I have a Spring mvc application, and I'm using websockets to communicate a phisical device that sends data with an angular 2 front end.
the architecture is like this
device ----> Spring Mvc <-----angular 2 front end
I have a datasource listener that publish to a websocket topic everytime a new message appears and I consume that topic from angular.
My problem is that this is working properly in my local tomcat install but when I upload it to a faster server it doesn't.
The main problem I'm having is that is buffering the messages and is reaching the limit and closing the websocket session.
What I noticed checking the logs is that in my local server messages come 20 milliseconds after last one is finished but in the other server sometimes are coming at the same time and they are being buffered throwing the session limit exception.
I tried setting a higher buffer size.
Also tried a thread.sleep but it doesn't worked.
Do you have some ideas what can I do ? should I implement some kind of message queue ?
Thanks in advance
Related
I am in the process of building a Blazor Server-Side database application.
One of my requirements is that the user can open each website page in a different tab.
I have found that after 5 tabs are opened, any new pages are blocked from rendering. If I close one page, then the 6th page can render. Apparently this is due to the fact that browsers can support a limited number of SignalR connections at one time. I have read the limit for Chrome is 6 at a time (although I can only get 5 working).
Error Messages in Chrome:
Error: Connection disconnected with error 'Error: Server returned handshake error: Handshake was canceled.'
Error: Error: Server returned handshake error: Handshake was canceled.
Uncaught (in promise) Error: Cannot send data if the connection is not in the 'Connected' State.
at e.send (blazor.server.js:1)
Is there a solution for this problem? Or do I need to explore porting to Blazor Client?
I found the following article about this topic but not sure it it can be applied to a Blazor application:
SignalR and Browser Connection limit
It's a little scary as I have already built quite a bit of code, and don't want to spend too much time trying to hack a workaround.
I finally managed to replicate it on my internal network, it seems to have been resolved now that I have installed WebSockets.
Open Server Manager
Open Add Roles and Features
Expand WebServer (IIS)
Expand Application Development
Select WebSocket Protocol
After installing this, I opened 20 tabs of my blazor server application, each one on a different page and the issue did not re-occur (I also did a couple of refreshes on each to be sure).
I came across this after reading
Blazor works best when using WebSockets as the SignalR transport due to lower latency, reliability, and security. Long Polling is used by SignalR when WebSockets isn't available or when the app is explicitly configured to use Long Polling.
From the Blazor docs.
I really need your advice on this.
I have many TCP Client Devices. The Web application is going to be accessed by many users after an authentication.
The problem I need to solve is -
Create a TCP Listener for these client machines and that should be accessed by every user -
Solution I think - create a tcp connection on a page. Every user will create a new tcp connection from their device(local host) once the page is load . This is possible because every user pc is diferent so its going to be entirely different connection. But this solution is not going with problem 2.
The Machine broadcasts data every 30 seconds. So my application should be able to catch that data and update on the page.
This is I think is the main problem.
I know live data update on a web page can be done using SignalR. But SignalR does not connect with TCP Client machine directly. So what I was trying to do is -
1st - I tried making a WCF Service for TCP listener. WCF service will get data from machine and save into database from where signalR will do its job. But Whenever I am using wcf service my system is getting hang. So I dont know if its a right way to do that.
2nd - I tried creating Windows service as tcp listener. But I dont think its gonna work with web application.
To be very frank, I am not able to understand what should I do for this functionality.
From my side - I just want a TCP connection on application level that should be persistent, independent of user and should not close on any page reload.
Whenever that connection receives data it should be updated on every user's web browser without any reload.
I cannot use timer. It should be realtime.
According to what I found and understood, TCP connection is with a device so signalR can not be used directly. We need something else(like a service) in between to make it work with signalR.
So at the end, What should I do?
I hope I am clear enough to state my problem.
I just want to discuss so that my doubts can get clear and I may find the desired result at the end.
EDIT 1 :
In websocket, signalR... normally client refers to web browser.
Can a device(Multimedia control device) be a client similar to web browser for signalR?
We are using application request routing with 5 servers running IIS 7.5 and have just recently implemented a messaging system using SignalR in our application.
The SignalR connections are working as we expect (with the only drawback being that a message sent from one server doesn't get activated on the other 4).
The problem(?) we are having is that the Response Time of some requests on IIS that are shown in the load balancer (ARR) are coming up as 2-3 minutes sometimes, which I am assuming are because of connections using something like long-polling.
Our ARR is set to load balance using lowest response time, but it seems like this metric will be completely incorrect because of these SignalR connections. Is there any way to fix these connections so they don't get used in the ARR calculation for response time? Are we stuck having to move the SignalR messages to a separate server to avoid this type of thing (which admittedly would solve other things as well)?
I think the article below will help you. Try setting the "response buffer threshold" to 0 in ARR
http://matthewmanela.com/blog/using-signalr-in-an-arr-cluster/
I created a web application, here is the architecture :
Tomcat7 deploy on Amazon EC2
Granite DS
nginx to redirect HTTPS throught the tomct7 port 8181
Flex application that uses RemoteObject on a secure Channel.
Occasionaly, maybye when a request takes to long time, the execution of a RemoteObject in Flex triggers this error :
faultCode:Channel.Call.Failed faultString:'error' faultDetail:'NetConnection.Call.Failed: HTTP: Status 504'
But in the most time, the response of the Remote object is correct.
Could you tell me if Nginx could block something? Or if BlazeDs has a tomeout?Any clues?
Thank you very much
We've had this issue for a long time...problem is we haven't been able to find a repeatable way to force it to disconnect.
Here the most comprehensive list of things to try that i've been able to find:
http://www.bopit.in.th/2009/10/14/flex-channel-connect-failed-error-netconnection-call-failed-http-status-200/
We've tried a couple of those solutions and it seems like we're getting less client disconnects.
There also may be a problem with AVG's linkscanner hijacking the request as it leaves the browser, and then losing it somewhere. We had one machine in our shop that would disconnect when using IE, and since uninstalling AVG, it's never happened on that machine again.
another thing you could check is the socket timeout:
NetConnection.Call.Failed happening sporadically in Flex3/Tomcat/BlazeDS/Spring
and here is a thread on adobe forum about the issue:
http://forums.adobe.com/thread/552133
The blazeds server-side don't know the client-side has disconnected. But it seems to know the client-side's network has down.
In my case, I use the polling channel, I download the blazeds's source code, and add some log output in the FlexClientOutboundQueueProcessor.flush(MessageClient messageClient, List<Message> outboundQueue) method.
Then I saw this, when a client subscibed, the server-side invoke the FlexClientOutboundQueueProcessor.flush method every 3 seconds, and print what I added in the flush method, then I only shut down the client's network, not close browser(client and server with difference network), I found the server-side don't print anything, it means that the server-side don't invoke the flush method.
And after more than 30 minutes I recover the client's network, the server-side continue to invoke the flush method (the client's session isn't destroyed, if I close the client's browser, after 30 minutes the server-side will destroy the session).
Now, I have two questions,:
How the server-side know the client's network has downed? Is there a listener to monitor the client's network? If so, where is it? If not, how and where the codes?
It seems that the server-side will invoke the FlexClientOutboundQueueProcessor.flush method every 3 seconds, can this interval be configured? And where the code to start or stop this timing task?
Here answer on your first question: Detecting (on the server side) when a Flex client disconnects from BlazeDS destination
About configuration. You can configure in services-config.xml.
Example BlazeDS applications
Configuring channels with servlet-based endpoints