I have a service that always returns the same results for a given parameter. So naturally I would like to cache those results on the client.
Is there a way to introduce caching and other effect inside the WCF pipeline? Perhaps a custom binding class that could site between the client and the actual HTTP binding.
EDIT:
Just to be clear, I'm not talking about HTTP caching. The endpoint may not necessarily be HTTP and I am looking at far more effects than just caching. For example, one effect I need is to prevent multiple calls with the same parameters.
The WCF service can use Cache-Control directives in the HTTP header to say the client how it should use the client side cache. There are many options, which are the part of HTTP protocol. So you can for example define how long the client can just get the data from the local cache instead of making requests to the server. All clients implemented HTTP, like all web browsers, will follow the instructions. If your client use ajax requests to the WCF server, then the corresponding ajax call just return the data from the local cache.
Moreover one can implement many interesting caching scenarios. For example if one set "Cache-Control" to "max-age=0" (see here an example), then the client will always make revalidation of the cache by the server. Typically the server send so named "ETag" in the header together with the data. The "ETag" represent the MD5 hash or any other free information which will be changed if the data are changed. The client send automatically the "ETag", received previously from the server, together inside the header of the GET request to the server. The server can answer with the special response HTTP/1.1 304 Not Modified (instead of the typical HTTP/1.1 200 OK response) and with the body having no data. In the case the client will safe to get the data from the local cache.
I use "Cache-Control:max-age=0" additionally with Cache-Control: private which switch off caching the data on the proxy and declare that the data could be cached, but not shared with another users.
If you want read more about caching control with respect of HTTP headers I'll recommend you to read the following Caching Tutorial.
UPDATED: If you want implement some general purpouse caching you can use Microsoft Enterprise Library which contains Caching Application Block. The Microsoft Enterprise Library are published on the CodePlex with the source code. As an alternative in .NET 4.0 you can use System.Runtime.Caching. It can be used not only in ASP.NET (see here)
I continue recommend you to use HTTP binding with HTTP caching if it only possible in your environment. In the way you could save many time of development and receive at the end more simple, scalable and effective application. Because HTTP is so important, one implemened already so much useful things which you can use out-of-the-box. Caching is oly one from the features.
Related
ASP.NET Core 7 preview 6 just introduced Output caching which caches the endpoint output. However ASP.NET already has Response caching which seems to already provide the same feature.
What is the difference between the two and when should one be used and when should the other be used?
I was looking for aswers and trying to understand the differences between both, and really took a huge amount of time to understand the diferences between the two, and when (or not) to use each other.
As of November 2022 .Net 7 has been released, but the documentation is not very clear about the differences between them. The documentation and all videos only talk about the OutputCache as a replacement for the ResponseCache.
Also searching for OutputCache, it comes up with a lot of results from the old AspNet (Full framework) MVC 5.
So let´s clarify the differences and how we could use each other.
ResponseCache
First, the ResponseCache can be divided in 2 parts, that work independently and are different concepts of how and where the information would be cached. Let´s catch them up:
ResponseCacheAttribute: Basically it manipulates cache header like Vary, Cache-Control and others. It works telling the browsers or proxies to store (or not) the response content. This technique can reduce the number of requests done to the server, if used correctly.
The ResponseCache attribute sets response caching headers. Clients and
intermediate proxies should honor the headers for caching responses
under the HTTP 1.1 Caching specification
Response Caching Middleware: Basically it is used to make server side caching based on headers defined by ResponseCacheAttribute. Depending on the Request Headers sent to the server, the response would never be cached on server side.
Enables caching server responses based on HTTP cache headers.
Implements the standard HTTP caching semantics. Caches based on HTTP
cache headers like proxies do.
Is typically not beneficial for UI apps such as Razor Pages because
browsers generally set request headers that prevent caching. Output
caching, which is available in ASP.NET Core 7.0 and later, benefits UI
apps. With output caching, configuration decides what should be cached
independently of HTTP headers.
And at this point that OutputCache comes as a replacement for Response Caching Middleware.
OutputCache (available in ASP.NET Core 7.0 and later)
The OutputCache configuration decides what should be cached (server side) independently of HTTP headers. Also it comes with a lot of new features like cache entry invalidation, storage medium extensibility and others.
Conclusion
To take the benefits from both worlds you can use:
ResponseCacheAttribute: To manipulate response headers and enable the clients/proxies to store content on client side;
OutputCache: To store responses on server side and increase throuthput when responses are cached.
Both work independently. You can choose the one that fits best you application.
I haven't watch the video CodingMytra provided. But I think Output caching has some enhancements over Response caching. For example, you can specify a few seconds of caching.
I found a useful video, and it has some demos you learn more about the Output caching in .Net7. I think you can find the difference in this video.
We can find out why there is a need for Output caching in this github issue.
Link : Add support for Output Caching #27387
i am taking a course in web data so i understand that when we want to retrive a webpage on a browser we do a request response cycle using a communication protocol like http or https and a web service is a piece of software which i dont know where it is stored or how it is accessed so we can make two applications from different architectures communicate using a serialization language like XML or JSON i dont know what is the difference between a web service and http they are both a way to connect 2 different computers together and what confused me the more is api which according to the research i did is something used to access web services.
Let's begin with defining all the terms in your question since it's a bit all over the place.
HTTP (Hypertext-Transport Protocol): Allows you to transfer data over the web. Your browser will perform a request using HTTP to your web service.
Service: Any software that performs a specific task. We are interested in a web service, which is typically invoked via HTTP, however this can be anything else such as a Linux signal.
For now, let's assume it listens on HTTP.
API (Application Programming Interface): An interface by which all clients of your software have to abide by to use it. For example, in our web service, we can dictate an API so requests follow some convention.
Let's put it all together now.
You're making a website that wants to calculate the sum of two numbers. First, users will go to http://yoursite.com, and then the browser will always do an HTTP request to the domain yoursite.com on port 80. This will hit either your hosting site or some backend server.
Here you have the option if you're using something like GitHub pages to serve static content or you have some server (i.e., serverd) that will load a file and serve it.
So now the web-browser did an HTTP request and your webpage should load with an index.html. The user can now click on buttons, and everything looks good until they press Calculate -- what happens now?
We want to offload the computation to our backend. We perform an HTTP request to our backend server. We can define an API, that is in our case an endpoint, so that the HTTP request can hit it and it'll return the sum of the two numbers.
How do we return the result? We need to represent the data somehow, and this can be done through a body payload that is encoded as either JSON or XML. Again, this is a serialization format and can encode it in various different ways. JSON is nice because you can parse it easily with JavaScript on the client side.
Great -- so now we got an entire site and it works! Now we can do an HTTP request from our browser straight to the backend according to our setup endpoint and it should fulfill our request. Notice how now we're using the API from the backend server from within our site.
Other keywords you can may run into: CORS, AJAX, Apache Server; good luck!
I'm looking at various methods of RESTfully versioning APIs, and there are three major contenders. I believe I've all but settled on using X-API-Version. Putting that debate aside, one of the arguments against using that header, and custom headers in general, is that you can't control when headers are manipulated by proxy servers. I'm curious about what real-world examples there are of this, when it happens on the internet at large, or when it might be used on an intranet or server cluster, or when it might occur in any other situation.
The Guidelines for Web Content Transformation Proxies 1.0 is pretty much the definitive guide to understanding and predicting standards-compliant proxy server behavior. In terms of your question, the Proxy Forwarding of Request portion of the document might be especially helpful.
Each proxy software package and their individual configurations will be vary but, HTTP proxies are generally expected to follow the W3C Guidelines. Here are some highlights.
4.1 Proxy Forwarding of Request:
Other than to convert between HEAD and GET proxies must not alter request methods.
If the request contains a Cache-Control: no-transform directive, proxies must not alter the request other than to comply with transparent HTTP behavior defined in [RFC 2616 HTTP] sections section 14.9.5 and section 13.5.2 and to add header fields as described in 4.1.6 Additional HTTP Header Fields below.
4.1.3 Treatment of Requesters that are not Web browsers
Before altering aspects of HTTP requests and responses proxies need to take account of the fact that HTTP is used as a transport mechanism for many applications other than "Traditional Browsing". Increasingly browser based applications involve exchanges of data using XMLHttpRequest (see 4.2.8 Proxy Decision to Transform) and alteration of such exchanges is likely to cause misoperation.
4.1.5 Alteration of HTTP Header Field Values
Other than the modifications required by [RFC 2616 HTTP] proxies should not modify the values of header fields other than the User-Agent, Accept, Accept-Charset, Accept-Encoding, and Accept-Language header fields and must not delete header fields (see 4.1.5.5 Original Header Fields).
Other than to comply with transparent HTTP operation, proxies should not modify any request header fields unless one of the following applies:
the user would be prohibited from accessing content as a result of the server responding that the request is "unacceptable" (see 4.2.4 Server Rejection of HTTP Request);
the user has specifically requested a restructured desktop experience (see 4.1.5.3 User Selection of Restructured Experience);
the request is part of a sequence of requests comprising either included resources or linked resources on the same Web site (see 4.1.5.4 Sequence of Requests).
These circumstances are detailed in the following sections.
Note:
It is emphasized that requests must not be altered in the presence of Cache-Control: no-transform as described under 4.1.2 no-transform directive in Request.
The URI referred to in the request plays no part in determining whether or not to alter HTTP request header field values. In particular the patterns mentioned in 4.2.8 Proxy Decision to Transform are not material.
4.1.6 Additional HTTP Header Fields
Irrespective of the presence of a no-transform directive:
proxies should add the IP address of the initiator of the request to the end of a comma separated list in an X-Forwarded-For HTTP header field;
proxies must (in accordance with RFC 2616) include a Via HTTP header field (see 4.1.6.1 Proxy Treatment of Via Header Field).
There is also lots of information regarding the alteration of response headers and being able to detect those changes.
As for web service REST API versioning, there is a very lucid and useful SO thread at Best practices for API versioning? that should provide a wealth of helpful insight.
I hope all of this helps. Take care.
This isn't an answer per se, but rather a mention of real-world scenario.
My current environment uses a mixed CAS/AD solution in order to allow SSO across several different platforms (classic ASP, ASP.NET, J2EE, you name it).
Recently we identified some issues - part of the solution involves aggregating Auth tokens to HTTP headers whenever necessary to propagate credentials. One specific solution, making considerable heavy usage of cookies, was chained with an nginx implementation, whose HTTP header limit was set to 4KiB. If the cookie payload went over 2KiB, it would start leaking out headers.
Consequently, applications that had some sort of state/scope control being coordinated via HTTP headers (session cookies included) suddenly started behaving erratically.
On an interesting, related note, REST services using URL versioning (http://server/api/vX.X/resource, for example) were unaffected.
I would like to POST/PUT files on a web server with certain HTTP headers, and have the web server return those headers on each GET requests for those files.
Is there a way included inside the protocol to guarantee this, or is this behavior dependent on having a proprietary web server?
Thanks.
It depends on the web server. Most won't store data from request header fields.
I searched some of the similar questions, but haven't had a right solution yet.
I need to test a web cluster (which consists of many nodes, to provide some set of REST-ful APIs).
Not only HTTP GET request, I need to generate dynamic POST/PUT request in some manners. There are many tools, but I couldn't find right tool for generating POST/PUT request with non-static data.
Since I need to generate quite a large amount of requests, the load test tool should run in distributed nodes. In shorts:
ability to write the custom request for HTTP GET, POST and PUT. (any kind of major language such as Java, Ruby, etc. is okay)
ability to works in distributed Linux environment. (i.e. use multiple nodes to generate the requests)
ability to works on both HTTP and HTTPS
optional: generating nice-looking graphs
optional: construct a new request and queue for later (for state-ful API testing)
Based on certain condition, the request generator needs to parse JSON document in the HTTP body, and process it to make another GET/POST/PUT request.
Checkout Tsung, Faban, and Rain. Most likely, you have to edit some scripts within their frameworks.