We have a web site that does not have a favourite icon favicon.
Therefore, we get a lot of http 404 errors for the file favicon.ico.
For the functionality of the web site it does not make a difference.
But I was wondering if the system uses more time looking for a file that is not there, rather than returning a 304 not modified?
At max load we have ca. 15,000 concurrent connections across all frontend servers.
No, the performance difference is insignificant - if you don't want to have a favicon, I'd suggest creating a 0-byte /favicon.ico : the logs will stop complaining, and the browsers will behave as if there's no favicon.
Also, you could set a far future Expires header for your favicon - that way, the clients will only request it once, further reducing the load.
In terms of the load the request causes on the server, there is no difference.
In terms of network bandwidth, a valid 304 response will be a bit bigger, since you also have to include at least a Date and an Expires or ETag headers in the response.
If the idea is to send a response without content, then I think 204 No Content is more appropriate.
If you are absolutely sure that the web site will never ever have a favicon, you could use a 410 Gone response. That tells the client/browser to don't come back and ask again. It is also more likely to be cached by a proxy server than a 404.
Related
I have a web server which returns 200 OK with a bunch of set-cookies, and an HTML page which loads a bunch of scripts from the same server.
However, the subsequent loads that was spawned from that HTML page submits a different cookie on their HTTP request headers.
What could be causing that? Surely there's some policy I'm missing out on, but I don't see why it works on some pages and not others?
I'm using chrome as the browser, but this behavior also happened from iOS, so I'm guessing it's not browser specific.
So after a lot more reading and troubleshooting, it turns out that when you don't set a cookie path, it'll default to whatever path the original request set-cookie was sent to. And because my resource paths had a different path, the cookie was not sent.
Adding Path=/ fixed it for my issue. Of course, if you don't want your cookie to be accessible to all pages this is bad, but my web-server requires requests to come with cookies because they are sensitive data (for security reasons).
I know this question is asked for several times. But Still I am not clear about the concept. After reading many blogs and answers in SO what I got is,
Expiry headers are used when you don’t even want client (and proxies/caches) to make a request to
the server. In ETAG, the client will check with the server for the update, but in expiry
headers, the client will know, when to expire the file and check for an update, till then it
(browsers and proxies/caches) won’t bother server for checking the update.
So basically it say if we use expires/max-age header , It will not even check for the server for an updated file. So I thought to test it locally.
So I have created on simple html file including 2 js files and 1 image file. In IIS , I have set the Expires header to 2 days for the image folder. So as per my understanding , after getting the image file from the server once, for next request it should not send a request to the server to check the image file is modified or not.
But what I got is each time I refresh the page I see a request sent to the server and the server returns a 304 not modified status. But as per the specs/blogs I read It should not send a request to the server.
Someone please explain.
For what you have described
It is clear that ETag works as it expected to be by responding with 304 not modified for the request with If-None-Match field and ETag value.
so now the browser will load the image from cache instead of getting a new image from server costing bandwidth and time.
It seems that caching is disabled in your browser.That's why a new request has been sent before the cache expiration or else a request wouldn't have been sent in the first place.
Here is a wonderful article that explains how to find caching is disabled in browser programatically
Here is a another wonderful article that explains caching and Etag in depth.
Note:
Generally speaking
If you are using multiple servers with load balancer to host your website
then simple Etag configurations likely going to cost more bandwidth by having Etag in their header and it has no purpose which is checking if browser cache is valid.(Its always going to say invalid)
The important part is what you said: I refresh the page. In this case browser is trying provide you the fresh content so it has no other option than to contact server and check all resources. (There is cache control extension immutable which prevents this behaviour but is not widely used and implemented).
If you want to see behaviour of your browser which respects caches without reload you have to use "standard page entry". Either follow a link to the page or use another tab and write the page url to the url bar and press enter.
Caches respects expiration time so if document is not stale then is returned from the cache. If expired that ETag is used to validation of the resource (and after validation it is possible that resource is still not modified - 304 response)
When updating my website, I shift the server into "update" mode. Any requests for the main domain (example.com), result in a static page saying the site is being updated. But how does one respond to other requests, such as images, form submissions etc, which are normally valid, but are in the process of being updated ?
Which HTTP code should be returned so the client knows that the request is temporarily unavailable ?
4XX is not suitable, because it is not a user error.
5XX seems unsuitable, because there isn't an internal error. It is intentionally not serving any requests except for displaying a maintenance page
3XX seems unsuitable because the files (images, pages etc), are not moving anywhere. They are just temporarily inaccessible.
Perhaps to better understand what I'm saying, if you've ever visited the apple website during a Keynote, they take it offline for maintenance and display a yellow "sticky" image saying they will be back soon.
EDIT: For the main page I don't want to return a 503, because it won't display in the browser. But for other assets that are being updated it makes sense.
HTTP Error 503 - Service unavailable
The server is currently unavailable (because it is overloaded or down for maintenance). Generally, this is a temporary state.
I'm trying to optimize the loading time of a website. One of the things I've done is set a far-futures expires header for static content so that they are cached (as described by Yahoo). However, even though they are cached, the browser still sends a request and gets back a 304 (Not Modified) response for that resource.
I realize the 304 response is very small and probably has minimal performance effect, but is there a way to make it such that the browser will no longer send the request at all and just always use the cache for that resource?
You may want to try turning off ETags if you are sending both etags and expires. Some people suggest turning off eTags, especially if you have a load balancer.
Also, note, when you press reload on your page, Firefox WILL recheck all the resources. These will come back with 304's. If you press shift-reload, it will re-request all the resources without etags. So don't use the refresh/reload button to test your last-modifed/etag settings.
I'm trying to figure out if redirecting all www.example.com requests to example.com will be beneficial for caching or not, to which end I have 2 questions. SEO is not an issue here.
If the browser requests an image from the www URL (#1) and gets HTTP redirected to the www-less version (#2), will it store the result as cache value for just #2, or #1 as well.
The browser will occasionally ask for a new version of the image (and might get it, or a "Not Modified" response). There will then be an overhead for having to process the redirect every time. Is this overhead larger than the cost of storing two versions of the same image?
If the browser requests an image from the www URL (#1) and gets HTTP redirected to the www-less version (#2), will it store the result as cache value for just #2, or #1 as well.
#: See W3C Status Code Definitions for 301. If it's a 301 redirect, it 'should' be cacheable. See How to Redirect a Web Page (301).
The browser will occasionally ask for a new version of the image (and might get it, or a "Not Modified" response). There will then be an overhead for having to process the redirect every time. Is this overhead larger than the cost of storing two versions of the same image?
#: I'm not exactly sure of this, I suppose if the redirect is handled by the webserver (IIS, apache etc), the overhead should be minimal. Don't quote me though :P