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Synchronous standbys#46

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Merged
ildus merged 8 commits intopostgrespro:masterfromzilder:syncrep
Aug 8, 2019
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8 changes: 8 additions & 0 deletionsdocs/source/testgres.rst
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Expand Up@@ -61,6 +61,14 @@ testgres.node
.. autoclass:: testgres.node.ProcessProxy
:members:

testgres.standby
----------------

.. automodule:: testgres.standby
:members:
:undoc-members:
:show-inheritance:

testgres.pubsub
---------------

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4 changes: 4 additions & 0 deletionstestgres/__init__.py
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Expand Up@@ -24,3 +24,7 @@
get_bin_path, \
get_pg_config, \
get_pg_version

from .standby import \
First, \
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IMHO those names are too generic to be exported at top level.

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I think names are ok but should be used with the of module, likestandby.First

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@ildus I agree.

Any
44 changes: 43 additions & 1 deletiontestgres/node.py
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Expand Up@@ -6,6 +6,7 @@
import subprocess
import time

from collections import Iterable
from shutil import rmtree
from six import raise_from, iteritems
from tempfile import mkstemp, mkdtemp
Expand DownExpand Up@@ -65,6 +66,8 @@

from .pubsub import Publication, Subscription

from .standby import First

from .utils import \
PgVer, \
eprint, \
Expand DownExpand Up@@ -671,7 +674,7 @@ def restart(self, params=[]):

def reload(self, params=[]):
"""
Reload config files using pg_ctl.
Asynchronously reload config files using pg_ctl.

Args:
params: additional arguments for pg_ctl.
Expand DownExpand Up@@ -1036,6 +1039,45 @@ def replicate(self, name=None, slot=None, **kwargs):
with clean_on_error(self.backup(**kwargs)) as backup:
return backup.spawn_replica(name=name, destroy=True, slot=slot)

def set_synchronous_standbys(self, standbys):
"""
Set standby synchronization options. This corresponds to
`synchronous_standby_names <https://www.postgresql.org/docs/current/static/runtime-config-replication.html#GUC-SYNCHRONOUS-STANDBY-NAMES>`_
option. Note that :meth:`~.PostgresNode.reload` or
:meth:`~.PostgresNode.restart` is needed for changes to take place.

Args:
standbys: either :class:`.First` or :class:`.Any` object specifying
sychronization parameters or just a plain list of
:class:`.PostgresNode`s replicas which would be equivalent
to passing ``First(1, <list>)``. For PostgreSQL 9.5 and below
it is only possible to specify a plain list of standbys as
`FIRST` and `ANY` keywords aren't supported.

Example::

from testgres import get_new_node, First

master = get_new_node().init().start()
with master.replicate().start() as standby:
master.append_conf("synchronous_commit = remote_apply")
master.set_synchronous_standbys(First(1, [standby]))
master.restart()

"""
if self._pg_version >= '9.6':
if isinstance(standbys, Iterable):
standbys = First(1, standbys)
else:
if isinstance(standbys, Iterable):
standbys = u", ".join(
u"\"{}\"".format(r.name) for r in standbys)
else:
raise TestgresException("Feature isn't supported in "
"Postgres 9.5 and below")

self.append_conf("synchronous_standby_names = '{}'".format(standbys))

def catchup(self, dbname=None, username=None):
"""
Wait until async replica catches up with its master.
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49 changes: 49 additions & 0 deletionstestgres/standby.py
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@@ -0,0 +1,49 @@
# coding: utf-8

import six


@six.python_2_unicode_compatible
class First:
"""
Specifies a priority-based synchronous replication and makes transaction
commits wait until their WAL records are replicated to ``num_sync``
synchronous standbys chosen based on their priorities.

Args:
sync_num (int): the number of standbys that transaction need to wait
for replies from
standbys (:obj:`list` of :class:`.PostgresNode`): the list of standby
nodes
"""

def __init__(self, sync_num, standbys):
self.sync_num = sync_num
self.standbys = standbys

def __str__(self):
return u"{} ({})".format(self.sync_num, u", ".join(
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тут мне кажется лучше добавить ключевое слово first, чтобы было явно

u"\"{}\"".format(r.name) for r in self.standbys))


@six.python_2_unicode_compatible
class Any:
"""
Specifies a quorum-based synchronous replication and makes transaction
commits wait until their WAL records are replicated to at least ``num_sync``
listed standbys. Only available for Postgres 10 and newer.

Args:
sync_num (int): the number of standbys that transaction need to wait
for replies from
standbys (:obj:`list` of :class:`.PostgresNode`): the list of standby
nodes
"""

def __init__(self, sync_num, standbys):
self.sync_num = sync_num
self.standbys = standbys

def __str__(self):
return u"ANY {} ({})".format(self.sync_num, u", ".join(
u"\"{}\"".format(r.name) for r in self.standbys))
44 changes: 44 additions & 0 deletionstests/test_simple.py
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Expand Up@@ -40,6 +40,10 @@
get_pg_config, \
get_pg_version

from testgres import \
First, \
Any

# NOTE: those are ugly imports
from testgres import bound_ports
from testgres.utils import PgVer
Expand DownExpand Up@@ -409,6 +413,46 @@ def test_replicate(self):
res = node.execute('select * from test')
self.assertListEqual(res, [])

def test_synchronous_replication(self):
with get_new_node() as master:
old_version = not pg_version_ge('9.6')

master.init(allow_streaming=True).start()

if not old_version:
master.append_conf('synchronous_commit = remote_apply')

# create standby
with master.replicate() as standby1, master.replicate() as standby2:
standby1.start()
standby2.start()

# check formatting
self.assertEqual(
'1 ("{}", "{}")'.format(standby1.name, standby2.name),
str(First(1, (standby1, standby2)))) # yapf: disable
self.assertEqual(
'ANY 1 ("{}", "{}")'.format(standby1.name, standby2.name),
str(Any(1, (standby1, standby2)))) # yapf: disable

# set synchronous_standby_names
master.set_synchronous_standbys([standby1, standby2])
master.restart()

# the following part of the test is only applicable to newer
# versions of PostgresQL
if not old_version:
master.safe_psql('create table abc(a int)')

# Create a large transaction that will take some time to apply
# on standby to check that it applies synchronously
# (If set synchronous_commit to 'on' or other lower level then
# standby most likely won't catchup so fast and test will fail)
master.safe_psql(
'insert into abc select generate_series(1, 1000000)')
res = standby1.safe_psql('select count(*) from abc')
self.assertEqual(res, b'1000000\n')

@unittest.skipUnless(pg_version_ge('10'), 'requires 10+')
def test_logical_replication(self):
with get_new_node() as node1, get_new_node() as node2:
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