Re: mod_proxy Cache-Control: no-cache=directive support Apache 1.3
Let me try to contribute my $0.02 to the discussion: [Like Graham, I prefer to ignore the word 1.3 in the subject line...] Originally, there was a need to INTEGRATE two modules in order to enjoy the features of both. Later, thanks to the filtering infrastructure, it is possible to do without a real merge. You still need to change some things in the original module (and of course, to port the additional module to be a filter rather than a simple module), but the two modules/filters can live together, side by side. Then, integration with mod_proxy still needed, because the connection of mod_proxy with the backend server was still done directly, and not through the filtering infrastructure. Now, that this issue is being resolved too, it's the time to try to add features to mod_proxy WITHOUT modifying it (well, you still need some minor fixes in mod_proxy. For example, if it removes a header, no filter can do anything about it...). Trying to add so many features to mod_proxy, may meet the objection of members here, who want a simple and stable mod_proxy, and may fear that all of these additions may make mod_proxy a monster (even if it's not true). I think that the right way to advance this idea (to integrate both modules), is to make mod_accel a filter. I don't have any experience with mod_accel, so I can't promise that it's possible; However, in the worst case, we can add filters to both sides (between the client and the proxy, and between the proxy and the backend), plus some minor fixes to mod_proxy, the sky is the limit... Of course, you have to deal with many filtering chains, even 4 (2 types - input/output, in 2 sides - between the proxy and the client, and between the proxy and the backend), and even more (when headers can't be manipulated in the same filter as the input/output one). I, for myself, am going to play with adding filters to the sessions between the proxy and the backend; I think that some cool things can be done using it. -- Eli Marmor [EMAIL PROTECTED] CTO, Founder Netmask (El-Mar) Internet Technologies Ltd. __ Tel.: +972-9-766-1020 8 Yad-Harutzim St. Fax.: +972-9-766-1314 P.O.B. 7004 Mobile: +972-50-23-7338 Kfar-Saba 44641, Israel
Re: mod_proxy Cache-Control: no-cache=directive support Apache 1.3
Graham - At Wed, 27 Feb 2002 06:36:45 +0200, Graham Leggett wrote: [1 text/plain; us-ascii (7bit)] Joseph Wayne Norton wrote: In conjunction with mod_rewrite as url filter, I would like to be able to use mod_accel as a proxy for only the http request portion of a client request and allow for the http response portion to be served directly from the backend to the client. This would be useful in situations where the response does not (or should not) have to be cached by the mod_accel cache. However, I think this type of tcp-handoff cannot be performed soley by an application process such as apache. Have you a similiar requirement or experience? The request and response come after the other on the same connection, so what you're asking to do is impossible. What exactly are you trying to achieve? If you don't want a response to be cached, use the Pragma: no-cache and Cache-Control: headers correctly. Yes, I understand that what I'm asking to do is impossible with the same connection. I'm interested in learning how to build a better web server cluster to support dynamic content (generated by backend servers). I have run across the following paper ... http://www.crpc.rice.edu/softlib/scalableRD.html#papers entitled Scalable Content-aware Request Distribution I found it to be quite interesting. It presents a scalable method for distributing the operaton of tcp connection and handoff among back-end nodes rather than relying entirely on a centralized node. It also helps solves an issue of trying to keep a single, web client's session to being served by a particular back-end node (this helps with cacheing). The paper discusses about having a Distributor component and a Server component. I have simply been thinking about how this Distributor component could be implemented by using apache's mod_rewrite, mod_proxy, and mod_cache modules. The Server component would be a backend server that is proxied by mod_proxy (or mod_accel). For dynamic content that has been cached or can be cached, the Distributor component would simply send the response back to the client (as mod_proxy does now after talking with the backend). For dynamic content that cannot be cached or doesn't need to be cached, the Distributor would implement a form of TCP handoff that would allow the backend to serve the response directly to the client. This later step probably cannot be done without some additional kernel-level module. Anyway, my questions are just ideas right now ... nothing more. mod_proxy is very ancient module and it's hard to maintain it. Is it possible to integrate apache 2.0's mod_cache with mod_accel and/or add mod_accel's features to mod_proxy? Mod_proxy is no longer ancient nor hard to maintain, and as far as I am aware the new mod_proxy does almost everything mod_accel does - if it doesn't, tell me what's broken and I'll try to fix it. I haven't spent any time examining the source (or trying to extend) of mod_proxy or mod_accel so I am not able to judge either module. The 2 main points that I picked up from Igor's mail that I'm not sure if mod_proxy supports or not: a. It frees backend as soon as possible. mod_proxy can keep busy backend with slow client, i.e, using mod_proxy to accelerate backend is not worked with slow clients . b. It can use busy locks and limit number of connection to backend. One additional feature that I would like to have with mod_proxy is to have a way to install error_handler documents for all or individual backends. This would allow apache to return a customized error page for individual backends for cases when the backend is not reachable, etc. I hope that I have made myself clear. Any thoughts or comments? Regards, - jn
Re: mod_proxy Cache-Control: no-cache=directive support Apache 1.3
Igor - After I read your posting, I downloaded but haven't tried to install the mod_accel. From you description, it looks like a very, powerful module with pretty much the features that I have been looking for. Can mod_accel work with the mod_rewrite module (in a fashion similar? In conjunction with mod_rewrite as url filter, I would like to be able to use mod_accel as a proxy for only the http request portion of a client request and allow for the http response portion to be served directly from the backend to the client. This would be useful in situations where the response does not (or should not) have to be cached by the mod_accel cache. However, I think this type of tcp-handoff cannot be performed soley by an application process such as apache. Have you a similiar requirement or experience? At Tue, 19 Feb 2002 14:49:44 +0300 (MSK), Igor Sysoev wrote: mod_proxy is very ancient module and it's hard to maintain it. Is it possible to integrate apache 2.0's mod_cache with mod_accel and/or add mod_accel's features to mod_proxy? thanks, - Joe N.
mod_proxy Cache-Control: no-cache=directive support Apache 1.3
Hi, Due to a requirement on a project we are currently working on involving using Apache as a caching reverse proxy server to WebLogic. We are considering implementing the Cache-Control: no-cache=directive for the Apache 1.3 mod_proxy module so allow us to prevent the caching of certain headers served by WebLogic. (In particular the session cookie.) Has/is anyone working in this area? Is there any specific reason why this has deliberately not been implemented already? (E.g. performance hit?) Any views on this directive? Thanks, Brian Logica UK Ltd. This e-mail and any attachment is for authorised use by the intended recipient(s) only. It may contain proprietary material, confidential information and/or be subject to legal privilege. It should not be copied, disclosed to, retained or used by, any other party. If you are not an intended recipient then please promptly delete this e-mail and any attachment and all copies and inform the sender. Thank you.
RE: mod_proxy Cache-Control: no-cache=directive support Apache 1.3
Hi Graham, I don't think mod_proxy does currently conform to RFC2616 in respect of Cache-Control: no-cache=directive It preventing the caching of specific headers, I can't find any code implementing this in the mod_proxy distribution and the following example fails... I have a small test.jsp which just sets Expires, Last-Modified and Cache-Control: no-cache=Set-Cookie headers and configured Apache to act as a Reverse Proxy Server for the page. With an empty cache the initial request gives ... ~ GET -edP http://FCODEVWS2/communities/test.jsp; Cache-Control: no-cache=Set-Cookie Connection: close Date: Tue, 19 Feb 2002 12:37:33 GMT Server: Apache/1.3.23 (Win32) Content-Length: 8 Content-Type: text/html Expires: Tue, 19 Feb 2002 13:06:34 GMT Last-Modified: Tue, 19 Feb 2002 12:06:34 GMT Client-Date: Tue, 19 Feb 2002 12:37:35 GMT Client-Response-Num: 1 Set-Cookie: WebLogicSession=PHJG0oDVfgz68YWMM8DpXAUxFVZ5gugPKyuKQbIf716lkw6bRRBM |-1484200219301769473/-1628821962/6/7001/7001/7002/7002/7001/-1; path=/ X-Cache: MISS from fcomain After which a cached version of the content and headers is created in the cache, but it still contains the Set-Cookie directive which it should not, I don't think ... - 3C72473E 3C723FCA 3C724DDA 0001 3C72470D 3C724710 0008 X-URL: http://fcontdevserver1/communities/test.jsp Connection: close Host: FCODEVWS2 User-Agent: lwp-request/1.40 HTTP/1.1 200 OK Server: Netscape-Enterprise/4.1 Date: Tue, 19 Feb 2002 12:38:22 GMT Content-length: 8 Content-type: text/html Expires: Tue, 19 Feb 2002 13:06:34 GMT Last-modified: Tue, 19 Feb 2002 12:06:34 GMT Cache-control: no-cache=Set-Cookie Set-cookie: WebLogicSession=PHJG0oDVfgz68YWMM8DpXAUxFVZ5gugPKyuKQbIf716lkw6bRRBM|-148420 0219301769473/-1628821962/6/7001/7001/7002/7002/7001/-1; path=/ Test - A subsequent request to the proxy gives a hit to the cache which is correct but it should NOT serve back the Set-Cookie header. ~ GET -edP http://FCODEVWS2/communities/test.jsp; Cache-Control: no-cache=Set-Cookie Connection: close Date: Tue, 19 Feb 2002 12:38:42 GMT Age: 69 Server: Apache/1.3.23 (Win32) Content-Length: 8 Content-Type: text/html Expires: Tue, 19 Feb 2002 13:06:34 GMT Last-Modified: Tue, 19 Feb 2002 12:06:34 GMT Client-Date: Tue, 19 Feb 2002 12:38:40 GMT Client-Response-Num: 1 Set-Cookie: WebLogicSession=PHJG0oDVfgz68YWMM8DpXAUxFVZ5gugPKyuKQbIf716lkw6bRRBM |-1484200219301769473/-1628821962/6/7001/7001/7002/7002/7001/-1; path=/ X-Cache: HIT from fcomain The relevant part of the HTTP spec I think is no-cache If the no-cache directive does not specify a field-name, then a cache MUST NOT use the response to satisfy a subsequent request without successful revalidation with the origin server. This allows an origin server to prevent caching even by caches that have been configured to return stale responses to client requests. If the no-cache directive does specify one or more field-names, then a cache MAY use the response to satisfy a subsequent request, subject to any other restrictions on caching. However, the specified field-name(s) MUST NOT be sent in the response to a subsequent request without successful revalidation with the origin server. This allows an origin server to prevent the re-use of certain header fields in a response, while still allowing caching of the rest of the response. I am missing something? Cheers, Brian -Original Message- From: Graham Leggett [mailto:[EMAIL PROTECTED]] Sent: 19 February 2002 11:59 To: [EMAIL PROTECTED] Subject: Re: mod_proxy Cache-Control: no-cache=directive support Apache 1.3 Fowler, Brian wrote: Due to a requirement on a project we are currently working on involving using Apache as a caching reverse proxy server to WebLogic. We are considering implementing the Cache-Control: no-cache=directive for the Apache 1.3 mod_proxy module so allow us to prevent the caching of certain headers served by WebLogic. (In particular the session cookie.) Has/is anyone working in this area? Is there any specific reason why this has deliberately not been implemented already? (E.g. performance hit?) Any views on this directive? I'm not 100% sure what your question is. The apache proxy follows RFC2616 when it comes to understanding and honouring the Cache-Control directive. The responsibility of setting this header correctly is that of your Weblogic application. If the application is braindead, you should be able to use the capability of mod_headers to add the cache-control header within apache itself. (As I am aware this should work, as long as mod_headers comes before mod_proxy in your config. In v2.0, this should work automatically - but test it first). Regards, Graham -- - [EMAIL PROTECTED]There's a moon over Bourbon Street tonight... This e-mail
Re: mod_proxy Cache-Control: no-cache=directive support Apache 1.3
Fowler, Brian wrote: I don't think mod_proxy does currently conform to RFC2616 in respect of Cache-Control: no-cache=directive I just checked - a small note in my copy of RFC2616 says not done yet.. doh...! The relevant part of the HTTP spec I think is no-cache [snip] If the no-cache directive does specify one or more field-names, then a cache MAY use the response to satisfy a subsequent request, subject to any other restrictions on caching. However, the specified field-name(s) MUST NOT be sent in the response to a subsequent request without successful revalidation with the origin server. This allows an origin server to prevent the re-use of certain header fields in a response, while still allowing caching of the rest of the response. So which of the following two senarios is the correct behavior: - If the header specified is not in the request, ignore that Cache-Control header. - If the header IS specified in the request, behave like Cache-Control: max-age=0 OR - If the header specified is not in the request, ignore that Cache-Control header. - If the header IS specified in the request, strip that header and return the request with the header removed. From the text quoted above, either seem valid, or am I reading it wrong...? Regards, Graham -- - [EMAIL PROTECTED]There's a moon over Bourbon Street tonight... smime.p7s Description: S/MIME Cryptographic Signature
