Yaws process died - erlang

Question

I do performance testing of our Erlang application with OpenSTA. The test runs with 100 virtual users. At some point the following errors start popping up:
Yaws process died: {{badmatch,{error,eacces}},
[{yaws_server,ut_read,1},
{yaws_server,deliver_dyn_file,5},
{yaws_server,aloop,3},
{yaws_server,acceptor0,2},
{proc_lib,init_p_do_apply,3}]}
The test continues to run. I cannot find info about this error. Does eacces mean Error accessing a resource?
EDIT: As pointed out by #Muzaaya Joshua the call file:read_file(UT#urltype.fullpath) crashes in function ut_read(UT). I recompiled the module and printed the context. The error is eacces and UT holds:
{urltype,yaws,
{file_info,14088,regular,read_write,
{{2011,9,13},{11,51,42}},
{{2011,10,17},{17,59,44}},
{{2011,3,16},{13,18,58}},
33206,1,3,0,0,0,0},
"/handler.yaws",
"c:/Temp/harmony/script/../www/handler.yaws",
"/",undefined,undefined,"text/html",
"/handler.yaws",undefined}
This file handler.yaws is the entry point of our app and is called on every request. When I run the test with 100 or less virtual users I don't see these errors. So how can it be Missing permission for reading the file, or for searching one of the parent directories. as the error is described in the read_file documentation?
Thanks in advance.
Martin

Answer 1

eacces means access denied, the error codes are described at the end of the file documenation: http://www.erlang.org/doc/man/file.html#write_file_info-2

Answer 2

Yaws has failed to open a file. This is a file read permission denied to the user running yaws application. If you add permissions to the user running yaws to own all folders concerning yaws, this may be fixed. to check it out, try running yaws as root , if at all these paths are owned by root. The yaws_server.erl source file at the point is as follows:
ut_read(UT) ->
?Debug("ut_read() UT.fullpath = ~p~n", [UT#urltype.fullpath]),
case yaws:outh_get_content_encoding() of
identity ->
case UT#urltype.data of
undefined ->
?Debug("ut_read reading\n",[]),
{ok, Bin} = file:read_file(UT#urltype.fullpath),
?Debug("ut_read read ~p\n",[size(Bin)]),
Bin;
B when is_binary(B) ->
B
end;
deflate ->
case UT#urltype.deflate of
B when is_binary(B) ->
?Debug("ut_read using deflated binary of size ~p~n",
[size(B)]),
B
end
end.
The line in bold in the above source is where the bad match occurs.
Check wether yaws is running as a user with permissions to access its folders such as the doc root, ssl folders and other paths that yaws may access files. Does the user running yaws have access to all required files ?

Answer 3

In windows, this makes it easy. Now go to your Local disk C, Program Files (In windows 7, could be Program Files (x86)), lastly to where yaws is installed. This will be a folder: Yaws-VERSION e.g. Yaws-1.89. Now, when you right click this, you select Properties, then in the pop-up window you select Security. Under Security, you click edit. Now under Group or usernames, you select each user (and each type of account) and give it all permissions i.e. read, write, full control e.t.c. click Apply, wait for windows to perform the changes, then click Ok and close. Your users must now have all required permissions.

Answer 4

I managed to fix this errors by increasing the file size of the allowed in cache files in the YAWS configuration max_size_cached_file. This made our .yaws file to be loaded in memory and not accessess with file:read_file all the time. Hopefully this will save someone else couple of hours (or days :))