Add test for page server restart.

test_runner/batch_others/test_pageserver_restart.py

@@ -0,0 +1,66 @@
+import pytest
+import random
+import time
+
+from contextlib import closing
+from multiprocessing import Process, Value
+from fixtures.zenith_fixtures import WalAcceptorFactory, ZenithPageserver, PostgresFactory
+
+pytest_plugins = ("fixtures.zenith_fixtures")
+
+# Check that dead minority doesn't prevent the commits: execute insert n_inserts
+# times, with fault_probability chance of getting a wal acceptor down or up
+# along the way. 2 of 3 are always alive, so the work keeps going.
+def test_pageserver_restart(zenith_cli, pageserver: ZenithPageserver, postgres: PostgresFactory, wa_factory: WalAcceptorFactory):
+
+    # One safekeeper is enough for this test.
+    wa_factory.start_n_new(1)
+
+    zenith_cli.run(["branch", "test_pageserver_restart", "empty"])
+    pg = postgres.create_start('test_pageserver_restart',
+                               wal_acceptors=wa_factory.get_connstrs())
+
+    pg_conn = pg.connect()
+    cur = pg_conn.cursor()
+
+    # Create table, and insert some rows. Make it big enough that it doesn't fit in
+    # shared_buffers, otherwise the SELECT after restart will just return answer
+    # from shared_buffers without hitting the page server, which defeats the point
+    # of this test.
+    cur.execute('CREATE TABLE foo (t text)')
+    cur.execute('''
+        INSERT INTO foo
+            SELECT 'long string to consume some space' || g
+            FROM generate_series(1, 100000) g
+    ''')
+
+    # Verify that the table is larger than shared_buffers
+    cur.execute('''
+        select setting::int * pg_size_bytes(unit) as shared_buffers, pg_relation_size('foo') as tbl_ize
+        from pg_settings where name = 'shared_buffers'
+    ''')
+    row = cur.fetchone()
+    print("shared_buffers is {}, table size {}", row[0], row[1]);
+    assert int(row[0]) < int(row[1])
+
+    # Stop and restart pageserver. This is a more or less graceful shutdown, although
+    # the page server doesn't currently have a shutdown routine so there's no difference
+    # between stopping and crashing.
+    pageserver.stop();
+    pageserver.start();
+
+    # Stopping the pageserver breaks the connection from the postgres backend to
+    # the page server, and causes the next query on the connection to fail. Start a new
+    # postgres connection too, to avoid that error. (Ideally, the compute node would
+    # handle that and retry internally, without propagating the error to the user, but
+    # currently it doesn't...)
+    pg_conn = pg.connect()
+    cur = pg_conn.cursor()
+
+    cur.execute("SELECT count(*) FROM foo")
+    assert cur.fetchone() == (100000, )
+
+    # Stop the page server by force, and restart it
+    pageserver.stop();
+    pageserver.start();
+