Re: ring - setting no-cache for everything?

[Fluid Dynamics]

On Friday, June 19, 2015 at 12:14:10 PM UTC-4, Thomas Heller wrote:
>
>
>> Cache-control is evil. Users concerned with seeing the most up-to-date 
>> information know to hit reload (and probably do anyway, just to be sure), 
>> and there's also the option of AJAX polling for that (or whatever precisely 
>> sites like Facebook do).
>>
>>  
> I don't even  a wrong Cache-Control will cause problems but 
> Cache-Control is probably one of the most important headers to set for your 
> webapp. It is also one of the harder ones to get right but the benefits are 
> significant.
>
> As for preventing users from seeing stale CSS/Javascript I'd recommend 
> serving files with a unique name which changes with each new release.
>

Doing that will break bookmarks and deep links! Unless you keep all the old 
versions around, with ways to get to the newest for users who want to. It's 
almost always better to rely on the user knowing when to reload (to be sure 
they have the latest) and when to use the Wayback Machine (for when they 
specifically want to look at an old version). The latter also works much 
better if the URL for your page stays stable, so all of its versions are 
presented with a single timeline on that site.

Do what you suggested with *just* the CSS/JS files, maybe, but do not do it 
with the page itself, or images or other stuff meant for the end user to 
see! Though then the user will still have stale scripts until they reload 
and get a new version of the page pointing to the new scripts. Which then 
means you need to update every HTML file on the site every time you change 
to a new version of some script, so that it now points to the new scripts 
... which is another giant mess that suggests it's better to just keep all 
of them at stable URLs too and rely on the browser reload button DTRT by 
checking all assets for 304 Not Modified vs. shiny and new.

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Re: ring - setting no-cache for everything?

[Magnar Sveen]

Sounds like your URLs could use some cache busting. :) Then you can add far 
future Expires headers, with no worries that users are seeing stale files. 
Optimus is one way to inject some front-end performance in your 
Ring-app. https://github.com/magnars/optimus

On Friday, June 19, 2015 at 11:00:57 AM UTC+2, Colin Yates wrote:
>
> Hi all, is there a quick way to disable caching for everything or 
> alternatively hash based on the contents of the resource. I am talking 
> specifically about CSS and javascript issues served from the JAR's class 
> path?
>

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Re: ring - setting no-cache for everything?

[Thomas Heller]

>
>
> Cache-control is evil. Users concerned with seeing the most up-to-date 
> information know to hit reload (and probably do anyway, just to be sure), 
> and there's also the option of AJAX polling for that (or whatever precisely 
> sites like Facebook do).
>
>  
I don't even  a wrong Cache-Control will cause problems but 
Cache-Control is probably one of the most important headers to set for your 
webapp. It is also one of the harder ones to get right but the benefits are 
significant.

As for preventing users from seeing stale CSS/Javascript I'd recommend 
serving files with a unique name which changes with each new release. This 
way old HTML refers to old CSS and new HTML to new CSS, plus you can add 
"Cache-Control: public, max-age=31536000" to the static files which allows 
the browser to actually SKIP checking if a resource was modified (ie. huge 
speed gains, no if-modified-since->not modified round trip).

Disabling cache is usually the least desirable option and if you care about 
performance at all you should think twice before doing so (yes, even for 
intranet sites). 

/thomas

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Re: ring - setting no-cache for everything?

[Colin Yates]

None of this is applicable for closed intranet sites, and cache-control solves 
the very annoying situation where users are running an old version of CSS or 
Javascript.

I agree with these points for public facing ‘web sites’. For ‘enterprise SPAs’ 
there is usually a different context and set of requirements/restrictions to 
deal with.

> On 19 Jun 2015, at 13:56, Fluid Dynamics  wrote:
> 
> On Friday, June 19, 2015 at 5:54:03 AM UTC-4, James Reeves wrote:
> Ring doesn't set any caching headers unless you add in middleware to do so.
> 
> The most common middleware is wrap-not-modified, which returns a 304 response 
> if the etag or last-modified dates indicate the resource hasn't been 
> modified. For resources in jar files, the last-modified date is set to the 
> modification date of the containing jar.
> 
> You could add some middleware to force the browser not to cache resources via 
> the cache-control header (see here 
> ),
>  or if this is just for development, then Chrome at least has a checkbox in 
> the developer tools for disabling caching.
> 
> Cache-control is evil. Users concerned with seeing the most up-to-date 
> information know to hit reload (and probably do anyway, just to be sure), and 
> there's also the option of AJAX polling for that (or whatever precisely sites 
> like Facebook do).
> 
> Meanwhile, cache-control has all of the following very annoying consequences 
> for users (at lease one of which hits the web site too):
> 
> * Every page load and navigation step is painfully slow because of all of the 
> various reloading assets and such, if the user is on any typical consumer 
> "broadband" connection rather than real broadband.
> * In particular, normally instant back-arrow and forward-arrow navigation are 
> annoyingly slow.
> * If the user's connection is noticeably flaky, then the page is likely to 
> only partly load, and using back-arrow forward-arrow to try to force the 
> missing elements to load also loses the elements that were already loaded, 
> instead of incrementally loading more and more of the page until eventually 
> it's all there.
> * It costs both the user and the web site bandwidth. Important to you, and 
> important to at least your mobile users, who probably have metered *and* 
> tightly capped data plans.
> * In Firefox, at least, cache-control breaks image right-click save-as, 
> because right-click save-as just copies the cached image normally, but if 
> it's not cached instead tries to download it again. If that's combined with 
> typical hotlinking blocking, the result tends to be errors or corrupt jpegs. 
> To see this effect go to a Photobucket album, which serves either the image 
> itself or a webpage with the image in it depending on referer and which also 
> uses cache-control. If you right-click save-as the image you'll get a corrupt 
> jpeg file that, when opened in Notepad, is actually full of HTML. Of course, 
> blocking hotlinking and playing "clever" redirection tricks with referer is 
> evil too, but cache-control compounds that evil a thousandfold. (The only 
> correct use of referer is for log analysis to discover how your users 
> navigate around your site. Using it to discriminate against users based on 
> where they were linked in from is evil and wrong.)
> 
> Upshot: Use Ajax push/pull if you really want users to always see up-to-date 
> information, and otherwise let them use "refresh" as appropriate. And don't 
> get cute serving different content for the same URI depending on referer; 
> that's just wrong. :)
> 
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Re: ring - setting no-cache for everything?

[Fluid Dynamics]

On Friday, June 19, 2015 at 5:54:03 AM UTC-4, James Reeves wrote:
>
> Ring doesn't set any caching headers unless you add in middleware to do so.
>
> The most common middleware is wrap-not-modified, which returns a 304 
> response if the etag or last-modified dates indicate the resource hasn't 
> been modified. For resources in jar files, the last-modified date is set to 
> the modification date of the containing jar.
>
> You could add some middleware to force the browser not to cache resources 
> via the cache-control header (see here 
> ),
>  
> or if this is just for development, then Chrome at least has a checkbox in 
> the developer tools for disabling caching.
>

Cache-control is evil. Users concerned with seeing the most up-to-date 
information know to hit reload (and probably do anyway, just to be sure), 
and there's also the option of AJAX polling for that (or whatever precisely 
sites like Facebook do).

Meanwhile, cache-control has all of the following very annoying 
consequences for users (at lease one of which hits the web site too):

* Every page load and navigation step is painfully slow because of all of 
the various reloading assets and such, if the user is on any typical 
consumer "broadband" connection rather than real broadband.
* In particular, normally instant back-arrow and forward-arrow navigation 
are annoyingly slow.
* If the user's connection is noticeably flaky, then the page is likely to 
only partly load, and using back-arrow forward-arrow to try to force the 
missing elements to load also loses the elements that were already loaded, 
instead of incrementally loading more and more of the page until eventually 
it's all there.
* It costs both the user and the web site bandwidth. Important to you, and 
important to at least your mobile users, who probably have metered *and* 
tightly capped data plans.
* In Firefox, at least, cache-control breaks image right-click save-as, 
because right-click save-as just copies the cached image normally, but if 
it's not cached instead tries to download it again. If that's combined with 
typical hotlinking blocking, the result tends to be errors or corrupt 
jpegs. To see this effect go to a Photobucket album, which serves either 
the image itself or a webpage with the image in it depending on referer and 
which also uses cache-control. If you right-click save-as the image you'll 
get a corrupt jpeg file that, when opened in Notepad, is actually full of 
HTML. Of course, blocking hotlinking and playing "clever" redirection 
tricks with referer is evil too, but cache-control compounds that evil a 
thousandfold. (The only correct use of referer is for log analysis to 
discover how your users navigate around your site. Using it to discriminate 
against users based on where they were linked in from is evil and wrong.)

Upshot: Use Ajax push/pull if you really want users to always see 
up-to-date information, and otherwise let them use "refresh" as 
appropriate. And don't get cute serving different content for the same URI 
depending on referer; that's just wrong. :)

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Re: ring - setting no-cache for everything?

[Colin Yates]

It is worth mentioning for others that if you are using 
ring.middleware.defaults/wrap-defaults then this middleware is already in play.

> On 19 Jun 2015, at 10:53, James Reeves  wrote:
> 
> Ring doesn't set any caching headers unless you add in middleware to do so.
> 
> The most common middleware is wrap-not-modified, which returns a 304 response 
> if the etag or last-modified dates indicate the resource hasn't been 
> modified. For resources in jar files, the last-modified date is set to the 
> modification date of the containing jar.
> 
> You could add some middleware to force the browser not to cache resources via 
> the cache-control header (see here 
> ),
>  or if this is just for development, then Chrome at least has a checkbox in 
> the developer tools for disabling caching.
> 
> - James
> 
> On 19 June 2015 at 10:00, Colin Yates  > wrote:
> Hi all, is there a quick way to disable caching for everything or 
> alternatively hash based on the contents of the resource. I am talking 
> specifically about CSS and javascript issues served from the JAR's class path?
> 
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Re: ring - setting no-cache for everything?

[Colin Yates]

Thanks James.

> On 19 Jun 2015, at 10:53, James Reeves  wrote:
> 
> Ring doesn't set any caching headers unless you add in middleware to do so.
> 
> The most common middleware is wrap-not-modified, which returns a 304 response 
> if the etag or last-modified dates indicate the resource hasn't been 
> modified. For resources in jar files, the last-modified date is set to the 
> modification date of the containing jar.
> 
> You could add some middleware to force the browser not to cache resources via 
> the cache-control header (see here 
> ),
>  or if this is just for development, then Chrome at least has a checkbox in 
> the developer tools for disabling caching.
> 
> - James
> 
> On 19 June 2015 at 10:00, Colin Yates  > wrote:
> Hi all, is there a quick way to disable caching for everything or 
> alternatively hash based on the contents of the resource. I am talking 
> specifically about CSS and javascript issues served from the JAR's class path?
> 
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Re: ring - setting no-cache for everything?

[James Reeves]

Ring doesn't set any caching headers unless you add in middleware to do so.

The most common middleware is wrap-not-modified, which returns a 304
response if the etag or last-modified dates indicate the resource hasn't
been modified. For resources in jar files, the last-modified date is set to
the modification date of the containing jar.

You could add some middleware to force the browser not to cache resources
via the cache-control header (see here
),
or if this is just for development, then Chrome at least has a checkbox in
the developer tools for disabling caching.

- James

On 19 June 2015 at 10:00, Colin Yates  wrote:

> Hi all, is there a quick way to disable caching for everything or
> alternatively hash based on the contents of the resource. I am talking
> specifically about CSS and javascript issues served from the JAR's class
> path?
>
> --
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ring - setting no-cache for everything?

[Colin Yates]

Hi all, is there a quick way to disable caching for everything or 
alternatively hash based on the contents of the resource. I am talking 
specifically about CSS and javascript issues served from the JAR's class 
path?

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