CODEWITHSUNDEEP
javavaadinvaadin7
Shankar Guru
Shankar Guru

Reputation: 1161

Any properties needs to be changed for multi user application

Please consider me as a novice and this is my first web app I am creating.

I am planning to develop a web application where the traffic I am expecting is around 50 users will access the application at a single time.

The webapp is developed with Vaadin (for UI) and respective business logic implemented with Java. DB used would be MySQL. The war will be deployed in Tomcat.

So, my question is do I need to modify anything in Tomcat properties or anywhere to make the web app as multi user application (i.e. each users need to access and use application as though they are only one using the application)?

I tried to access a prototype developed using Vaadin in both Chrome and Firefox and could see both sessions running without an impact on another.

But please let me know suggestions.

Upvotes: 2

Views: 130

Answers (3)

Basil Bourque
Basil Bourque

Reputation: 339669

Vaadin is built on top of Jakarta Servlet technology (formerly known as Java Servlet). See Wikipedia. Indeed, Vaadin is a servlet, a much bigger and more sophisticated servlet than most.

Within a Java Servlet container (engine) such as Apache Tomcat or Eclipse Jetty, any particular servlet has only a single instance running. If three requests from three users arrive at the same time, there are three threads running through that same single instance for that particular servlet. So a servlets are inherently a highly threaded environment.

If you share any variables or resources between those threads, you must be very careful. That means mandatory reading, rereading, and fierce study of the book Java Concurrency in Practice by Brian Goetz, et al.

Cover of the book titled Java Concurrency In Practice

While the Web and HTTP were designed to be stateless delivery of single documents, that original vision has been warped by the desire to make web apps. To maintain state, a servlet automatically maintains a session. Vaadin represents this session state in its VaadinSession object. All data in all the forms, along with business logic, running for each user is maintained as part of that session.

Depending on your particular Vaadin app, and when multiplied by the number of concurrent users, this may add to a large amount of memory. You should monitor your server to make sure you have enough available RAM on your server.

do I need to modify anything in Tomcat properties or anywhere to make the web app as multi user application (i.e. each users need to access and use application as though they are only one using the application)?

No, nothing for you to set or enable. Tracking the requests/responses and session for each user is the very purpose of a servlet container. From the moment it launches, every servlet container expects multiple users. As a Servlet, Vaadin is built to expect multiple users as well. The only trick is making your own code thread-safe, hence the book suggestion.

I tried to access a prototype developed using Vaadin in both Chrome and Firefox and could see both sessions running without an impact on another.

Concurrency problems can be very tricky to detect and debug. Often potential problems occur on the random chance of coincidental timing. You need to focus on properly designing your code in the first place, rather than relying on testing. Again, hence the book recommendation.

Of special note, since you mentioned using a database, is JDBC drivers. Deploying them in a Servlet environment can be tricky. Basically you need to not bundle them within your Vaadin web app WAR file. Instead, deploy the JDBC driver separately within a shared library folder within Tomcat. If using Maven to drive your project, direct Maven in the POM file to give the dependency for your JDBC driver a scope of provided. This has nothing to do with Vaadin specifically, it applies to all servlets. Search Stack Overflow as this issue has been extensively addressed.

Upvotes: 0

Joel
Joel

Reputation: 2404

You must keep in mind that even if tomcat and vaadin manage multiple sessions, your server application will have only 1 instance. So if you use singletons, static methods or fields, use them with care: they should never hold session-dependant content. Try to favour stateless methods over statefull.

Apart from that, there shouldn't be any problem.

Upvotes: 1

RP-
RP-

Reputation: 5837

It should not have any code changes if you handle the session and your business logic with statefulness properly.

There might be some configuration changes, like increasing the database connection pool size, it depends on what kind of connection pooling you are using and what is the default size etc.

Apart from that it should work just fine.

Upvotes: 1

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