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44111e3ba3
This introduces new timeline field latest_gc_cutoff. It is updated before each gc iteration. New check is added to branch_timelines to prevent branch creation with start point less than latest_gc_cutoff. Also this adds a check to get_page_at_lsn which asserts that lsn at which the page is requested was not garbage collected. This check currently is triggered for readonly nodes which are pinned to specific lsn and because they are not tracked in pageserver garbage collection can remove data that still might be referenced. This is a bug and will be fixed separately.
122 lines
4.6 KiB
Python
122 lines
4.6 KiB
Python
import subprocess
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from contextlib import closing
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import psycopg2.extras
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import pytest
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from fixtures.log_helper import log
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from fixtures.utils import print_gc_result
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from fixtures.zenith_fixtures import ZenithEnv
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pytest_plugins = ("fixtures.zenith_fixtures")
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#
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# Create a couple of branches off the main branch, at a historical point in time.
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#
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def test_branch_behind(zenith_simple_env: ZenithEnv):
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env = zenith_simple_env
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# Branch at the point where only 100 rows were inserted
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env.zenith_cli(["branch", "test_branch_behind", "empty"])
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pgmain = env.postgres.create_start('test_branch_behind')
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log.info("postgres is running on 'test_branch_behind' branch")
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main_pg_conn = pgmain.connect()
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main_cur = main_pg_conn.cursor()
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main_cur.execute("SHOW zenith.zenith_timeline")
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timeline = main_cur.fetchone()[0]
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# Create table, and insert the first 100 rows
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main_cur.execute('CREATE TABLE foo (t text)')
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# keep some early lsn to test branch creation on out of date lsn
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main_cur.execute('SELECT pg_current_wal_insert_lsn()')
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gced_lsn = main_cur.fetchone()[0]
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main_cur.execute('''
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INSERT INTO foo
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SELECT 'long string to consume some space' || g
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FROM generate_series(1, 100) g
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''')
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main_cur.execute('SELECT pg_current_wal_insert_lsn()')
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lsn_a = main_cur.fetchone()[0]
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log.info(f'LSN after 100 rows: {lsn_a}')
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# Insert some more rows. (This generates enough WAL to fill a few segments.)
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main_cur.execute('''
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INSERT INTO foo
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SELECT 'long string to consume some space' || g
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FROM generate_series(1, 200000) g
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''')
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main_cur.execute('SELECT pg_current_wal_insert_lsn()')
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lsn_b = main_cur.fetchone()[0]
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log.info(f'LSN after 200100 rows: {lsn_b}')
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# Branch at the point where only 100 rows were inserted
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env.zenith_cli(["branch", "test_branch_behind_hundred", "test_branch_behind@" + lsn_a])
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# Insert many more rows. This generates enough WAL to fill a few segments.
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main_cur.execute('''
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INSERT INTO foo
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SELECT 'long string to consume some space' || g
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FROM generate_series(1, 200000) g
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''')
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main_cur.execute('SELECT pg_current_wal_insert_lsn()')
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main_cur.execute('SELECT pg_current_wal_insert_lsn()')
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lsn_c = main_cur.fetchone()[0]
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log.info(f'LSN after 400100 rows: {lsn_c}')
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# Branch at the point where only 200100 rows were inserted
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env.zenith_cli(["branch", "test_branch_behind_more", "test_branch_behind@" + lsn_b])
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pg_hundred = env.postgres.create_start("test_branch_behind_hundred")
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pg_more = env.postgres.create_start("test_branch_behind_more")
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# On the 'hundred' branch, we should see only 100 rows
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hundred_pg_conn = pg_hundred.connect()
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hundred_cur = hundred_pg_conn.cursor()
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hundred_cur.execute('SELECT count(*) FROM foo')
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assert hundred_cur.fetchone() == (100, )
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# On the 'more' branch, we should see 100200 rows
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more_pg_conn = pg_more.connect()
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more_cur = more_pg_conn.cursor()
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more_cur.execute('SELECT count(*) FROM foo')
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assert more_cur.fetchone() == (200100, )
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# All the rows are visible on the main branch
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main_cur.execute('SELECT count(*) FROM foo')
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assert main_cur.fetchone() == (400100, )
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# Check bad lsn's for branching
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# branch at segment boundary
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env.zenith_cli(["branch", "test_branch_segment_boundary", "test_branch_behind@0/3000000"])
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pg = env.postgres.create_start("test_branch_segment_boundary")
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cur = pg.connect().cursor()
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cur.execute('SELECT 1')
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assert cur.fetchone() == (1, )
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# branch at pre-initdb lsn
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#
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# FIXME: This works currently, but probably shouldn't be allowed
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try:
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env.zenith_cli(["branch", "test_branch_preinitdb", "test_branch_behind@0/42"])
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# FIXME: assert false, "branch with invalid LSN should have failed"
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except subprocess.CalledProcessError:
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log.info("Branch creation with pre-initdb LSN failed (as expected)")
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# check that we cannot create branch based on garbage collected data
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with closing(env.pageserver.connect()) as psconn:
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with psconn.cursor(cursor_factory=psycopg2.extras.DictCursor) as pscur:
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# call gc to advace latest_gc_cutoff
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pscur.execute(f"do_gc {env.initial_tenant} {timeline} 0")
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row = pscur.fetchone()
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print_gc_result(row)
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with pytest.raises(Exception, match="(we might've already garbage collected needed data)"):
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# this gced_lsn is pretty random, so if gc is disabled this woudln't fail
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env.zenith_cli(["branch", "test_branch_create_fail", f"test_branch_behind@{gced_lsn}"])
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