I am a newbie to web development. I am trying to develop a web site and it uses fairly large
number of ajax requests. In between i came across a friend who said that excessive dependency
on ajax request can be a performance concern and makes the browser to utilize huge amount of
network utility and cpu usage. Is this true..?
Does excessive dependency on ajax pose serious performance issues.?
If you are using a lot of Ajax requests, you are going to want to do some things to speed up your application
1) Make the server as fast as possible by using caching, returning limited sets of data, etc.
2) Make sure you actually need every ajax request. For example, you can wire a select box up to an ajax response, but if the data rarely changes, maybe you should load it only once, when the user loads the app.
3) Dont load too much data -- loading a table with 1000 rows in it via ajax can take a while, both to get the data and to render the response. If possible, use paging or similar techniques to get the request size down.
Any ajax enabled site can have usability issues if the network is slow, if the server is slow, if the browser is slow. This is just part of the game, and the fun and joy of modern web development. Do what you can to mitigate these types of issues.
Asking if you can have excessive dependency on ajax is kind of like asking if you can have excessive dependencies on 'divs'. Ajax is a tool, and like all tools, there are ways to use it properly.
No. If you'd have to reload the whole page every time you make an ajax request, you would need much more cpu time and network traffic. Though, if you use ajax to reload the clock in the status bar every second from the server, you should replace this with a javascript function...
Related
This is a technical doubt I had after reading some articles about WP ajax process (cannot find them though).
Is it faster and cheaper to load WP content (any content, page, post, widgets etc...) using WP ajax API than making a full canonical page request?
I thought about this because maybe passing through wp-admin/admin-ajax.php is lighter than loading a new page running the whole WP stack altogether.
Am I right?
Thanks
Yes it typically is.
Bit I've hit situations where the Wordpress Ajax api is slow:
https://wordpress.stackexchange.com/questions/41808/ajax-takes-10x-as-long-as-it-should-could
So if you are hitting a bug or issue with the Wordpress ajax api... it might be slower.
But that's not Ajax's fault. Ajax itself is way faster.
Ajax is usually faster because it avoids reloading the entire page for minor changes. This is a huge win, especially for things like commenting on a huge article. You can imagine if you have to re-load the article after each comment, ouch. Ajax avoids that.
I say it all depends on how much processing is going on in your wordpress page. If your widgets take a long time to process because they are making soap/external api calls then it would be in your best interest to load those widgets via ajax. Loading them via ajax will make your page load faster which looks better to google. If they all load pretty quickly then ajaxing the page will just put more stress on your db and webserver since it will take more traffic to deliver a single page.
Also, I would only use ajax for areas on the page that you'd like to change without doing a reload of the page, such as commenting or a data stream.
Ever since I've started asp.net mvc development my experience is almost 80% jQuery, only 20% C#.
Now I am begginning to use Knockout.js to enable myself to better control view on the page.
The question I am now facing is: should I be feeding the browser the "sceleton markup page" and load all data via ajax call, which in turn populates a js viewmodel object and therefore the view, or should I initially populate data via a partial view, and use js page data management for subsequent client experience?
Right now I am doing the latter, but this requires me to write two data retrieval/display logic - one in js, one in mvc razor view.
I am not planning to support browsers with js disabled, so maybe I should do everything via js knockout view model initialization?
There are many additional variables.
How many request per second should your app handle in future? If many, then with full page generation maybe you can cache resulting web page, decreasing load on server.
What kind of clients do you have? If they are slow (like low cost mobile phones), then generating full HTML on client can be slow.
Do your clients appreciate fast response over slow network? With full server page generation you can achieve smaller number of requests and faster response.
On the opposite side, if this is an internal department level business app with good network, low number of requests and good client computers, then you can surely go with minimal initial page and populating everything with AJAX. Also, as Arbiter pointed out, JSON can be smaller in size than HTML, so if you have a big amount of data then you can save on network via JSON.
There is also a middle third way. You can generate JSON data and embed them directly in the webpage (like <script>CallMyJSGenerateMethod({generatedJSON: "goes here"})</script>). This way you'd have only one (JavaScript) procedure for HTML generation, small number of requests (with even lower amount of data) and ability to cache web page. Still, you'd have to have a good clients, so point 2 still stands.
This is more of an opinion, but in my estimation, its the most oft asked question I get regarding building web apps: do I build the pages with HTML/MVC on the server or do I use all JS? There is no clear right answer here that fits all scenarios. Both are great choices. Dmitry's points are all valid, too.
Other things to consider are whether you need to stick with ASP.NET on the server or if other server tech will be used (PHP?). What skills does your dev team have? Will the pages you are creating change a lot on the client, or are they relatively static?
I personally lean towards the client space instead of server side generation, but its mostly a preference.
I am currently designing an application that will have a few different pages, and each page will have components that update through AJAX. The layout is similar to the new Twitter design where 'Home', 'Discover', and 'Connect' are separate pages, but interacting within the page (such as clicking 'Followers' or 'Following') uses AJAX.
Since the design requires an initial page load with several components (in the context of Twitter: tweets, followers, following), each of which can be updated individually through AJAX, I thought it'd be best to have a default controller for serving pages, and other controllers with actions that, rather than serving full pages, strictly handle querying the database and returning JSON objects. This way, on initial page load several HMVC requests can be made to gather the data for each component, and AJAX calls can also be made to update each component individually.
My idea is to have a Controller_Default that handles serving pages. In the context of Twitter, Controller_Default would contain:
action_home()
action_connect()
action_discover()
I would then have other Controllers that don't deal with serving full pages, but rather components of pages. For instance, in the context of Twitter Controller_Tweet may have:
action_get()
which returns a JSON object containing tweets for a specific user. Action_home() could then make several HMVC requests to get the data for the several different components of the page (i.e. make requests to 'tweet/get', 'followers/get', 'following/get'). While on the page, however, AJAX calls could be made to the function specific controllers (i.e. 'tweet/get') to update the content.
My question: is this a good design? Does it make sense to have the pages served through a default controller, with page components served (in JSON format) through other function specific controllers?
If there is any confusion regarding the question please feel free to ask for clarification!
One of the strengths of the HMVC pattern is that employing this type of layered application doesn't lock you into a workflow that might be difficult to change later on.
From what you've indicated above, this would be perfectly acceptable as a way of serving content to a client; the default controller wraps sub-requests, which avoids multiple AJAX calls from the client to achieve the same goal.
Two suggestions I might make:
Ensure that your Twitter back-end requests are abstracted out and managed in a library to make the application DRY'er and easier to maintain.
Consider whether the default controller is making only the absolutely necessary calls on each request. Employ caching to avoid pulling infrequently changed data on every request (e.g., followers might only be updated every 30 seconds). This of course depends entirely on your application requirements, but if you get heavily loaded you could quickly find your Twitter API request limit being reached.
One final observation: if you do find the server is experiencing high load and Twitter API requests are taking a long time to return, consider provisioning another server and installing a copy of your application. You can then "point" sub-requests from the default gateway application to your second application server, which should help improve response times if the two servers are connected by a high-speed link.
I'm still pretty new to AJAX and javascript, but I'm getting there slowly.
I have a web-based application that relies heavily on mySQL and there are individual user accounts that are accessed and the UI is populated with user specific data.
I'm working on getting rid of a tabbed navigation bar that currently loads new pages because all that changes from page to page is information within one box.
The thing is that box needs to reload info from the database, etc.
I have had great help from users here showing that I need to call the database within the php page that ajax is calling.
OK-so pardon the lengthy intro-what I'm wondering is are there any specific limitations to what ajax can call that I need to know about? IE: someone mentioned that it's best not to call script files and that I should remove scripts from the php page that is being called and keep those in the 'parent' page. Any other things like this I need to keep in mind?
To clarify: I'm not looking to discuss the merits/drawbacks of the technology. I'm wondering about specific coding implementation that I need to be aware of (for example-I didn't until yesterday realize that if even if I had established a mySQL connection on the page, that I would need to re establish that connection in my called page as well...makes perfect sense now).
XMLHttpRequest which powers ajax has a number of limitations. I recommend brushing up on the same origin policy. This is a pivotal rule because it limits where AJAX calls can be made.
First, you can't have Javascript embedded in the HTTP response to an AJAX call. That's a security issue.
No mention of the dynamics of the database, but if the data to be displayed in tabs doesn't have to be real-time, why not cache it server-side?
I find that like any other protocol, Ajax works best in tightly controlled conditions. It wouldn't make much sense for updating nearly the whole page, unless you find that the user experience is improved with an on-page 'loader'. Without going into workarounds, disadvantages will include losing the browser back button / history, issues such as the one your friend mentioned, and also embedded resources and other rich content can suffer as well, and just having an extra layer of complexity to deal with in your app. Don't treat it as magic sauce for your app - make sure every use delivers specific results that benefit your client / audience.
IMHO, it's best to put your client side javascript in a separate page and then import it - neater container. one thing I've faced before is how to call xml back which contains code to run such as more javascript - it's worth checking if this is likely earlier on and avoiding, than having to look at evals.
Mildly interesting.
Are there any disadvantages to using AJAX?
No integration with the browser's history.
If you build a site that requires Ajax to see content and perform tasks, you have several major problems. Ajax-only content/functions are invisible/unavailable to:
search bots
many mobiles
people with Javascript turned off
etc etc.
However, if you build a site using the progressive enhancement principle, those problems are solved, and you still get to serve nice-to-use Ajax to most users.
Progressive enhancement involves first creating your site using bare-bones (X)HTML, on REST-like principles (at least to the extent of requiring POST requests for state changes). Simple semantic markup; forget about CSS and Javascript.
Step one is to get that right, and have your entire site (or as much of it as makes sense) working nicely this way for search bots and Lynx-like user agents.
Then add a visual layer: CSS/graphics/media for visual polish, but don't significantly change your original (X)HTML markup; allow the original text-only site to stay intact and functioning. Keep your markup clean!
Third is to add a behavioural layer: Javascript (Ajax). Offer things that make the experience faster, smoother, nicer for users/browsers with Ajax-capable JS... but only those users.
Browser compatibility.
Asynchronized access to data means it's harder to make things go correctly in every combination of actions.
Dependency of javascript makes the site unusable for some. Also javascript performance can be a bottleneck in resource limited environments.
User may not know via the client that an AJAX operation was made, or if it failed. It can be difficult to recover from client side errors caused by a failed AJAX call.
Makes it really Hard to do functional testing .
Inability to update the client without "polling", which means querying the server every X seconds.
It requires javascript. And you have to admit to your friends how "Web 2.0" you are. Instead of being hard core old school: It's all tables for layout and frames for navigation for me.
Yes, Ajax is not supported by old browsers or browsers which don't have javascript enabled. Nowadays, most of the browsers do have support for Ajax -- even mobile browser like the one on the IPhone.
The biggest issue for me is that Ajax adds complexity to the project.
There are many ajax libraries out there, which are suppose to make life easier. In most cases, these libraries are easy to use to create a "Hello World" application. One of the main issues which is most of the times kept asside by Ajax libraries is (client-side) error handling/logging.
For larger projects, the developer has to understand the internals of the library, which adds a new learning discipline to the project.
Some of our big clients -for security reasons- took a corporate decision of having javascript switched off. Therefore no AJAX is possible.
If you are going to develop something using AJAX for a given client be sure that your client are allowed to use javascript.
Restrict your application to a reasonable number of browsers and browsers versions.
Crossbrowser compatibility can make your life miserable.
Ultimately, the problem is that it introduces is complexity. Most problems inherent with AJAX sites (bookmarking, browser history, graceful degradation, etc...) can be overcome with a good design, so there are not really any disadvantages to a well designed AJAX enabled site. The problem is a creating such a site requires a lot of design and very good developers who can manage the complexity.