Remote Procedure Calls (RPC)
Advanced task communication
Introduction
Cowait provides a simple RPC system for advanced communication between tasks. RPC-callable methods are defined directly on the task classes and marked with the @rpc decorator. RPC calls can accept any JSON serializable arguments and return any JSON serializable value.
RPC communication can be used to send commands or updates to and from tasks, after they've been created. Defining RPC methods on tasks is a good place to introduce side effects to your tasks.
Parent to Child RPC
The parent task can call RPC methods on child tasks by invoking methods on the remote task reference object.
- Define an RPC method on your child task
rpc_child.py
from cowait.tasks Task, rpc, sleep
class RpcChild(Task):
async def run(self):
# wait forever
while True:
await sleep(1)
@rpc
async def some_rpc_call(self):
return 1337- Call it from the parent, after saving a reference to the child task.
rpc_parent.py
from cowait.tasks Task
from rpc_child import RpcChild # your child task
class RpcParent(Task):
async def run(self):
child = RpcChild()
result = await child.some_rpc_call()
print('RPC result:', result)
return resultChild to parent RPC
Similarly, child tasks can call RPC methods on their parent task by invoking methods on self.parent
- Have your parent task create the child task.
rpc_parent.py
from cowait.tasks import Task, rpc, sleep
from rpc_child import RpcChild
class RpcParent(Task):
async def run(self):
self.called = False
# spawn child and wait for it to make an RPC call:
child = RpcChild()
while not self.called:
await sleep(1)
@rpc
async def set_called(self):
self.called = True- Call the parent's RPC method through
self.parent:
rpc_child.py
from cowait.tasks import Task
class RpcChild(Task):
async def run(self):
# rpc call to parent:
await self.parent.set_called()