[MapProxy] logging problem - source request either cached or log buffered

[Oliver Christen]

Dear List

Im having a problem with logging source requests.

I enabled the logging, but doing a "tail -f source-requests.log" doesnt 
show the source request every time an image is requested from the 
configured source,

instead I'm seeing some kind of random burst of log, being outputed 
without any time relation to what's being displayed in my browser,
as if the logging was buffered, maybe,
so I dont really know if Mapproxy is simply not doing the source 
request, or if it is doing it, but the request is outputed later in the 
log, making it difficult to know if the related images have been 
effectively requested or not at the certain time.

see below my layer and source config and my logging config

is there something wrong in the way I configured either my logger or the 
layer?
is the logging intended to buffer content before updating the log file? 
if so, is there any way to prevent that?

thank you for reading me

best regards
Oliver Christen

layer and cache configuration:

layers:
   - name: Taxi
     title: Taxi
     sources: [TaxiCache]

caches:
     TaxiCache:
       grids: [swissgrid]
       sources: [TaxiS3]
       disable_storage: true

   TaxiS3:
     type: tile
     url: 
'http://path_to_tiles/Taxi/default/swissgrid/%(z)s/%(y)s/%(x)s.png'
     grid: swisstopo
     transparent: true
     on_error:
       403:
         response: transparent
         cache: True


logging configuration:

from logging.config import fileConfig
import os.path
fileConfig(r'/path_to/log.ini')

log.ini:

[formatters]
keys=default,requests

[logger_root]
level=INFO
handlers=mapproxy

[logger_source_requests]
level=DEBUG
qualname=mapproxy.source.request
# propagate=0 -> do not show up in logger_root
propagate=0
handlers=source_requests

[handler_mapproxy]
class=FileHandler
formatter=default
args=(r"/path_to/mapproxy.log", "a")

[handler_source_requests]
class=FileHandler
formatter=requests
args=(r"/path_to/source-requests.log", "a")

[formatter_default]
format=%(asctime)s - %(levelname)s - %(name)s - %(message)s

[formatter_requests]
format=[%(asctime)s] %(message)s


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