I have read near 20 other posts about this particular error, but most seem to be issues with the code calling Response.Close or similar, which is not our case. I understand that this particular error means that typically a user browsed away from the web page or cancelled the request midway, but in our case we are getting this error without cancelling a request. I can observe the error just after a few seconds, the download just fails in the browser (both Chrome and IE, so it's not browser specific).
We have a web api controller that serves a file download.
[HttpGet]
public HttpResponseMessage Download()
{
//
// Enumerates a directory and returns a Read-only FileStream of the download
var stream = dataProvider.GetServerVersionAssemblyStream(configuration.DownloadDirectory, configuration.ServerVersion);
if (stream == null)
{
return new HttpResponseMessage(HttpStatusCode.NotFound);
}
var response = new HttpResponseMessage(HttpStatusCode.OK)
{
Content = new StreamContent(stream)
};
response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
response.Content.Headers.ContentDisposition.FileName = $"{configuration.ServerVersion}.exe";
response.Content.Headers.ContentType = new MediaTypeHeaderValue(MediaTypeNames.Application.Octet);
response.Content.Headers.ContentLength = stream.Length;
return response;
}
Is there something incorrect we are doing in our Download method, or is there something we need to tweak in IIS?
This happens sporadically. I can't observe a pattern, it works sometimes and other times it fails repeatedly.
The file download is about 150MB
The download is initiated from a hyperlink on our web page, there is no special calling code
The download is over HTTPS (HTTP is disabled)
The Web Api is hosted on Azure
It doesn't appear to be timing out, it can happen just after a second or two, so it's not hitting the default 30 second timeout values
I also noticed I can't seem to initiate multiple file downloads from the server at once, which is concerning. This needs to be able to serve 150+ businesses and multiple simultaneous downloads, so I'm concerned there is something we need to tweak in IIS or the Web Api.
I was able to finally fix our problem. For us it turned out to be a combination of two things: 1) we had several memory leaks and CPU intensive code in our Web Api that was impacting concurrent downloads, and 2) we ultimately resolved the issue by changing MinBytesPerSecond (see: https://blogs.msdn.microsoft.com/benjaminperkins/2013/02/01/its-not-iis/) to a lower value, or 0 to disable. We have not had an issue since.
I have a RESTful Web API that is running properly as I can test it with Fiddler. I see calls going through, I see responses coming back.
I am developing a tablet application that needs to use the Web API in order to fetch data or make updates in the repository.
My calls do not return and there is not a single trace in the Fiddler to show that my calls even reach the server.
The first call I need to make is to login. The URI would be this:
http://localhost:53060/api/user
This call would normally return some information about the user (such as group membership, level of authorization and so on). The Web API uses Windows Authentication, so the repository is able to resolve all these fields based on the credentials passed in. As I said, in Fiddler I see the three calls made to the URI as the authentication is negotiated between the caller and the server. The third call returns with a JSON object that contains all information generated from the repository as expected.
Now, moving to my client I have the following:
var webApiClient = new HttpClient(new HttpClientHandler()
{
UseDefaultCredentials = true
})
{
BaseAddress = new Uri("http://localhost:53060/")
};
webApiClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
HttpResponseMessage response = await webApiClient.GetAsync("api/user");
var userLoginInfo = await response.Content.ReadAsAsync<UserLoginInformation>();
My call to "GetAsync" never returns and, like I said, I see no trace of it in Fiddler.
Any idea of what I'm doing wrong?
Changing the URL where the Web API was exposed seemed to have fixed the problem. Thanks to #Nkosi for the suggestion.
For anyone stumbling onto this question and asking themselves how to change the URL of the Web API, there are two ways. If the simulator is running on the same machine with the Web API, the change has to be made in the "applicationhost.config" file for IIS Express. You can locate this file by right-clicking on the IIS Express icon in the Notification Area (the bottom right corner) and selecting show all websites. Highlight the desired Web API and it will show where the application host configuration file is located. In there, one needs to locate the following section:
<bindings>
<binding protocol="http" bindingInformation="*:53060:localhost" />
</bindings>
and replace the "localhost" name with the IP address of the machine where the Web API is running.
However, this approach will not work once you start testing your tablet app with a real device. IIS Express must be coerced into exposing the Web API to the outside world. I found an excellent node.js package that can help with that. It is called IISExpress-proxy.
I have built a complex AIR application which has been successfully running for quite some time of many PCs. Unfortunately, I have a plaguing problem with internet connectivity and I was wondering if anyone had encountered this issue before.
Every once in a while, the program will completely stop talking to the internet (all services start faulting). I wrote special code in my program to monitor the situation in which I use two different services to contact the same server.
The first service:
var req:URLRequest = new URLRequest("myURL.com");
this.urlMonitor = new URLMonitor(req, [200, 304]); // Acceptable status codes
this.urlMonitor.pollInterval = 60 * 1000; // Every minute
this.urlMonitor.addEventListener(StatusEvent.STATUS, onStatusChange);
this.urlMonitor.start();
private function onStatusChange(e:StatusEvent):void
{
if (this.urlMonitor.available)
{
pollStatusOnline = true;
Online = true;
}
else
{
pollStatusOnline = false;
Online = false;
}
}
The secondary method is a normal HTTP Service call:
checkInService = new HTTPService();
checkInService.method = "POST";
checkInService.addEventListener(ResultEvent.RESULT,sendResult);
checkInService.addEventListener(FaultEvent.FAULT, faultResult);
checkInService.addEventListener(InvokeEvent.INVOKE, invokeAttempt);
checkInService.url = "myURL.com";
checkInService.concurrency = Concurrency.LAST;
checkInService.send(params);
These two services point to the same location and work 98% of the time. Sometimes, after a few hours, I have noticed that both services no longer can connect to the website. The HTTP Service returns a StatusCode 0. I am able to open command prompt and ping the server directly with no problem from the PC which is failing. The services will not function again until the program is restarted.
I have been working on this issue for many months now without resolution. If anyone is able to even point me in a somewhat possible, maybe this might be the problem, possibly, direction, I would really appreciate it.
Thank you in advance.
Check the code value of the StatusEvent you receive from the URLMonitor - this might give more info than the HTTPService (you might also want to try passing a null value to URLMonitor constructor, to widen the acceptable status codes).
If you have access to the server(s?) in question, check their logs. Could the server config have changed such that it might now consider such frequent requests as flooding?
You should also be able to use an HTTP debugger like Fiddler or Charles on the client machine to see more information about the requests going out of your application.
As windows phone 8 provides us with this method for programmatically terminate an app, will there be any issue while app submission if we use this in app for terminating a page while there is no backentry in the navigation history?
There won't be any issue in certification when using this call, but make sure you have saved all data in your app when calling this, because this call effectively kills your app immediately - ApplicationClosing even handler won't be raised after it!
Why would you call Application.Terminate when navigating back with an empty back stack? Just let the app close itself. Seems a bit pointless to me to overuse Application.Terminate().
I can't say much about the new Terminate method, but I do have an app (NOTE: Not a game) that does the following at certain points
private void Kill()
{
new Microsoft.Xna.Framework.Game().Exit();
}
This app passed certification without any problems. This was an app for both WP7 and WP8 so I did not have the ability to use Terminate().
I'm looking for a way to create a simple HTML table that can be updated in real-time upon a database change event; specifically a new record added.
In other words, think of it like an executive dashboard. If a sale is made and a new line is added in a database (MySQL in my case) then the web page should "refresh" the table with the new line.
I have seen some information on the new using EVENT GATEWAY but all of the examples use Coldfusion as the "pusher" and not the "consumer". I would like to have Coldfusion both update / push an event to the gateway and also consume the response.
If this can be done using a combination of AJAX and CF please let me know!
I'm really just looking to understand where to get started with real-time updating.
Thank you in advance!!
EDIT / Explanation of selected answer:
I ended up going with #bpeterson76's answer because at the moment it was easiest to implement on a small scale. I really like his Datatables suggestion, and that's what I am using to update in close to real time.
As my site gets larger though (hopefully), I'm not sure if this will be a scalable solution as every user will be hitting a "listener" page and then subsequently querying my DB. My query is relatively simple, but I'm still worried about performance in the future.
In my opinion though, as HTML5 starts to become the web standard, the Web Sockets method suggested by #iKnowKungFoo is most likely the best approach. Comet with long polling is also a great idea, but it's a little cumbersome to implement / also seems to have some scaling issues.
So, let's hope web users start to adopt more modern browsers that support HTML5, because Web Sockets is a relatively easy and scalable way to get close to real time.
If you feel that I made the wrong decision please leave a comment.
Finally, here is some source code for it all:
Javascript:
note, this is a very simple implementation. It's only looking to see if the number of records in the current datatable has changed and if so update the table and throw an alert. The production code is much longer and more involved. This is just showing a simple way of getting a close to real-time update.
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.1/jquery.js"></script>
<script type="text/javascript" charset="utf-8">
var originalNumberOfRecsInDatatable = 0;
var oTable;
var setChecker = setInterval(checkIfNewRecordHasBeenAdded,5000); //5 second intervals
function checkIfNewRecordHasBeenAdded() {
//json object to post to CFM page
var postData = {
numberOfRecords: originalNumberOfRecsInDatatable
};
var ajaxResponse = $.ajax({
type: "post",
url: "./tabs/checkIfNewItemIsAvailable.cfm",
contentType: "application/json",
data: JSON.stringify( postData )
})
// When the response comes back, if update is available
//then re-draw the datatable and throw an alert to the user
ajaxResponse.then(
function( apiResponse ){
var obj = jQuery.parseJSON(apiResponse);
if (obj.isUpdateAvail == "Yes")
{
oTable = $('#MY_DATATABLE_ID').dataTable();
oTable.fnDraw(false);
originalNumberOfRecsInDatatable = obj.recordcount;
alert('A new line has been added!');
}
}
);
}
</script>
Coldfusion:
<cfset requestBody = toString( getHttpRequestData().content ) />
<!--- Double-check to make sure it's a JSON value. --->
<cfif isJSON( requestBody )>
<cfset deserializedResult = deserializeJSON( requestBody )>
<cfset numberOFRecords = #deserializedResult.originalNumberOfRecsInDatatable#>
<cfquery name="qCount" datasource="#Application.DBdsn#" username="#Application.DBusername#" password="#Application.DBpw#">
SELECT COUNT(ID) as total
FROM myTable
</cfquery>
<cfif #qCount.total# neq #variables.originalNumberOfRecsInDatatable#>
{"isUpdateAvail": "Yes", "recordcount": <cfoutput>#qCount.total#</cfoutput>}
<cfelse>
{"isUpdateAvail": "No"}
</cfif>
</cfif>
This isn't too difficult. The simple way would be to add via .append:
$( '#table > tbody:last').append('<tr id="id"><td>stuff</td></tr>');
Adding elements real-time isn't entirely possible. You'd have to run an Ajax query that updates in a loop to "catch" the change. So, not totally real-time, but very, very close to it. Your user really wouldn't notice the difference, though your server's load might.
But if you're going to get more involved, I'd suggest looking at DataTables. It gives you quite a few new features, including sorting, paging, filtering, limiting, searching, and ajax loading. From there, you could either add an element via ajax and refresh the table view, or simply append on via its API. I've been using DataTables in my app for some time now and they've been consistently cited as the number 1 feature that makes the immense amount of data usable.
--Edit --
Because it isn't obvious, to update the DataTable you call set your Datatables call to a variable:
var oTable = $('#selector').dataTable();
Then run this to do the update:
oTable.fnDraw(false);
UPDATE -- 5 years later, Feb 2016:
This is much more possible today than it was in 2011. New Javascript frameworks such as Backbone.js can connect directly to the database and trigger changes on UI elements including tables on change, update, or delete of data....it's one of these framework's primary benefits. Additionally, UI's can be fed real-time updates via socket connections to a web service, which can also then be caught and acted upon. While the technique described here still works, there are far more "live" ways of doing things today.
You can use SSE (Server Sent Events) a feature in HTML5.
Server-Sent Events (SSE) is a standard describing how servers can initiate data transmission towards clients once an initial client connection has been established. They are commonly used to send message updates or continuous data streams to a browser client and designed to enhance native, cross-browser streaming through a JavaScript API called EventSource, through which a client requests a particular URL in order to receive an event stream.
heres a simple example
http://www.w3schools.com/html/html5_serversentevents.asp
In MS SQL, you can attach a trigger to a table insert/delete/update event that can fire a stored proc to invoke a web service. If the web service is CF-based, you can, in turn, invoke a messaging service using event gateways. Anything listening to the gateway can be notified to refresh its contents. That said, you'd have to see if MySQL supports triggers and accessing web services via stored procedures. You'd also have to have some sort of component in your web app that's listening to the messaging gateway. It's easy to do in Adobe Flex applications, but I'm not sure if there are comparable components accessible in JavaScript.
While this answer does not come close to directly addressing your question, perhaps it will give you some ideas as to how to solve the problem using db triggers and CF messaging gateways.
M. McConnell
With "current" technologies, I think long polling with Ajax is your only choice. However, if you can use HTML5, you should take a look at WebSockets which gives you the functionality you want.
http://net.tutsplus.com/tutorials/javascript-ajax/start-using-html5-websockets-today/
WebSockets is a technique for two-way communication over one (TCP) socket, a type of PUSH technology. At the moment, it’s still being standardized by the W3C; however, the latest versions of Chrome and Safari have support for WebSockets.
http://html5demos.com/web-socket
Check out AJAX long polling.
Place to start Comet
No, you can't have any db code execute server side code. But you could write a service to poll the db periodically to see if a new record has been added then notify the code you have that needs pseudo real-time updates.
The browser can receive real-time updates via BOSH connection to Jabber/XMPP server. All bits and pieces can be found in this book http://professionalxmpp.com/ which I highly recommend. If you can anyhow send XMPP message upon record addition in your DB, then it is relatively easy to build the dashboard you want. You need strophe.js, Jabber/XMPP server (e.g. ejabberd), http server for proxying http-bind requests. All the details can be found in the book. A must read which I strongly believe will solve your problem.
The way I would achieve the notification is after the database update has been successfully committed I would publish an event that would tell any listening systems or even web pages that the change has occurred. I've detailed one way of doing this using an e-commerce solution in a recent blog post. The blog post shows how to trigger the event in ASP.NET but the same thing can easily be done in any other language since ultimately the trigger is performed via a REST API call.
The solution in this blog post uses Pusher but there's not reason why you couldn't install your own real-time server or use a Message Queue to communication between your app and the realtime server, which would then push the notification to the web page or client application.