASE, false);
	username = shm_toc_lookup(toc, PG_CRON_KEY_USERNAME, false);
	command = shm_toc_lookup(toc, PG_CRON_KEY_COMMAND, false);
	mq = shm_toc_lookup(toc, PG_CRON_KEY_QUEUE, false);

	shm_mq_set_sender(mq, MyProc);
	responseq = shm_mq_attach(mq, seg, NULL);
	pq_redirect_to_shm_mq(seg, responseq);

	BackgroundWorkerInitializeConnection(database, username, 0);

	/* Prepare to execute the query. */
	SetCurrentStatementStartTimestamp();
	debug_query_string = command;
	pgstat_report_activity(STATE_RUNNING, command);
	StartTransactionCommand();
	if (StatementTimeout > 0)
		enable_timeout_after(STATEMENT_TIMEOUT, StatementTimeout);
	else
		disable_timeout(STATEMENT_TIMEOUT, false);

	/* Execute the query. */