Fix init of WAL page header at startup

test_runner/regress/test_twophase.py

@@ -8,6 +8,7 @@
     PgBin,
     fork_at_current_lsn,
     import_timeline_from_vanilla_postgres,
+    wait_for_wal_insert_lsn,
 )
 
 
@@ -22,11 +23,6 @@ def twophase_test_on_timeline(env: NeonEnv):
     conn = endpoint.connect()
     cur = conn.cursor()
 
-    # FIXME: Switch to the next WAL segment, to work around the bug fixed in
-    # https://github.com/neondatabase/neon/pull/8914.  When that is merged, this can be
-    # removed.
-    cur.execute("select pg_switch_wal()")
-
     cur.execute("CREATE TABLE foo (t text)")
 
     # Prepare a transaction that will insert a row
@@ -140,3 +136,28 @@ def test_twophase_nonzero_epoch(
     vanilla_pg.stop()  # don't need the original server anymore
 
     twophase_test_on_timeline(env)
+
+
+def test_twophase_at_wal_segment_start(neon_simple_env: NeonEnv):
+    """
+    Same as 'test_twophase' test, but the server is started at an LSN at the beginning
+    of a WAL segment. We had a bug where we didn't initialize the "long XLOG page header"
+    at the beginning of the segment correctly, which was detected when the checkpointer
+    tried to read the XLOG_XACT_PREPARE record from the WAL, if that record was on the
+    very first page of a WAL segment and the server was started up at that first page.
+    """
+    env = neon_simple_env
+    timeline_id = env.neon_cli.create_branch("test_twophase", "main")
+
+    endpoint = env.endpoints.create_start(
+        "test_twophase", config_lines=["max_prepared_transactions=5"]
+    )
+    endpoint.safe_psql("SELECT pg_switch_wal()")
+
+    # to avoid hitting https://github.com/neondatabase/neon/issues/9079, wait for the
+    # WAL to reach the pageserver.
+    wait_for_wal_insert_lsn(env, endpoint, env.initial_tenant, timeline_id)
+
+    endpoint.stop_and_destroy()
+
+    twophase_test_on_timeline(env)

vendor/revisions.json

@@ -1,18 +1,18 @@
 {
   "v17": [
     "17rc1",
-    "dadd6fe208bb906cc0a48980f2ab4e13c47ba3ad"
+    "2cf120e7393ca5f537c6a38b457585576dc035fc"
   ],
   "v16": [
     "16.4",
-    "d009084a745cb4d5e6de222c778b2a562c8b2767"
+    "1d7081a3b076ddf5086e0b118d4329820e6a7427"
   ],
   "v15": [
     "15.8",
-    "1dbd6f316416c8360bbd4f3d6db956cf70937cf0"
+    "16c3c6b64f1420a367a2a9b2510f20d94f791af8"
   ],
   "v14": [
     "14.13",
-    "f9c51c12438b20049b6905eb4e43d321defd6ff2"
+    "a38d15f3233a4c07f2bf3335fcbd874dd1f4e386"
   ]
 }