From dae203ef692415428977d49bdf116c3a5fed344e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Arpad=20M=C3=BCller?= <arpad-m@users.noreply.github.com>
Date: Thu, 5 Jun 2025 01:02:31 +0200
Subject: [PATCH] pgxn: support generations in safekeepers_cmp (#12129)

`safekeepers_cmp` was added by #8840 to make changes of the safekeeper
set order independent: a `sk1,sk2,sk3` specifier changed to
`sk3,sk1,sk2` should not cause a walproposer restart. However, this
check didn't support generations, in the sense that it would see the
`g#123:` as part of the first safekeeper in the list, and if the first
safekeeper changes, it would also restart the walproposer.

Therefore, parse the generation properly and make it not be a part of
the generation.

This PR doesn't add a specific test, but I have confirmed locally that
`test_safekeepers_reconfigure_reorder` is fixed with the changes of PR
#11712 applied thanks to this PR.

Part of https://github.com/neondatabase/neon/issues/11670
---
 pgxn/neon/walproposer.c    |  4 ++++
 pgxn/neon/walproposer_pg.c | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/pgxn/neon/walproposer.c b/pgxn/neon/walproposer.c
index f42103c7cd..c63edb1398 100644
--- a/pgxn/neon/walproposer.c
+++ b/pgxn/neon/walproposer.c
@@ -119,6 +119,10 @@ WalProposerCreate(WalProposerConfig *config, walproposer_api api)
 		{
 			wp_log(FATAL, "failed to parse neon.safekeepers generation number: %m");
 		}
+		if (*endptr != ':')
+		{
+			wp_log(FATAL, "failed to parse neon.safekeepers: no colon after generation");
+		}
 		/* Skip past : to the first hostname. */
 		host = endptr + 1;
 	}
diff --git a/pgxn/neon/walproposer_pg.c b/pgxn/neon/walproposer_pg.c
index d15bf91d24..c90702a282 100644
--- a/pgxn/neon/walproposer_pg.c
+++ b/pgxn/neon/walproposer_pg.c
@@ -272,6 +272,30 @@ split_safekeepers_list(char *safekeepers_list, char *safekeepers[])
 	return n_safekeepers;
 }
 
+static char *split_off_safekeepers_generation(char *safekeepers_list, uint32 *generation)
+{
+	char	   *endptr;
+
+	if (strncmp(safekeepers_list, "g#", 2) != 0)
+	{
+		return safekeepers_list;
+	}
+	else
+	{
+		errno = 0;
+		*generation = strtoul(safekeepers_list + 2, &endptr, 10);
+		if (errno != 0)
+		{
+			wp_log(FATAL, "failed to parse neon.safekeepers generation number: %m");
+		}
+		if (*endptr != ':')
+		{
+			wp_log(FATAL, "failed to parse neon.safekeepers: no colon after generation");
+		}
+		return endptr + 1;
+	}
+}
+
 /*
  * Accept two coma-separated strings with list of safekeeper host:port addresses.
  * Split them into arrays and return false if two sets do not match, ignoring the order.
@@ -283,6 +307,16 @@ safekeepers_cmp(char *old, char *new)
 	char	   *safekeepers_new[MAX_SAFEKEEPERS];
 	int			len_old = 0;
 	int			len_new = 0;
+	uint32		gen_old = INVALID_GENERATION;
+	uint32		gen_new = INVALID_GENERATION;
+
+	old = split_off_safekeepers_generation(old, &gen_old);
+	new = split_off_safekeepers_generation(new, &gen_new);
+
+	if (gen_old != gen_new)
+	{
+		return false;
+	}
 
 	len_old = split_safekeepers_list(old, safekeepers_old);
 	len_new = split_safekeepers_list(new, safekeepers_new);