From 32e3b7dfd22741e5a4986ff48f2effceaa631437 Mon Sep 17 00:00:00 2001
From: Konstantin Knizhnik <knizhnik@neon.tech>
Date: Tue, 27 May 2025 17:39:39 +0300
Subject: [PATCH] Do not explicitly launch wal_proposer: rely on
 BgWorkerStart_RecoveryFinished

---
 pgxn/neon/walproposer.c                     |  6 +--
 pgxn/neon/walproposer.h                     |  1 -
 pgxn/neon/walproposer_pg.c                  | 49 +++------------------
 test_runner/regress/test_replica_promote.py |  8 ++--
 4 files changed, 13 insertions(+), 51 deletions(-)

diff --git a/pgxn/neon/walproposer.c b/pgxn/neon/walproposer.c
index 4cb9aec258..4bcbe9078a 100644
--- a/pgxn/neon/walproposer.c
+++ b/pgxn/neon/walproposer.c
@@ -1380,7 +1380,7 @@ ProcessPropStartPos(WalProposer *wp)
 	 * we must bail out, as clog and other non rel data is inconsistent.
 	 */
 	walprop_shared = wp->api.get_shmem_state(wp);
-	if (!wp->config->syncSafekeepers && !wp->api.get_shmem_state(wp)->bgw_started)
+	if (!wp->config->syncSafekeepers)
 	{
 		/*
 		 * Basebackup LSN always points to the beginning of the record (not
@@ -1407,8 +1407,8 @@ ProcessPropStartPos(WalProposer *wp)
 				 * However, don't dump core as this is kinda expected
 				 * scenario.
 				 */
-				disable_core_dump();
-				wp_log(PANIC,
+				//disable_core_dump();
+				wp_log(LOG,
 					   "collected propTermStartLsn %X/%X, but basebackup LSN %X/%X",
 					   LSN_FORMAT_ARGS(wp->propTermStartLsn),
 					   LSN_FORMAT_ARGS(wp->api.get_redo_start_lsn(wp)));
diff --git a/pgxn/neon/walproposer.h b/pgxn/neon/walproposer.h
index 57cfabeb23..cca20e746b 100644
--- a/pgxn/neon/walproposer.h
+++ b/pgxn/neon/walproposer.h
@@ -384,7 +384,6 @@ typedef struct WalproposerShmemState
 	XLogRecPtr	donor_lsn;
 
 	slock_t		mutex;
-	bool        bgw_started;
 	pg_atomic_uint64 mineLastElectedTerm;
 	pg_atomic_uint64 backpressureThrottlingTime;
 	pg_atomic_uint64 currentClusterSize;
diff --git a/pgxn/neon/walproposer_pg.c b/pgxn/neon/walproposer_pg.c
index 3fdab359df..daacf9f035 100644
--- a/pgxn/neon/walproposer_pg.c
+++ b/pgxn/neon/walproposer_pg.c
@@ -86,7 +86,7 @@ static void nwp_prepare_shmem(void);
 static uint64 backpressure_lag_impl(void);
 static uint64 startup_backpressure_wrap(void);
 static bool backpressure_throttling_impl(void);
-static void walprop_register_bgworker(bool dynamic);
+static void walprop_register_bgworker(void);
 
 static void walprop_pg_init_standalone_sync_safekeepers(void);
 static void walprop_pg_init_walsender(void);
@@ -161,13 +161,9 @@ WalProposerMain(Datum main_arg)
 {
 	WalProposer *wp;
 
-	walprop_shared->bgw_started = true;
-
-	while (*wal_acceptors_list == '\0')
+	if (*wal_acceptors_list == '\0')
 	{
-		/* Wait until wal acceptors list GUC changes are propagated */
-		pg_usleep(GUC_POLL_DELAY);
-		CHECK_FOR_INTERRUPTS();
+		elog(PANIC, "Safekeepers list is empty");
 	}
 
 	init_walprop_config(false);
@@ -199,9 +195,7 @@ pg_init_walproposer(void)
 	PrevProcessInterruptsCallback = ProcessInterruptsCallback;
 	ProcessInterruptsCallback = backpressure_throttling_impl;
 
-	/* If no wal acceptors are specified, don't start the background worker. */
-	if (*wal_acceptors_list != '\0')
-		walprop_register_bgworker(false);
+	walprop_register_bgworker();
 }
 
 static void
@@ -319,29 +313,12 @@ safekeepers_cmp(char *old, char *new)
 	return true;
 }
 
-/*
- * GUC assign_hook for neon.safekeepers. Restarts walproposer through FATAL if
- * the list changed.
- */
 static void
 assign_neon_safekeepers(const char *newval, void *extra)
 {
 	char	   *newval_copy;
 	char	   *oldval;
 
-	/* Promotion of replica */
-	if (*wal_acceptors_list == '\0' && *newval != '\0' && walprop_shared && IsUnderPostmaster)
-	{
-		SpinLockAcquire(&walprop_shared->mutex);
-		if (!walprop_shared->bgw_started)
-		{
-			walprop_shared->bgw_started = true;
-			walprop_register_bgworker(true);
-		}
-		SpinLockRelease(&walprop_shared->mutex);
-		return;
-	}
-
 	if (!am_walproposer)
 		return;
 
@@ -534,13 +511,13 @@ BackpressureThrottlingTime(void)
  * Register a background worker proposing WAL to wal acceptors.
  */
 static void
-walprop_register_bgworker(bool dynamic)
+walprop_register_bgworker(void)
 {
 	BackgroundWorker bgw;
 
 	memset(&bgw, 0, sizeof(bgw));
 	bgw.bgw_flags = BGWORKER_SHMEM_ACCESS;
-	bgw.bgw_start_time = dynamic ? BgWorkerStart_ConsistentState : BgWorkerStart_RecoveryFinished;
+	bgw.bgw_start_time = BgWorkerStart_RecoveryFinished;
 	snprintf(bgw.bgw_library_name, BGW_MAXLEN, "neon");
 	snprintf(bgw.bgw_function_name, BGW_MAXLEN, "WalProposerMain");
 	snprintf(bgw.bgw_name, BGW_MAXLEN, "WAL proposer");
@@ -548,19 +525,7 @@ walprop_register_bgworker(bool dynamic)
 	bgw.bgw_restart_time = 1;
 	bgw.bgw_notify_pid = 0;
 	bgw.bgw_main_arg = (Datum) 0;
-
-	if (dynamic)
-	{
-		BackgroundWorkerHandle* handle;
-		if (!RegisterDynamicBackgroundWorker(&bgw, &handle))
-		{
-			elog(FATAL, "Failed to start walproposer");
-		}
-	}
-	else
-	{
-		RegisterBackgroundWorker(&bgw);
-	}
+	RegisterBackgroundWorker(&bgw);
 }
 
 /* shmem handling */
diff --git a/test_runner/regress/test_replica_promote.py b/test_runner/regress/test_replica_promote.py
index 67a39159ef..1afa89af2d 100644
--- a/test_runner/regress/test_replica_promote.py
+++ b/test_runner/regress/test_replica_promote.py
@@ -52,17 +52,15 @@ def test_replica_promotes(neon_simple_env: NeonEnv, pg_version: PgVersion):
     wait_replica_caughtup(primary, secondary)
     primary.stop()
 
-    secondary_conn = secondary.connect()
-    secondary_cur = secondary_conn.cursor()
-    secondary_cur.execute("SELECT * FROM pg_promote()")
-    assert secondary_cur.fetchone() == (True,)
-
     secondary_conn = secondary.connect()
     secondary_cur = secondary_conn.cursor()
 
     secondary_cur.execute(f"alter system set neon.safekeepers='{safekeepers}'")
     secondary_cur.execute("select pg_reload_conf()")
 
+    secondary_cur.execute("SELECT * FROM pg_promote()")
+    assert secondary_cur.fetchone() == (True,)
+
     new_primary = secondary
     old_primary = primary