We are developing an application for Web. Inside that application, to download a file, I have created a WCF Rest service that will download the files based on this link Download using WCF Rest. The purpose is to check for user authentication before downloading. I used streaming concept to download the file. It is now that I have found out few things
When the user downloads the file, he is not able to determine what are the file size and the time remaining. I analyzed and found out that the reason is because, it’s using the “Transfer Encoding: chunked” in the header so that the file will be downloaded in chunks. One of the advantages is that the memory consumption is less in the server even when there are many users downloading a file. So I thought of adding “Content-Length” header, but I found out that you can use only either one of the headers not both. So I was thinking how Hotmail and Gmail were downloading attachments. From my investigation, I found out that Hotmail uses chunking header whereas Gmail uses Content-length header. Also in the case of Gmail, it is also checking if the session is active or not then downloads the file accordingly. I want to achieve the following
a) Like Gmail, I want to check if the session is active or not and then downloads the files accordingly. What will be the method for me to implement it?
b) When downloading the file, I want to use Content-Length header instead of Chunked header. Also the memory consumption should be less. Can we achieve it in WCF Rest? If so how?
c) Is it possible for me to add a header in WCF that will display the file size in the browser Downloads window?
d) When downloading an inline images from WCF, I found out that the image after loading is not cached in local machine. I was thinking that once an image is shown in an HTML page, it will get automatically cached and the next time user visits the page, the image will load from cache instead from server. I want to cache the inline images to cache, what is the option that I can use for it? Are there any headers that I need to specify when downloading an inline image from server?
e) When I download a zip file using WCF in IPhone Chrome browser, it’s not downloading at all. But the same link works in Android Chrome browser. What could be the problem? Am I missing header in WCF?
Are there any methods that will achieve the above?
Regards,
Jollyguy
Related
I have a PWA which has been developed in ASP.net Core and hosted on an Azure App Service (Linux).
When a new version of the PWA was released, I found that devices failed to update without clearing the browser cache.
To resolve this, I discovered a tag helper called asp-append-version that will clear cache for a specific file. I also discovered that I can append the version of the src attribute that specifies the URL of a file to trigger the browser to retrieve the latest file. For example, src="/scripts/pwa.js?v=1". Each time I update the pwa.js file I would also change the version i.e. v=2.
I’ve now discovered that my PWA is caching other JavaScript files in my application which results in the app not working on devices that have been updated to the new version however failed to clear the cache on specific files.
I believed that if I didn’t specify any cache control headers such as Cache-Control that the browser would not cache any files however this appears not to be the case.
To resolve this issue, is the recommended approach to add the appropriate Cache-Control headers (Cache-Control, Pragma, and Expires) to prevent browser caching or should I only add the tag helper asp-append-version to for example scripts tags to auto clear cache for that specific file?
I would preferably like the browser to store for example images rather than going to the server each time to retrieve these. I believe setting the header Cache-Control: no-cache would work as this would check if the file has changed before retrieving the updated version?
Thanks.
Thanks # SteveSandersonMS for your insights, In your web server returns correct HTTP cache control headers, browsers will know not to re-use cached resources.
Refer here link 1 & link 2 for Cache control headers on Linux app service
For example, if you use the "ASP.NET Core hosted" version of the Blazor WebAssembly template, the server will return Cache-Control: no-cache headers which means the browser will always check with the server whether updated content is present (and this uses etags, so the server will return 304 meaning "keep using your cached content" if nothing has changed since the browser last updated its content).
If you use a different web server or service, you need to configure the web server to return correct caching headers. Blazor WebAssembly can't control or even influence that.
Refer here
User will upload the videos from browser which need to be stored on server and playback. First understanding from google suggest I need to go for HTTP live streaming(HLS) here.
But I am not sure how it works internally ?
There are three components in above workflow i.e. client/server/data store for saving and retrieving videos.
Save flow :
I believe I need to plugin the HLS client for sending the streaming data.
Does Client in itself divide the file into chunks while sending and maintain the chaining of these chunk where each chunks points to next one ? something like this as I believe server is dumb and will work in same fashion as http upload functionality and no other intelligence is required here ?
But not sure how HLS server side component works here i.e. Will it save as single file or single file is split in to multiple files and then saved on disk ?
I believe it store the file as single file like regular http upload file ?
Retrieval part
In normal regular http file download, client asks for file data and server sends the response back in chunks but all response chunks are sent back against the same request.
I believe in case of HLS , its pull based where client initiate the pull request for each stream request. In each chunk pull request client gets the file name of next chunk and send the request to serverthe relevant chunk from single file for each poll request etc ? So for server its kind of regular http file download request and all intelligence lies with client
Save flow: When you upload a video, it must be converted into HLS format. You can use FFMPEG to do that. You'll end up creating manifest files, and all the segments of the video.
Retrieval part:
The player will read the manifest file to know which segments to request. I've written a post on how HLS playback works with the manifest files: https://api.video/blog/video-trends/what-is-hls-video-streaming-and-how-does-it-work
I'm trying to add a test coverage badge to the Readme of a private repository on GitHub. Our continuous integration process saves out the image to a secured Google Cloud Storage bucket that's not accessible to the public, and should remain that way.
Google's authorization layer is smart enough that if I go to the URL for the image, I'm automatically redirected to the resource with a valid auto-generated signed URL.
E.g., if I go to http://storage.cloud.google.com/secret-files/mysecretfile.png, then if I'm logged in and allowed to view it, I'm automatically redirected to something like https://blahblah-apidata.googleusercontent.com/download/storage/v1/b/secret-files/o/mysecretfile.png?key=verylongkey, where I can load the image.
This seemed perfect. Reference the canonical path in the GitHub Readme, authenticated users see the image, unauthenticated users are still blocked, we don't have to make the file public, and we don't have to do anything complicated.
Except that GitHub is proxying the image request, meaning that it will always be unauthenticated. My browser is loading something like https://camo.githubusercontent.com/mysecretimage.png.
Is there a clever way to work around this? Or do I need to go back to the drawing board?
All images on github.com are proxied using the Camo image proxy. There are a couple reasons for this:
It preserves the privacy of users. It isn't possible for a document to track users by directing them to a different site or using cookies to track them.
It means images can be cached and served at an appropriate size.
GitHub can have a very strict content security policy that does not allow loading from untrusted sites, which means that any sort of accidental security problem (like an XSS) is a lot less likely to work.
Note the last part. Even if you found some sneaky way to get another image URL to render properly in the website, your browser wouldn't load it because it violates the Content-Security-Policy header the site sent, and moreover, your browser would tattle about that to the reporting URL that GitHub provided.
So any image URL you provide will need to be readable by GitHub's image proxy and it won't be possible to serve different content to different users.
I have an application it will upload every captured images to the server. Now I have to perform server performance testing. I have to verify how it will perform if 100 devices are trying to upload the photos to same server at a time.
You need to consider next few things:
Add a HTTP Header Manager with relevant User-Agent string to simulate mobile browser or application.
Make sure that POST request is being used and the "Use multipart/form-data for POST" box is checked.
See Upload and Download Scenarios with Apache JMeter guide for detailed walkthrough.
When the browser requests a website, any website from a HTTP server, which of the two parses the site's content in order to know which other files need to be included on the webpage?
What I mean is this:
the browser asks for the html file and then observers that it needs to import some external css files and HE is the one who requests them.
OR
the HTTP server when faced with a request for a website, parses (already knows) which sites need to be linked to a certain webpage and sends them alongside the html page?
I'm guessing the first case is the correct one, but if someone can confirm and maybe clarify it, I'd appreciate it.
It's all done by the client (which is usually a browser). When it sees <script>, <iframe>, <img>, <link>, etc. tags that reference other documents, it downloads them if necessary.
According to Wikipedia -
The primary function of a web server is to cater web page to the
request of clients using the Hypertext Transfer Protocol (HTTP). This
means delivery of HTML documents and any additional content that may
be included by a document, such as images, style sheets and scripts.
and
The primary purpose of a web browser is to bring information resources
to the user ("retrieval" or "fetching"), allowing them to view the
information ("display", "rendering"), and then access other
information ("navigation", "following links").
It is the Browser that parses the HTML and request for the associated contents.