Editing 1854: Refresh Types

{{comic
| number    = 1854
| date      = June 23, 2017
| title     = Refresh Types
| image     = refresh_types.png
| titletext = The hardest refresh requires both a Mac keyboard and a Windows keyboard as a security measure, like how missile launch systems require two keys to be turned at once.
}}

==Explanation==
In this comic [[Randall]] presents five different levels of refresh operations for web applications. The first three (''soft refresh'', ''normal refresh'', and ''hard refresh'') are common operations to keep the content in the browser retrieved from the server up to date. The other two (''harder refresh'' and ''hardest refresh'') are fictional operations to perform ''refresh'' operations on remote resources. The terms are probably adopted from {{w|Reboot (computing)|soft}} and {{w|Hardware reset|hard reset}} operations used to restart broken computers or e.g. smartphones.

=== Soft refresh ===
''Soft refresh'' refers to an operation in a web page, commonly known as {{w|Ajax (programming)|Ajax}}, that requests new information without reloading the entire page. The given example, {{w|Gmail}}, includes a feature that allows users to poll new emails and show it in the inbox interface. It is a command using {{w|JavaScript}} to load new contents from the server in the background and only update necessary components of the page. Modern web applications do this automatically in short time intervals such that these buttons are mostly unnecessary - for example, in Gmail, a user will see a new message instantly.

=== Normal refresh ===
The ''normal refresh'' is a browser operation that reloads the complete web page, text and other content that has changed since the original load will be updated. The operation can be triggered by refresh buttons in browsers, though it also can be requested using the common keyboard commands as listed by Randall. Many pages -- like the main page at xkcd.com -- don't have a refresh button. If the page has been opened before a new comic release, pressing F5 afterwards causes reload and the new comic is shown.

=== Hard refresh ===
What Randall calls ''hard refresh'' is a less common browser operation forcing the browser to re-download every part of the web page, ignoring any cached content. Caching is a common way of decreasing web page load times. Browsers save resources such as images or {{w|Cascading Style Sheets|CSS stylesheets}} on the first visit on a web page and use the local copy on subsequent visits. It allows them to decrease amount of transfer needed to show the web page, but can prevent showing changes made to the resources (for example a web developer changing the stylesheet). In those cases the ''hard refresh'' ensures that each part of the website is downloaded in its newest form.

If there is a {{w|Proxy server|proxy}} or a cache (like used for this wiki) in between the browser and the server this type of refreshing may not work. In this case, unless a purge link is available, the user has to wait until the cache entry is expired and a new request to the web server is done. Some browsers may try to avoid this behavior by including special headers in the HTTP request to control caching, but not all proxies or clouds follow these instructions.

=== Harder refresh ===
''Harder refresh'' is a joke that extends the existing naming scheme. The joke is that if a ''hard refresh'' resets the browser display and cache, a ''harder refresh'' should reset the source of the data by cycling power in the data center. Assuming no damage was done, this would reset the memory on the server, erasing any information that had not been written to disk, and setting the server to the state it was in at launch. This would cause considerable downtime, and would be unlikely to help the user at all.

In {{w|Orchestration (computing)|orchestrated}} environment it may indirectly cause some virtual machines in the {{w|Cloud computing|cloud}} to be rebooted and assigned to another web server needing more workload. But a growing workload is caused by hundreds or thousands additional requests and not just a single key combination from one browser. While there are administrative web tools allowing to perform a reboot (physical or virtual server) just by clicking a single button, this is not what is being referred to in the comic. A standard (non-administrative) user rebooting an actual physical server using a common web page is not possible, unless there is a software or operating system bug that will cause exactly this. This would be considered an extremely critical problem and its resolution would be given an extremely high priority by the server owners.

The ''harder refresh'' uses six keys, including the non-standard '[https://askubuntu.com/questions/19558/what-are-the-meta-super-and-hyper-keys HYPER]' key, a feature of the {{w|Space cadet keyboard}}. Hyper could also refer to the Linux modifier key Hyper, similar to Control, Alt, and Super.

=== Hardest refresh ===
The fifth option, ''hardest refresh'', moves beyond resetting the source of the data and resets the entire internet back to {{w|ARPANET}}, an early military network which was a forerunner to the modern internet. The implications of this are not made clear, but it should be noted that it wouldn't help to immediately fix any problems a user is experiencing in-browser, as {{w|HTTP}}, the protocol by which web pages are sent, was not developed until late 1990, the year ARPANET was decommissioned.

The ''hardest refresh'' shortcut uses fifteen keys, including non-standard ones such as Ø and ⏏. (The former is a key found on Danish and Norwegian keyboards, the latter is the "eject" key found on Mac keyboards and some laptops.) The shortcut makes amusing comparisons about a shortcut that includes not only the F5 function key, but also the keys for the letter "F" and the digit "5", as well as the similarity in appearance between O, 0, and Ø.

The title text suggests that the inclusion of both the {{w|Windows key}} and {{w|Command key}} in the ''hardest refresh'' shortcut is a security measure akin to the {{w|Two-man rule}}, as it would require two keyboards to enter. Normally this would not work in practice as the modifier keys are handled per keyboard and not combined across keyboards for most operating systems allowing more than one keyboard.

==Transcript==
:[A table with three columns is shown. The header is:]
:Refresh Type; Example Shortcuts; Effect

:[First row:]
:Soft Refresh
:[The word refresh has a border to mimic a button:]
:Gmail <span style="border: 1px solid black">REFRESH</span> Button 
:Requests update within JavaScript

:[Second row:]
:Normal Refresh
:[Two PC shortcuts and the Apple command key followed by an R:]
:F5, CTRL-R,  &#x2318;R
:Refreshes page

:[Third row:]
:Hard Refresh
:[One PC shortcut, the combination Control plus Shift, and the Apple command key followed by Shift and R:]
:CTRL-F5, CTRL-&#x21E7;,  &#x2318;&#x21E7;R 
:Refreshes page including cached files

:[Fourth row:]
:Harder Refresh
:[One single combination using Control plus Shift plus Hyper plus Escape plus R plus F5:]
:CTRL-&#x21E7;-HYPER-ESC-R-F5
:Remotely cycles power to datacenter

:[Fifth row:]
:Hardest Refresh 
:[One single combination using Control plus the Apple command key plus the Windows key plus Shift plus the hash key plus R plus F5 plus F plus 5 plus Escape plus the letter O plus a slashed zero with a small slash plus a slashed zero with a long slash plus an eject sign plus Scroll Lock:]
:CTRL-&#x2318;<span title="Windows key logo">&#x229E;</span>&#x21E7;#-R-F5-F-5-ESC-O-0-Ø-&#x23CF;-SCROLL LOCK 
:Internet starts over from ARPANET

==Trivia==

* One of the shortcuts listed for Hard Refresh, “CTRL-&#x21E7;”, is incorrect – it should be “CTRL-&#x21E7;-R”.

{{comic discussion}}

[[Category:Computers]]
[[Category:Internet]]