Re: Background worker with Listen

From: Ihnat Peter | TSS Group a(dot)s(dot) <Ihnat(at)TSSGROUP(dot)sk>>
>> I got 2 problems:
>>
>> -          Worker is receiving notifications from every channel not only the registered channel (in my case "foo")
>>
>> -          Notifications are not logged in the server log - I cannot store the payloads for further work
>> Any help is welcomed.
>>
>> Here is the code:
>>
>> PG_MODULE_MAGIC;
>>
>> void _PG_init(void);
>> void _PG_fini(void);
>>
>> static volatile sig_atomic_t got_sigterm = false;
>> static volatile sig_atomic_t got_sigusr1 = false;
>> static char *notify_database = NULL;
>> static emit_log_hook_type prev_log_hook = NULL;
>>
>> static void
>> bgw_sigterm(SIGNAL_ARGS)
>> {
>>                 int save_errno = errno;
>>                 got_sigterm = true;
>>                 if (MyProc)
>>                                 SetLatch(&MyProc->procLatch);
>>                 errno = save_errno;
>> }
>>
>> static void
>> bgw_sigusr1(SIGNAL_ARGS)
>> {
>>                 int save_errno = errno;
>>                 got_sigusr1 = true;
>>                 if (MyProc)
>>                                 SetLatch(&MyProc->procLatch);
>>                errno = save_errno;
>> }
>>
>> static void
>> notify_main(Datum main_arg)
>> {
>>                 pqsignal(SIGTERM, bgw_sigterm);
>>                 pqsignal(SIGUSR1, bgw_sigusr1);
>>
>>                 BackgroundWorkerUnblockSignals();
>>                 BackgroundWorkerInitializeConnection(notify_database, NULL);
>>                  EnableNotifyInterrupt();
>>
>>                 pgstat_report_activity(STATE_RUNNING, "background_worker");
>>                 StartTransactionCommand();
>>                 Async_Listen("foo");
>>                 CommitTransactionCommand();
>>                 pgstat_report_activity(STATE_IDLE, NULL);
>>
>>                 while (!got_sigterm)
>>                 {
>>                                 int           rc;
>>
>>                                 rc = WaitLatch(&MyProc->procLatch, WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH, 10000L);
>>                                 ResetLatch(&MyProc->procLatch);
>>
>>                                 if (rc & WL_POSTMASTER_DEATH)
>>                                                 proc_exit(1);
>>
>>                                 if (got_sigusr1)
>>                                 {
>>                                                 got_sigusr1 = false;
>>                                                 elog(INFO, " background_worker: notification received");
>>                                                 // DO SOME WORK WITH STORED NOTIFICATIONS
>>                                 }
>>
>>                 }
>>
>>                 elog(LOG, "background_worker: finished");
>>                 proc_exit(0);
>> }
>>
>> static void
>> store_notification(ErrorData *edata)
>> {
>>                 // HERE STORE THE NOTIFICATION FROM SERVER LOG
>>
>>                 if (prev_log_hook)
>>                                 (*prev_log_hook) (edata);
>> }
>>
>> void
>> _PG_init(void)
>> {
>>                 BackgroundWorker worker;
>>                 DefineCustomStringVariable("postgres", NULL, NULL, &notify_database,
>>                                            "postgres",
>>                                            PGC_POSTMASTER, 0, NULL, NULL, NULL);
>>
>>                 MemSet(&worker, 0, sizeof(BackgroundWorker));
>>                 snprintf(worker.bgw_name, BGW_MAXLEN, "background_worker");
>>                 worker.bgw_flags = BGWORKER_SHMEM_ACCESS | BGWORKER_BACKEND_DATABASE_CONNECTION;
>>                 worker.bgw_start_time = BgWorkerStart_RecoveryFinished;
>>                 worker.bgw_main = notify_main;
>>                 worker.bgw_restart_time = 10;
>>                 worker.bgw_main_arg = (Datum) 0;
>>                 worker.bgw_notify_pid = 0;
>>                 RegisterBackgroundWorker(&worker);
>>
>>                 prev_log_hook = emit_log_hook;
>>                 emit_log_hook = store_notification;
>> }
>>
>> void
>> _PG_fini(void)
>> {
>>                 emit_log_hook = prev_log_hook;
>> }