nim-chronos/chronos/debugutils.nim
Jacek Sieka 4abd7a5645
exception tracking (#166)
* exception tracking

This PR adds minimal exception tracking to chronos, moving the goalpost
one step further.

In particular, it becomes invalid to raise exceptions from `callSoon`
callbacks: this is critical for writing correct error handling because
there's no reasonable way that a user of chronos can possibly _reason_
about exceptions coming out of there: the event loop will be in an
indeterminite state when the loop is executing an _random_ callback.

As expected, there are several issues in the error handling of chronos:
in particular, it will end up in an inconsistent internal state whenever
the selector loop operations fail, because the internal state update
functions are not written in an exception-safe way. This PR turns this
into a Defect, which probably is not the optimal way of handling things
- expect more work to be done here.

Some API have no way of reporting back errors to callers - for example,
when something fails in the accept loop, there's not much it can do, and
no way to report it back to the user of the API - this has been fixed
with the new accept flow - the old one should be deprecated.

Finally, there is information loss in the API: in composite operations
like `poll` and `waitFor` there's no way to differentiate internal
errors from user-level errors originating from callbacks.

* store `CatchableError` in future
* annotate proc's with correct raises information
* `selectors2` to avoid non-CatchableError IOSelectorsException
* `$` should never raise
* remove unnecessary gcsafe annotations
* fix exceptions leaking out of timer waits
* fix some imports
* functions must signal raising the union of all exceptions across all
platforms to enable cross-platform code
* switch to unittest2
* add `selectors2` which supercedes the std library version and fixes
several exception handling issues in there

* fixes

* docs, platform-independent eh specifiers for some functions

* add feature flag for strict exception mode

also bump version to 3.0.0 - _most_ existing code should be compatible
with this version of exception handling but some things might need
fixing - callbacks, existing raises specifications etc.

* fix AsyncCheck for non-void T
2021-03-24 10:08:33 +01:00

66 lines
2.2 KiB
Nim

#
# Chronos Debugging Utilities
#
# (c) Copyright 2020-Present Status Research & Development GmbH
#
# Licensed under either of
# Apache License, version 2.0, (LICENSE-APACHEv2)
# MIT license (LICENSE-MIT)
{.push raises: [Defect].}
import ./asyncloop
const
AllFutureStates* = {FutureState.Pending, FutureState.Cancelled,
FutureState.Finished, FutureState.Failed}
WithoutFinished* = {FutureState.Pending, FutureState.Cancelled,
FutureState.Failed}
OnlyPending* = {FutureState.Pending}
OnlyFinished* = {FutureState.Finished}
proc dumpPendingFutures*(filter = AllFutureStates): string =
## Dump all `pending` Future[T] objects.
##
## This list will contain:
## 1. Future[T] objects with ``FutureState.Pending`` state (this Futures are
## not yet finished).
## 2. Future[T] objects with ``FutureState.Finished/Cancelled/Failed`` state
## which callbacks are scheduled, but not yet fully processed.
var count = 0
var res = ""
when defined(chronosFutureTracking):
for item in pendingFutures():
if item.state in filter:
inc(count)
let loc = item.location[LocCreateIndex][]
let procedure = $loc.procedure
let filename = $loc.file
let procname = if len(procedure) == 0:
"\"unspecified\""
else:
"\"" & procedure & "\""
let item = "Future[" & $item.id & "] with name " & $procname &
" created at " & "<" & filename & ":" & $loc.line & ">" &
" and state = " & $item.state & "\n"
res.add(item)
result = $count & " pending Future[T] objects found:\n" & $res
proc pendingFuturesCount*(filter: set[FutureState]): int =
## Returns number of `pending` Future[T] objects which satisfy the ``filter``
## condition.
##
## If ``filter`` is equal to ``AllFutureStates`` Operation's complexity is
## O(1), otherwise operation's complexity is O(n).
when defined(chronosFutureTracking):
if filter == AllFutureStates:
pendingFuturesCount()
else:
var res = 0
for item in pendingFutures():
if item.state in filter:
inc(res)
res
else:
0