import time
import logging
import rethinkdb as r
from bigchaindb import backend
from bigchaindb.backend.exceptions import BackendError
from bigchaindb.backend.changefeed import ChangeFeed
from bigchaindb.backend.utils import module_dispatch_registrar
from bigchaindb.backend.rethinkdb.connection import RethinkDBConnection
logger = logging.getLogger(__name__)
register_changefeed = module_dispatch_registrar(backend.changefeed)
[docs]class RethinkDBChangeFeed(ChangeFeed):
"""This class wraps a RethinkDB changefeed."""
def run_forever(self):
for element in self.prefeed:
self.outqueue.put(element)
while True:
try:
self.run_changefeed()
break
except (BackendError, r.ReqlDriverError) as exc:
logger.exception('Error connecting to the database, retrying')
time.sleep(1)
def run_changefeed(self):
for change in self.connection.run(r.table(self.table).changes()):
is_insert = change['old_val'] is None
is_delete = change['new_val'] is None
is_update = not is_insert and not is_delete
if is_insert and (self.operation & ChangeFeed.INSERT):
self.outqueue.put(change['new_val'])
elif is_delete and (self.operation & ChangeFeed.DELETE):
self.outqueue.put(change['old_val'])
elif is_update and (self.operation & ChangeFeed.UPDATE):
self.outqueue.put(change['new_val'])
@register_changefeed(RethinkDBConnection)
[docs]def get_changefeed(connection, table, operation, *, prefeed=None):
"""Return a RethinkDB changefeed.
Returns:
An instance of
:class:`~bigchaindb.backend.rethinkdb.RethinkDBChangeFeed`.
"""
return RethinkDBChangeFeed(table, operation, prefeed=prefeed,
connection=connection)