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#!/usr/bin/env python
# Copyright (c) 2015, 2016 IBM. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
Module containing the Feed class which provides iterator support for consuming
continuous and non-continuous feeds like ``_changes`` and ``_db_updates``.
"""
import json
from ._2to3 import iteritems_, next_, unicode_, STRTYPE, NONETYPE
from .error import CloudantArgumentError, CloudantFeedException
from ._common_util import feed_arg_types, TYPE_CONVERTERS
class Feed(object):
"""
Provides an iterator for consuming client and database feeds such as
``_db_updates`` and ``_changes``. A Feed object is constructed with a
:mod:`~cloudant.client` or a :mod:`~cloudant.database` which it uses to
issue HTTP requests to the appropriate feed endpoint. Instead of using this
class directly, it is recommended to use the client APIs
:func:`~cloudant.client.CouchDB.db_updates`,
:func:`~cloudant.client.Cloudant.db_updates`, or the database API
:func:`~cloudant.database.CouchDatabase.changes`. Reference those methods
for a list of valid feed options.
:param source: Either a :mod:`~cloudant.client` object or a
:mod:`~cloudant.database` object.
:param bool raw_data: If set to True then the raw response data will be
streamed otherwise if set to False then JSON formatted data will be
streamed. Default is False.
"""
def __init__(self, source, raw_data=False, **options):
self._r_session = source.r_session
self._raw_data = raw_data
self._options = options
self._source = source.__class__.__name__
if self._source == 'CouchDB':
self._url = '/'.join([source.server_url, '_db_updates'])
# Set CouchDB _db_updates option defaults as they differ from
# the _changes and Cloudant _db_updates option defaults
self._options['feed'] = self._options.get('feed', 'longpoll')
self._options['heartbeat'] = self._options.get('heartbeat', True)
elif self._source == 'Cloudant':
self._url = '/'.join([source.server_url, '_db_updates'])
else:
self._url = '/'.join([source.database_url, '_changes'])
self._chunk_size = self._options.pop('chunk_size', 512)
self._resp = None
self._lines = None
self._last_seq = None
self._stop = False
@property
def last_seq(self):
"""
Returns the last sequence identifier for the feed. Only available after
the feed has iterated through to completion.
:returns: A string representing the last sequence number of a feed.
"""
return self._last_seq
def stop(self):
"""
Stops a feed iteration.
"""
self._stop = True
def _start(self):
"""
Starts streaming the feed using the provided session and feed options.
"""
params = self._translate(self._options)
self._resp = self._r_session.get(self._url, params=params, stream=True)
self._resp.raise_for_status()
self._lines = self._resp.iter_lines(self._chunk_size)
def _translate(self, options):
"""
Perform translation of feed options passed in as keyword
arguments to CouchDB/Cloudant equivalent.
"""
translation = dict()
for key, val in iteritems_(options):
self._validate(key, val, feed_arg_types(self._source))
try:
if isinstance(val, STRTYPE):
translation[key] = val
elif not isinstance(val, NONETYPE):
arg_converter = TYPE_CONVERTERS.get(type(val))
translation[key] = arg_converter(val)
except Exception as ex:
raise CloudantArgumentError(115, key, ex)
return translation
def _validate(self, key, val, arg_types):
"""
Ensures that the key and the value are valid arguments to be used with
the feed.
"""
if key not in arg_types:
raise CloudantArgumentError(116, key)
if (not isinstance(val, arg_types[key]) or
(isinstance(val, bool) and int in arg_types[key])):
raise CloudantArgumentError(117, key, arg_types[key])
if isinstance(val, int) and val < 0 and not isinstance(val, bool):
raise CloudantArgumentError(118, key, val)
if key == 'feed':
valid_vals = ('continuous', 'normal', 'longpoll')
if self._source == 'CouchDB':
valid_vals = ('continuous', 'longpoll')
if val not in valid_vals:
raise CloudantArgumentError(119, val, valid_vals)
if key == 'style' and val not in ('main_only', 'all_docs'):
raise CloudantArgumentError(120, val)
def __iter__(self):
"""
Makes this object an iterator.
"""
return self
def __next__(self):
"""
Provides Python3 compatibility.
"""
return self.next()
def next(self):
"""
Handles the iteration by pulling the next line out of the stream,
attempting to convert the response to JSON if necessary.
:returns: Data representing what was seen in the feed
"""
while True:
if not self._resp:
self._start()
if self._stop:
raise StopIteration
skip, data = self._process_data(next_(self._lines))
if not skip:
break
return data
def _process_data(self, line):
"""
Validates and processes the line passed in and converts it to a
Python object if necessary.
"""
skip = False
if self._raw_data:
return skip, line
else:
line = unicode_(line)
if not line:
if (self._options.get('heartbeat', False) and
self._options.get('feed') in ('continuous', 'longpoll') and
not self._last_seq):
line = None
else:
skip = True
elif line in ('{"results":[', '],'):
skip = True
elif line[-1] == ',':
line = line[:-1]
elif line[:10] == ('"last_seq"'):
line = '{' + line
try:
if line:
data = json.loads(line)
if data.get('last_seq'):
self._last_seq = data['last_seq']
skip = True
else:
data = None
except ValueError:
data = {"error": "Bad JSON line", "line": line}
return skip, data
class InfiniteFeed(Feed):
"""
Provides an infinite iterator for consuming client and database feeds such
as ``_db_updates`` and ``_changes``. An InfiniteFeed object is constructed
with a :class:`~cloudant.client.Cloudant` object or a
:mod:`~cloudant.database` object which it uses to issue HTTP requests to the
appropriate feed endpoint. An infinite feed is NOT supported for use with a
:class:`~cloudant.client.CouchDB` object and unlike a
:class:`~cloudant.feed.Feed` which can be a ``normal``, ``longpoll``,
or ``continuous`` feed, an InfiniteFeed can only be ``continuous`` and the
iterator will only stream formatted JSON objects. Instead of using this
class directly, it is recommended to use the client
API :func:`~cloudant.client.Cloudant.infinite_db_updates` or the database
API :func:`~cloudant.database.CouchDatabase._infinite_changes`. Reference
those methods for a valid list of feed options.
Note: The infinite iterator is not exception resilient so if an
unexpected exception occurs, the iterator will terminate. Any unexpected
exceptions should be handled in code outside of this library. If you wish
to restart the infinite iterator from where it left off that can be done by
constructing a new InfiniteFeed object with the ``since`` option set to the
sequence number of the last row of data prior to termination.
:param source: Either a :class:`~cloudant.client.Cloudant` object or a
:mod:`~cloudant.database` object.
"""
def __init__(self, source, **options):
super(InfiniteFeed, self).__init__(source, False, **options)
# Default feed to continuous if not explicitly set
self._options['feed'] = self._options.get('feed', 'continuous')
def _validate(self, key, val, arg_types):
"""
Ensures that the key and the value are valid arguments to be used with
the feed.
"""
if key == 'feed' and val != 'continuous':
raise CloudantArgumentError(121, val)
super(InfiniteFeed, self)._validate(key, val, arg_types)
def next(self):
"""
Handles the iteration by pulling the next line out of the stream and
converting the response to JSON.
:returns: Data representing what was seen in the feed
"""
while True:
if self._source == 'CouchDB':
raise CloudantFeedException(101)
if self._last_seq:
self._options.update({'since': self._last_seq})
self._resp = None
self._last_seq = None
if not self._resp:
self._start()
if self._stop:
raise StopIteration
skip, data = self._process_data(next_(self._lines))
if not skip:
break
return data
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