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[Erlyaws-list] Fwd: YAWS noob: first yaws app. Caching??
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From: Russell B. <rus...@ma...> - 2008-08-23 12:44:22
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Oops. I sent direct to Edwin rather than to the list.
Turns out this is not a YAWS issue at all but a noob-not-understanding-
random-module-of-erlang issue. Now the n_bonds module calls
random:seed(A, B , B) there is no obvious pattern to the results and
they are different for each request.
Thanks for the help in getting this far.
Regards
Russell
Begin forwarded message:
> From: Russell Brown <rus...@ma...>
> Date: 23 August 2008 09:28:46 BST
> To: Edwin Fine <em...@gm...>
> Subject: Re: [Erlyaws-list] YAWS noob: first yaws app. Caching??
>
> Hi edwin,
> First up, thanks for taking so much time to help me with my problem.
> Going to the lengths you have gone is above and beyond and all that
> so I really am very grateful.
>
> I tried the inets:start(). http:request("http://wombat.me:8000/bonds/10
> "). as you suggested and I get the same response everytime. What has
> piqued my interest is you mention of random numbers. Yes I use
> random numbers to shuffle the bonds square. So I created a number of
> processes to run bonds_square_for_xml and each process gets the same
> result the first call and each process gets the same result for the
> second call (but different from the first call). So I guess YAWS
> creates a process per request and so each process gets the first
> "random" shuffle in the sequence. Hmmm. I need to learn more about
> how random works don't I? What successive calls to
> bonds_square_for_xml get is a sequence of shuffled bonds. But the
> sequence is all the same. It always starts with the same order of
> bonds and so on.
>
> You have been a real help. Thank you very much.
>
> I have to take my son to football (soccer) now but I will read up on
> erlang random numbers when I get back.
>
> Thanks again
>
> Russell
>
> PS you can have a look at the "game" at wombat.me:8000 to see whay I
> am doing this if you like.
> On 22 Aug 2008, at 22:59, Edwin Fine wrote:
>
>> Russell,
>>
>> I was intrigued by this so I decided to do a small test appmod that
>> works like yours. Ok, I know I should not be manually creating XML,
>> but this *is* a test :)
>>
>> -module(getxml).
>> -export([out/1]).
>>
>> out(_A) ->
>> {content, "application/xml", somexml()}.
>>
>> somexml() ->
>> {_,_,U} = Now = now(),
>> {{Y,Mo,D},{H,M,S}} = calendar:now_to_local_time(Now),
>> Host = net_adm:localhost(),
>> io_lib:format(
>> "<info>\n"
>> " <host name='~s'/>\n"
>> " <date year='~B' mon='~B' day='~B'/>\n"
>> " <time hour='~B' min='~B' sec='~B' usec='~B'/>\n"
>> "</info>\n",
>> [Host, Y, Mo, D, H, M, S, U]
>> ).
>>
>> I compiled this in /tmp:
>>
>> erlc -W getxml.erl
>>
>> Then I copied the standard yaws.conf to /tmp, and added this
>> virtual server config (the rest of yaws.conf is the same except I
>> removed all the other virtual server configs).
>>
>> <server ender>
>> port = 8080
>> listen = 0.0.0.0
>> docroot = /tmp
>> appmods = <getxml, getxml>
>> </server>
>>
>> Then I started Yaws in interactive mode.
>>
>> yaws -i --conf /tmp/yaws.conf
>>
>> I used inets (http:request) to post to the URL http://ender:8080/getxml
>> :
>>
>> 1> inets:start().
>> ok
>> 2> http:request("http://ender:8080/getxml").
>> {ok,{{"HTTP/1.1",200,"OK"},
>> [{"date","Fri, 22 Aug 2008 21:54:00 GMT"},
>> {"server","Yaws/1.77 Yet Another Web Server"},
>> {"content-length","137"},
>> {"content-type","application/xml"}],
>> "<info>\n <host name='example.com'/>\n <date year='2008'
>> mon='8' day='22'/>\n <time hour='17' min='54' sec='0' usec='37845'/
>> >\n</info>\n\n"}}
>> 3> http:request("http://ender:8080/getxml").
>> {ok,{{"HTTP/1.1",200,"OK"},
>> [{"date","Fri, 22 Aug 2008 21:54:02 GMT"},
>> {"server","Yaws/1.77 Yet Another Web Server"},
>> {"content-length","138"},
>> {"content-type","application/xml"}],
>> "<info>\n <host name='example.com'/>\n <date year='2008'
>> mon='8' day='22'/>\n <time hour='17' min='54' sec='2'
>> usec='990860'/>\n</info>\n\n"}}
>> 4> http:request("http://ender:8080/getxml").
>> {ok,{{"HTTP/1.1",200,"OK"},
>> [{"date","Fri, 22 Aug 2008 21:54:03 GMT"},
>> {"server","Yaws/1.77 Yet Another Web Server"},
>> {"content-length","138"},
>> {"content-type","application/xml"}],
>> "<info>\n <host name='example.com'/>\n <date year='2008'
>> mon='8' day='22'/>\n <time hour='17' min='54' sec='3'
>> usec='340745'/>\n</info>\n\n"}}
>> 5> http:request("http://ender:8080/getxml").
>> {ok,{{"HTTP/1.1",200,"OK"},
>> [{"date","Fri, 22 Aug 2008 21:54:04 GMT"},
>> {"server","Yaws/1.77 Yet Another Web Server"},
>> {"content-length","138"},
>> {"content-type","application/xml"}],
>> "<info>\n <host name='example.com'/>\n <date year='2008'
>> mon='8' day='22'/>\n <time hour='17' min='54' sec='4'
>> usec='117845'/>\n</info>\n\n"}}
>>
>> I used curl, too:
>>
>> efine@ender:/tmp$ curl http://ender:8080/getxml
>> <info>
>> <host name='example.com'/>
>> <date year='2008' mon='8' day='22'/>
>> <time hour='17' min='55' sec='9' usec='725669'/>
>> </info>
>>
>> efine@ender:/tmp$ curl http://ender:8080/getxml
>> <info>
>> <host name='example.com'/>
>> <date year='2008' mon='8' day='22'/>
>> <time hour='17' min='55' sec='10' usec='821024'/>
>> </info>
>>
>> As you can see, it changes every time. I later requested the URL
>> 100 times in a tight loop, and every return was different. I even
>> used Firefox and pressed F5 repeatedly. Different result every
>> time. Is there any possibility that your nbonds module behaves
>> differently when run in the context of Yaws than when run from the
>> shell? Do you use random numbers somewhere?
>>
>> Could you maybe try the getxml appmod and see if it works for you?
>> Also take a look at the output of Yaws when you run it in
>> interactive (-i) mode. Any error messages?
>>
>> Hope this helps.
>>
>> Ed
>>
>> On Fri, Aug 22, 2008 at 4:57 PM, Edwin Fine <em...@gm...>
>> wrote:
>> Russell,
>>
>> The thing is, I use Yaws with appmods a lot in my work, and do
>> something similar (use a browser to HTTP GET run-time statistics
>> for an application) and I do in fact get different responses every
>> time. That's why I don't think it's necessarily Yaws-related. I am
>> using Yaws 1.77, Erlang R12B-3, Ubuntu Linux x86_64. Then again,
>> in the case of the GET, I am returning HTML, not XML. Hmmm.
>>
>> Have you tried sending the GET using something other than a browser
>> (for example, wget or curl?). I'd be very interested in seeing the
>> full headers and all that you get back. Are you using Linux or
>> MacOS (PLEASE say yes...!)? What's your setup?
>>
>> Please could you try this for me in the shell:
>>
>> inets:start(), http:request("http://wombat.me:8000/bonds/10").
>>
>> Maybe you can send the request a few times (you only need to call
>> inets:start() once). I'd be interested in seeing the raw responses...
>>
>> Also, what's your yaws.conf?
>>
>> Ed
>>
>>
>> On Fri, Aug 22, 2008 at 3:05 PM, Russell Brown
>> <rus...@ma...> wrote:
>> Hi Edwin,
>> Thanks for the response.
>>
>> I understand you asking me question 1. I have tried a few times
>> just to check. Yup...it get a different result. Here is a session:-
>>
>> 2> n_bonds:bonds_square_for_xml(10).
>> {bonds,[{for,"10"},{total,"16"}],
>> [{bond,[{b1,10},{b2,0}],["10+0"]},
>> {bond,[{b1,1},{b2,8}],["1+8"]},
>> {bond,[{b1,8},{b2,2}],["8+2"]},
>> {bond,[{b1,2},{b2,8}],["2+8"]},
>> {bond,[{b1,0},{b2,10}],["0+10"]},
>> {bond,[{b1,6},{b2,4}],["6+4"]},
>> {bond,[{b1,0},{b2,9}],["0+9"]},
>> {bond,[{b1,7},{b2,3}],["7+3"]},
>> {bond,[{b1,5},{b2,4}],["5+4"]},
>> {bond,[{b1,9},{b2,0}],["9+0"]},
>> {bond,[{b1,3},{b2,7}],["3+7"]},
>> {bond,[{b1,1},{b2,9}],["1+9"]},
>> {bond,[{b1,5},{b2,5}],["5+5"]},
>> {bond,[{b1,9},{b2,1}],["9+1"]},
>> {bond,[{b1,4},{b2,6}],["4+6"]},
>> {bond,[{b1,3},{b2,8}],["3+8"]}]}
>> 3> n_bonds:bonds_square_for_xml(10).
>> {bonds,[{for,"10"},{total,"16"}],
>> [{bond,[{b1,9},{b2,1}],["9+1"]},
>> {bond,[{b1,4},{b2,6}],["4+6"]},
>> {bond,[{b1,3},{b2,7}],["3+7"]},
>> {bond,[{b1,2},{b2,8}],["2+8"]},
>> {bond,[{b1,2},{b2,9}],["2+9"]},
>> {bond,[{b1,5},{b2,5}],["5+5"]},
>> {bond,[{b1,0},{b2,10}],["0+10"]},
>> {bond,[{b1,1},{b2,9}],["1+9"]},
>> {bond,[{b1,6},{b2,4}],["6+4"]},
>> {bond,[{b1,7},{b2,3}],["7+3"]},
>> {bond,[{b1,8},{b2,2}],["8+2"]},
>> {bond,[{b1,4},{b2,5}],["4+5"]},
>> {bond,[{b1,8},{b2,3}],["8+3"]},
>> {bond,[{b1,6},{b2,5}],["6+5"]},
>> {bond,[{b1,0},{b2,9}],["0+9"]},
>> {bond,[{b1,10},{b2,0}],["10+0"]}]}
>> 4> n_bonds:bonds_square_for_xml(10).
>> {bonds,[{for,"10"},{total,"16"}],
>> [{bond,[{b1,2},{b2,7}],["2+7"]},
>> {bond,[{b1,10},{b2,0}],["10+0"]},
>> {bond,[{b1,8},{b2,3}],["8+3"]},
>> {bond,[{b1,5},{b2,4}],["5+4"]},
>> {bond,[{b1,2},{b2,8}],["2+8"]},
>> {bond,[{b1,8},{b2,2}],["8+2"]},
>> {bond,[{b1,4},{b2,6}],["4+6"]},
>> {bond,[{b1,1},{b2,9}],["1+9"]},
>> {bond,[{b1,8},{b2,1}],["8+1"]},
>> {bond,[{b1,7},{b2,3}],["7+3"]},
>> {bond,[{b1,0},{b2,10}],["0+10"]},
>> {bond,[{b1,5},{b2,5}],["5+5"]},
>> {bond,[{b1,3},{b2,6}],["3+6"]},
>> {bond,[{b1,3},{b2,7}],["3+7"]},
>> {bond,[{b1,6},{b2,4}],["6+4"]},
>> {bond,[{b1,9},{b2,1}],["9+1"]}]}
>>
>>
>>
>> I tried the suggestions you gave but I was and still am pretty sure
>> that it is not the browser that is doing the caching. Even with the
>> cache headers set the behavior is the same. I recompiled the
>> n_bonds module and for the first run I got different results but
>> now they are the same each subsequent run. Curious.
>>
>> I suppose it is not a massive issue since this is just a toy for my
>> son but I am pretty curious as to what is going on. i think I am
>> going to have to (try) and read the source code.
>>
>> Cheers again
>>
>> Russell
>>
>> On 22 Aug 2008, at 19:17, Edwin Fine wrote:
>>
>>> Oops, that should have been
>>>
>>> http://wombat.me:8000/bonds?n=10&dummy=1
>>>
>>> not
>>>
>>> http://wombat.me:8000/bonds/n=10&dummy=1
>>>
>>> On Fri, Aug 22, 2008 at 2:14 PM, Edwin Fine <em...@gm...>
>>> wrote:
>>> Hi Russell,
>>>
>>> I'm not a Yaws expert but have used it a bit. I can think of a few
>>> questions:
>>> I know this is obvious but I want to ask it anyway: If you call
>>> the function n_bonds:bonds_square_for_xml/1 "manually" using the
>>> shell, does it come back with different answers every time? Are
>>> you sure that the function itself is working like it should?
>>> If yes (and I am sure it is yes), then maybe you can force caching
>>> off as follows:
>>> out(A) ->
>>> Bonds =
>>> n_bonds:bonds_square_for_xml(list_to_integer(A#arg.appmoddata)),
>>> Export = xmerl:export_simple([Bonds],xmerl_xml),
>>> [
>>> {header, {cache_control, "no-cache, must-revalidate"}},
>>> {header, "Expires: Mon, 26 Jul 1997 05:00:00 GMT"},
>>>
>>> {content, "application/xml", lists:flatten(Export)}
>>> ].
>>>
>>> Another easy trick the HTML people use to avoid caching GETs is to
>>> make a varying query in the URL, for example
>>>
>>> http://wombat.me:8000/bonds/n=10&dummy=1
>>> http://wombat.me:8000/bonds/n=10&dummy=2
>>> http://wombat.me:8000/bonds/n=10&dummy=3
>>>
>>> Then all you have to do extra in out(A) is parse the query to get
>>> "n":
>>>
>>> out(A) ->
>>> QueryList = yaws_api:parse_query(A), % e.g. [{"n","10"},
>>> {"dummy", "1"}]
>>> Content = case proplists:get_value("n", QueryList) of
>>> undefined ->
>>> {content, "application/xml", "<error>Bad query string</
>>> error>"};
>>> NStr ->
>>> N = list_to_integer(NStr) ,
>>> Bonds = n_bonds:bonds_square_for_xml(N),
>>> lists:flatten(xmerl:export_simple([Bonds],xmerl_xml))
>>> end,
>>> {content, "application/xml", Content}.
>>>
>>> Hope this helps.
>>>
>>> Edwin
>>>
>>>
>>>
>>>
>>> ContentFun(
>>> formatted_process_list(
>>> ProcInfo,
>>> ResponseFun,
>>> ErrFun))
>>> ].
>>>
>>>
>>>
>>>
>>> On Fri, Aug 22, 2008 at 10:06 AM, Russell Brown <rus...@ma...
>>> > wrote:
>>> Hi,
>>> I am new to YAWS and erlang. I have knocked up a quick toy
>>> application
>>> for my son to practice his "number bonds" (a maths teaching method
>>> for
>>> primary school in the UK). I am using an appmod. The code is below:-
>>>
>>> -module(bonds_yaws).
>>> -export([out/1]).
>>> -include("/home/russell/erlang/yaws/lib/yaws/include/yaws_api.hrl").
>>>
>>>
>>> out(A) ->
>>> Bonds =
>>> n_bonds:bonds_square_for_xml(list_to_integer(A#arg.appmoddata)),
>>> Export=xmerl:export_simple([Bonds],xmerl_xml),
>>> {content, "application/xml", lists:flatten(Export)}.
>>>
>>>
>>> The code for n_bonds:bonds_square_for_xml(N) takes an integer and
>>> generates a tuple that I turn into xml and then YAWS sends it to the
>>> client. n_bonds:bonds_square_for_xml produces a term like this
>>>
>>> {bonds,[{for,"10"},{total,"16"}],
>>> [{bond,[{b1,10},{b2,0}],["10+0"]},
>>> {bond,[{b1,8},{b2,2}],["8+2"]},
>>> {bond,[{b1,6},{b2,4}],["6+4"]},
>>> {bond,[{b1,1},{b2,9}],["1+9"]},
>>> {bond,[{b1,3},{b2,7}],["3+7"]},
>>> {bond,[{b1,5},{b2,5}],["5+5"]},
>>> {bond,[{b1,2},{b2,9}],["2+9"]},
>>> {bond,[{b1,1},{b2,8}],["1+8"]},
>>> {bond,[{b1,4},{b2,6}],["4+6"]},
>>> {bond,[{b1,3},{b2,6}],["3+6"]},
>>> {bond,[{b1,3},{b2,8}],["3+8"]},
>>> {bond,[{b1,5},{b2,4}],["5+4"]},
>>> {bond,[{b1,2},{b2,8}],["2+8"]},
>>> {bond,[{b1,7},{b2,3}],["7+3"]},
>>> {bond,[{b1,9},{b2,1}],["9+1"]},
>>> {bond,[{b1,0},{b2,10}],["0+10"]}]}
>>>
>>>
>>> Basically a set of bonds. The a called function of
>>> bonds_square_for_xml
>>> shuffles the order of the bond rows. The shuffle works well enough
>>> so
>>> that if you call n_bonds:bonds_square_for_xml(10) twice in a row you
>>> will probably get the bonds in a different order and also probably
>>> get
>>> different data too (there are some incorrect answers thrown in for
>>> good
>>> measure). However if you hit the Yaws url a few times you *always*
>>> get
>>> the same answer. So http://wombat.me:8000/bonds/10 always shows
>>> the same
>>> xml.
>>>
>>> Does YAWS cache the result of executing the erlang? Can I stop it
>>> from
>>> doing that? How?
>>>
>>> Many thanks if you can help.
>>>
>>> Cheers
>>>
>>> Russell
>>>
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>>>
>>> --
>>> For every expert there is an equal and opposite expert - Arthur C.
>>> Clarke
>>>
>>>
>>>
>>> --
>>> For every expert there is an equal and opposite expert - Arthur C.
>>> Clarke
>>
>>
>> -------------------------------------------------------------------------
>> This SF.Net email is sponsored by the Moblin Your Move Developer's
>> challenge
>> Build the coolest Linux based applications with Moblin SDK & win
>> great prizes
>> Grand prize is a trip for two to an Open Source event anywhere in
>> the world
>> http://moblin-contest.org/redirect.php?banner_id=100&url=/
>> _______________________________________________
>> Erlyaws-list mailing list
>> Erl...@li...
>> https://lists.sourceforge.net/lists/listinfo/erlyaws-list
>>
>>
>>
>>
>> --
>> For every expert there is an equal and opposite expert - Arthur C.
>> Clarke
>>
>>
>>
>> --
>> For every expert there is an equal and opposite expert - Arthur C.
>> Clarke
>
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