Lift Cookbook Avoiding CSS and JavaScript Caching - css

I am trying to use the data-lift="with-resource-id" parameter to the tag as described in the Lift Cookbook (http://cookbook.liftweb.net/#AvoidAssetCaching) to avoid asset caching in the browser. I've copied the code sample provided in the cookbook and modified it to my environment in order to introduce a random value into the parameter path.
My assets are stored in two root directories -- one called "css" and one called "js" for css and javascript respectively.
My code looks like:
import net.liftweb.http._
import net.liftweb.util._
object AssetCacheBuster {
def init() : Unit = {
val resourceId = Helpers.nextFuncName
LiftRules.attachResourceId = (path: String) => {
val PathRegex = """\/cached(\/css\/|\/js\/)(\S+)""".r
try {
val PathRegex(root, rest) = path
"/cached" + root + resourceId + "/" + rest
} catch {
case e: scala.MatchError => path
}
}
// Remove the cache/{resourceId} from the request if there is one
LiftRules.statelessRewrite.prepend( NamedPF("BrowserCacheAssist") {
case RewriteRequest(ParsePath("cached" :: "css" :: id :: file :: Nil, suffix, _, _), _, _) =>
RewriteResponse("css" :: file :: Nil, suffix)
case RewriteRequest(ParsePath("js" :: id :: file :: Nil, suffix, _, _), _, _) =>
RewriteResponse("js" :: file :: Nil, suffix)
})
}
}
I embed the css files, for example, with a call like:
<link data-lift="with-resource-id" rel="stylesheet" type="text/css" href="/cached/css/standard.css" />
The way I expect it to work is that attachResourceId logic will recognize embedded css files by the path "/cached/css" and inject a unique value in the path. So, for example, /cached/css/standard.css becomes /cached/css/F7017951738702RYSX0/standard.css. By inspecting elements using Chrome, I can see that this is indeed occurring, so I believe this is working as expected.
In the rewriting logic at the bottom, I expect it to look for requests that start with "/cached/css" and remove the /cached and unique id components. By tracing in the debugger, this too seems to be working. In the debugger I can see the the resulting url it is trying to rewrite is "/css/standard.css". And I can verify that if I enter this value in my browser URL, that content does indeed get served. Yet, the browser is showing an error (which I can see via Chrome's console) that the .css file is not found.

Here's what I think you're seeing...
Typically Lift will ignore CSS and JS files, and they will be served by the underlying engine, such as Jetty or Tomcat. That all happens outside of the Lift.
In this case, the end result of the rewrite is (as an example) a request for /css/standard.css, which is correct. But that final resource is being resolved inside Lift (because that's where we are -- the re-writes aren't HTTP redirects, so we stay inside the Lift pipeline). And because Lift doesn't serve those files by default, you're seeing a 404.
This is also why /css/standard.css works for you directly in a browser, because Lift is ignoring the request and Tomcat (or similar) is serving the content.
So why does it work in the book example? In that case, the example is for /classpath/jquery.js, and that URL is something Lift knows how to serve (via ResourceServer).
Here's what you can do about it....
I'd say the simple solution is to teach Lift how to serve up these files. You can do that by matching on the path you care about, and streaming back the content:
LiftRules.statelessDispatch.append {
case Req("css" :: file :: Nil, "css", _) =>
() => for (in <- LiftRules.getResource("/css/"+file+".css").map(_.openStream))
yield {
StreamingResponse(in, () => in.close, size = -1,
headers = Nil, cookies = Nil, code=200)
}
}
The same applies for the JS files, so you can probably generalise that code a little, or adjust to your needs. There's a chapter on streaming content in the Cookbook.
If that works for you, let me know, and I'll update the book.
As an aside, you might get more eyeballs on the problem if you post to the Lift mailing list. Don't get me wrong: I totally love Stackoverflow, but just due to the history of Lift, the mailing list is where you find users and committers looking at questions and problems.

Do you really need this complex logic?
By default, lift's resources will look like /static/css/example.css?F745187285965AXEHTY=_. In this case, if you use either nginx / jetty / tomcat / embedded jetty, you'll just see everything working.
The reason of that is that jetty/tomcat/nginx take the main resource example.css instead of example.css?asdfadf=_ if they can't find the latter. And the resource with ?asdfasdf=_ will be cached by the browser. So, the browser remembers the content of the full css address.
This is a common technique to avoid caching, BTW. It's not only Lift related. By default, developers update resources and write some HTML like: /static/css/example.css?14 where 14 is the virtual version of the resource. This way they don't have to rename the resource itself.

You need to inject the random value as a GET value not a path. Changing the path would result in not finding the file (unless you are dynamically writing the css file every time to the random location).
This can be done inline with javascript.
<script>
document.write("<link rel=\"stylesheet\"type=\"text/css\" href=\"/cached/css/standard.css?" + Math.random() + "\" />");
</script>

Related

Django Static Files Won't Reload On Firefox [duplicate]

I have noticed that some browsers (in particular, Firefox and Opera) are very zealous in using cached copies of .css and .js files, even between browser sessions. This leads to a problem when you update one of these files, but the user's browser keeps on using the cached copy.
What is the most elegant way of forcing the user's browser to reload the file when it has changed?
Ideally, the solution would not force the browser to reload the file on every visit to the page.
I have found John Millikin's and da5id's suggestion to be useful. It turns out there is a term for this: auto-versioning.
I have posted a new answer below which is a combination of my original solution and John's suggestion.
Another idea that was suggested by SCdF would be to append a bogus query string to the file. (Some Python code, to automatically use the timestamp as a bogus query string, was submitted by pi..)
However, there is some discussion as to whether or not the browser would cache a file with a query string. (Remember, we want the browser to cache the file and use it on future visits. We only want it to fetch the file again when it has changed.)
This solution is written in PHP, but it should be easily adapted to other languages.
The original .htaccess regex can cause problems with files like json-1.3.js. The solution is to only rewrite if there are exactly 10 digits at the end. (Because 10 digits covers all timestamps from 9/9/2001 to 11/20/2286.)
First, we use the following rewrite rule in .htaccess:
RewriteEngine on
RewriteRule ^(.*)\.[\d]{10}\.(css|js)$ $1.$2 [L]
Now, we write the following PHP function:
/**
* Given a file, i.e. /css/base.css, replaces it with a string containing the
* file's mtime, i.e. /css/base.1221534296.css.
*
* #param $file The file to be loaded. Must be an absolute path (i.e.
* starting with slash).
*/
function auto_version($file)
{
if(strpos($file, '/') !== 0 || !file_exists($_SERVER['DOCUMENT_ROOT'] . $file))
return $file;
$mtime = filemtime($_SERVER['DOCUMENT_ROOT'] . $file);
return preg_replace('{\\.([^./]+)$}', ".$mtime.\$1", $file);
}
Now, wherever you include your CSS, change it from this:
<link rel="stylesheet" href="/css/base.css" type="text/css" />
To this:
<link rel="stylesheet" href="<?php echo auto_version('/css/base.css'); ?>" type="text/css" />
This way, you never have to modify the link tag again, and the user will always see the latest CSS. The browser will be able to cache the CSS file, but when you make any changes to your CSS the browser will see this as a new URL, so it won't use the cached copy.
This can also work with images, favicons, and JavaScript. Basically anything that is not dynamically generated.
Simple Client-side Technique
In general, caching is good... So there are a couple of techniques, depending on whether you're fixing the problem for yourself as you develop a website, or whether you're trying to control cache in a production environment.
General visitors to your website won't have the same experience that you're having when you're developing the site. Since the average visitor comes to the site less frequently (maybe only a few times each month, unless you're a Google or hi5 Networks), then they are less likely to have your files in cache, and that may be enough.
If you want to force a new version into the browser, you can always add a query string to the request, and bump up the version number when you make major changes:
<script src="/myJavascript.js?version=4"></script>
This will ensure that everyone gets the new file. It works because the browser looks at the URL of the file to determine whether it has a copy in cache. If your server isn't set up to do anything with the query string, it will be ignored, but the name will look like a new file to the browser.
On the other hand, if you're developing a website, you don't want to change the version number every time you save a change to your development version. That would be tedious.
So while you're developing your site, a good trick would be to automatically generate a query string parameter:
<!-- Development version: -->
<script>document.write('<script src="/myJavascript.js?dev=' + Math.floor(Math.random() * 100) + '"\><\/script>');</script>
Adding a query string to the request is a good way to version a resource, but for a simple website this may be unnecessary. And remember, caching is a good thing.
It's also worth noting that the browser isn't necessarily stingy about keeping files in cache. Browsers have policies for this sort of thing, and they are usually playing by the rules laid down in the HTTP specification. When a browser makes a request to a server, part of the response is an Expires header... a date which tells the browser how long it should be kept in cache. The next time the browser comes across a request for the same file, it sees that it has a copy in cache and looks to the Expires date to decide whether it should be used.
So believe it or not, it's actually your server that is making that browser cache so persistent. You could adjust your server settings and change the Expires headers, but the little technique I've written above is probably a much simpler way for you to go about it. Since caching is good, you usually want to set that date far into the future (a "Far-future Expires Header"), and use the technique described above to force a change.
If you're interested in more information on HTTP or how these requests are made, a good book is "High Performance Web Sites" by Steve Souders. It's a very good introduction to the subject.
Google's mod_pagespeed plugin for Apache will do auto-versioning for you. It's really slick.
It parses HTML on its way out of the webserver (works with PHP, Ruby on Rails, Python, static HTML -- anything) and rewrites links to CSS, JavaScript, image files so they include an id code. It serves up the files at the modified URLs with a very long cache control on them. When the files change, it automatically changes the URLs so the browser has to re-fetch them. It basically just works, without any changes to your code. It'll even minify your code on the way out too.
Instead of changing the version manually, I would recommend you use an MD5 hash of the actual CSS file.
So your URL would be something like
http://mysite.com/css/[md5_hash_here]/style.css
You could still use the rewrite rule to strip out the hash, but the advantage is that now you can set your cache policy to "cache forever", since if the URL is the same, that means that the file is unchanged.
You can then write a simple shell script that would compute the hash of the file and update your tag (you'd probably want to move it to a separate file for inclusion).
Simply run that script every time CSS changes and you're good. The browser will ONLY reload your files when they are altered. If you make an edit and then undo it, there's no pain in figuring out which version you need to return to in order for your visitors not to re-download.
I am not sure why you guys/gals are taking so much pain to implement this solution.
All you need to do if get the file's modified timestamp and append it as a querystring to the file.
In PHP I would do it as:
<link href="mycss.css?v=<?= filemtime('mycss.css') ?>" rel="stylesheet">
filemtime() is a PHP function that returns the file modified timestamp.
You can just put ?foo=1234 at the end of your CSS / JavaScript import, changing 1234 to be whatever you like. Have a look at the Stack Overflow HTML source for an example.
The idea there being that the ? parameters are discarded / ignored on the request anyway and you can change that number when you roll out a new version.
Note: There is some argument with regard to exactly how this affects caching. I believe the general gist of it is that GET requests, with or without parameters should be cachable, so the above solution should work.
However, it is down to both the web server to decide if it wants to adhere to that part of the spec and the browser the user uses, as it can just go right ahead and ask for a fresh version anyway.
I've heard this called "auto versioning". The most common method is to include the static file's modification time somewhere in the URL, and strip it out using rewrite handlers or URL configurations:
See also:
Automatic asset versioning in Django
Automatically Version Your CSS and JavaScript Files
The 30 or so existing answers are great advice for a circa 2008 website. However, when it comes to a modern, single-page application (SPA), it might be time to rethink some fundamental assumptions… specifically the idea that it is desirable for the web server to serve only the single, most recent version of a file.
Imagine you're a user that has version M of a SPA loaded into your browser:
Your CD pipeline deploys the new version N of the application onto the server
You navigate within the SPA, which sends an XMLHttpRequest (XHR) to the server to get /some.template
(Your browser hasn't refreshed the page, so you're still running version M)
The server responds with the contents of /some.template — do you want it to return version M or N of the template?
If the format of /some.template changed between versions M and N (or the file was renamed or whatever) you probably don't want version N of the template sent to the browser that's running the old version M of the parser.†
Web applications run into this issue when two conditions are met:
Resources are requested asynchronously some time after the initial page load
The application logic assumes things (that may change in future versions) about resource content
Once your application needs to serve up multiple versions in parallel, solving caching and "reloading" becomes trivial:
Install all site files into versioned directories: /v<release_tag_1>/…files…, /v<release_tag_2>/…files…
Set HTTP headers to let browsers cache files forever
(Or better yet, put everything in a CDN)
Update all <script> and <link> tags, etc. to point to that file in one of the versioned directories
That last step sounds tricky, as it could require calling a URL builder for every URL in your server-side or client-side code. Or you could just make clever use of the <base> tag and change the current version in one place.
† One way around this is to be aggressive about forcing the browser to reload everything when a new version is released. But for the sake of letting any in-progress operations to complete, it may still be easiest to support at least two versions in parallel: v-current and v-previous.
In Laravel (PHP) we can do it in the following clear and elegant way (using file modification timestamp):
<script src="{{ asset('/js/your.js?v='.filemtime('js/your.js')) }}"></script>
And similar for CSS
<link rel="stylesheet" href="{{asset('css/your.css?v='.filemtime('css/your.css'))}}">
Example HTML output (filemtime return time as as a Unix timestamp)
<link rel="stylesheet" href="assets/css/your.css?v=1577772366">
Don’t use foo.css?version=1!
Browsers aren't supposed to cache URLs with GET variables. According to http://www.thinkvitamin.com/features/webapps/serving-javascript-fast, though Internet Explorer and Firefox ignore this, Opera and Safari don't! Instead, use foo.v1234.css, and use rewrite rules to strip out the version number.
Here is a pure JavaScript solution
(function(){
// Match this timestamp with the release of your code
var lastVersioning = Date.UTC(2014, 11, 20, 2, 15, 10);
var lastCacheDateTime = localStorage.getItem('lastCacheDatetime');
if(lastCacheDateTime){
if(lastVersioning > lastCacheDateTime){
var reload = true;
}
}
localStorage.setItem('lastCacheDatetime', Date.now());
if(reload){
location.reload(true);
}
})();
The above will look for the last time the user visited your site. If the last visit was before you released new code, it uses location.reload(true) to force page refresh from server.
I usually have this as the very first script within the <head> so it's evaluated before any other content loads. If a reload needs to occurs, it's hardly noticeable to the user.
I am using local storage to store the last visit timestamp on the browser, but you can add cookies to the mix if you're looking to support older versions of IE.
The RewriteRule needs a small update for JavaScript or CSS files that contain a dot notation versioning at the end. E.g., json-1.3.js.
I added a dot negation class [^.] to the regex, so .number. is ignored.
RewriteRule ^(.*)\.[^.][\d]+\.(css|js)$ $1.$2 [L]
Interesting post. Having read all the answers here combined with the fact that I have never had any problems with "bogus" query strings (which I am unsure why everyone is so reluctant to use this) I guess the solution (which removes the need for Apache rewrite rules as in the accepted answer) is to compute a short hash of the CSS file contents (instead of the file datetime) as a bogus querystring.
This would result in the following:
<link rel="stylesheet" href="/css/base.css?[hash-here]" type="text/css" />
Of course, the datetime solutions also get the job done in the case of editing a CSS file, but I think it is about the CSS file content and not about the file datetime, so why get these mixed up?
For ASP.NET 4.5 and greater you can use script bundling.
The request http://localhost/MvcBM_time/bundles/AllMyScripts?v=r0sLDicvP58AIXN_mc3QdyVvVj5euZNzdsa2N1PKvb81 is for the bundle AllMyScripts and contains a query string pair v=r0sLDicvP58AIXN_mc3QdyVvVj5euZNzdsa2N1PKvb81. The query string v has a value token that is a unique identifier used for caching. As long as the bundle doesn't change, the ASP.NET application will request the AllMyScripts bundle using this token. If any file in the bundle changes, the ASP.NET optimization framework will generate a new token, guaranteeing that browser requests for the bundle will get the latest bundle.
There are other benefits to bundling, including increased performance on first-time page loads with minification.
For my development, I find that Chrome has a great solution.
https://superuser.com/a/512833
With developer tools open, simply long click the refresh button and let go once you hover over "Empty Cache and Hard Reload".
This is my best friend, and is a super lightweight way to get what you want!
Thanks to Kip for his perfect solution!
I extended it to use it as an Zend_view_Helper. Because my client run his page on a virtual host I also extended it for that.
/**
* Extend filepath with timestamp to force browser to
* automatically refresh them if they are updated
*
* This is based on Kip's version, but now
* also works on virtual hosts
* #link http://stackoverflow.com/questions/118884/what-is-an-elegant-way-to-force-browsers-to-reload-cached-css-js-files
*
* Usage:
* - extend your .htaccess file with
* # Route for My_View_Helper_AutoRefreshRewriter
* # which extends files with there timestamp so if these
* # are updated a automatic refresh should occur
* # RewriteRule ^(.*)\.[^.][\d]+\.(css|js)$ $1.$2 [L]
* - then use it in your view script like
* $this->headLink()->appendStylesheet( $this->autoRefreshRewriter($this->cssPath . 'default.css'));
*
*/
class My_View_Helper_AutoRefreshRewriter extends Zend_View_Helper_Abstract {
public function autoRefreshRewriter($filePath) {
if (strpos($filePath, '/') !== 0) {
// Path has no leading '/'
return $filePath;
} elseif (file_exists($_SERVER['DOCUMENT_ROOT'] . $filePath)) {
// File exists under normal path
// so build path based on this
$mtime = filemtime($_SERVER['DOCUMENT_ROOT'] . $filePath);
return preg_replace('{\\.([^./]+)$}', ".$mtime.\$1", $filePath);
} else {
// Fetch directory of index.php file (file from all others are included)
// and get only the directory
$indexFilePath = dirname(current(get_included_files()));
// Check if file exist relativ to index file
if (file_exists($indexFilePath . $filePath)) {
// Get timestamp based on this relativ path
$mtime = filemtime($indexFilePath . $filePath);
// Write generated timestamp to path
// but use old path not the relativ one
return preg_replace('{\\.([^./]+)$}', ".$mtime.\$1", $filePath);
} else {
return $filePath;
}
}
}
}
I have not found the client-side DOM approach creating the script node (or CSS) element dynamically:
<script>
var node = document.createElement("script");
node.type = "text/javascript";
node.src = 'test.js?' + Math.floor(Math.random()*999999999);
document.getElementsByTagName("head")[0].appendChild(node);
</script>
Say you have a file available at:
/styles/screen.css
You can either append a query parameter with version information onto the URI, e.g.:
/styles/screen.css?v=1234
Or you can prepend version information, e.g.:
/v/1234/styles/screen.css
IMHO, the second method is better for CSS files, because they can refer to images using relative URLs which means that if you specify a background-image like so:
body {
background-image: url('images/happy.gif');
}
Its URL will effectively be:
/v/1234/styles/images/happy.gif
This means that if you update the version number used, the server will treat this as a new resource and not use a cached version. If you base your version number on the Subversion, CVS, etc. revision this means that changes to images referenced in CSS files will be noticed. That isn't guaranteed with the first scheme, i.e. the URL images/happy.gif relative to /styles/screen.css?v=1235 is /styles/images/happy.gif which doesn't contain any version information.
I have implemented a caching solution using this technique with Java servlets and simply handle requests to /v/* with a servlet that delegates to the underlying resource (i.e. /styles/screen.css). In development mode I set caching headers that tell the client to always check the freshness of the resource with the server (this typically results in a 304 if you delegate to Tomcat's DefaultServlet and the .css, .js, etc. file hasn't changed) while in deployment mode I set headers that say "cache forever".
You could simply add some random number with the CSS and JavaScript URL like
example.css?randomNo = Math.random()
Google Chrome has the Hard Reload as well as the Empty Cache and Hard Reload option. You can click and hold the reload button (in Inspect Mode) to select one.
I recently solved this using Python. Here is the code (it should be easy to adopt to other languages):
def import_tag(pattern, name, **kw):
if name[0] == "/":
name = name[1:]
# Additional HTML attributes
attrs = ' '.join(['%s="%s"' % item for item in kw.items()])
try:
# Get the files modification time
mtime = os.stat(os.path.join('/documentroot', name)).st_mtime
include = "%s?%d" % (name, mtime)
# This is the same as sprintf(pattern, attrs, include) in other
# languages
return pattern % (attrs, include)
except:
# In case of error return the include without the added query
# parameter.
return pattern % (attrs, name)
def script(name, **kw):
return import_tag('<script %s src="/%s"></script>', name, **kw)
def stylesheet(name, **kw):
return import_tag('<link rel="stylesheet" type="text/css" %s href="/%s">', name, **kw)
This code basically appends the files time-stamp as a query parameter to the URL. The call of the following function
script("/main.css")
will result in
<link rel="stylesheet" type="text/css" href="/main.css?1221842734">
The advantage of course is that you do never have to change your HTML content again, touching the CSS file will automatically trigger a cache invalidation. It works very well and the overhead is not noticeable.
You can force a "session-wide caching" if you add the session-id as a spurious parameter of the JavaScript/CSS file:
<link rel="stylesheet" src="myStyles.css?ABCDEF12345sessionID" />
<script language="javascript" src="myCode.js?ABCDEF12345sessionID"></script>
If you want a version-wide caching, you could add some code to print the file date or similar. If you're using Java you can use a custom-tag to generate the link in an elegant way.
<link rel="stylesheet" src="myStyles.css?20080922_1020" />
<script language="javascript" src="myCode.js?20080922_1120"></script>
For ASP.NET I propose the following solution with advanced options (debug/release mode, versions):
Include JavaScript or CSS files this way:
<script type="text/javascript" src="Scripts/exampleScript<%=Global.JsPostfix%>" />
<link rel="stylesheet" type="text/css" href="Css/exampleCss<%=Global.CssPostfix%>" />
Global.JsPostfix and Global.CssPostfix are calculated by the following way in Global.asax:
protected void Application_Start(object sender, EventArgs e)
{
...
string jsVersion = ConfigurationManager.AppSettings["JsVersion"];
bool updateEveryAppStart = Convert.ToBoolean(ConfigurationManager.AppSettings["UpdateJsEveryAppStart"]);
int buildNumber = System.Reflection.Assembly.GetExecutingAssembly().GetName().Version.Revision;
JsPostfix = "";
#if !DEBUG
JsPostfix += ".min";
#endif
JsPostfix += ".js?" + jsVersion + "_" + buildNumber;
if (updateEveryAppStart)
{
Random rand = new Random();
JsPosfix += "_" + rand.Next();
}
...
}
If you're using Git and PHP, you can reload the script from the cache each time there is a change in the Git repository, using the following code:
exec('git rev-parse --verify HEAD 2> /dev/null', $gitLog);
echo ' <script src="/path/to/script.js"?v='.$gitLog[0].'></script>'.PHP_EOL;
Simply add this code where you want to do a hard reload (force the browser to reload cached CSS and JavaScript files):
$(window).load(function() {
location.reload(true);
});
Do this inside the .load, so it does not refresh like a loop.
For development: use a browser setting: for example, Chrome network tab has a disable cache option.
For production: append a unique query parameter to the request (for example, q?Date.now()) with a server-side rendering framework or pure JavaScript code.
// Pure JavaScript unique query parameter generation
//
//=== myfile.js
function hello() { console.log('hello') };
//=== end of file
<script type="text/javascript">
document.write('<script type="text/javascript" src="myfile.js?q=' + Date.now() + '">
// document.write is considered bad practice!
// We can't use hello() yet
</script>')
<script type="text/javascript">
hello();
</script>
For developers with this problem while developing and testing:
Remove caching briefly.
"keep caching consistent with the file" .. it's way too much hassle ..
Generally speaking, I don't mind loading more - even loading again files which did not change - on most projects - is practically irrelevant. While developing an application - we are mostly loading from disk, on localhost:port - so this increase in network traffic issue is not a deal breaking issue.
Most small projects are just playing around - they never end-up in production. So for them you don't need anything more...
As such if you use Chrome DevTools, you can follow this disable-caching approach like in the image below:
And if you have Firefox caching issues:
Do this only in development. You also need a mechanism to force reload for production, since your users will use old cache invalidated modules if you update your application frequently and you don't provide a dedicated cache synchronisation mechanism like the ones described in the answers above.
Yes, this information is already in previous answers, but I still needed to do a Google search to find it.
It seems all answers here suggest some sort of versioning in the naming scheme, which has its downsides.
Browsers should be well aware of what to cache and what not to cache by reading the web server's response, in particular the HTTP headers - for how long is this resource valid? Was this resource updated since I last retrieved it? etc.
If things are configured 'correctly', just updating the files of your application should (at some point) refresh the browser's caches. You can for example configure your web server to tell the browser to never cache files (which is a bad idea).
A more in-depth explanation of how that works is in How Web Caches Work.
Just use server-side code to add the date of the file... that way it will be cached and only reloaded when the file changes.
In ASP.NET:
<link rel="stylesheet" href="~/css/custom.css?d=#(System.Text.RegularExpressions.Regex.Replace(File.GetLastWriteTime(Server.MapPath("~/css/custom.css")).ToString(),"[^0-9]", ""))" />
<script type="text/javascript" src="~/js/custom.js?d=#(System.Text.RegularExpressions.Regex.Replace(File.GetLastWriteTime(Server.MapPath("~/js/custom.js")).ToString(),"[^0-9]", ""))"></script>
This can be simplified to:
<script src="<%= Page.ResolveClientUrlUnique("~/js/custom.js") %>" type="text/javascript"></script>
By adding an extension method to your project to extend Page:
public static class Extension_Methods
{
public static string ResolveClientUrlUnique(this System.Web.UI.Page oPg, string sRelPath)
{
string sFilePath = oPg.Server.MapPath(sRelPath);
string sLastDate = System.IO.File.GetLastWriteTime(sFilePath).ToString();
string sDateHashed = System.Text.RegularExpressions.Regex.Replace(sLastDate, "[^0-9]", "");
return oPg.ResolveClientUrl(sRelPath) + "?d=" + sDateHashed;
}
}
You can use SRI to break the browser cache. You only have to update your index.html file with the new SRI hash every time. When the browser loads the HTML and finds out the SRI hash on the HTML page didn't match that of the cached version of the resource, it will reload your resource from your servers. It also comes with a good side effect of bypassing cross-origin read blocking.
<script src="https://jessietessie.github.io/google-translate-token-generator/google_translate_token_generator.js" integrity="sha384-muTMBCWlaLhgTXLmflAEQVaaGwxYe1DYIf2fGdRkaAQeb4Usma/kqRWFWErr2BSi" crossorigin="anonymous"></script>

How to "package" other resources with deno

In deno you can load related modules or other code by just referencing the relative path to those ES6 modules. Deno will handle loading them appropriately. What's the way to do this for non-es6 modules? For example: say I wanted to include some custom css with my deno project? Deno doesn't allow doing import mycss from "./relative.css";.
Deno file operations do work for local files, but they're evaluated relative to the cwd not the current file, and they don't work for arbitrary URLs. fetch, on the other hand, should be perfect, but currently doesn't support file schemes and the decision isn't being actively considered. Combining these yields the only solution I can come up with, but I really don't like it:
async function loadLocal(relative: string): Promise<string> {
const url = new URL(relative, import.meta.url);
if (url.protocol === 'file:') {
return await Deno.readTextFile(url.pathname);
} else {
const resp = await fetch(url.href);
return await resp.text();
}
}
This seems like it should mostly work, but it seems like a terrible way to hack in something that I expected would be supported by design in deno. It also must be redeclared in each file, or have the callers URL passed in, although there might be a way to avoid that. It doesn't work on windows without modifying the path delimiter.
Update
Deno.emit seems close to what I would want, however for some reason it has different behavior than standard importing:
If the rootSpecifier is a relative path, then the current working directory of the Deno process will be used to resolve the specifier. (Not relative to the current module!)
It also still requires that the paths be to valid modules, instead of arbitrary text.
As #Zwiers pointed out, deno 1.6 now supports fetch with the file protocol, so this is now irrelevant.

Serving static files using Racket servlets

I'm trying to learn about servers using Racket, and I'm getting caught up on trying to use static assets. From this answer, I was able to include a static stylesheet like so:
#lang racket
(require web-server/servlet
web-server/servlet-env
web-server/configuration/responders)
(define (home req)
(response/xexpr
'(html
(head (link ([rel "stylesheet"] [type "text/css"] [href "/style.css"])))
(body
(span ([class "emph"]) "Hello, world!")))))
(define-values (dispatch input-url)
(dispatch-rules
[("home") home]
[("style.css") (λ (_) (file-response 200 #"OK" "style.css"))]))
(serve/servlet dispatch
#:servlet-regexp #rx""
#:servlet-path "/home"
#:server-root-path (current-directory))
However, I'm still confused as to how to do this in general, i.e. serving all files in #:extra-files-paths without making a dispatch rule for each of them. I tried Jay's advice and changed the dispatcher order in the definition of serve/servlet by moving the htdocs and extra-files-paths parts up (I probably shouldn't copy that whole thing here) and I broke the ability to resolve MIME types somehow. Overall it was a mess.
So any of these questions would be related/relevant to my problem (from less to more general):
Is there a better way to include static files using tools at the level of serve/servlet?
Can anyone outline specifically how I might rearrange the pieces in serve/servlet without breaking things?
Is there a better place than the docs to learn about how to use the lower level server tools in Racket? (I'm pretty new in this particular area so "learn more about servers" may be a valid response to this question)
It looks to me like the problem is your #:servlet-regexp, which is set to the empty regexp, meaning that it will match anything. One easy solution is to restrict this regexp so that it only matches the non-static assets; then, all of the other requests should be served from the #:extra-files-paths.
Perhaps there's some reason why you need to intercept all requests and handle them in your code? Not sure.

Laravel/blade caching css files

I am working on Nginx server, with PHP-FPM. I installed Laravel 4.1 and bootstrap v3.1.1., and here is the problem. For the last 30 minutes, I have been trying to change a css rule that I first declared to check boostrap.
.jumbotron{
background: red;
}
The first time it worked. The jumbotron container was red. So, I removed that css value and started working, but still no matter which browse I use, the container is red. I even checked the css file through the Google Chromes inspection tool, and it is showing me that first value when jumbotron had a background:red. I deleted the css file and renamed it and add new styles, I configured chrome not to cache pages. But Still the same value. I'm convinced now, that Laravel has kept a cache of the first style declaration.
Is there any way to disable this at all?
General explanation
When you access a Laravel Blade view, it will generate it to a temporary file so it doesn't have to process the Blade syntax every time you access to a view. These files are stored in app/storage/view with a filename that is the MD5 hash of the file path.
Usually when you change a view, Laravel regenerate these files automatically at the next view access and everything goes on. This is done by comparing the modification times of the generated file and the view's source file through the filemtime() function. Probably in your case there was a problem and the temporary file wasn't regenerated. In this case, you have to delete these files, so they can be regenerated. It doesn't harm anything, because they are autogenerated from your views and can be regenerated anytime. They are only for cache purposes.
Normally, they should be refreshed automatically, but you can delete these files anytime if they get stuck and you have problems like these, but as I said these should be just rare exceptions.
Code break down
All the following codes are from laravel/framerok/src/Illuminate/View/. I added some extra comments to the originals.
Get view
Starting from Engines/CompilerEngine.php we have the main code we need to understand the mechanics.
public function get($path, array $data = array())
{
// Push the path to the stack of the last compiled templates.
$this->lastCompiled[] = $path;
// If this given view has expired, which means it has simply been edited since
// it was last compiled, we will re-compile the views so we can evaluate a
// fresh copy of the view. We'll pass the compiler the path of the view.
if ($this->compiler->isExpired($path))
{
$this->compiler->compile($path);
}
// Return the MD5 hash of the path concatenated
// to the app's view storage folder path.
$compiled = $this->compiler->getCompiledPath($path);
// Once we have the path to the compiled file, we will evaluate the paths with
// typical PHP just like any other templates. We also keep a stack of views
// which have been rendered for right exception messages to be generated.
$results = $this->evaluatePath($compiled, $data);
// Remove last compiled path.
array_pop($this->lastCompiled);
return $results;
}
Check if regeneration required
This will be done in Compilers/Compiler.php. This is an important function. Depending on the result it will be decided whether the view should be recompiled. If this returns false instead of true that can be a reason for views not being regenerated.
public function isExpired($path)
{
$compiled = $this->getCompiledPath($path);
// If the compiled file doesn't exist we will indicate that the view is expired
// so that it can be re-compiled. Else, we will verify the last modification
// of the views is less than the modification times of the compiled views.
if ( ! $this->cachePath || ! $this->files->exists($compiled))
{
return true;
}
$lastModified = $this->files->lastModified($path);
return $lastModified >= $this->files->lastModified($compiled);
}
Regenerate view
If the view is expired it will be regenerated. In Compilers\BladeCompiler.php we see that the compiler will loop through all Blade keywords and finally give back a string that contains the compiled PHP code. Then it will check if the view storage path is set and save the file there with a filename that is the MD5 hash of the view's filename.
public function compile($path)
{
$contents = $this->compileString($this->files->get($path));
if ( ! is_null($this->cachePath))
{
$this->files->put($this->getCompiledPath($path), $contents);
}
}
Evaluate
Finally in Engines/PhpEngine.php the view is evaluated. It imports the data passed to the view with extract() and include the file with the passed path in a try and catch all exceptions with handleViewException() that throws the exception again. There are some output buffering too.
Same issue here. I am using VirtualBox with Shared Folders pointing to my document root.
This pointed me in the right direction:
https://stackoverflow.com/a/26583609/1036602
Which led me to this:
http://www.danhart.co.uk/blog/vagrant-virtualbox-modified-files-not-updating-via-nginx-apache
and this:
https://forums.virtualbox.org/viewtopic.php?f=1&t=24905
If you're mounting your local dev root via vboxsf Shared Folders, set EnableSendFile Off in your apache2.conf (or sendfile off if using Nginx).
For what it's worth and because this answer came up first in my google search...
I had the same problem. The CSS and JS files wouldn't update. Deleting the cache files didn't work. The timestamps were not the problem. The only way I could update them was to change the filename, load it directly to get the 404 error, and then change the name back to the original name.
In the end the problem was not related to Laravel or the browser cache at all. The problem was due to NginX using sendfile which doesn't work with remote file systems. In my case, I was using VirtualBox for the OS and the remote file system was vboxsf through Guest Additions.
I hope this saves someone else some time.
In Laravel 5.8+ you can use so:
The version method will automatically append a unique hash to the filenames of all compiled files, allowing for more convenient cache busting:
mix.js('resources/js/app.js', 'public/js').version();
After generating the versioned file, you won't know the exact file name. So, you should use Laravel's global mix function within your views to load the appropriately hashed asset. The mix function will automatically determine the current name of the hashed file:
<script src="{{ mix('/js/app.js') }}"></script>
full document: https://laravel.com/docs/5.8/mix

Request multiple S3 files into one request

Is there a way to get multiple files from S3 (or any CDN) in one request?
For example, I have four files on S3:
example.com/cdn/one.js
example.com/cdn/two.js
example.com/cdn/three.js
example.com/cdn/four.js
I would like to be able to request any combination of them at a time. I currently have to include them separately:
<script src="example.com/cdn/one.js" />
<script src="example.com/cdn/two.js" />
But I would like to include them as one request:
example.com/cdn/code.js?one&two
I've considered combining the needed combinations into single files, but there will be way too many combinations for that to be realistic. I've also considered combining all of them into one file, but that would be ridiculously large.
First of all: Your question is more a JS thing than related to S3 / CDNs in general. And to answer your question: You can't "combine" them in one http request.
If you don't want to concatenate and minify them you should take a look at RequireJS, which could handle loading of your scripts – it's async and won't block the browser from rendering.
This is a really great article about async loading: css-tricks.com - Thinking Async which will give you a better insight.
EDIT after comment:
You can in fact use PHP to concatenate & minify your JS files on the fly, but this will put additional load on your server and you'll loose the benefits you get from a CDN … Another approach would be using a build system, which packs everything before it goes into production.
For further information on this topic take a look at the following links:
PHP5 - minify
PHP5 - Assetic
How do I concatenate JavaScript files into one file?
To do on the fly minifaction on your dev system (if it's a Mac) you may want to try CodeKit.
Here is one way you could do that (assuming you just use one&two&three and note file=one&file=two&file=3):
function getJs() {
var url = window.location.toString();
var query = url.split("?");
var params = query.split("&");
// iterate through array of params and write JS
for (i=0; i<params.length; i++) {
var name = params[i] + ".js";
document.write("<script defer language='javascript' type='text/javascript' src='" + name + "'><\/sc" + "ript>");
}
}
This should load after the page is loaded. Then in in your HTML perhaps. I haven't tested this but should be what you're looking for I reckon.

Resources