[Python-Dev] PEP 578: Python Runtime Audit Hooks

[Steve Dower]

On 29Mar.2019 2020, Inada Naoki wrote:
> I don't like adding more Python callback from low level.
> 
> Python runtime is very complicated already, especially __del__,
> shutdown process, and multi threading.  Python callback from low level
> is source of very difficult bugs always.

Asynchronous callbacks, sure. These are all synchronous and always as
part of a Python operation while the GIL is held (I think putting them
immediately after parameter validation is the best place, but am
hesitant to make that a hard rule).

> Additionally, if we used the PEP for logging complex application,
> the log will be unreliable.  

I think "then don't do that" is a valid response here. There are plenty
of ways to use Python features incorrectly and cause problems (I've
diagnosed many of them :) ). This doesn't make that any more or less true.

> 1. Want to open file A in C code, call callback.
> 2. In the callback, "A is opened" is logged.
> 3. In the same callback, import may be happened and logged.
> 4. In the same callback, other thread may be run and any thing can be logged.
> 5. Many many other things happens and callback is called.
> 6. Then, open the file A.
> 
> In this example, logged event ordering and timing is very different from
> real event ordering and timing.

Yep. If you implement a bad hook then you get bad results. But at least
the user can fix that themselves (since they caused it themselves).

I've already used these hooks for a number of useful purposes, and it
isn't difficult to write one that works just fine.

> I prefer low level tool to trace low level thing, although it lacks some
> application context.  Maybe, DTrace will become more important tool.
> 
> https://techcommunity.microsoft.com/t5/Windows-Kernel-Internals/DTrace-on-Windows/ba-p/362902

See my other reply about this. DTrace on Windows is a very long way from
being suitable for production environments.

Cheers,
Steve