How does listeners work

What is meant by Dom? It defines the logical structure of documents and the way a document is accessed and manipulated. What is a event listener? An event listener is a procedure or function in a computer program that waits for an event to occur. The listener is programmed to react to an input or signal by calling the event's handler. The term event listener is often specific to Java and JavaScript.

Can I use passive event listeners? Event listeners created with the passive: true option cannot cancel preventDefault the events they receive. Primarily intended to be used with touch events and wheel events. Since they cannot prevent scrolls, passive event listeners allow the browser to perform optimizations that result in smoother scrolling. What is add event listener? The addEventListener method attaches an event handler to an element without overwriting existing event handlers.

You can add many event handlers of the same type to one element, i. What is useCapture? Definition there is: If true, useCapture indicates that the user wishes to initiate capture. In this case it has to act in a similar way as a dedicated server on Windows. The listener sends a redirect request to the client, who reconnects to the dispatcher.

Now it is very simple to understand a load balance in RAC environment as well. If the listener we are connected to decides to connect us to the local instance, it creates a new server process to which it hands-off or redirects the connection, and everything is exactly as in a single instance. If it decides to connect us to a remote instance, it will send a redirect request to the client to ask it to reconnect to a different node. Again, comments are very welcome, hope you enjoyed.

Hiee actually i wanted know that how many listeners we can configure is there any hard limit in oracle and also how many concurrent listener can run at one time…? Hi Max, There is no hard limit on the number of listeners, each will be a process in the operating system and you can configure and run as many as you want. The only thing you need to know is that the combination of IP and port must be unique per listener. Each listener can listens on more than a single IP and more than a single port.

I hope it helps. Your email address will not be published. Notify me of follow-up comments by email. Notify me of new posts by email. What does it mean? So no, it's not a polling pull mechanism, but the opposite - a push callback. This is an example of 'don't call us, we'll call you' programming.

Because everything in your code runs off a single thread the event loop you don't have to worry about synchronizing between different events - so your code is threadsafe. There is an event loop that is implemented into core of AWT. It receives all events and sends them to appropriate listeners. I think the UI implementation of the JComponent will fire call all registered events upon the user interacting with it I think.

For example, when a user clicks a JButton , the button or it's ui, or some other internal handler will lookup all registered ActionListeners and call their actionPerformed Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. But suppose I have a database service whcihs is running on single instance only. Inthis case how the connection establish? In this situation as per round robbin method if a connection paases to scan listener 2 whihs is ruuning on node 2.

Kishore, SCAN is a virtual network layer which is primary contact to the application. It works this way. SCAN is just a routing listener as per my experience and understanding. Mr pawan Kumar I love u … The way u explained it ….

I wasted much of my time in understanding the whole concept but u blow my eyes.. Thanks so much for the simple explanation spend so many time in understanding the scan listener and your explanation is so easy to understand. Thanks much.. Awesome stuff bro.. Impressed with your explanations.. Awesome Stuff bro.. Impressed with your explanations. I deployed exadata with port , but I see port is also configured with local listener,.

Please could you explain Regards Ramachandra. If I am having 16 nodes RAC than how it will work. After three nodes are occupied with three scan IPs how it will work for next connection and so on. SCAN listeners are logical listeners and you configure them to forward the request to any of the nodes.

But a scan listener can be associated with only one IP. So you have to take a call of whether increasing SCAN and utilise other nodes in the setup. Save my name, email, and website in this browser for the next time I comment. Currently you have JavaScript disabled. In order to post comments, please make sure JavaScript and Cookies are enabled, and reload the page. Click here for instructions on how to enable JavaScript in your browser. Oracle DBA. Pawan Kumar Yaddanapudi December 17, Thank you Bolla.

Normally our load on RAC1 and RAC2 takes load average 4,,but yesterday it took , What happend to it and it which cases it would be like that. Ankit Chanpuria March 10, Nice explanation , looking for some examples on administering cluster services…. Pawan Kumar Yaddanapudi March 10,