Unable to find the Engine

RichP1

Hi,

I know that some people have had this error message before, but this is quite a strange scenario.

We have a Lightstreamer app running on a test server. For the last two weeks (and this morning) it has been running happily.

We restarted the Lightstreamer and web server (Tomcat) today. Now, when we try to connect to our Lightstreamer adapters we get:

ER bind Unable to find the Engine. Please check your configuration.

Nothing has been changed on the machine. The same is happening in all other environments that we've set up. It's as if a switch has been tripped to stop it from working!

Can anybody shed some light on what possible causes there are for this problem? It hints at some kind of licensing issue, what confuses us is that it just seems to be a problem with the web client.

This is the code we are using to bind. This has been working fine up until now!

var context = location.pathname.substring(0, location.pathname.substring(1).indexOf("/") + 1);
var cfgUrl = "lsengine_config.js";
lsPage.loadEngine(context + "/ls/lsengine.html?config=" + escape(cfgUrl));

Any help / suggestions will be much appreciated.

Cheers,

Richard

Mone

Hello,
your case is quite strange.

First of all, which web client version are you using? We advice you to upgrade to the latest version.
The loadEngine method was deprecated and now has been dropped, so your code should become like this:
[syntax="JS"]
var context = location.pathname.substring(0,location.pathname.substring(1).indexOf("/") + 1);
lsPage.createEngine("YourEngineName",context + "/ls/");
[/syntax]
then the code inside your lsengine_config.js file will be moved inside the onEngineCreation callback. See these links for further details:
http://www.lightstreamer.com/docs/client_web_jsdoc/PushPage.html#createEngine
http://www.lightstreamer.com/docs/client_web_jsdoc/PushPage.html#onEngineCreation

I assume that after the message the push on the page is not starting, right?
Does it happens on different browsers?

It hints at some kind of licensing issue

Do you mean that the client says you have an invalid license?
See here: http://www.lightstreamer.com/vb/faq.php?faq=sales#faq_licenses (read the response to "Can you explain the types of licenses (EVAL, DEV, DEMO, PROD) available for Allegro/Presto/Vivace editions?")

Maybe you updated the library some times ago but the old library was cached into tomcat so that restarting it made the application run with a different version that maybe (again) does not support anymore the syntax you used on the loadEngine call.

I'm looking forward to hearing from you.
Bye.

RichP1

Hi,

We've been developing for IE and haven't tested the app with Firefox.

So I tried bringing up the web page in Firefox ... and it works! So does IE 7. However IE 6 still throws the exception. The problem is that we're developing for IE 6!

Maybe a Windows update has done something to IE 6?

We're using web client 4.0.8. This has been in place since April and I don't think the libraries have ever been upgraded. We'll certainly look into upgrading to see if that helps.

The client doesn't mention an invalid license and the server is starting up correctly, so I'm not convinced that it's a licensing issue. Especially as the client works in Firefox/IE 7.

Thanks for your input,

Richard

RichP1

Ok, this looks like it's an issue with the latest Microsoft security update, which landed on Tuesday.

It looks as if some Active X controls have been disabled, this appears to have an effect on Lightstreamer, although I don't know what or why exactly.

We found a workaround by adding our webserver as a trusted site in IE6. Then we reset the custom settings for the trusted sites zone to 'Low' and enabled the option "Initialize and script ActiveX controls not marked as safe". The lightstreamer app is now working as it should.

I don't know quite how we're going to cope with this going forward, it may be that we recommend that the clients use Firefox or IE7, where this problem doesn't exist. For the meantime at least we have this somewhat awkward workaround :Smile_Ab:

Cheers,

Richard

Mone

Hello,

I've tried to reproduce the issue but I wasn't able to do so.
In the case that IE6 even if is showing "internet" on the status bar is behaving like "local intranet", can you check these demos?
http://app.lightstreamer.com/StockListDemoQ <-WC 4.0.8
http://app.lightstreamer.com/StockListDemo <- WC 4.3 alpha2
http://app.lightstreamer.com/WC3_StockListDemo <- WC 3

Do you see the issue there?
The Active X behavior should not affect our library because we have some fallback so that the library should work correctly without them.

Do you have a publicly available PoC showing the issue that I can see?
We'd like to understand the issue even if it is related to old client versions.

Thank you.

RichP1

Only one of those demos works for us - the one using client 4.3 alpha 2.

The other two versions fail in the same way that our application fails. Am I right in thinking that 4.2.2 is the latest client release? I'll try upgrading the client to see if that makes a difference.

Unfortunately we don't have a demo available to demonstrate the problem. Is there anything else we could give you that might help, IE settings, source code etc?

Thanks,

Richard

Mone

Hello,
I've tried the demos from outside the local LAN.
I've used a PC with Windows 2000 5.00.2195 service pack 4 updated with the latest updates available with windows update.
The browser is IE:

Version: 6.0.2800.1106
Update Versions:; SP1; Q822925; Q330994; Q828750;
Q824145; Q823353; Q833989; Q903235;

With this environment the three demos are working correctly, can you see any difference with your environment?

Yes, version 4.2.2 is the latest available. A demo with that version is available here: http://app.lightstreamer.com/StockListDemoA/