Pull Technology
Pull technology is a type of communication that takes place over the Internet when a client initiates a transaction by requesting information from a server.
When you type a URL into the address bar on your browser, and your browser sends that request over the Internet to a server, you have just implemented pull technology. Pull technology is used anytime the transfer of information is initiated by a request sent from a client to a server. Push technology, on the other hand, is implemented any time a transfer of information is initiated by a server without waiting on a request from a client.
Pull technology is used to deliver content to many different types of applications and devices:
- Websites are delivered to a browser using pull technology after they are requested by the browser. Once the website has loaded, some content, such as automatically updated sports scores, may be pushed to the browser, but the initial request to load a webpage is always initiated by the client, which is a browser in this case.
- Web applications employ pull technology if they must be manually refreshed in order to display updated content.
- Computer, tablet, and smartphone applications employ pull technologies if they only check for updated content while they are being used.
Also See: Server, Push Technology, Client
Frequently Asked Questions
What are some examples of pull technologies?
Pull technology is part of the fundamental backdrop of the World Wide Web. Websites do not send themselves to web browsers unbidden. They are only sent after a browser requests the website from the server. While certain parts of the website may be updated automatically once the webpage has loaded, the request to load the page is always initiated by the client.
POP3 and IMAP, the protocols used by email applications to access mail servers, are pull technologies. They check in with the server every few minutes and download any email messages that are waiting for delivery on the mail server. In addition, RSS readers work by employing pull strategies, and check RSS feeds for updates periodically.
My email is delivered even if I don't tell my email application to check for new email. Doesn't that mean my email is a push technology?
In some cases, such as when you use an integrated webmail application like Gmail or the Gmail app on a smartphone, your email is being delivered on a push basis. However, if you're using any third-party application to access your email, and you have to set up a POP3 or IMAP connection to transfer the email, the application is using pull technology. The reason it appears that push technology is in play is that the application checks the mail server for new messages without your knowledge. So it may look like your email is being delivered in real-time by push technology, but in reality what's happening is that your application is sending a pull request to the server in the background every few seconds or minutes.
The same method is used by RSS readers. A website's RSS feed never sends out updates. Instead, RSS readers check the feed on a periodic basis and download the latest content.
This sort of pull-that-looks-like-push strategy can actually be very hard for a network or server to handle, and RSS feeds that have grown to be exceptionally popular have found that they have to increase the power of their web server over time to keep up with all of the requests their server gets for feed updates. Push technologies make much more efficient use of network and server resources by only pushing information once it's ready.