"""
Restful json clients.
Use `Resource`_ for a connection to a single host.
Use `Pool`_ for persistent thread-safe connections to a single host.
Use `Resources`_ for multiple hosts with simple partitioning or replication.
Use `Shards`_ for horizontally partitioning hosts by different keys.
Use `Replicas`_ in coordination with automatic host synchronization.
`Resources`_ optionally reuse connections, handling request timeouts.
Broadcasting to multiple resources is parallelized with asynchronous requests and responses.
The load balancing strategy is randomized, biased by the number of cached connections available.
This inherently provides limited failover support, but applications must still handle exceptions as desired.
`Replicas`_ will automatically retry if host is unreachable.
"""
from future_builtins import map, zip
import warnings
import random
import time
import itertools
import collections
import io
import gzip
import shutil
import httplib
import urllib
import urlparse
import errno
from .utils import json, suppress
[docs]class Response(httplib.HTTPResponse):
"A completed response which handles json and caches its body."
content_type = 'application/json'
def end(self):
self.body = self.read()
self.time = float(self.getheader('x-response-time', 'nan'))
if 'gzip' in self.getheader('content-encoding', ''):
self.body = gzip.GzipFile(fileobj=io.BytesIO(self.body)).read()
[docs] def __nonzero__(self):
"Return whether status is successful."
return httplib.OK <= self.status < httplib.MULTIPLE_CHOICES
[docs] def __call__(self):
"Return evaluated response body or raise exception."
body = self.body
if body and self.getheader('content-type').startswith(self.content_type):
body = json.loads(body)
code, agent, text = self.getheader('warning', ' ').split(' ', 2)
if agent == 'lupyne':
warnings.warn(json.loads(text))
if self:
return body
raise httplib.HTTPException(self.status, self.reason, body)
[docs]class Resource(httplib.HTTPConnection):
"Synchronous connection which handles json responses."
response_class = Response
headers = {'accept-encoding': 'compress, gzip', 'content-length': '0'}
[docs] def request(self, method, path, body=None):
"Send request after handling body and headers."
headers = dict(self.headers)
if body is not None:
body = json.dumps(body)
headers.update({'content-length': str(len(body)), 'content-type': self.response_class.content_type})
httplib.HTTPConnection.request(self, method, path, body, headers)
[docs] def getresponse(self, filename=''):
"Return completed response, optionally write response body to a file."
response = httplib.HTTPConnection.getresponse(self)
if response and filename:
with open(filename, 'w') as output:
shutil.copyfileobj(response, output)
response.end()
return response
[docs] def call(self, method, path, body=None, params=(), redirect=False):
"Send request and return completed `response`_."
if params:
path += '?' + urllib.urlencode(params, doseq=True)
self.request(method, path, body)
response = self.getresponse()
if redirect and httplib.MULTIPLE_CHOICES <= response.status < httplib.NOT_MODIFIED:
url = urlparse.urlparse(response.getheader('location'))
assert url.netloc.startswith(self.host)
warnings.warn('{}: {}'.format(response.reason, url.path), DeprecationWarning)
return self.call(method, url.path, body, params, redirect - 1)
return response
[docs] def download(self, path, filename):
"Download response body from GET request to a file."
self.request('GET', path)
return self.getresponse(filename)()
[docs] def multicall(self, *requests):
"Pipeline requests (method, path[, body]) and generate completed responses."
responses = []
for request in requests:
self.request(*request)
responses.append(self.response_class(self.sock, self.debuglevel, self.strict, self._method))
self._HTTPConnection__state = 'Idle'
return (response.begin() or response.end() or response for response in responses)
[docs] def get(self, path, **params):
"Return response body from GET request."
return self.call('GET', path, params=params)()
[docs] def post(self, path, body=None, **kwargs):
"Return response body from POST request."
return self.call('POST', path, body, **kwargs)()
[docs] def put(self, path, body=None, **kwargs):
"Return response body from PUT request."
return self.call('PUT', path, body, **kwargs)()
[docs] def delete(self, path, **params):
"Return response body from DELETE request."
return self.call('DELETE', path, params=params)()
[docs] def patch(self, path, body=None, **kwargs):
"Return response body from PATCH request."
return self.call('PATCH', path, body, **kwargs)()
if hasattr(httplib, 'HTTPSConnection'): # pragma: no branch
class SResource(Resource, httplib.HTTPSConnection, object):
pass
[docs]class Pool(collections.deque):
"Thread-safe resource pool for one host."
resource_class = Resource
def __init__(self, host, limit=0):
collections.deque.__init__(self, maxlen=limit)
self.host = host
[docs] def stream(self, method, path, body=None):
"Generate resource, initial response, and final response while handling timeouts."
try:
resource = self.popleft()
except IndexError:
resource = self.resource_class(self.host)
resource.request(method, path, body)
response = yield resource
with suppress(httplib.BadStatusLine, IOError, errno=errno.ECONNRESET):
response = resource.getresponse()
timeout = response.status == httplib.BAD_REQUEST and response.body == 'Illegal end of headers.'
if response is None or response.status == httplib.REQUEST_TIMEOUT or timeout:
resource.close()
resource.request(method, path, body)
yield response
yield resource.getresponse()
else:
self.append(resource)
yield response
yield response
[docs] def call(self, method, path, body=None):
"Send request and return completed `response`_."
return list(self.stream(method, path, body))[-1]
[docs]class Resources(dict):
"""Thread-safe mapping of hosts to resource pools.
:param hosts: host[:port] strings
:param limit: maximum number of cached resources per host
"""
def __init__(self, hosts, limit=0):
self.update((host, Pool(host, limit)) for host in hosts)
[docs] def priority(self, host):
"Return priority for host. None may be used to eliminate from consideration."
return -len(self[host])
[docs] def choice(self, hosts):
"Return chosen host according to priority."
priorities = collections.defaultdict(list)
for host in hosts:
priorities[self.priority(host)].append(host)
priorities.pop(None, None)
return random.choice(priorities[min(priorities)])
[docs] def unicast(self, method, path, body=None, hosts=()):
"Send request and return `response`_ from any host, optionally from given subset."
host = self.choice(tuple(hosts) or self)
return self[host].call(method, path, body)
[docs] def broadcast(self, method, path, body=None, hosts=()):
"Send requests and return responses from all hosts, optionally from given subset."
hosts = tuple(hosts) or self
streams = [self[host].stream(method, path, body) for host in hosts]
return list(zip(*streams))[-1]
[docs]class Shards(dict):
"""Mapping of keys to host clusters, with associated `resources`_.
:param items: host, key pairs
:param limit: maximum number of cached connections per host
:param multimap: mapping of hosts to multiple keys
"""
choice = Resources.__dict__['choice']
def __init__(self, items=(), limit=0, **multimap):
pairs = ((host, key) for host in multimap for key in multimap[host])
for host, key in itertools.chain(items, pairs):
self.setdefault(key, set()).add(host)
self.resources = Resources(itertools.chain(*self.values()), limit)
[docs] def priority(self, hosts):
"Return combined priority for hosts."
priorities = list(map(self.resources.priority, hosts))
if None not in priorities:
return len(priorities), sum(priorities)
[docs] def unicast(self, key, method, path, body=None):
"Send request and return `response`_ from any host for corresponding key."
return self.resources.unicast(method, path, body, self[key])
[docs] def broadcast(self, key, method, path, body=None):
"Send requests and return responses from all hosts for corresponding key."
return self.resources.broadcast(method, path, body, self[key])
[docs] def multicast(self, keys, method, path, body=None):
"""Send requests and return responses from a minimal subset of hosts which cover all corresponding keys.
Response overlap is possible depending on partitioning.
"""
shards = frozenset(),
for key in keys:
shards = {hosts.union([host]) for hosts, host in itertools.product(shards, self[key])}
return self.resources.broadcast(method, path, body, self.choice(shards))
[docs]class Replicas(Resources):
"""Resources which failover assuming the hosts are being automatically synchronized.
Writes are dispatched to the first host and sequentially failover.
Reads are balanced among all remaining hosts.
"""
get, post, put, delete = map(Resource.__dict__.__getitem__, ['get', 'post', 'put', 'delete'])
def __init__(self, hosts, limit=0):
self.hosts = collections.deque(hosts)
Resources.__init__(self, self.hosts, limit)
for pool in self.values():
pool.failure = 0
def priority(self, host):
pool = self[host]
if not pool.failure:
return -len(pool)
[docs] def call(self, method, path, body=None, params=(), retry=False):
"""Send request and return completed `response`_, even if hosts are unreachable.
:param retry: optionally retry request on http errors as well, such as waiting for indexer promotion
"""
if params:
path += '?' + urllib.urlencode(params, doseq=True)
host = self.choice(self) if method == 'GET' else self.hosts[0]
try:
response = self[host].call(method, path, body)
except IOError:
self[host].failure = time.time()
if method != 'GET':
with suppress(ValueError):
self.hosts.remove(host)
return self.call(method, path, body, retry=retry)
return response if (response or not retry) else self.call(method, path, body, retry=retry - 1)