Re: [squid-users] Generell Squid setup

Hi Amos,

thank you for your response.
I think I didn't explain the problem correctly. Let me mention that
the http-Post request contains
- one or two URLs,
- name and parameters of one mathematical function from a set of
server functions,
- mime-type of the response.

The client sends a http-Post request to the server

The server ...
(1) fetches the data (xml, up to 100 MB) via http-Get using the
reference which is embedded in the client http-Post request,
(2) computes a complete new dataset (xml, up to 100 MB) using the
fetched data and the requested function and parameters,
(3) converts the dataset to the requested mime-type,
(4) returns the resulting dataset as a response of the http-Post
request to the client.

If we would implement a simple server cache the process would be like this:
(- client sends request via http-Post to the server)
- server generates a unique key of the client http-Post request,
because the URL of the http-Post request is always the same,
- server checks if the unique key / filename is in the cache; no:
normal process,
- server checks via http-Head (origin server) if the cached data is
fresh: no normal process,
- server sends the cached data associated to the unique key / filename
as response of the http-Post request to the client; end,
- normal process: server fetches the data via http-Get; server
computes the result dataset using the fetched data and the requested
function and parameters; server stores data in cache; server sends the
result data as response of the http-Post request to the client; end.

I wonder if Squid could help us to cache the data accosiated to the
client http-Post request. My idea is to generate a unique key of the
http-Post request to make it cacheable.

Thanks so much for your response.
Farkas

On 8 September 2012 04:48, Amos Jeffries <squid3_at_treenet.co.nz> wrote:
> On 7/09/2012 9:39 a.m., Farkas H wrote:
>>
>> Hi Amos,
>>
>> thanks for your response.
>> I modified the web application. Now we have the following infrastructure.
>> client --> http-Post [embedded http-Get] --> Server / web application
>> --> http-Get --> Squid -> Servers (-> Squid -> Server / web
>> application -> client)
>> Advantage: The Server / web application doesn't have to request data
>> from the remote servers if it's in the Squid cache.
>>
>> Additionally I want to cache the http-Post requests.
>> client --> http-Post --> Squid --> Server / web apllication /
>> processing the response (-> Squid -> client)
>
>
> Requests body is not cacheable in HTTP.
>
> The body content is the state to be changed at end-server resource in the
> URL. Caching it is meaningless, since next time the state needs to be
> changed you CANNOT simply reply from a middleware cache saying "server state
> now changed" without passing any of those details to the server.
>
> Additionally, your translation service is re-writing the POST into GET
> requests so the POST ceases to exist at your gateway service. There is
> nothing to cache.
>
>
>
>>
>> The idea: We modify the header of the http-post request to make it unique.
>> The information whether Squid has a stored response to the modified
>> request (true or false) should be added to the request / should be
>> forwarded to the destination server. There are two possibilities.
>> (1) The modified request is not stored in Squid (new request).
>> (2) The modified request is stored in Squid. We don't know yet if the
>> data is still fresh.
>> The request should be forwarded in both(!) possibilities, (1) and (2),
>> to the destination server.
>> Is that possible with Squid?
>
>
> Of course. That is dependent on the Cache-Control: headers the server
> supplies to Squid with its responses and applies to each response
> independent of anythign else.
>
> Send "Cache-Control: must-revalidate" and Squid will query the server for
> each request asking if there are updates.
>
> Amos
Received on Thu Sep 20 2012 - 16:26:19 MDT