Allow discovery of whether a dynamic background worker is running.

[postgresql] / contrib / worker_spi / worker_spi.c

diff --git a/contrib/worker_spi/worker_spi.c b/contrib/worker_spi/worker_spi.c
index 14b5045caa487e6ac058870adc326a7939ce75f5..8aec9b2199db1992953de95b4364ee498efbfb62 100644 (file)
--- a/contrib/worker_spi/worker_spi.c
+++ b/contrib/worker_spi/worker_spi.c
@@ -365,6 +365,9 @@ worker_spi_launch(PG_FUNCTION_ARGS)
 {
        int32           i = PG_GETARG_INT32(0);
        BackgroundWorker worker;
+       BackgroundWorkerHandle *handle;
+       BgwHandleStatus status;
+       pid_t           pid;
 
        worker.bgw_flags = BGWORKER_SHMEM_ACCESS |
                BGWORKER_BACKEND_DATABASE_CONNECTION;
@@ -375,6 +378,25 @@ worker_spi_launch(PG_FUNCTION_ARGS)
        sprintf(worker.bgw_function_name, "worker_spi_main");
        snprintf(worker.bgw_name, BGW_MAXLEN, "worker %d", i);
        worker.bgw_main_arg = Int32GetDatum(i);
-
-       PG_RETURN_BOOL(RegisterDynamicBackgroundWorker(&worker));
+       /* set bgw_notify_pid so that we can use WaitForBackgroundWorkerStartup */
+       worker.bgw_notify_pid = MyProcPid;
+
+       if (!RegisterDynamicBackgroundWorker(&worker, &handle))
+               PG_RETURN_NULL();
+
+       status = WaitForBackgroundWorkerStartup(handle, &pid);
+
+       if (status == BGWH_STOPPED)
+               ereport(ERROR,
+                               (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+                                errmsg("could not start background process"),
+                                errhint("More details may be available in the server log.")));
+       if (status == BGWH_POSTMASTER_DIED)
+               ereport(ERROR,
+                               (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+                                errmsg("cannot start background processes without postmaster"),
+                                errhint("Kill all remaining database processes and restart the database.")));
+       Assert(status == BGWH_STARTED);
+
+       PG_RETURN_INT32(pid);
 }