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Concurrent access to Scout application [message #1855584] Fri, 21 October 2022 12:57 Go to next message
Miloslav Frajdl is currently offline Miloslav FrajdlFriend
Messages: 48
Registered: June 2018
Member
Hi.
I have Scout application and I testing it.
I tried opening the page from several different computers and also from several different browser tabs at the same time. I found this:
When I have less than 5 accesses open, the app seems to work fine. During the sixth and subsequent accesses, page loading is significantly slowed down, it takes up to several minutes, sometimes the error "Initialization failed" also occurs. When I close one of the previously opened tabs, the loading in the newly opened tab is usually instantaneous again.

Unfortunately, I don't know Scout well enough to know where this problem might be coming from. Can anyone give me some advice on what to focus on? Where can the problem be?

The application runs on Linux under Tomcat and communicates with an Oracle database on the same machine. Unfortunately, I didn't install or configure the system, so I don't know the exact parameters at this point.

Thank you in advance.
Re: Concurrent access to Scout application [message #1855586 is a reply to message #1855584] Fri, 21 October 2022 14:41 Go to previous messageGo to next message
Arthur van Dorp is currently offline Arthur van DorpFriend
Messages: 48
Registered: October 2015
Member
Is your use case having many users with their own sessions using the system? That case is very well supported. Do you want to have dozens of tabs open in the same browser? That is less well supported as each tab will have a connection open to the server. As you have found out, having many tabs open slows down all the tabs. The reason is, that your browser only allows a few connections per domain or ip address at the same time. So tabs will have randomly closed their connections which leads to what you are seeing.
Re: Concurrent access to Scout application [message #1855588 is a reply to message #1855586] Fri, 21 October 2022 15:43 Go to previous messageGo to next message
Miloslav Frajdl is currently offline Miloslav FrajdlFriend
Messages: 48
Registered: June 2018
Member
Thank you for answer.

A typical use will be that multiple (up to tens, perhaps hundreds) of users can be accessing from different locations at one time. Data from the database will be loaded. Mostly in one tab. But I couldn't verify it other than trying it from one machine in multiple tabs (I have the ability to test it on a few machines at a time, which is not enough).

Unfortunately, I need some assurance that it won't crash in real-world conditions, or know what to do to prevent it from happening. Can you give me some advice in this regard?
Re: Concurrent access to Scout application [message #1856396 is a reply to message #1855588] Thu, 08 December 2022 12:20 Go to previous messageGo to next message
Beat Schwarzentrub is currently offline Beat SchwarzentrubFriend
Messages: 205
Registered: November 2010
Senior Member
Opening the application in 10 tabs in the same browser is not a good test. It's not a realistic scenario. There will be only one instead of 10 HTTP sessions, since the session cookie is shared between all tabs. You will also run into the max-connections-per-host limit enforced by the browser. This limit is quite low (I think 5 or 6 in Chrome, a bit higher in Firefox). Unfortunately, there is nothing you can do about this.

You also need to make sure that your application has enough resources (RAM, CPU). If you are running it behind a firewall or reverse proxy, check the connection limits. If you access the database, check the limits on the connection pool, the JDBC driver and the database itself. Generally, the resources available and the limits set should match the kind of application (small and simple vs. large and computation-heavy) and the number of users.

We have large Scout applications running with hundreds of concurrent users every day without any issues.

Regards,
Beat
Re: Concurrent access to Scout application [message #1862576 is a reply to message #1855584] Tue, 12 December 2023 11:23 Go to previous message
Matthias Villiger is currently offline Matthias VilligerFriend
Messages: 232
Registered: September 2011
Senior Member
Hi Miloslav

If you use a reverse-proxy, WAF or load-balancer in front of your Scout application (recommended), you could try to enable HTTP/2 and https (TLS) on it. Modern browsers will then automatically use HTTP/2 which supports TCP multiplexing. This should solve the issue of having multiple tabs to the same Scout application open on a client.

If users connect to a e.g. Tomcat directly, you can enable HTTP/2 and TLS there.

Scout version >= 24 will also enable HTTP/2 on the Jetty server by default.

Hope this helps
Mat
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