mapnik/mod_tile/tirex warning message in logs

Hi,

I have a mapnik/mod_tile/tirex stack, which works fine to produce new tiles, but I see warning in the logs when I am requesting tiles which have been already rendered and are expired. On the client side I still get the old tiles so it is not a problem right now but I am worried that it is wasting resources.

I have installed mapnik 2.0 from distribution Debian 7.0.0 modtile from source https://github.com/openstreetmap/mod_tile tirex from source http://svn.openstreetmap.org/applications/utils/tirex

==> apache2/error.log <==
--------------------------
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(1281): [client 217.198.117.32] tile_translate: uri(/tiles/15/17859/11195.png)
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(1298): [client 217.198.117.32] tile_translate: testing baseuri(/tiles/) name(default) extension(png)
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(1344): [client 217.198.117.32] tile_translate: request for default was 17859 11195 32768
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(317): [client 217.198.117.32] get_storage_backend: Retrieving storage back end for tile layer 0 in pool 7f2c71447028 and thread 139828855555904
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(339): [client 217.198.117.32] get_storage_backend: Found backends (7f2c71447e30) for this lifecycle 7f2c71447028 in thread 139828855555904
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(350): [client 217.198.117.32] get_storage_backend: Storage backend found in current lifecycle 7f2c71447028 for current tile layer 0 in thread 139828855555904
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(1383): [client 217.198.117.32] tile_translate: op(tile_serve) xml(default) mime(image/png) z(15) x(17859) y(11195)
[Mon Jun 02 10:42:05 2014] [info] [client 217.198.117.32] tile_storage_hook: handler(tile_serve), uri(/tiles/15/17859/11195.png)
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(367): [client 217.198.117.32] tile_state: determined state of default 17859 11195 15 on store 7f2c735ca1d0: Tile size: 465286, expired: 1 created: 1401143927
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(166): [client 217.198.117.32] Connecting to renderd on Unix socket /var/lib/tirex/modtile.sock
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(183): [client 217.198.117.32] socket connect succeed for: /var/lib/tirex/modtile.sock 
[Mon Jun 02 10:42:05 2014] [info] [client 217.198.117.32] Requesting style(default) z(15) x(17859) y(11195) from renderer with priority 7
[Mon Jun 02 10:42:05 2014] [warn] [client 217.198.117.32] request_tile: Failed to read response from rendering socket No such file or directory r=0
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(1186): [client 217.198.117.32] tile_handler_serve: xml(default) z(15) x(17859) y(11195)
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(1210): [client 217.198.117.32] Read tile of length 6988 from file:///var/lib/mod_tile/default/15/0/66/91/203/8.meta: 
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(367): [client 217.198.117.32] tile_state: determined state of default 17859 11195 15 on store 7f2c735ca1d0: Tile size: 465286, expired: 1 created: 1401143927
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(444): [client 217.198.117.32] expires(tile_serve), uri(/tiles/15/17859/11195.png),, path_info((null))\n
[Mon Jun 02 10:42:05 2014] [debug] ./src/mod_tile.c(494): [client 217.198.117.32] Setting tiles maxAge to 1327\n

output from  tirex-master --debug:
----------------------------------
tirex-master[20256]: connection from mod_tile accepted
tirex-master[20256]: connection from mod_tile accepted
tirex-master[20256]: connection from mod_tile accepted
tirex-master[20256]: read request from mod_tile: ver=2 cmd=7 x=17859 y=11193 z=15 map=default
tirex-master[20256]: read request from mod_tile: ver=2 cmd=7 x=17859 y=11194 z=15 map=default
tirex-master[20256]: read request from mod_tile: ver=2 cmd=7 x=17860 y=11194 z=15 map=default
tirex-master[20256]: connection from mod_tile accepted
tirex-master[20256]: connection from mod_tile accepted
tirex-master[20256]: read request from mod_tile: ver=2 cmd=7 x=17860 y=11195 z=15 map=default
tirex-master[20256]: read request from mod_tile: ver=2 cmd=7 x=17860 y=11193 z=15 map=default
tirex-master[20256]: connection from mod_tile accepted
tirex-master[20256]: read request from mod_tile: ver=2 cmd=7 x=17859 y=11195 z=15 map=default

while tirex-backend-manager --debug does not produce any output on the console for this request.

Any suggestions? Thanks!