# Copyright BigchainDB GmbH and BigchainDB contributors
# SPDX-License-Identifier: (Apache-2.0 AND CC-BY-4.0)
# Code is Apache-2.0 and docs are CC-BY-4.0
from time import time
from requests.exceptions import ConnectionError
from .connection import Connection
from .exceptions import TimeoutError
from .pool import Pool
NO_TIMEOUT_BACKOFF_CAP = 10 # seconds
[docs]class Transport:
"""Transport class.
"""
[docs] def __init__(self, *nodes, timeout=None):
"""Initializes an instance of
:class:`~bigchaindb_driver.transport.Transport`.
Args:
nodes: each node is a dictionary with the keys `endpoint` and
`headers`
timeout (int): Optional timeout in seconds.
"""
self.nodes = nodes
self.timeout = timeout
self.connection_pool = Pool([Connection(node_url=node['endpoint'],
headers=node['headers'])
for node in nodes])
[docs] def forward_request(self, method, path=None,
json=None, params=None, headers=None):
"""Makes HTTP requests to the configured nodes.
Retries connection errors
(e.g. DNS failures, refused connection, etc).
A user may choose to retry other errors
by catching the corresponding
exceptions and retrying `forward_request`.
Exponential backoff is implemented individually for each node.
Backoff delays are expressed as timestamps stored on the object and
they are not reset in between multiple function calls.
Times out when `self.timeout` is expired, if not `None`.
Args:
method (str): HTTP method name (e.g.: ``'GET'``).
path (str): Path to be appended to the base url of a node. E.g.:
``'/transactions'``).
json (dict): Payload to be sent with the HTTP request.
params (dict)): Dictionary of URL (query) parameters.
headers (dict): Optional headers to pass to the request.
Returns:
dict: Result of :meth:`requests.models.Response.json`
"""
error_trace = []
timeout = self.timeout
backoff_cap = NO_TIMEOUT_BACKOFF_CAP if timeout is None \
else timeout / 2
while timeout is None or timeout > 0:
connection = self.connection_pool.get_connection()
start = time()
try:
response = connection.request(
method=method,
path=path,
params=params,
json=json,
headers=headers,
timeout=timeout,
backoff_cap=backoff_cap,
)
except ConnectionError as err:
error_trace.append(err)
continue
else:
return response.data
finally:
elapsed = time() - start
if timeout is not None:
timeout -= elapsed
raise TimeoutError(error_trace)