The protocol layer¶
Any protocol is implemented by deriving from RPCProtocol
and implementing all of its members:
These require implementations of the following classes as well:
Every protocol deals with multiple kinds of structures: data
arguments are
always byte strings, either messages or replies, that are sent via or received
from a transport.
There are two protocol-specific subclasses of
RPCRequest
and RPCResponse
, these
represent well-formed requests and responses.
Finally, if an error occurs during parsing of a request, a
BadRequestError
instance must be thrown. These need to be
subclassed for each protocol as well, since they generate error replies.
Batch protocols¶
Some protocols may support batch requests. In this case, they need to derive
from RPCBatchProtocol
.
Batch protocols differ in that their
parse_request()
method may return an instance of
RPCBatchRequest
. They also possess an addional method in
create_batch_request()
.
Handling a batch request is slightly different, while it supports
error_respond()
, to make actual responses,
create_batch_response()
needs to be used.
No assumptions are made whether or not it is okay for batch requests to be handled in parallel. This is up to the server/dispatch implementation, which must be chosen appropriately.
Supported protocols¶
Any supported protocol is used by instantiating its class and calling the
interface of RPCProtocol
. Note that constructors are not
part of the interface, any protocol may have specific arguments for its
instances.
Protocols usually live in their own module because they may need to import
optional modules that needn’t be a dependency for all of tinyrpc
.
Example¶
The following example shows how to use the
JSONRPCProtocol
class in a custom
application, without using any other components:
Server¶
from tinyrpc.protocols.jsonrpc import JSONRPCProtocol
from tinyrpc import BadRequestError, RPCBatchRequest
rpc = JSONRPCProtocol()
# the code below is valid for all protocols, not just JSONRPC:
def handle_incoming_message(self, data):
try:
request = rpc.parse_request(data)
except BadRequestError as e:
# request was invalid, directly create response
response = e.error_respond(e)
else:
# we got a valid request
# the handle_request function is user-defined
# and returns some form of response
if hasattr(request, create_batch_response):
response = request.create_batch_response(
handle_request(req) for req in request
)
else:
response = handle_request(request)
# now send the response to the client
if response != None:
send_to_client(response.serialize())
def handle_request(request):
try:
# do magic with method, args, kwargs...
return request.respond(result)
except Exception as e:
# for example, a method wasn't found
return request.error_respond(e)
Client¶
from tinyrpc.protocols.jsonrpc import JSONRPCProtocol
rpc = JSONRPCProtocol()
# again, code below is protocol-independent
# assuming you want to call method(*args, **kwargs)
request = rpc.create_request(method, args, kwargs)
reply = send_to_server_and_get_reply(request)
response = rpc.parse_reply(reply)
if hasattr(response, 'error'):
# error handling...
else:
# the return value is found in response.result
do_something_with(response.result)
Another example, this time using batch requests:
# or using batch requests:
requests = rpc.create_batch_request([
rpc.create_request(method_1, args_1, kwargs_1)
rpc.create_request(method_2, args_2, kwargs_2)
# ...
])
reply = send_to_server_and_get_reply(request)
responses = rpc.parse_reply(reply)
for responses in response:
if hasattr(reponse, 'error'):
# ...
Finally, one-way requests are requests where the client does not expect an answer:
request = rpc.create_request(method, args, kwargs, one_way=True)
send_to_server(request)
# done