mirror of https://github.com/nocturn9x/giambio.git
544 lines
22 KiB
Python
544 lines
22 KiB
Python
"""
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The main runtime environment for giambio
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Copyright (C) 2020 nocturn9x
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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"""
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# Import libraries and internal resources
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import types
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import socket
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from time import sleep as wait
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from timeit import default_timer
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from giambio.objects import Task, TimeQueue, DeadlinesQueue
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from giambio.traps import want_read, want_write
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from giambio.util.debug import BaseDebugger
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from itertools import chain
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from selectors import DefaultSelector, EVENT_READ, EVENT_WRITE
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from giambio.exceptions import (InternalError,
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CancelledError,
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ResourceBusy,
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GiambioError,
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TooSlowError
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)
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IOInterrupt = (BlockingIOError, InterruptedError)
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IO_SKIP_LIMIT = 5 # TODO: Inspect this
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class AsyncScheduler:
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"""
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A simple asynchronous scheduler implementation. Tries to mimic the threaded
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model in its simplicity, without using actual threads, but rather alternating
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across coroutines execution to let more than one thing at a time to proceed
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with its calculations. An attempt to fix the threaded model has been made
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without making the API unnecessarily complicated.
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A few examples are tasks cancellation and exception propagation.
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"""
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def __init__(self, clock: types.FunctionType = default_timer, debugger: BaseDebugger = None):
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"""
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Object constructor
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"""
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# The debugger object. If it is none we create a dummy object that immediately returns an empty
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# lambda every time you access any of its attributes to avoid lots of if self.debugger clauses
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if debugger:
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assert issubclass(type(debugger),
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BaseDebugger), "The debugger must be a subclass of giambio.util.BaseDebugger"
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self.debugger = debugger or type("DumbDebugger", (object, ), {"__getattr__": lambda *args: lambda *arg: None})()
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# Tasks that are ready to run
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self.tasks = []
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# Selector object to perform I/O multiplexing
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self.selector = DefaultSelector()
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# This will always point to the currently running coroutine (Task object)
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self.current_task = None
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# Monotonic clock to keep track of elapsed time reliably
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self.clock = clock
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# Tasks that are asleep
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self.paused = TimeQueue(self.clock)
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# All active Event objects
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self.events = set()
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# Data to send back to a trap
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self.to_send = None
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# Have we ever ran?
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self.has_ran = False
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# The current pool
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self.current_pool = None
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# How many times we skipped I/O checks to let a task run
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# We limit the number of times we skip such checks to avoid
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# I/O starvation in highly concurrent systems
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self.io_skip = 0
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# A heap queue of deadlines to be checked
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self.deadlines = DeadlinesQueue()
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def done(self):
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"""
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Returns True if there is work to do
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"""
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if any([self.paused, self.tasks, self.events, self.selector.get_map()]):
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return False
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return True
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def shutdown(self):
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"""
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Shuts down the event loop
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"""
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self.selector.close()
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def run(self):
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"""
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Starts the loop and 'listens' for events until there is work to do,
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then exits. This behavior kinda reflects a kernel, as coroutines can
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request the loop's functionality only trough some fixed entry points,
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which in turn yield and give execution control to the loop itself.
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"""
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while True:
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try:
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if self.done():
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# If we're done, which means there are no
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# sleeping tasks, no events to deliver,
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# no I/O to do and no running tasks, we
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# simply tear us down and return to self.start
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self.close()
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break
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elif not self.tasks:
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# We start by checking for I/O
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self.check_io()
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if self.paused:
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# Next, if there are no actively running tasks
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# we try to schedule the asleep ones
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self.awake_sleeping()
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# Then we try to awake event-waiting tasks
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if self.events:
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self.check_events()
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# Otherwise, while there are tasks ready to run, well, run them!
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while self.tasks:
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# Sets the currently running task
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self.current_task = self.tasks.pop(0)
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# Sets the current pool (for nested pools)
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self.current_pool = self.current_task.pool
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self.debugger.before_task_step(self.current_task)
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if self.current_task.cancel_pending:
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# We perform the deferred cancellation
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# if it was previously scheduled
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self.do_cancel()
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if self.to_send and self.current_task.status != "init":
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# A little setup to send objects from and to
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# coroutines outside the event loop
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data = self.to_send
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else:
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# The first time coroutines' method .send() wants None!
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data = None
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# Run a single step with the calculation
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method, *args = self.current_task.run(data)
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# Some debugging and internal chatter here
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self.current_task.status = "run"
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self.current_task.steps += 1
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self.debugger.after_task_step(self.current_task)
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# If data has been sent, reset it to None
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if self.to_send and self.current_task != "init":
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self.to_send = None
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# Sneaky method call, thanks to David Beazley for this ;)
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getattr(self, method)(*args)
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except AttributeError: # If this happens, that's quite bad!
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# This exception block is meant to be triggered by other async
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# libraries, which most likely have different trap names and behaviors.
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# If you get this exception and you're 100% sure you're not mixing
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# async primitives from other libraries, then it's a bug!
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raise InternalError("Uh oh! Something very bad just happened, did"
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" you try to mix primitives from other async libraries?") from None
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except CancelledError:
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# When a task needs to be cancelled, giambio tries to do it gracefully
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# first: if the task is paused in either I/O or sleeping, that's perfect.
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# But we also need to cancel a task if it was not sleeping or waiting on
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# any I/O because it could never do so (therefore blocking everything
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# forever). So, when cancellation can't be done right away, we schedule
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# if for the next execution step of the task. Giambio will also make sure
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# to re-raise cancellations at every checkpoint until the task lets the
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# exception propagate into us, because we *really* want the task to be
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# cancelled, and since asking kindly didn't work we have to use some
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# force :)
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self.current_task.status = "cancelled"
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self.current_task.cancelled = True
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self.current_task.cancel_pending = False
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self.debugger.after_cancel(self.current_task)
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self.join(self.current_task)
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except StopIteration as ret:
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# At the end of the day, coroutines are generator functions with
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# some tricky behaviors, and this is one of them. When a coroutine
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# hits a return statement (either explicit or implicit), it raises
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# a StopIteration exception, which has an attribute named value that
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# represents the return value of the coroutine, if any. Of course this
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# exception is not an error and we should happily keep going after it,
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# most of this code below is just useful for internal/debugging purposes
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self.current_task.status = "end"
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self.current_task.result = ret.value
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self.current_task.finished = True
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self.debugger.on_task_exit(self.current_task)
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self.join(self.current_task)
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except BaseException as err:
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# TODO: We might want to do a bit more complex traceback hacking to remove any extra
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# frames from the exception call stack, but for now removing at least the first one
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# seems a sensible approach (it's us catching it so we don't care about that)
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self.current_task.exc = err
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self.current_task.exc.__traceback__ = self.current_task.exc.__traceback__.tb_next
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self.current_task.status = "crashed"
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self.debugger.on_exception_raised(self.current_task, err)
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self.join(self.current_task) # This propagates the exception
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def do_cancel(self, task: Task = None):
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"""
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Performs task cancellation by throwing CancelledError inside the given
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task in order to stop it from running. The loop continues to execute
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as tasks are independent
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"""
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task = task or self.current_task
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if not task.cancelled and not task.exc:
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self.debugger.before_cancel(task)
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task.throw(CancelledError())
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def get_current(self):
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"""
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Returns the current task to an async caller
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"""
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self.tasks.append(self.current_task)
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self.to_send = self.current_task
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def check_events(self):
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"""
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Checks for ready or expired events and triggers them
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"""
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for event in self.events.copy():
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if event.set:
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event.event_caught = True
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self.tasks.extend(event.waiters)
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self.events.remove(event)
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def awake_sleeping(self):
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"""
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Reschedules sleeping tasks if their deadline
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has elapsed
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"""
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while self.paused and self.paused[0][0] < self.clock():
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# Reschedules tasks when their deadline has elapsed
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task = self.paused.get()
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slept = self.clock() - task.sleep_start
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task.sleep_start = 0.0
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self.tasks.append(task)
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self.debugger.after_sleep(task, slept)
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def check_io(self):
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"""
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Checks and schedules task to perform I/O
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"""
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before_time = self.clock() # Used for the debugger
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if self.tasks or self.events:
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self.io_skip += 1
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if self.io_skip == IO_SKIP_LIMIT:
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# We can't skip every time there's some task ready
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# or else we might starve I/O waiting tasks
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# when a lot of things are running at the same time
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self.io_skip = 0
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timeout = 86400
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else:
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# If there are either tasks or events and no I/O, don't wait
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# (unless we already skipped this check too many times)
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timeout = 0.0
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elif self.paused:
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# If there are asleep tasks, wait until the closest deadline
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if not self.deadlines:
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timeout = min([max(0.0, self.paused[0][0] - self.clock())])
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else:
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deadline = self.deadlines.get()
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timeout = min([max(0.0, self.paused[0][0] - self.clock()), deadline])
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if timeout != deadline:
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# If a sleeping tasks has to run
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# before another deadline, we schedule the former
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# first and put back the latter on the queue
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self.deadlines.put(deadline)
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else:
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# If there is *only* I/O, we wait a fixed amount of time
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timeout = 86400 # Thanks trio :D
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if self.selector.get_map():
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self.debugger.before_io(timeout)
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io_ready = self.selector.select(timeout)
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# Get sockets that are ready and schedule their tasks
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for key, _ in io_ready:
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self.tasks.append(key.data) # Resource ready? Schedule its task
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self.debugger.after_io(self.clock() - before_time)
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else:
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# Since select() does not work with 0 fds registered
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# we need to call time.sleep() if we need to pause
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# and no I/O has been registered
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wait(timeout)
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def start(self, func: types.FunctionType, *args):
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"""
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Starts the event loop from a sync context
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"""
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entry = Task(func(*args), func.__name__ or str(func), None)
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self.tasks.append(entry)
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self.debugger.on_start()
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self.run()
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self.has_ran = True
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self.debugger.on_exit()
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if entry.exc:
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raise entry.exc
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def reschedule_joiners(self, task: Task):
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"""
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Reschedules the parent(s) of the
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given task, if any
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"""
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for t in task.joiners:
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if t not in self.tasks:
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# Since a task can be the parent
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# of multiple children, we need to
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# make sure we reschedule it only
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# once, otherwise a RuntimeError will
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# occur
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self.tasks.append(t)
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def get_event_tasks(self):
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"""
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Returns all tasks currently waiting on events
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"""
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return set(waiter for waiter in (evt.waiters for evt in self.events))
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def cancel_all_from_current_pool(self, pool=None):
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"""
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Cancels all tasks in the current pool (or the given one)
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"""
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pool = pool or self.current_pool
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if pool:
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for to_cancel in pool.tasks:
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self.cancel(to_cancel)
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pool.cancelled = True
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return all([t.cancelled or t.finished or t.exc for t in pool.tasks])
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else: # If we're at the main task, we're sure everything else exited
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return True
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def cancel_all(self):
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"""
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Cancels ALL tasks, this method is called as a result
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of self.close()
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"""
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for to_cancel in chain(self.tasks, self.paused, self.get_event_tasks()):
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self.cancel(to_cancel)
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return all([t.cancelled or t.exc or t.finished for t in chain(self.tasks, self.paused, self.get_event_tasks())])
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def close(self, *, ensure_done: bool = True):
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"""
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Closes the event loop, terminating all tasks
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inside it and tearing down any extra machinery.
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If ensure_done equals False, the loop will cancel *ALL*
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running and scheduled tasks and then tear itself down.
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If ensure_done equals False, which is the default behavior,
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this method will raise a GiambioError if the loop hasn't
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finished running.
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"""
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if ensure_done:
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self.cancel_all()
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elif not self.done():
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raise GiambioError("event loop not terminated, call this method with ensure_done=False to forcefully exit")
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self.shutdown()
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def join(self, task: Task):
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"""
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Joins a task to its callers (implicitly, the parent
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task, but also every other task who called await
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task.join() on the task object)
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"""
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if self.current_pool is None:
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if not self.done():
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return
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else:
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self.reschedule_joiners(task)
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return
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task.joined = True
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if task.finished or task.cancelled:
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if all([t.finished or t.cancelled for t in self.current_pool.tasks]):
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self.reschedule_joiners(task)
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elif task.exc:
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if self.cancel_all_from_current_pool():
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# This will reschedule the parent
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# only if all the tasks inside it
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# have finished executing, either
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# by cancellation, an exception
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# or just returned
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self.reschedule_joiners(task)
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def sleep(self, seconds: int or float):
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"""
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Puts the caller to sleep for a given amount of seconds
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"""
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self.debugger.before_sleep(self.current_task, seconds)
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if seconds: # if seconds == 0, this acts as a switch!
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self.current_task.status = "sleep"
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self.current_task.sleep_start = self.clock()
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self.paused.put(self.current_task, seconds)
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self.current_task.next_deadline = self.clock() + seconds
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else:
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self.tasks.append(self.current_task)
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def cancel(self, task: Task):
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"""
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Schedules the task to be cancelled later
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or does so straight away if it is safe to do so
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"""
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if task.status in ("io", "sleep", "init"):
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# We cancel immediately only in a context where it's safer to do
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# so. The concept of "safer" is quite tricky, because even though the
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# task is technically not running, it might leave some unfinished state
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# or dangling resource open after being cancelled, so maybe we need
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# a different approach altogether
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try:
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self.do_cancel(task)
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except CancelledError:
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# Task was cancelled
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task.status = "cancelled"
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task.cancelled = True
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task.cancel_pending = False
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self.debugger.after_cancel(task)
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else:
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# If we can't cancel in a somewhat "graceful" way, we just
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# defer this operation for later (check run() for more info)
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task.cancel_pending = True # Cancellation is deferred
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def event_set(self, event):
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"""
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Sets an event
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"""
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self.events.add(event)
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event.set = True
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self.tasks.append(self.current_task)
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def event_wait(self, event):
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"""
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Pauses the current task on an event
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"""
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event.waiters.append(self.current_task)
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# Since we don't reschedule the task, it will
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# not execute until check_events is called
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# TODO: More generic I/O rather than just sockets (threads)
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def read_or_write(self, sock: socket.socket, evt_type: str):
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"""
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Registers the given socket inside the
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selector to perform I/0 multiplexing
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"""
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self.current_task.status = "io"
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if self.current_task.last_io:
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if self.current_task.last_io == (evt_type, sock):
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# Socket is already scheduled!
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return
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# TODO: Inspect why modify() causes issues
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self.selector.unregister(sock)
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self.current_task.last_io = evt_type, sock
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evt = EVENT_READ if evt_type == "read" else EVENT_WRITE
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try:
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self.selector.register(sock, evt, self.current_task)
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except KeyError:
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# The socket is already registered doing something else
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raise ResourceBusy("The given resource is busy!") from None
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# noinspection PyMethodMayBeStatic
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async def read_sock(self, sock: socket.socket, buffer: int):
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"""
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Reads from a socket asynchronously, waiting until the resource is
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available and returning up to buffer bytes from the socket
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"""
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await want_read(sock)
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return sock.recv(buffer)
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# noinspection PyMethodMayBeStatic
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async def accept_sock(self, sock: socket.socket):
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"""
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Accepts a socket connection asynchronously, waiting until the resource
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is available and returning the result of the sock.accept() call
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"""
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# TODO: Is this ok?
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# This does not feel right because the loop will only
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# exit when the socket has been accepted, preventing other
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# stuff from running
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while True:
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try:
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return sock.accept()
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except IOInterrupt: # Do we need this exception thingy everywhere?
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# Some methods have never errored out, but this did and doing
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# so seemed to fix the issue, needs investigation
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await want_read(sock)
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|
# noinspection PyMethodMayBeStatic
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|
async def sock_sendall(self, sock: socket.socket, data: bytes):
|
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"""
|
|
Sends all the passed bytes trough a socket asynchronously
|
|
"""
|
|
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|
while data:
|
|
await want_write(sock)
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|
sent_no = sock.send(data)
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|
data = data[sent_no:]
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|
|
# TODO: This method seems to cause issues
|
|
async def close_sock(self, sock: socket.socket):
|
|
"""
|
|
Closes a socket asynchronously
|
|
"""
|
|
|
|
await want_write(sock)
|
|
sock.close()
|
|
self.selector.unregister(sock)
|
|
self.current_task.last_io = ()
|
|
|
|
# noinspection PyMethodMayBeStatic
|
|
async def connect_sock(self, sock: socket.socket, addr: tuple):
|
|
"""
|
|
Connects a socket asynchronously
|
|
"""
|
|
|
|
await want_write(sock)
|
|
return sock.connect(addr)
|
|
|
|
def __del__(self):
|
|
"""
|
|
Garbage collects itself
|
|
"""
|
|
|
|
self.close()
|