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Re: Negative last modified

From: olga <olga@goliath.eai.com>
Date: Tue, 26 Jan 1999 09:21:10 -0600 (CST)
Message-ID: <XFMail.990126092110.olga@eai.com>
To: Henrik Frystyk Nielsen <frystyk@w3.org>
Cc: olga <olga@goliath.eai.com>, www-lib@w3.org
Hi,

As I understand, on starting the w3c library the .index is read and anchors are
created for all the files in cache. When the HT_C_IMS header is created - an
anchor for the location is referenced for LM date. In those parts everything
goes throug the library - I have not changed anything there...

There is what is in the meta-file:

olga@nile 58: more AAAa0000a.meta 
Content-Type: application/x-jt
Content-Length: 5844
Accept-Ranges: bytes
ETag: "3c000ac-16d4-0
Last-Modified: Thu, 01 Jan 1970 00:00:00 GMT
Server: Apache/1.3.1 (Unix)
Date: Mon, 25 Jan 1999 22:32:45 GMT

---------------------------------------------------

Here is what it is parsed to later on :

-----------------------------------------------------------

TTP... in HTTPEvent 
HTTP_BEGIN: === Connecting to server ===
HTHost parse Looking up `kingkong' on port 1080
Host info... REUSING CHANNEL 1002c868
Host info... Added Net 100309f0 (request 1002c4c0) to pipe on Host 1002c7b8, 2
requests made, 1 requests in pipe, 0 pending
Timer....... Deleted timer 10028c50
HTHost...... No ActivateRequest callback handler registered
Channel..... Semaphore increased to 1 for channel 1002c868
Host connect Unlocking Host 1002c7b8
HTTP_NEED_STREAM: === Constructing stream ===
StreamStack. Constructing stream stack for text/x-http to */*
Tee......... Created stream 10048468 with resolver 45c770
HTTP........ Dumping request to `w3chttp.out'
HTTP_CONNECTED, HTEvent_WRITE: ===== Flushing request ===
HTTP........ If-Modified-Since,  lm = -3600
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


HTTP........ Generating HTTP/1.x Request Headers
HTTP........ Generating General Headers
Buffer...... Flushing 1002ae40
....

-------------------------------------------------------------

And here is the corresponding entry in w3chttp.out:


GET /projects/Demos/fishing_reel/fishing_reel.jt HTTP/1.1
Accept: */*
TE: trailers
Authorization: Basic ZWFpOmVhaQ==
Host: kingkong:1080
User-Agent: VisNetwork/1.1 libwww/5.1l
Connection: TE,Keep-Alive

The reasons that I am not using the HTCacheFilter is that I want to read
directly from cache (for efficiency) if the file is there and cache verification
scheme is currently set to "not verify". This was working in previous version
of library I had. Now, when I got newer version (2 weeks ago) it stopped
working (I think in part of parsing the date, but I might be wrong of course). 
       
Thanks,

Olga Antropova.










On 25-Jan-99 Henrik Frystyk Nielsen wrote:
> 
> 
> olga wrote:
> 
>> I am not using the HTCacheFilter and instead add the header HT_C_IMS (If-
>> modified-since) to the GET request. Often the header is not added because
>> the
>> Last-modified field in anchor is parsed to a negative value. Why is that
>> happening?
> 
> Unless there is something wrong in the date parser (or the format) then
> it is because it doesn't have a LM date and hence it returns -1. What
> the persistent cache allows you to do is to use etags instead and to
> maintain these etags persistently so that you can start the app at a
> later time and still be able to use conditional GET requests.
>  
>> Also even if Last-modified is parsed to positive value, and
>> If-modified-since
>> is added to headers the file is still loaded from server and 200 is
>> returned.
> 
> If the server sends back a 200 then it is because it thinks that the
> document has changed.
> 
> Is there any reason why you can't use the normal libwww persistent
> cache? Amaya, Web Commander, and the webbot are all using it.
> 
> Henrik
> 
> --
> Henrik Frystyk Nielsen,
> World Wide Web Consortium
> http://www.w3.org/People/Frystyk

----------------------------------
E-Mail: olga <olga@eai.com>
Date: 25-Jan-99
Time: 16:33:52

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Received on Tuesday, 26 January 1999 10:17:28 GMT

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