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"""Catch moment when tables are in sync on master and slave.
"""
import sys, time, skytools
class Syncer(skytools.DBScript):
"""Walks tables in primary key order and checks if data matches."""
def __init__(self, args):
"""Syncer init."""
skytools.DBScript.__init__(self, 'londiste3', args)
self.set_single_loop(1)
# compat names
self.queue_name = self.cf.get("pgq_queue_name", '')
self.consumer_name = self.cf.get('pgq_consumer_id', '')
# good names
if not self.queue_name:
self.queue_name = self.cf.get("queue_name")
if not self.consumer_name:
self.consumer_name = self.cf.get('consumer_name', self.job_name)
self.lock_timeout = self.cf.getfloat('lock_timeout', 10)
if self.pidfile:
self.pidfile += ".repair"
def set_lock_timeout(self, curs):
ms = int(1000 * self.lock_timeout)
if ms > 0:
q = "SET LOCAL statement_timeout = %d" % ms
self.log.debug(q)
curs.execute(q)
def init_optparse(self, p=None):
"""Initialize cmdline switches."""
p = skytools.DBScript.init_optparse(self, p)
p.add_option("--force", action="store_true", help="ignore lag")
return p
def check_consumer(self, setup_curs):
"""Before locking anything check if consumer is working ok."""
q = "select extract(epoch from ticker_lag) from pgq.get_queue_info(%s)"
setup_curs.execute(q, [self.queue_name])
ticker_lag = setup_curs.fetchone()[0]
q = "select extract(epoch from lag)"\
" from pgq.get_consumer_info(%s, %s)"
setup_curs.execute(q, [self.queue_name, self.consumer_name])
res = setup_curs.fetchall()
if len(res) == 0:
self.log.error('No such consumer')
sys.exit(1)
consumer_lag = res[0][0]
if consumer_lag > ticker_lag + 10 and not self.options.force:
self.log.error('Consumer lagging too much, cannot proceed')
sys.exit(1)
def get_subscriber_table_state(self, dst_db):
"""Load table states from subscriber."""
dst_curs = dst_db.cursor()
q = "select * from londiste.get_table_list(%s) where local"
dst_curs.execute(q, [self.queue_name])
res = dst_curs.dictfetchall()
dst_db.commit()
return res
def work(self):
"""Syncer main function."""
dst_db = self.get_database('db', isolation_level = skytools.I_SERIALIZABLE)
provider_loc = self.get_provider_location(dst_db)
lock_db = self.get_database('lock_db', connstr = provider_loc)
setup_db = self.get_database('setup_db', autocommit = 1, connstr = provider_loc)
src_db = self.get_database('provider_db', connstr = provider_loc,
isolation_level = skytools.I_SERIALIZABLE)
setup_curs = setup_db.cursor()
self.check_consumer(setup_curs)
state_list = self.get_subscriber_table_state(dst_db)
state_map = {}
full_list = []
for ts in state_list:
name = ts['table_name']
full_list.append(name)
state_map[name] = ts
if len(self.args) > 2:
tlist = self.args[2:]
else:
tlist = full_list
for tbl in tlist:
tbl = skytools.fq_name(tbl)
if not tbl in state_map:
self.log.warning('Table not subscribed: %s' % tbl)
continue
st = state_map[tbl]
if st['merge_state'] != 'ok':
self.log.info('Table %s not synced yet, no point' % tbl)
continue
self.check_table(tbl, lock_db, src_db, dst_db, setup_curs)
lock_db.commit()
src_db.commit()
dst_db.commit()
def force_tick(self, setup_curs):
q = "select pgq.force_tick(%s)"
setup_curs.execute(q, [self.queue_name])
res = setup_curs.fetchone()
cur_pos = res[0]
start = time.time()
while 1:
time.sleep(0.5)
setup_curs.execute(q, [self.queue_name])
res = setup_curs.fetchone()
if res[0] != cur_pos:
# new pos
return res[0]
# dont loop more than 10 secs
dur = time.time() - start
if dur > 10 and not self.options.force:
raise Exception("Ticker seems dead")
def check_table(self, tbl, lock_db, src_db, dst_db, setup_curs):
"""Get transaction to same state, then process."""
lock_curs = lock_db.cursor()
src_curs = src_db.cursor()
dst_curs = dst_db.cursor()
if not skytools.exists_table(src_curs, tbl):
self.log.warning("Table %s does not exist on provider side" % tbl)
return
if not skytools.exists_table(dst_curs, tbl):
self.log.warning("Table %s does not exist on subscriber side" % tbl)
return
# lock table in separate connection
self.log.info('Locking %s' % tbl)
lock_db.commit()
self.set_lock_timeout(lock_curs)
lock_time = time.time()
lock_curs.execute("LOCK TABLE %s IN SHARE MODE" % skytools.quote_fqident(tbl))
# now wait until consumer has updated target table until locking
self.log.info('Syncing %s' % tbl)
# consumer must get futher than this tick
tick_id = self.force_tick(setup_curs)
# try to force second tick also
self.force_tick(setup_curs)
# take server time
setup_curs.execute("select to_char(now(), 'YYYY-MM-DD HH24:MI:SS.MS')")
tpos = setup_curs.fetchone()[0]
# now wait
while 1:
time.sleep(0.5)
q = "select now() - lag > timestamp %s, now(), lag"\
" from pgq.get_consumer_info(%s, %s)"
setup_curs.execute(q, [tpos, self.queue_name, self.consumer_name])
res = setup_curs.fetchall()
if len(res) == 0:
raise Exception('No such consumer')
row = res[0]
self.log.debug("tpos=%s now=%s lag=%s ok=%s" % (tpos, row[1], row[2], row[0]))
if row[0]:
break
# limit lock time
if time.time() > lock_time + self.lock_timeout and not self.options.force:
self.log.error('Consumer lagging too much, exiting')
lock_db.rollback()
sys.exit(1)
# take snapshot on provider side
src_db.commit()
src_curs.execute("SELECT 1")
# take snapshot on subscriber side
dst_db.commit()
dst_curs.execute("SELECT 1")
# release lock
lock_db.commit()
# do work
self.process_sync(tbl, src_db, dst_db)
# done
src_db.commit()
dst_db.commit()
def process_sync(self, tbl, src_db, dst_db):
"""It gets 2 connections in state where tbl should be in same state.
"""
raise Exception('process_sync not implemented')
def get_provider_location(self, dst_db):
curs = dst_db.cursor()
q = "select * from pgq_node.get_node_info(%s)"
rows = self.exec_cmd(dst_db, q, [self.queue_name])
return rows[0]['provider_location']
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