Qlik Fix: How to Fix Connection Lost Error

[Troy_Raney]

This video is part of the Qlik Fix Video series. If you found this video useful, check out the other Qlik Fix Videos.

This video explain how to configure a Web Socket Ping Interval setting on Qlik Sense to help resolve Connection Lost errors in the hub or script editor.

Here is a link to more information in the Support Knowledge Base:
https://qliksupport.force.com/articles/000055708

Attached is a downloadable .mp4 video file for those who cannot view YouTube videos.

[QFabian]

👍

@Troy_Raney 

[vegard_bakke]

To help you debug what might cause the Connection lost, I have forked and extended https://github.com/flautrup/QlikSenseWebsocketConnectivityTester,  by including additional inactive websockets.

Hopefully, the times that this web page reports, might help you identify the actual cause for why the websockets drop.

Download from: https://github.com/vbakke/QlikSenseWebsocketConnectivityTester

[JohnLBevan]

FYI: We also had this issue after introducing a NetScaler (load balancer / firewall) in front of the service; with the error showing the moment the site was loaded.

The cause there was down to how web sockets are treated by the NetScaler. Detail  and fix here: https://support.citrix.com/article/CTX206986

Their proposed solution:

Recommended the customer to enable "Websocket Connection" in default http profile or by creating a new http profile and enabling that option. Then bind the new http profile to Netscaler Gateway vserver.

[vegard_bakke]

Also, make sure you turn up the "kill idle websockets" from the default value. 
I think Netscaler terminates idle websocket after 2 minutes,  and Azure Gateway does the same after 4 minutes. 

[JohnLBevan]

@vegard_bakke good shout.  I had a look around whilst trying to find a good value to set that to, and stumbled across a TCP Keep Alive setting, which allows QlikSense to change how often the client connects / presumably setting this would satisfy the netscaler/gateway:

https://community.qlik.com/t5/Knowledge/Enabling-TCP-Keep-Alive-Functionality-In-Qlik-Sense/ta-p/171...

If I've understood the article correctly, for most browsers the default settings should mean that users don't hit this issue (as the client's keep alive values are smaller/more frequent than the loadbalancer/firewall's timeout).  However, users with FireFox may have issues (since the keep alive changes to once every 10 minutes after the first 2 mins), or if someone disabled the keep alive option by setting the `WebSocketPingInterval` to 0, or to a much higher value.

Setting `WebSocketPingInterval`  to `60 ` seems a suitable fix for all browsers.

Full details of where to find this setting / how to apply the fix on the above link.