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ColinM's questions

Martin Hope
ColinM
Asked: 2012-12-22 22:28:09 +0800 CST
  • 6

I'm using Apache 2.4.3 as a reverse proxy due to it's advertised compliance with RFC 2616. My app uses headers like this to enable caching at the proxy:

Cache-Control: public, s-maxage=0
Expires: ... (+1 day)
X-Group: A
Vary: X-Group
ETag: W/"foo1"

After the first request warms the cache, if my app changes to respond with this:

Cache-Control: public, s-maxage=0
Expires: ... (+1 day)
X-Group: B
Vary: X-Group
ETag: W/"foo2"

The app will respond with 304 Not Modified if the If-None-Match header from Apache matches the origin-generated ETag. However, Apache then caches the second 200 response and replaces the "foo1" record with the new response instead of caching both of the responses with different ETags. Therefore, instead of If-None-Match: W/"foo1", W/"foo2" the next revalidate request is just If-None-Match: W/"foo2". So the cache is constantly getting misses instead of always getting hits.

From the RFC 2616 section 12.1:

However, an origin server is not limited to these dimensions and MAY vary the response based on any aspect of the request, including information outside the request-header fields or within extension header fields not defined by this specification.

I've tried the following combinations for Vary:

Vary: X-Foo
Vary: *
Vary: User-Agent

I've also tried both strong and weak ETags and no matter what I cannot get Apache to cache the two responses simultaneously, it always saves over the previous one. If it can't save more than one variance of a page then ETag is useless, Last-Modified would be just as good.

From the Apache 2.4 docs:

mod_cache implements an RFC 2616 compliant HTTP content caching filter, with support for the caching of content negotiated responses containing the Vary header.

Note that it says "responses" plural. Am I mis-interpreting the HTTP spec or does Apache 2.4 just not fully support ETags after-all?

http
Martin Hope
ColinM
Asked: 2012-11-20 16:04:22 +0800 CST
  • 1

Possible Duplicate:
How can email possibly be routed to the right place with no to: address?

I've seen this quite a few times now. I will receive an email at a domain that I manage ([email protected]) from an @yahoo.com account but the To header has an email at some entirely unrelated domain name! The DKIM signature contains the To header and they pass validation. How can this be?

Example:

Return-Path: <[email protected]>
Received: from nm8.bullet.mail.ukl.yahoo.com (nm8.bullet.mail.ukl.yahoo.com [217.146.182.249]) by mx.example.com with SMTP;
   Mon, 19 Nov 2012 16:38:59 -0500
Received: from [217.12.10.106] by nm8.bullet.mail.ukl.yahoo.com with NNFMP; 19 Nov 2012 21:38:56 -0000
Received: from [217.146.183.128] by tm20.bullet.mail.ukl.yahoo.com with NNFMP; 19 Nov 2012 21:38:40 -0000
Received: from [127.0.0.1] by smtp113.mail.ukl.yahoo.com with NNFMP; 19 Nov 2012 21:38:40 -0000
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1353361120; bh=uCWr2zakkKwpxVn224ejIuEu24fxI7P+IKguxaa4T50=; h=X-Yahoo-Newman-Id:X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Message-ID:Date:From:Subject:To:Content-Type:X-Mailer; b=O6...(shortened)
X-Yahoo-Newman-Id: [email protected]
X-Yahoo-Newman-Property: ymail-3
X-YMail-OSG: 7YH8p9Y...(shortened)
Received: from uxprj ([email protected] with login)
        by smtp113.mail.ukl.yahoo.com with SMTP; 19 Nov 2012 13:38:40 -0800 PST
Message-ID: <[email protected]>
Date: Mon, 19 Nov 2012 15:38:40 -0600
From: "[email protected]" <[email protected]>
Subject: You have (1) new ecard!
To: [email protected]
Content-Type: text/plain; charset=UTF-8
X-Mailer: Opera/6.05 (Windows 2000; U) [fi]

Click here to read it now! http://bit.ly/TMCHTA

To clarify: The above is an actual email that was sent to [email protected] even though the To header shows an sbcglobal.net address.

Perhaps if I understand how the spammers are doing this I can prevent it on my server. If it matters, my server is running SmarterMail 10.x.

email
Martin Hope
ColinM
Asked: 2012-02-11 20:46:36 +0800 CST
  • 8

I'm developing a caching system for an ecommerce platform that will use a reverse proxy for caching. I plan to handle invalidation by using proper HTTP/1.1 headers. That is, I will set an ETag on first generation of the content and cache that ETag value in the application. The Cache-Control header will specify "must-revalidate" so the proxy should set If-None-Match header on subsequent requests with the ETag. The application will lookup the cached ETag value and if it matches it will send a 304 response, otherwise it will generate a full 200 response.

I hoped to use nginx but I can't tell for sure that it supports ETags (docs indicate it doesn't but maybe they are out of date?). Varnish is another option but I'm not positive here either..

Which reverse proxy servers out there have full support for ETags? I'd like it to actually cache multiple versions so I can do things like split testing without having to disable the cache. That is, HTTP/1.1 specifies that a client can send If-None-Match with multiple ETag values and the server should respond with which ETag matched (if any). If the reverse proxy kept multiple copies rather than just the last-seen value and let the server specify on each request which to use, that would be ideal.

http nginx varnish reverse-proxy etags
Martin Hope
ColinM
Asked: 2011-08-13 13:58:47 +0800 CST
  • 4

I'm trying to debug an exim configuration issue (Ubuntu) and I see lots of lines in the config such as:

remote_smtp:
   debug_print = "T: remote_smtp for $local_part@$domain"
   driver = smtp

However, I cannot figure out how to get the output of these statements. I've tried editing /etc/default/exim4 and adding various CLI parameters there such as -v, -d, -d+all and while they do have an effect, the debug_print lines are nowhere to be found (stderr,stdout,/var/log/exim4/mainlog).

How do enable and where do I then find the "T: remote_smtp for ..." output?

ubuntu exim
Martin Hope
ColinM
Asked: 2011-05-13 11:27:13 +0800 CST
  • 5

I've got PHP 5.3.3 and nginx 0.8.47 compiled from source running a Wordpress blog. The RSS feed generated by Wordpress was getting truncated at roughly 16k (including header was 16k+90b). By adding the following to my nginx config:

fastcgi_buffers 8 16k;
fastcgi_buffer_size 32k;

the problem went away.. However, from what I read on the Nginx wiki page the buffers only determine when buffering will overflow onto disk. There is nothing that indicates the response can be truncated due to the buffers being too small..

So my question is, why was the response being truncated before changing this setting? It seems the request should not have been truncated, just a little slower due to disk buffering.

Additional info:

  • Ubuntu 10.04.2 32bit
  • PAGESIZE 4k
fastcgi nginx php-fpm
Martin Hope
ColinM
Asked: 2010-09-25 21:40:18 +0800 CST
  • 0

I am running Magento (ecommerce PHP app) behind nginx as a reverse proxy to Apache which is running the PHP app. Static content is served directly by nginx. Magento has a "maintenance mode" which uses a 503 HTTP response. With my configuration when maintenance mode is enabled nginx returns a blank page with a 500 response instead of Magento's nice maintenance mode page with the 503 response. How can I make nginx let the 503 page pass through to the client?

Here is my nginx config:

upstream examplecluster       { server 1.2.3.4:80; }
server {
  listen       1.2.3.5:80;
  server_name  www.example.com;
  root         /var/www/example.com/www;

  # security
  location ~ (/(app/|includes/|lib/|pkginfo/|var/|report/config.xml|downloader/(pearlib|template|Maged)/)|/\.svn/|/\.ht.+) {
    return 404;
  }

  location ~ \.php$ {
    proxy_pass http://examplecluster;
    proxy_redirect default;
  }

  # static content
  location / {
    try_files $uri @apache;
    expires 7d;
  }

  # Apache
  location @apache {
    proxy_pass http://examplecluster;
    proxy_redirect default;
  }
}
magento nginx reverse-proxy
Martin Hope
ColinM
Asked: 2010-06-16 19:30:29 +0800 CST
  • 1

I am running Exim 4.71. I want to:

  1. Route all email from A.com through mail.A.com
  2. Route all email from [B-E].com through mail.B.com
  3. Send all other email directly.

Here is the configuration I have that doesn't work like I hoped:

domainlist a_domains = a.com
domainlist b_domains = b.com : c.com : d.com : e.com

begin routers

smart_route_a:
  driver = manualroute
  domains = +a_domains
  transport = remote_smtp
  route_list = +a_domains mail.a.com
  no_more

smart_route_b:
  driver = manualroute
  domains = +b_domains
  transport = remote_smtp
  route_list = +b_domains mail.mollenhour.com
  no_more

dnslookup:
  driver = dnslookup
  domains = ! +local_domains
  transport = remote_smtp
  ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
  no_more

When I send an email e.g. with PHP's mail() or Zend_Mail_Transport_Smtp setting both From: and Return-Path: as [email protected], the smart_route_a router is not used, the dnslookup is used instead. Disabling dnslookup results in no mail being sent.

From the logs it appears that email sent to [email protected] uses smart_route_a, but the same email sent from [email protected] to [email protected] is sent using dnslookup.

How do I make email from [email protected] be relayed via mail.a.com?

smtp exim smarthost