Http caching - style.css?123 or style_123.css? - http

I'm currently playing around with a build / deployment script for minifying static resources. Following good practice I'd like to set an expire header far into the future for most of my javascript, stylesheet and images.
To my question, when one or more of the static files has changed clients should ask for the newest version of the file. Will adding something like /css/style.css ?1235 after the url be enough to trigger a new request? Or do I have to rename all my static files for each build (something like /css/style _12345.css)?
Update: Just to clarify, the reason that I'm asking is that I've noticed that a lot of other deployment scripts seems to take the "hard" path by renaming each file.

Will adding something like
/css/style.css ?1235 after the url be
enough to trigger a new request?
Yes, of course.
You can do it like this:
style.css?UNIXTIMESTAMP
where UNIXTIMESTAMP is the time when the file was created in unix timestamp format

RFC 2616 3.2 Uniform Resource Identifiers says:
As far as HTTP is concerned, Uniform Resource Identifiers are simply formatted strings which identify--via name, location, or any other characteristic--a resource.
So, http://foo/bar is a different resource to http://foo/bar?baz.
Some URIs are treated as equivalent, so http://foo/bar?baz is the same resource as http://foo/bar?BAZ (see 3.2.3 URI Comparison).
HTTP does contain some caching exceptions for handling the query part (see 13.9 Side Effects of GET and HEAD). I understand these to only apply to the exact same query.

if you can use mod_rewrite i add a rule like this:
RewriteRule ^/((.*)_[0-9]+(\.(?:js|css|swf).*))$ /$2$3 [NC,L]
which rewrites any javascript, css or flash file back to the original name so
/css/style_1234.css
gets rewritten back to
/css/style.css

Related

Should the server treat such endpoints as different? [duplicate]

When should a trailing slash be used in a URL? For example - should my URL look like /about-us/ or like /about-us?
I am fully aware of the SEO-related issues - duplicate content and the canonical thing; I'm trying to figure out which one I should use in the context of serving pages correctly alone.
For example, my colleague is thinking that a trailing slash at the end means it's a "folder" - a "directory", so this is not a correct style. But I think that without a slash in the end - it's not quite correct either, because it almost looks like a folder, but it isn't and it's not a normal file either, but a filename without extension.
Is there a proper way of knowing which to use?
It is not a question of preference. /base and /base/ have different semantics. In many cases, the difference is unimportant. But it is important when there are relative URLs.
child relative to /base/ is /base/child.
child relative to /base is (perhaps surprisingly) /child.
In my personal opinion trailing slashes are misused.
Basically the URL format came from the same UNIX format of files and folders, later on, on DOS systems, and finally, adapted for the web.
A typical URL for this book on a Unix-like operating system would be a file path such as file:///home/username/RomeoAndJuliet.pdf, identifying the electronic book saved in a file on a local hard disk.
Source: Wikipedia: Uniform Resource Identifier
Another good source to read: Wikipedia: URI Scheme
According to RFC 1738, which defined URLs in 1994, when resources contain references to other resources, they can use relative links to define the location of the second resource as if to say, "in the same place as this one except with the following relative path". It went on to say that such relative URLs are dependent on the original URL containing a hierarchical structure against which the relative link is based, and that the ftp, http,
and file URL schemes are examples of some that can be considered hierarchical, with the components of the hierarchy being separated by "/".
Source: Wikipedia Uniform Resource Locator (URL)
Also:
That is the question we hear often. Onward to the answers! Historically, it’s common for URLs with a trailing slash to indicate a directory, and those without a trailing slash to
denote a file:
http://example.com/foo/ (with trailing slash, conventionally a directory)
http://example.com/foo (without trailing slash, conventionally a file)
Source: Google WebMaster Central Blog - To slash or not to slash
Finally:
A slash at the end of the URL makes the address look "pretty".
A URL without a slash at the end and without an extension looks somewhat "weird".
You will never name your CSS file (for example) http://www.sample.com/stylesheet/ would you?
BUT I'm being a proponent of web best practices regardless of the environment.
It can be wonky and unclear, just as you said about the URL with no ext.
I'm always surprised by the extensive use of trailing slashes on non-directory URLs (WordPress among others). This really shouldn't be an either-or debate because putting a slash after a resource is semantically wrong. The web was designed to deliver addressable resources, and those addresses - URLs - were designed to emulate a *nix-style file-system hierarchy. In that context:
Slashes always denote directories, never files.
Files may be named anything (with or without extensions), but cannot contain or end with slashes.
Using these guidelines, it's wrong to put a slash after a non-directory resource.
That's not really a question of aesthetics, but indeed a technical difference. The directory thinking of it is totally correct and pretty much explaining everything. Let's work it out:
You are back in the stone age now or only serve static pages
You have a fixed directory structure on your web server and only static files like images, html and so on — no server side scripts or whatsoever.
A browser requests /index.htm, it exists and is delivered to the client. Later you have lots of - let's say - DVD movies reviewed and a html page for each of them in the /dvd/ directory. Now someone requests /dvd/adams_apples.htm and it is delivered because it is there.
At some day, someone just requests /dvd/ - which is a directory and the server is trying to figure out what to deliver. Besides access restrictions and so on there are two possibilities: Show the user the directory content (I bet you already have seen this somewhere) or show a default file (in Apache it is: DirectoryIndex: sets the file that Apache will serve if a directory is requested.)
So far so good, this is the expected case. It already shows the difference in handling, so let's get into it:
At 5:34am you made a mistake uploading your files
(Which is by the way completely understandable.) So, you did something entirely wrong and instead of uploading /dvd/the_big_lebowski.htm you uploaded that file as dvd (with no extension) to /.
Someone bookmarked your /dvd/ directory listing (of course you didn't want to create and always update that nifty index.htm) and is visiting your web-site. Directory content is delivered - all fine.
Someone heard of your list and is typing /dvd. And now it is screwed. Instead of your DVD directory listing the server finds a file with that name and is delivering your Big Lebowski file.
So, you delete that file and tell the guy to reload the page. Your server looks for the /dvd file, but it is gone. Most servers will then notice that there is a directory with that name and tell the client that what it was looking for is indeed somewhere else. The response will most likely be be:
Status Code:301 Moved Permanently with Location: http://[...]/dvd/
So, totally ignoring what you think about directories or files, the server only can handle such stuff and - unless told differently - decides for you about the meaning of "slash or not".
Finally after receiving this response, the client loads /dvd/ and everything is fine.
Is it fine? No.
"Just fine" is not good enough for you
You have some dynamic page where everything is passed to /index.php and gets processed. Everything worked quite good until now, but that entire thing starts to feel slower and you investigate.
Soon, you'll notice that /dvd/list is doing exactly the same: Redirecting to /dvd/list/ which is then internally translated into index.php?controller=dvd&action=list. One additional request - but even worse! customer/login redirects to customer/login/ which in turn redirects to the HTTPS URL of customer/login/. You end up having tons of unnecessary HTTP redirects (= additional requests) that make the user experience slower.
Most likely you have a default directory index here, too: index.php?controller=dvd with no action simply internally loads index.php?controller=dvd&action=list.
Summary:
If it ends with / it can never be a file. No server guessing.
Slash or no slash are entirely different meanings. There is a technical/resource difference between "slash or no slash", and you should be aware of it and use it accordingly. Just because the server most likely loads /dvd/index.htm - or loads the correct script stuff - when you say /dvd: It does it, but not because you made the right request. Which would have been /dvd/.
Omitting the slash even if you indeed mean the slashed version gives you an additional HTTP request penalty. Which is always bad (think of mobile latency) and has more weight than a "pretty URL" - especially since crawlers are not as dumb as SEOs believe or want you to believe ;)
When you make your URL /about-us/ (with the trailing slash), it's easy to start with a single file index.html and then later expand it and add more files (e.g. our-CEO-john-doe.jpg) or even build a hierarchy under it (e.g. /about-us/company/, /about-us/products/, etc.) as needed, without changing the published URL. This gives you a great flexibility.
Other answers here seem to favor omitting the trailing slash. There is one case in which a trailing slash will help with search engine optimization (SEO). That is the case that your document has what appears to be a file extension that is not .html. This becomes an issue with sites that are rating websites. They might choose between these two urls:
http://mysite.example.com/rated.example.com
http://mysite.example.com/rated.example.com/
In such a case, I would choose the one with the trailing slash. That is because the .com extension is an extension for Windows executable command files. Search engines and virus checkers often dislike URLs that appear that they may contain malware distributed through such mechanisms. The trailing slash seems to mitigate any concerns, allowing the page to rank in search engines and get by virus checkers.
If your URLs have no . in the file portion, then I would recommend omitting the trailing slash for simplicity.
Who says a file name needs an extension?? take a look on a *nix machine sometime...
I agree with your friend, no trailing slash.
From an SEO perspective, choosing whether or not to include a trailing slash at the end of a URL is irrelevant. These days, it is common to see examples of both on the web. A site will not be penalized either way, nor will this choice affect your website's search engine ranking or other SEO considerations.
Just choose a URL naming convention you prefer, and include a canonical meta tag in the <head> section of each webpage.
Search engines may consider a single webpage as two separate duplicate URLS when they encounter it with and without the trailing slash, ie example.com/about-us/ and example.com/about-us.
It is best practice to include a canonical meta tag on each page because you cannot control how other sites link to your URLs.
The canonical tag looks like this: <link rel="canonical" href="https://example.com/about-us" />. Using a canonical meta tag ensures that search engines only count each of your URLs once, regardless of whether other websites include a trailing slash when they link to your site.
The trailing slash does not matter for your root domain or subdomain. Google sees the two as equivalent.
But trailing slashes do matter for everything else because Google sees the two versions (one with a trailing slash and one without) as being different URLs.
Conventionally, a trailing slash (/) at the end of a URL meant that the URL was a folder or directory.
A URL without a trailing slash at the end used to mean that the URL was a file.
Read more
Google recommendation

Clear cache for JS and CSS only one time after release

I am working on .Net(C#) application. It's a quite old application and has classic Asp pages, Web Forms and MVC pages. And using single page application concept to load all these pages. All of them have different-different CSS and JS based on business logic they have.
Now the problem is, every time after our release we face same issue that is CSS and JS caching. I know there are couple of ways to deal with this issue, the most common is adding a version and change this version with every release. But the problem is we have thousands of such links so updating all of then I don't find it a solution that we should opt.
Another approach what we thought of is, we can have a module that intercept all the resource requests and we update the link for each CSS and JS file and add some version (what I mentioned in above paragraph). But the problem I can see here is, this will make application slow because of checking and executing some string (File path) manipulation code for each resource requests.
I am sure I am not the only one who is facing this problem, so if anyone can share their experience and approach to handle this problem with minimum changes in code.
As #tim suggested adding query string to the files will help you.
Considering the volume of changes required at your end, I think preparing a rewrite rule for .js and .css files (with pattern matching) and injecting the query string to target URL (with permanent redirection) will help you.
solution for similar query is available here
Please note that, with each build you might need to tweak the configuration as necessary.
What might help: it isn’t necessary to include a version number in your files. It is sufficient if a versionnumber exists in your link.
You could use a (fake) querystring for that. So instead of linking to your css or js file like “style.css” you could link to “style.css?version=1.02”. This querystring part is ignored, but the browser thinks it’s a new file.
Maybe you can go through all of your links one time; make them serverside (in case of webforms) and add this versionpart serverside based on the version of your build. Then for your next releases the problem is solved..

Putting dynamic CSS URLs in HTTP headers with Fastly CDN

I'm generating dynamic CSS URLs for cache-busting. I.e. they're in the format styles-thisisthecontenthash123.css.
I also want to use HTTP Link headers to load the files slightly faster. I.e. have the header Link: <styles-thisisthecontenthash123.css>; rel=stylesheet
I'm pretty sure it's possible to do this in Fastly using VCL, but I'm not familiar enough with the ecosystem to figure it out. The CSS URL is in index.html, which is cached. I'm thinking I can open index.html and maybe use regex to parse out the CSS URL. How would I do this?
If I'm understanding your question correctly, you want to include a link header for all requests for index.html. You can do that with Fastly, but if the URL for the CSS file is changing you're not going to be able to pull that info out with VCL (you can't inspect the response body).
You could use edge dictionaries and whenever your CSS filename changes, update the reference via the API.
Thing is, if you're going to make an API call whenever the file changes, might as well just keep the filename consistent (styles.css) and whenever you publish a new version send a cache invalidation (purge). Fastly will clear the cache in ~150ms, so you then all you have to do is add the header which is can be done in the Fastly web portal with a condition.

Serving virtual files in IIS

I have a page as part of my IIS 7 (ASP.NET) website which serves images from a database. It uses a querystring to select the image and sets the content type header appropriately (image/jpeg) so that, for example, image.aspx?ID=1234 will be displayed in the browser as a jpeg image.
What I want to do instead is offer a URI formed in a manner such as image/1234.jpg which will produce the same result. In other words, there is no actual file on the server named 1234.jpg, it's just the contents of a database record, but from the browser's perspective, it will appear as if there is such a file.
I'm sure this is possible, but I can't figure out how it's accomplished, or where to look for answers. I'm thinking it may be done with an ISAPI filter, but I haven't found an accessible path into the docs to know if that's even the correct basis for a solution.
Possibly the best option here would be to implement a URL rewrite rule that changes image/1234.jpg to image.aspx?ID=1234
You can find more on URL rewrite for IIS here.
If, for whatever reason, URL rewrite isn't an option to you, then another possible method might be to implement a custom 404 page. When your request to image/1234.jpg doesn't result in a real file, it'll end up there.
You should be able to detect the URI at that point and serve up the image.

Is it bad practice to rely on outbound rules for rewriting?

For the past few years, if I've wanted a URL of a page on a site rewritten I've put the rewritten URL into the link on the page.
E.g. If the page is /Product.aspx?filename=ProductA and it's rewritten to /Product/ProductA.aspx then I've put the following in my link:
...
However, with outbound rules I could just put the links in to the actual file paths, and rewrite with an outbound rule.
Is this a bad method? Would it cost the server unnessacery additional resources?
I would not consider this bad practice. Infact it affords you some additional flexibility as your mapping for friendly to real url's is all managed in one central location. If your seo team decide they want to change the url scheme, you dont have to pick through all the links on your site updating them- risking missing one!
One important limitation of the current version of the IIS rewrite module, is you cannot use outbound rewriting in conjunction with Static compression- However you can still use Dynamic compression. Static compression is nice because it will cache the compressed version of the page. See this article for instructions on getting url rewrite working with Dynamic compression: http://forums.iis.net/p/1165899/1950572.aspx

Resources