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Re: Serve *only* from cache for particular user-agents

Maxim Dounin
February 21, 2014 12:20PM
Hello!

On Fri, Feb 21, 2014 at 11:46:02AM -0500, rge3 wrote:

> Maxim Dounin Wrote:
> -------------------------------------------------------
> > Hello!
> >
> > On Fri, Feb 21, 2014 at 10:25:58AM -0500, rge3 wrote:
> >
> > > I havne't found any ideas for this and thought I might ask here. We
> > have a
> > > fairly straightforward proxy_cache setup with a proxy_pass backend.
> > We
> > > cache documents for different lengths of time or go the backend for
> > what's
> > > missing. My problem is we're getting overrun with bot and spider
> > requests.
> > > MSN in particular started hitting us exceptionally hard yesterday
> > and
> > > started bringing our backend servers down. Because they're crawling
> > the
> > > site from end to end our cache is missing a lot of those pages and
> > nginx has
> > > to pass the request on through.
> > >
> > > I'm looking for a way to match on User-Agent and say that if it
> > matches
> > > certain bots to *only* serve out of proxy_cache. Ideally I'd like
> > the logic
> > > to be: if it's in the cache, serve it. If it's not, then return
> > some 4xx
> > > error. But in the case of those user-agents, *don't* go to the
> > backend.
> > > Only give them cache. My first thought was something like...
> > >
> > > if ($http_user_agent ~* msn-bot) {
> > > proxy_pass http://devnull;
> > > }
> > >
> > > by making a bogus backend. But in nginx 1.4.3 (that's what we're
> > running) I
> > > get
> > > nginx: [emerg] "proxy_pass" directive is not allowed here
> > >
> > > Does anyone have another idea?
> >
> > The message suggests you are trying to write the snippet above at
> > server{} level. Moving things into a location should do the
> > trick.
> >
> > Please make sure to read http://wiki.nginx.org/IfIsEvil though.
>
> That seems to have done it! With a location block I now have...
>
> location / {
> proxy_cache_valid 200 301 302 30m;
>
> if ($http_user_agent ~* msn-bot) {
> proxy_pass http://devnull;
> }
>
> if ($http_user_agent !~* msn-bot) {
> proxy_pass http://productionrupal;
> }
> }

Second condition can be removed, it's surplus. Just a

location / {
if (...) {
proxy_pass ...
}

proxy_pass ...
}

should be enough.

> That seems to work perfectly. But is it a safe use of "if"? Is there a
> safer way to do it without an if?

As long as it's full configuration, there should be no problems.

--
Maxim Dounin
http://nginx.org/

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Subject Author Posted

Serve *only* from cache for particular user-agents

rge3 February 21, 2014 10:25AM

Re: Serve *only* from cache for particular user-agents

Maxim Dounin February 21, 2014 10:48AM

Re: Serve *only* from cache for particular user-agents

rge3 February 21, 2014 11:46AM

Re: Serve *only* from cache for particular user-agents

ajay February 21, 2014 12:00PM

Re: Serve *only* from cache for particular user-agents

rge3 February 21, 2014 01:13PM

Re: Serve *only* from cache for particular user-agents

Maxim Dounin February 21, 2014 12:20PM

Re: Serve *only* from cache for particular user-agents

Darren Pilgrim February 21, 2014 05:16PM



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