[OSM-dev] Trouble getting mod_tile and apache talking

Rory McCann rory at technomancy.org
Tue May 11 11:01:11 BST 2010


On 10/05/10 23:13, Frederik Ramm wrote:
> You can run Apache in single process mode and strace that (provided that
> Apache isn't needed for anything else at the time):
> 
> su
> /etc/init.d/apache2 stop
> export APACHE_RUN_USER=www-data
> export APACHE_RUN_GROUP=www-data
> strace -o outputfile -f apache2 -X
> 
> You should see mod_tile (a) trying to open the tile on disk (grep for
> the filename) and if unsuccessful (b) trying to contact renderd (grep
> for the renderd socket name).

I tried that. The strace file is here (
http://www.technomancy.org/openirishmap/apache-trying-to-load-mod-tile.strace.txt
) 190KiB.

It looks like it's loading the mod_tile:

6920  stat("/etc/apache2/mods-enabled/tile.load", {st_mode=S_IFREG|0644,
st_size=60, ...}) = 0
6920  open("/etc/apache2/mods-enabled/tile.load", O_RDONLY) = 5
6920  fstat(5, {st_mode=S_IFREG|0644, st_size=60, ...}) = 0
6920  read(5, "LoadModule tile_module /usr/lib/"..., 4096) = 60
6920  open("/usr/lib/apache2/modules/mod_tile.so", O_RDONLY) = 13
6920  read(13,
"\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0`+\0\0\0"..., 832) = 832


However when trying to go to the tiles, it is still looking for the raw
files.
6920  read(14, "GET /openirishmap_tiles/0/0/0.pn"..., 8000) = 391
6920  gettimeofday({1273569758, 377149}, NULL) = 0
6920  stat("/var/www/technomancy.org/openirishmap_tiles/0/0/0.png",
0x7fffffa26510) = -1 ENOENT (No such file or directory)
... (some .htaccess checking omitted) ...
6920  lstat("/var/www/technomancy.org/openirishmap_tiles",
{st_mode=S_IFDIR|0777, st_size=4096, ...}) = 0
6920  open("/var/www/technomancy.org/openirishmap_tiles/.htaccess",
O_RDONLY) = -1 ENOENT (No such file or directory)
6920  lstat("/var/www/technomancy.org/openirishmap_tiles/0",
0x7fffffa26510) = -1 ENOENT (No such file or directory)
6920  gettimeofday({1273569758, 378393}, NULL) = 0
6920  write(8, "[Tue May 11 09:22:38 2010] [erro"..., 124) = 124
6920  brk(0xab8000)                     = 0xab8000
6920  writev(14, [{"HTTP/1.1 404 Not Found\r\nDate: Tu"..., 217},
{"<!DOCTYPE HTML PUBLIC \"-//IETF//"..., 310}], 2) = 527


I can't see any reference to "render" in this strace, nor any reference
to the renderd socket. While this strace was running, renderd was
running in the foreground and showed no hint of anything happening.

It's as if mod_tile is loaded, but it's not being used.

Another time I delibrately misspelled the socket filename in my apache
conf, which should cause an error message
(http://trac.openstreetmap.org/browser/applications/utils/mod_tile/mod_tile.c#L178),
however once again, nothing happened.

Rory
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