I'm building a firefox add-on using the add-on sdk. I need to make a http request to a certain page and I want to handle the connection timeout but couldn't find anything in the api: https://addons.mozilla.org/en-US/developers/docs/sdk/latest/modules/sdk/request.html
What I'm actually looking is a callback in case the client couldn't connect to the server.
Is there a way to achieve this?
The SDK request will always call onComplete, when the request is considered done for the network. This means that onComplete is called in any case, disregarding if the request returned an error or a success.
In order to detect which error you've got, you need to check the Response object's (the object passed to the onComplete function) property "status" (response.status). It holds the status code for the request. To look up status codes, consider the list on the mozilla developer network. If the response status is 0, the request has failed completely and the user is probably offline, or the target couldn't be reached.
A timeout would either be a status code 504 or 0. The implementation would be similar to this:
var Request = require("sdk/request");
Request({
url: "http://foo.bar/request.target",
onComplete: function(response) {
if(response.status==0||response.status==504) {
// do connection timeout handling
}
// probably check for other status codes
else {
// assume the request went well
}
}
}).get();
I personally use a validation function on the request object, which returns me a number which depends whether I've got a correct response, an error from the web server or a connection issue (4xx and 0 status codes).
Related
I am using the TIdHTTP component and it's GET function.
The GET function sends a complete request, which is fine.
However I would like to spare/save some traffic from a GET response and only want to receive the Responsecode which is in the first "line" of a HTTP response.
Is there a possibility of disconnecting the connection in order to save traffic from any further content?
As mentioned, I only need the responsecode from a website.
I alternatively thought about using Indy's TCP component (with SSL IOHandler) and craft an own HTTP Request Header and then receive the responsecode and disconnect on success - but I don't know how to do that.
TIdHTTP has an OnHeadersAvailable event that is intended for this very task. It is triggered after the response headers have been read and before the body content is read, if any. It has a VContinue output parameter that you can set to False to cancel any further reading.
Update: Something I just discovered: When setting VContinue=False in the OnHeadersAvailable event, TIdHTTP will set Response.KeepAlive=False and skip reading the response body (OK so far), but after the response is done being processed, TIdHTTP checks the KeepAlive value, and the property getter returns True if the socket hasn't been closed on the server's end (HTTP 1.1 uses keep-alives by default). This causes TIdHTTP to not close its end of the socket, and will leave any response body unread. If you then re-use the same TIdHTTP object for a new HTTP request, it will end up processing any unread body data from the previous response before it sees thee response headers of the new request.
You can work around this issue by setting the Request.Connection property to 'close' before calling TIdHTTP.Get(). That tells the server to close its end of the socket connection after sending the response (although, I just found that when requesting an HTTPS url, especially after an HTTP request directs to HTTPS, TIdHTTP clears the Request.Connection value!). Or, simply call TIdHTTP.Disconnect() after TIdHTTP.Get() exits.
I have now updated TIdHTTP to:
no longer clear the Request.Connection when preparing an HTTPS request.
close its end of the socket connection if either:
OnHeadersAvailable returns VContinue=False
the Request.Connection property (or, if connected to a proxy, the Request.ProxyConnection property) has been set to 'close', regardless of the server's response.
Usually you would use TIdHttp.Head, because HEAD requests are intended for doing just that.
If the server does not accept HEAD requests like in OP's case, you can assign the OnWorkBegin event of your TIdHttp instance, and call TIdHttp(Sender).Disconnect; there. This immediately closes the connection, the download does not continue, but you still have the meta data like response code, content length etc.
I have a silex BootableProvider to check for some requirements on every request before executing calls to any of my end points. All works good, except that when I use the $app->abort('403', 'forbidden for some reason'); anywhere in the boot() method, the response always returns code 200. The 'forbidden' message is correctly displayed and execution is interrupted as expected fortunately, but not having a meaningful Status code on the response makes it hard/cumbersome to process these failure responses.
I'm using silex 2.0.4.
If i however, execute the $app->abort(...) from any of my endpoints which implement ControllerProviderInterface, in the same request thread, the responses have the correct response codes I specify in the abort, so I'm thinking it's a timing issue.
Any advise is greatly appreciated.
Sample Code:
class BootProvider implements BootableProviderInterface {
function boot(Application $app) {
$app->abort(403, 'not allowed');
}
}
...
$app->register(new My\Api\BootProvider());
I've tried passing headers to override the Status to no avail.
Thanks!
In you case you should get just exception Fatal error: Uncaught exception.... Service providers are booted before kernel handle cycle, so errors are not processed.
Try to add event listener or middleware that will be executed before controllers and will make all checks.
$app->before(function (Request $request, Application $app) {
$app->abort(403, 'not allowed');
});
http://silex.sensiolabs.org/doc/2.0/middlewares.html
If a POST request requires that i send four data elements in the body, like:
{
"name":abc,
"surname":xyz,
"contact_no":1234,
"address":random_value
}
What will happen if I miss out some of the elements, for example if I call the web service with elements like,
{
"name":abc,
"surname":xyz,
}
What error is the server likely to throw ? I am having this issue because I am making a API call and it's giving me a HTTP error 500, so I guess it's not an error on my part, but this is one doubt i wanted to clear. Thanks in advance.
Its depends on the service structure (if all fields are mandatory or not),
and HTTP error (500) returns to server error or (server or link) not found .
In Delphi, I'm using Indy's TIdHTTPWebBrokerBridge coupled with TIdHTTP to send/receive data via HTTP. On the Server, I don't have any fancy handling, I always just respond with a simple content stream. If there's any issues, I only return information about that issue in the response content (such as authentication failed, invalid request, etc.). So, on the client side, can I assume that every successful request I make to this server will always have a response code of 200 (OK)?
I'm wondering because on the client, the requests are wrapped inside functions which return just a boolean for the success of the request.
Inside this function:
IdHTTP.Get(SomeURL, AStream);
Result:= IdHTTP.ResponseCode = 200;
This function handles any and every request which could possibly fetch data. If there were any issues in the request, This function should return False. In my scenario, since I always return some sort of content on the server, would the client always receive a response code of 200 in this function?
I guess the real question is, if I always return some sort of content and handle all exceptions on the server, then will the server always return status code of 200 to each request?
"Does every successful HTTP request always return status code 200?"
See w3.org: HTTP/1.1 Status Code Definitions (RFC 2616)
The answer is No. All 2xx are considered successful.
That may depend on the HTTP method used.
Should your web-server application always return 200 upon success? That may as well depend on the request method and the signal it intends for the client . e.g.
for PUT method (emphasis is mine):
If an existing resource is modified, either the 200 (OK) or 204 (No
Content) response codes SHOULD be sent to indicate successful
completion of the request.
for POST method:
The action performed by the POST method might not result in a resource
that can be identified by a URI. In this case, either 200 (OK) or 204
(No Content) is the appropriate response status, depending on whether
or not the response includes an entity that describes the result.
If a resource has been created on the origin server, the response
SHOULD be 201 (Created) and contain an entity which describes the
status of the request and refers to the new resource, and a Location
header (see section 14.30). Responses to this method are not
cacheable, unless the response includes appropriate Cache-Control or
Expires header fields. However, the 303 (See Other) response can be
used to direct the user agent to retrieve a cacheable resource.
As you can learn from the RCF, every method SHOULD have it's own success status codes, depending on the implementation.
Your other question:
"can I assume that every successful request I make to this server will always have a response code of 200 (OK)?"
You can always expect Status code 200, if your web server always responds with Status 200. Your web server application controls what response it returns to the client.
That said, Status code 200 is the Standard response for successful HTTP requests (The actual response will depend on the request method used), and in the real world of web servers, SHOULD be set as default upon successful request, unless told otherwise (As explained in Remy's answer).
To answer your specific question:
can I assume that every successful request I make to this server will always have a response code of 200 (OK)?
The answer is Yes, because TIdHTTPWebBrokerBridge wraps TIdHTTPServer, which always sets the default response code to 200 for every request, unless you overwrite it with a different value yourself, or have your server do something that implicitly replies with a different response code (like Redirect() which uses 302, or SmartServeFile() which uses 304), or encounter an error that causes TIdHTTPServer to assign a 4xx or 5xx error response code.
However, in general, what others have told you is true. On the client side, you should handle any possible HTTP success response code, not just 200 by itself. Don't make any assumptions about the server implementation.
In fact, TIdHTTP already handles that for you. If TIdHTTP encounters a response code that it considers to be an error code, it will raise an EIdHTTPProtocolException exception into your code. So if you don't get an exception, assume the response is successful. You don't need to check the response code manually.
If there is a particular response code that normally raises an exception but you do not want it to, you can specify that value in the optional AIgnoreReplies parameter of TIdHTTP.Get() or TIdHTTP.DoRequest(). Or, if you are are using an up-to-date Indy 10 SVN revision, a new hoNoProtocolErrorException flag was recently added to the TIdHTTP.HTTPOptions property so the EIdHTTPProtocolException exception is not raised for any response code.
Successful resposes are 2xx List_of_HTTP_status_codes
i did the following. Process straight all 200`s and LOG exceptions. worked, not a single non 200 - except unauthorized and timeouts (password or sometimes unavaliable server). but many/all responses will be considered for a wide range of mainstream apps.
while (iRedo < 3) do begin
s := Self.HTTPComponent.Get( sUrl );
if self.HTTPComponent.ResponseCode = 200 then begin
break;
end;
// IDEIA - log what happend if not 200
logWhatHappend( s, HTTPComponent ); // then log content, headers, etc
inc( iRedo ); sleep( 5 );
end;
I'm implementing a REST API using ASP.NET MVC, and a little stumbling block has come up in the form of the Expect: 100-continue request header for requests with a post body.
RFC 2616 states that:
Upon receiving a request which
includes an Expect request-header
field with the "100-continue" expectation, an origin server MUST
either respond with 100 (Continue) status and continue to read
from the input stream, or respond with a final status code. The
origin server MUST NOT wait for the request body before sending
the 100 (Continue) response. If it responds with a final status
code, it MAY close the transport connection or it MAY continue
to read and discard the rest of the request. It MUST NOT
perform the requested method if it returns a final status code.
This sounds to me like I need to make two responses to the request, i.e. it needs to immediately send a HTTP 100 Continue response, and then continue reading from the original request stream (i.e. HttpContext.Request.InputStream) without ending the request, and then finally sending the resultant status code (for the sake of argument, lets say it's a 204 No Content result).
So, questions are:
Am I reading the specification right, that I need to make two responses to a request?
How can this be done in ASP.NET MVC?
w.r.t. (2) I have tried using the following code before proceeding to read the input stream...
HttpContext.Response.StatusCode = 100;
HttpContext.Response.Flush();
HttpContext.Response.Clear();
...but when I try to set the final 204 status code I get the error:
System.Web.HttpException: Server cannot set status after HTTP headers have been sent.
The .NET framework by default always sends the expect: 100-continue header for every HTTP 1.1 post. This behavior can be programmatically controlled per request via the System.Net.ServicePoint.Expect100Continue property like so:
HttpWebRequest httpReq = GetHttpWebRequestForPost();
httpReq.ServicePoint.Expect100Continue = false;
It can also be globally controlled programmatically:
System.Net.ServicePointManager.Expect100Continue = false;
...or globally through configuration:
<system.net>
<settings>
<servicePointManager expect100Continue="false"/>
</settings>
</system.net>
Thank you Lance Olson and Phil Haack for this info.
100-continue should be handled by IIS. Is there a reason why you want to do this explicitly?
IIS handles the 100.
That said, no it's not two responses. In HTTP, when the Expect: 100-continue comes in as part of the message headers, the client should be waiting until it receives the response before sending the content.
Because of the way asp.net is architected, you have little control over the output stream. Any data that gets written to the stream is automatically put in a 200 response with chunked encoding whenever you flush, be it that you're in buffered mode or not.
Sadly all this stuff is hidden away in internal methods all over the place, and the result is that if you rely on asp.net, as does MVC, you're pretty much unable to bypass it.
Wait till you try and access the input stream in a non-buffered way. A whole load of pain.
Seb