Logging

[William Pursell <wi...@wepay.com>]

I will be the first to admit that I'm a little confused about logging, but
I'm hoping someone can clarify what I think is a bug.  Or it's just my
misunderstanding of python.  Or a misunderstanding about logging.

I don't seem to be able to get much utility from having multiple log
handlers.  And I'm curious about this line of code:
https://github.com/apache/incubator-airflow/blob/master/airflow/www/views.py#L708

It feels like the code is trying to generate multiple possible handlers and
use the one that successfully finds the log, but the above mentioned line
is a bit of a fake generator.  In the sense that it calls 'next' to grab
the next value from the generator, but since the generator's scope is just
the local function, it always just grabs the first handler.  That is, other
than the default it might as well just be coded as a list comprehension:

handler = [handler for handler in logger.handlers if handler.name ==
task_log_reader][0]

So my question is: is this attempting to use multiple log handlers to find
the log and not doing so because  of a bug using 'next', or am I
misunderstanding what the log reader is trying to do?

Re: Logging

[Allison Wang <al...@gmail.com>]

Hi William,

The code is trying to use the first log handler that has name
task_log_handler to fetch the log. There can only be one log handler used
to retrieve the logs.

On Tue, Nov 21, 2017 at 8:28 AM William Pursell <wi...@wepay.com> wrote:

> I will be the first to admit that I'm a little confused about logging, but
> I'm hoping someone can clarify what I think is a bug.  Or it's just my
> misunderstanding of python.  Or a misunderstanding about logging.
>
> I don't seem to be able to get much utility from having multiple log
> handlers.  And I'm curious about this line of code:
>
> https://github.com/apache/incubator-airflow/blob/master/airflow/www/views.py#L708
>
> It feels like the code is trying to generate multiple possible handlers and
> use the one that successfully finds the log, but the above mentioned line
> is a bit of a fake generator.  In the sense that it calls 'next' to grab
> the next value from the generator, but since the generator's scope is just
> the local function, it always just grabs the first handler.  That is, other
> than the default it might as well just be coded as a list comprehension:
>
> handler = [handler for handler in logger.handlers if handler.name ==
> task_log_reader][0]
>
> So my question is: is this attempting to use multiple log handlers to find
> the log and not doing so because  of a bug using 'next', or am I
> misunderstanding what the log reader is trying to do?
>