`Cache-Control: no-cache` is generally used in a request header (sent from web browser to server) to force validation of the resource in the intermediate proxies.
If the client doesn&#39;t send this request to the server, intermediate proxies will return a copy of the content if it is fresh (has not expired according to `Expire` or `max-age` fields). `Cache-Control` directs these proxies to revalidate the copy even if it is fresh.


A client can send a `Cache-Control` header in a request in order to request specific caching behavior, such as revalidation, from the origin server and any intermediate proxy servers along the request path.

In addition to the above answer,&lt;br/&gt;
There might be a setup where cache chaining is implemented. In that case if the request comes to first cache where it is not satisfied, it might go to further chained cache.

Thus in order to get the response always from the server we include cache-control in request headers. This will insure that response is always from the server.

I have this code:

    res.sendfile( &#39;../../temp/index.html&#39; )

However, it throws this error:

    Error: Forbidden
    at SendStream.error (/Users/Oliver/Development/Personal/Reader/node_modules/express/node_modules/send/lib/send.js:145:16)
    at SendStream.pipe (/Users/Oliver/Development/Personal/Reader/node_modules/express/node_modules/send/lib/send.js:307:39)
    at ServerResponse.res.sendfile (/Users/Oliver/Development/Personal/Reader/node_modules/express/lib/response.js:339:8)
    at exports.boot (/Users/Oliver/Development/Personal/Reader/server/config/routes.js:18:9)
    at callbacks (/Users/Oliver/Development/Personal/Reader/node_modules/express/lib/router/index.js:161:37)
    at param (/Users/Oliver/Development/Personal/Reader/node_modules/express/lib/router/index.js:135:11)
    at pass (/Users/Oliver/Development/Personal/Reader/node_modules/express/lib/router/index.js:142:5)
    at Router._dispatch (/Users/Oliver/Development/Personal/Reader/node_modules/express/lib/router/index.js:170:5)
    at Object.router (/Users/Oliver/Development/Personal/Reader/node_modules/express/lib/router/index.js:33:10)
    at next (/Users/Oliver/Development/Personal/Reader/node_modules/express/node_modules/connect/lib/proto.js:199:15)

Can anyone tell me why this might be?

Express res.sendfile throwing forbidden error

Suppose we want to write a macro that defines an anonymous class with some type members or methods, and then creates an instance of that class that&#39;s statically typed as a structural type with those methods, etc. This is possible with the macro system in 2.10.0, and the type member part is extremely easy:

    object MacroExample extends ReflectionUtils {
      import scala.language.experimental.macros
      import scala.reflect.macros.Context

      def foo(name: String): Any = macro foo_impl
      def foo_impl(c: Context)(name: c.Expr[String]) = {
        import c.universe._
    
        val Literal(Constant(lit: String)) = name.tree
        val anon = newTypeName(c.fresh)
    
        c.Expr(Block(
          ClassDef(
            Modifiers(Flag.FINAL), anon, Nil, Template(
              Nil, emptyValDef, List(
                constructor(c.universe),
                TypeDef(Modifiers(), newTypeName(lit), Nil, TypeTree(typeOf[Int]))
              )
            )
          ),
          Apply(Select(New(Ident(anon)), nme.CONSTRUCTOR), Nil)
        ))
      }
    }

(Where `ReflectionUtils` is a [convenience trait][1] that provides my `constructor` method.)

This macro lets us specify the name of the anonymous class&#39;s type member as a string literal:

    scala&gt; MacroExample.foo(&quot;T&quot;)
    res0: AnyRef{type T = Int} = $1$$1@7da533f6

Note that it&#39;s appropriately typed. We can confirm that everything&#39;s working as expected:

    scala&gt; implicitly[res0.T =:= Int]
    res1: =:=[res0.T,Int] = &lt;function1&gt;

Now suppose that we try to do the same thing with a method:

    def bar(name: String): Any = macro bar_impl
    def bar_impl(c: Context)(name: c.Expr[String]) = {
      import c.universe._

      val Literal(Constant(lit: String)) = name.tree
      val anon = newTypeName(c.fresh)

      c.Expr(Block(
        ClassDef(
          Modifiers(Flag.FINAL), anon, Nil, Template(
            Nil, emptyValDef, List(
              constructor(c.universe),
              DefDef(
                Modifiers(), newTermName(lit), Nil, Nil, TypeTree(),
                c.literal(42).tree
              )
            )
          )
        ),
        Apply(Select(New(Ident(anon)), nme.CONSTRUCTOR), Nil)
      ))
    }

But when we try it out, we don&#39;t get a structural type:

    scala&gt; MacroExample.bar(&quot;test&quot;)
    res1: AnyRef = $1$$1@da12492

But if we stick an extra anonymous class in there:

    def baz(name: String): Any = macro baz_impl
    def baz_impl(c: Context)(name: c.Expr[String]) = {
      import c.universe._

      val Literal(Constant(lit: String)) = name.tree
      val anon = newTypeName(c.fresh)
      val wrapper = newTypeName(c.fresh)

      c.Expr(Block(
        ClassDef(
          Modifiers(), anon, Nil, Template(
            Nil, emptyValDef, List(
              constructor(c.universe),
              DefDef(
                Modifiers(), newTermName(lit), Nil, Nil, TypeTree(),
                c.literal(42).tree
              )
            )
          )
        ),
        ClassDef(
          Modifiers(Flag.FINAL), wrapper, Nil,
          Template(Ident(anon) :: Nil, emptyValDef, constructor(c.universe) :: Nil)
        ),
        Apply(Select(New(Ident(wrapper)), nme.CONSTRUCTOR), Nil)
      ))
    }

It works:

    scala&gt; MacroExample.baz(&quot;test&quot;)
    res0: AnyRef{def test: Int} = $2$$1@6663f834
    
    scala&gt; res0.test
    res1: Int = 42

This is extremely handy—it lets you do things like [this][2], for example—but I don&#39;t understand why it works, and the type member version works, but not `bar`. I know this [may not be defined behavior][3], but does it make any sense? Is there an cleaner way to get a structural type (with the methods on it) from a macro?


  [1]: https://gist.github.com/4552471
  [2]: https://github.com/travisbrown/rillit
  [3]: https://stackoverflow.com/q/13669974/334519

Getting a structural type with an anonymous class&#39;s methods from a macro

After reading about the `Cache-Control` field of the HTTP header, 

I understand that the `Cache-Control` field in the HTTP response header (server to client) specifies the directives for the intermediate proxy servers/client browser on how to handle the response, by sending different values for the `Cache-Control` field: `private`, `public`, `no-cache`, or `no-store` in the response header.

But I don&#39;t get why we need to send `Cache-Control` as a request header (client to server)?

Why is Cache-Control attribute sent in request header (client to server)?

After reading about the <code>Cache-Control</code> field of the HTTP header,
I understand that the <code>Cache-Control</code> field in the HTTP response header (server to client) specifies the directives for the intermediate proxy servers/client browser on how to handle the response, by sending different values for the <code>Cache-Control</code> field: <code>private</code>, <code>public</code>, <code>no-cache</code>, or <code>no-store</code> in the response header.
But I don't get why we need to send <code>Cache-Control</code> as a request header (client to server)?

I am getting stuck on something I think should be straight forward.  I need to take data from three different ajax calls, combine and process all three, and display the resulting array to the user.

In its simplest form my code looks like this:

    function giftControler ($scope, $http) {
      var names = $http.get(&quot;names.json&quot;),
          naughty = $http.get(&quot;naughty.json&quot;),
          nice = $http.get(&quot;nice.json&quot;);

I understand that my variables are assigned to promises, not actual results, and that the http request have been passed to the event queue. If I follow these with executable statements these variables will be undefined. I don&#39;t understand how to wait for these promises to resolve in order to continue processing them.

What I would like to do is immediately add the code:

          for (var i=0; i&lt;names.length; i++){
            for (var j=0; j&lt;nice.length; j++){
              if (names[i] === nice[j]){
                names[i] = names[i] + &quot;--Yay!!&quot;;
              };
            };
          };                
          $scope.kids = names;

The problem is that I can&#39;t just work off of the promises as if they were resolved arrays.  Javascript will see these for statements right after the http calls and try to execute them immediately, even though the promises have not been resolved.

Where I get stuck is that the [$http api][1] is giving me a promise object with three functions: `error`, `success` &amp; `then`.  I am not sure what to do with that in this case. I need a single success function for all three.  I need all three to resolve, then process the data in each, and then assign the result to an angular model.

I am sure I am missing something obvious, but does anyone have a suggestion? In my real work I have several ajax calls multiple data sources and a lot of processing (comparing values, sorting, concatenating, etc) to come up with one good data collection, but I can&#39;t get passed this issue.

Thanks,


  [1]: https://docs.angularjs.org/api/ng/service/$http

angular -- accessing data of multiple http calls - how to resolve the promises

In an HTTP **GET** request, parameters are sent as a ***query string***:

&lt;pre&gt;http://example.com/page&lt;b&gt;&lt;i&gt;?parameter=value&amp;also=another&lt;/i&gt;&lt;/b&gt;&lt;/pre&gt;

In an HTTP **POST** request, the parameters are not sent along with the URI.

***Where are the values?*** In the request header? In the request body? What does it look like?

How are parameters sent in an HTTP POST request?

I have a Node.js application that contains an http(s) server.

In a specific case, I need to shutdown this server programmatically. What I am currently doing is calling its `close()` function, but this does not help, as it waits for any kept alive connections to finish first.

So, basically, this shutdowns the server, but only after a minimum wait time of 120 seconds. But I want the server to shutdown immediately - even if this means breaking up with currently handled requests.

What I can not do is a simple

    process.exit();

as the server is only part of the application, and the rest of the application should remain running. What I am looking for is conceptually something such as `server.destroy();` or something like that.

How could I achieve this?

PS: The keep-alive timeout for connections is usually required, hence it is not a viable option to decrease this time.

How do I shutdown a Node.js http(s) server immediately?

Is there any way to get the http status of the current web page from javascript?

Spent some time searching on the web, but no luck at all... Seems like it&#39;s not possible, but wanted to check with Stack Overflow for maybe some fancy workaround.

(Providing it from the server as part of the response body is not acceptable, the status is supposed to be only available via the http header)

Get current page http status from javascript

I&#39;m trying to setup the HTTP client so that it uses a proxy, however I cannot quite understand how to do it. The documentation has multiple reference to &quot;proxy&quot; but none of the functions seem to allow to define the proxy. What I need is something like this:

    client := &amp;http.Client{}
    client.SetProxy(&quot;someip:someport&quot;) // pseudo code
    resp, err := client.Get(&quot;http://example.com&quot;) // do request through proxy

Any idea how to do this in Go?

Setting up proxy for HTTP client

I am making an API where in the access token for Facebook login will be sent in through header data.

How do I read this data from the header?

Reading header data in Ruby on Rails

I serve some of my files from my Github pages account. But when I check my &quot;js&quot; files&#39; headers, I saw following:

    Last-Modified:Sun, 10 Feb 2013 14:00:46 GMT 
    Expires:Sun, 10 Feb 2013 14:13:23 GMT
    Cache-Control:max-age=600


This file was commited 14 days ago. But I don&#39;t plan these files so frequent. So I need to make much bigger max-age value and change Last-Modified value to last commited date.

Is it possible to change headers of Github pages?

Github pages, HTTP headers

In Nginx, what&#39;s the difference between variables `$host` and `$http_host`.

What&#39;s the difference of $host and $http_host in Nginx

I am a novice to angular.js, and I am trying to add some headers to a request:

       var config = {headers: {
                &#39;Authorization&#39;: &#39;Basic d2VudHdvcnRobWFuOkNoYW5nZV9tZQ==&#39;,
                &#39;Accept&#39;: &#39;application/json;odata=verbose&#39;
            }
        };

       $http.get(&#39;https://www.example.com/ApplicationData.svc/Malls(1)/Retailers&#39;, config).success(successCallback).error(errorCallback);

I&#39;ve looked at all the documentation, and this seems to me like it should be correct.

When I use a local file for the URL in the `$http.get`, I see the following HTTP request on the network tab in Chrome:

    GET /app/data/offers.json HTTP/1.1
    Host: www.example.com
    Connection: keep-alive
    Cache-Control: max-age=0
    If-None-Match: &quot;0f0abc9026855b5938797878a03e6889&quot;
    Authorization: Basic Y2hhZHN0b25lbWFuOkNoYW5nZV9tZQ==
    Accept: application/json;odata=verbose
    X-Requested-With: XMLHttpRequest
    If-Modified-Since: Sun, 24 Mar 2013 15:58:55 GMT
    User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.22 (KHTML, like Gecko) Chrome/25.0.1364.172 Safari/537.22
    X-Testing: Testing
    Referer: http://www.example.com/app/index.html
    Accept-Encoding: gzip,deflate,sdch
    Accept-Language: en-US,en;q=0.8
    Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3

As you can see, both of the headers were added correctly. But when I change the URL to the one shown in the `$http.get` above (except using the real address, not example.com), then I get:

    OPTIONS /ApplicationData.svc/Malls(1) HTTP/1.1
    Host: www.datahost.net
    Connection: keep-alive
    Access-Control-Request-Method: GET
    Origin: http://mpon.site44.com
    User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.22 (KHTML, like Gecko) Chrome/25.0.1364.172 Safari/537.22
    Access-Control-Request-Headers: accept, origin, x-requested-with, authorization, x-testing
    Accept: */*
    Referer: http://mpon.site44.com/app/index.html
    Accept-Encoding: gzip,deflate,sdch
    Accept-Language: en-US,en;q=0.8
    Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3

The only difference in code between these two is one is for the first the URL is a local file, and for the second the URL is a remote server. If you look at the second Request header, there is no Authentication header, and the `Accept` appears to be using a default instead of the one specified. Also, the first line now says `OPTIONS` instead of `GET` (although `Access-Control-Request-Method` is `GET`).

Any idea what is wrong with the above code, or how to get the additional headers included using when not using a local file as a data source?

Adding a custom header to HTTP request using angular.js

I&#39;m building an analytic tool and I can currently get the user&#39;s IP address, browser and operating system from their user agent.

I&#39;m wondering if there is a possibility to detect the same user without using cookies or local storage? I&#39;m not expecting code examples here; just a simple hint of where to look further.

Forgot to mention that it would need to be cross-browser compatible if it&#39;s the same computer/device. Basically I&#39;m after device recognition not really the user.

Content Type	Original Author	Original Content on Stackoverflow
Question	Student	View Question on Stackoverflow
Solution 1 - Http	David	View Answer on Stackoverflow
Solution 2 - Http	bdash	View Answer on Stackoverflow
Solution 3 - Http	Loui	View Answer on Stackoverflow

Why is Cache-Control attribute sent in request header (client to server)?

Http Problem Overview

Http Solutions

Solution 1 - Http

Solution 2 - Http

Solution 3 - Http

Getting a structural type with an anonymous class's methods from a macro

Express res.sendfile throwing forbidden error

Attributions