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"""
old RemoteConsumer / SerialConsumer classes.
"""
import sys
from pgq.consumer import Consumer
__all__ = ['RemoteConsumer', 'SerialConsumer']
class RemoteConsumer(Consumer):
"""Helper for doing event processing in another database.
Requires that whole batch is processed in one TX.
"""
def __init__(self, service_name, db_name, remote_db, args):
Consumer.__init__(self, service_name, db_name, args)
self.remote_db = remote_db
def process_batch(self, db, batch_id, event_list):
"""Process all events in batch.
By default calls process_event for each.
"""
dst_db = self.get_database(self.remote_db)
curs = dst_db.cursor()
if self.is_last_batch(curs, batch_id):
return
self.process_remote_batch(db, batch_id, event_list, dst_db)
self.set_last_batch(curs, batch_id)
dst_db.commit()
def is_last_batch(self, dst_curs, batch_id):
"""Helper function to keep track of last successful batch
in external database.
"""
q = "select pgq_ext.is_batch_done(%s, %s)"
dst_curs.execute(q, [ self.consumer_name, batch_id ])
return dst_curs.fetchone()[0]
def set_last_batch(self, dst_curs, batch_id):
"""Helper function to set last successful batch
in external database.
"""
q = "select pgq_ext.set_batch_done(%s, %s)"
dst_curs.execute(q, [ self.consumer_name, batch_id ])
def process_remote_batch(self, db, batch_id, event_list, dst_db):
raise Exception('process_remote_batch not implemented')
class SerialConsumer(Consumer):
"""Consumer that applies batches sequentially in second database.
Requirements:
- Whole batch in one TX.
- Must not use retry queue.
Features:
- Can detect if several batches are already applied to dest db.
- If some ticks are lost. allows to seek back on queue.
Whether it succeeds, depends on pgq configuration.
"""
def __init__(self, service_name, db_name, remote_db, args):
Consumer.__init__(self, service_name, db_name, args)
self.remote_db = remote_db
self.dst_schema = "pgq_ext"
def startup(self):
if self.options.rewind:
self.rewind()
sys.exit(0)
if self.options.reset:
self.dst_reset()
sys.exit(0)
return Consumer.startup(self)
def init_optparse(self, parser = None):
p = Consumer.init_optparse(self, parser)
p.add_option("--rewind", action = "store_true",
help = "change queue position according to destination")
p.add_option("--reset", action = "store_true",
help = "reset queue pos on destination side")
return p
def process_batch(self, db, batch_id, event_list):
"""Process all events in batch.
"""
dst_db = self.get_database(self.remote_db)
curs = dst_db.cursor()
# check if done
if self.is_batch_done(curs):
return
# actual work
self.process_remote_batch(db, batch_id, event_list, dst_db)
# finish work
self.set_batch_done(curs)
dst_db.commit()
def is_batch_done(self, dst_curs):
"""Helper function to keep track of last successful batch
in external database.
"""
cur_tick = self.batch_info['tick_id']
prev_tick = self.batch_info['prev_tick_id']
dst_tick = self.get_last_tick(dst_curs)
if not dst_tick:
# seems this consumer has not run yet against dst_db
return False
if prev_tick == dst_tick:
# on track
return False
if cur_tick == dst_tick:
# current batch is already applied, skip it
return True
# anything else means problems
raise Exception('Lost position: batch %d..%d, dst has %d' % (
prev_tick, cur_tick, dst_tick))
def set_batch_done(self, dst_curs):
"""Helper function to set last successful batch
in external database.
"""
tick_id = self.batch_info['tick_id']
self.set_last_tick(dst_curs, tick_id)
def register_consumer(self):
new = Consumer.register_consumer(self)
if new: # fixme
self.dst_reset()
def unregister_consumer(self):
"""If unregistering, also clean completed tick table on dest."""
Consumer.unregister_consumer(self)
self.dst_reset()
def process_remote_batch(self, db, batch_id, event_list, dst_db):
raise Exception('process_remote_batch not implemented')
def rewind(self):
self.log.info("Rewinding queue")
src_db = self.get_database(self.db_name)
dst_db = self.get_database(self.remote_db)
src_curs = src_db.cursor()
dst_curs = dst_db.cursor()
dst_tick = self.get_last_tick(dst_curs)
if dst_tick:
q = "select pgq.register_consumer_at(%s, %s, %s)"
src_curs.execute(q, [self.queue_name, self.consumer_name, dst_tick])
else:
self.log.warning('No tick found on dst side')
dst_db.commit()
src_db.commit()
def dst_reset(self):
self.log.info("Resetting queue tracking on dst side")
dst_db = self.get_database(self.remote_db)
dst_curs = dst_db.cursor()
self.set_last_tick(dst_curs, None)
dst_db.commit()
def get_last_tick(self, dst_curs):
q = "select %s.get_last_tick(%%s)" % self.dst_schema
dst_curs.execute(q, [self.consumer_name])
res = dst_curs.fetchone()
return res[0]
def set_last_tick(self, dst_curs, tick_id):
q = "select %s.set_last_tick(%%s, %%s)" % self.dst_schema
dst_curs.execute(q, [ self.consumer_name, tick_id ])
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