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"""PgQ cooperative consumer for Python.
"""
from pgq.consumer import Consumer
__all__ = ['CoopConsumer']
class CoopConsumer(Consumer):
"""Cooperative Consumer base class.
There will be one dbscript process per subconsumer.
Config params::
## pgq.CoopConsumer
# name for subconsumer
subconsumer_name =
# pgsql interval when to consider parallel subconsumers dead,
# and take over their unfinished batch
#subconsumer_timeout = 1 hour
"""
def __init__(self, service_name, db_name, args):
"""Initialize new subconsumer.
@param service_name: service_name for DBScript
@param db_name: name of database for get_database()
@param args: cmdline args for DBScript
"""
Consumer.__init__(self, service_name, db_name, args)
self.subconsumer_name = self.cf.get("subconsumer_name")
self.subconsumer_timeout = self.cf.get("subconsumer_timeout", "")
def register_consumer(self):
"""Registration for subconsumer."""
self.log.info("Registering consumer on source queue")
db = self.get_database(self.db_name)
cx = db.cursor()
cx.execute("select pgq_coop.register_subconsumer(%s, %s, %s)",
[self.queue_name, self.consumer_name, self.subconsumer_name])
res = cx.fetchone()[0]
db.commit()
return res
def unregister_consumer(self):
"""Unregistration for subconsumer."""
self.log.info("Unregistering consumer from source queue")
db = self.get_database(self.db_name)
cx = db.cursor()
cx.execute("select pgq_coop.unregister_subconsumer(%s, %s, %s, 0)",
[self.queue_name, self.consumer_name, self.subconsumer_name])
db.commit()
def _load_next_batch(self, curs):
"""Allocate next batch. (internal)"""
if self.subconsumer_timeout:
q = "select pgq_coop.next_batch(%s, %s, %s, %s)"
curs.execute(q, [self.queue_name, self.consumer_name, self.subconsumer_name, self.subconsumer_timeout])
else:
q = "select pgq_coop.next_batch(%s, %s, %s)"
curs.execute(q, [self.queue_name, self.consumer_name, self.subconsumer_name])
return curs.fetchone()[0]
def _finish_batch(self, curs, batch_id, list):
"""Finish batch. (internal)"""
self._flush_retry(curs, batch_id, list)
curs.execute("select pgq_coop.finish_batch(%s)", [batch_id])
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