neon/test_runner/batch_others/test_readonly_node.py

import pytest
from fixtures.log_helper import log
from fixtures.neon_fixtures import NeonEnv, wait_for_last_record_lsn, wait_for_upload
from fixtures.utils import lsn_from_hex, lsn_to_hex, query_scalar
import time
from uuid import UUID


#
# Create read-only compute nodes, anchored at historical points in time.
#
# This is very similar to the 'test_branch_behind' test, but instead of
# creating branches, creates read-only nodes.
#
def test_readonly_node(neon_simple_env: NeonEnv):
    env = neon_simple_env
    env.neon_cli.create_branch('test_readonly_node', 'empty')
    pgmain = env.postgres.create_start('test_readonly_node')
    log.info("postgres is running on 'test_readonly_node' branch")

    main_pg_conn = pgmain.connect()
    main_cur = main_pg_conn.cursor()

    # Create table, and insert the first 100 rows
    main_cur.execute('CREATE TABLE foo (t text)')

    main_cur.execute('''
        INSERT INTO foo
            SELECT 'long string to consume some space' || g
            FROM generate_series(1, 100) g
    ''')
    main_cur.execute('SELECT pg_current_wal_insert_lsn()')
    lsn_a = query_scalar(main_cur, 'SELECT pg_current_wal_insert_lsn()')
    log.info('LSN after 100 rows: ' + lsn_a)

    # Insert some more rows. (This generates enough WAL to fill a few segments.)
    main_cur.execute('''
        INSERT INTO foo
            SELECT 'long string to consume some space' || g
            FROM generate_series(1, 200000) g
    ''')
    lsn_b = query_scalar(main_cur, 'SELECT pg_current_wal_insert_lsn()')
    log.info('LSN after 200100 rows: ' + lsn_b)

    # Insert many more rows. This generates enough WAL to fill a few segments.
    main_cur.execute('''
        INSERT INTO foo
            SELECT 'long string to consume some space' || g
            FROM generate_series(1, 200000) g
    ''')

    lsn_c = query_scalar(main_cur, 'SELECT pg_current_wal_insert_lsn()')
    log.info('LSN after 400100 rows: ' + lsn_c)

    # Create first read-only node at the point where only 100 rows were inserted
    pg_hundred = env.postgres.create_start(branch_name='test_readonly_node',
                                           node_name='test_readonly_node_hundred',
                                           lsn=lsn_a)

    # And another at the point where 200100 rows were inserted
    pg_more = env.postgres.create_start(branch_name='test_readonly_node',
                                        node_name='test_readonly_node_more',
                                        lsn=lsn_b)

    # On the 'hundred' node, we should see only 100 rows
    hundred_pg_conn = pg_hundred.connect()
    hundred_cur = hundred_pg_conn.cursor()
    hundred_cur.execute('SELECT count(*) FROM foo')
    assert hundred_cur.fetchone() == (100, )

    # On the 'more' node, we should see 100200 rows
    more_pg_conn = pg_more.connect()
    more_cur = more_pg_conn.cursor()
    more_cur.execute('SELECT count(*) FROM foo')
    assert more_cur.fetchone() == (200100, )

    # All the rows are visible on the main branch
    main_cur.execute('SELECT count(*) FROM foo')
    assert main_cur.fetchone() == (400100, )

    # Check creating a node at segment boundary
    pg = env.postgres.create_start(branch_name='test_readonly_node',
                                   node_name='test_branch_segment_boundary',
                                   lsn='0/3000000')
    cur = pg.connect().cursor()
    cur.execute('SELECT 1')
    assert cur.fetchone() == (1, )

    # Create node at pre-initdb lsn
    with pytest.raises(Exception, match="invalid basebackup lsn"):
        # compute node startup with invalid LSN should fail
        env.postgres.create_start(branch_name='test_readonly_node',
                                  node_name='test_readonly_node_preinitdb',
                                  lsn='0/42')

# Similar test, but with more data, and we force checkpoints
def test_timetravel(neon_simple_env: NeonEnv):
    env = neon_simple_env
    env.neon_cli.create_branch('test_timetravel', 'empty')
    pg = env.postgres.create_start('test_timetravel')

    client = env.pageserver.http_client()

    tenant_id = pg.safe_psql("show neon.tenant_id")[0][0]
    timeline_id = pg.safe_psql("show neon.timeline_id")[0][0]

    lsns = []

    with pg.cursor() as cur:
        cur.execute(f"""
        CREATE TABLE testtab(id serial primary key, iteration int, data text);
        INSERT INTO testtab (iteration, data) SELECT 0, 'data' FROM generate_series(1, 100000);
        """)
        current_lsn = lsn_from_hex(query_scalar(cur, "SELECT pg_current_wal_flush_lsn()"))
    lsns.append((0, current_lsn))

    for i in range(1, 5):
        with pg.cursor() as cur:
            cur.execute(f'UPDATE testtab SET iteration = {i}')
            current_lsn = lsn_from_hex(query_scalar(cur, "SELECT pg_current_wal_flush_lsn()"))
        lsns.append((i, current_lsn))

        # wait until pageserver receives that data
        wait_for_last_record_lsn(client, UUID(tenant_id), UUID(timeline_id), current_lsn)

        # run checkpoint manually to force a new layer file
        env.pageserver.safe_psql(f"checkpoint {tenant_id} {timeline_id}")

    ##### Restart pageserver
    env.postgres.stop_all()
    env.pageserver.stop()
    env.pageserver.start()

    for (i, lsn) in lsns:
        pg_old = env.postgres.create_start(branch_name='test_timetravel',
                                           node_name=f'test_old_lsn_{i}',
                                           lsn=lsn_to_hex(lsn))
        with pg_old.cursor() as cur:
            assert query_scalar(cur, f"select count(*) from testtab where iteration={i}") == 100000
            assert query_scalar(cur, f"select count(*) from testtab where iteration<>{i}") == 0