My company develops CDN / Web-Hosting solution. We have a middleware that's served as a business logic layer and exposes web service for the front-end.
I would like to seek for a clean solution to feature management - there're uncertainties and ugly workarounds/solutions in the software that the dev would say "when it happens or is broken, we will fix it".
For example, here're the following features that a web publisher can have:
Sites limit
Bandwidth limit
SSL feature + SSL configuration per site
If we downgrade a web publisher, when he's having 10 sites, down to 5 sites, we can choose not to suspend the rest of the 5 sites, or we shall prompt for suspension before the downgrade.
For the case of bandwidth limit, the downgrade is easy, when the bandwidth check happens, if the publisher has it exceeded, then we will suspend his account.
For the case of SSL feature. Every SSL configuration is tied to a site, what shall happen to these configuration object when the SSL feature is downgraded from enabled to disabled?
So as you can see, there're many different situations and there are different ways of handling it.
I can make a system that examines the impacts and prompts the user to make changes before the downgrade/upgrade.
Or a system that ignores the impacts and just upgrade/downgrade. Bad.
Or a system designed in a way that the client code need to be aware of the complex feature matrix (or I can expose a helper to the client code to check if a feature is not DEFUNCT)
There can be many ways that I am still thinking but puzzled. I am wondering, how would you tackle this issue and is there any recommended patterns or books or software that you think I can refer to?
Appreciate your help.
Related
I am redesigning a web application which previously has been rendered server side to a Single Page Application and started to read about websockets . The web application will be using sockets to have new records and/or messages pushed to the client. I have been wondering why most pages which make use of sockets don't handle all their communication over the socket. Most of the times there is RESTful backend in addition to the websocket. Would it be a bad idea to have the client query for new resources over the socket? If so why - other than that a RESTful api might be easier to use with other devices?
I can imagine that using websockets would probably not be the best idea in case the network connection is kind of bad like on mobile devices, but that probably should work quite well with a reasonable connection to the web.
I found this related question, however it is from 2011 and seems a little outdated:
websocket api to replace rest api?
No, it won´t be a bad idea. Actually I work in an application that uses a WebSocket connection for all what is data interaction, the web server only handles requests for resources, views under different languages, dimensions .. etc..
The problem may be the lack of frameworks/tools based on a persistent connection. For many years most of frameworks, front and back end, have been designed and built around the request/response model. The approach shift may be no so easy to accept.
Coming back to this question a few years later, I would like to point out a few aspects to illustrate that having all your communication through websockets does have its drawbacks:
there is no common support for compression. You can easily configure your webserver to compress http requests and browsers have been known to happily accept compressed responses for years, however for web sockets it is still not that easy (even though the situation has improved)
client frameworks often are build upon commonly used standards like rest. The further away you move from frameworks expectations, the less addons or features will be available.
caching in the browser is not as easy. By now this goes a long way, reaching into the realm of offline availability and PWAs.
when using technology, that is only used by a subset of users, it is more likely to find new bugs, or bugs might take longer to fix. And if it's not bugs, there might be an edge case somewhere around the corner. This isn't an issue per se - but something to be aware of. If one runs into those things, they often easily take up quite some time to fix or work around.
We're planning to introduce DMS to our customer's Sitecore installation. It's a rather popular site in our country and we have to use proxy caching server (it's Nginx in this case) to make it high-traffic-proof.
However, as far as we know, it's not possible to use all the DMS features with caching proxy enabled - for example personalization of content - if it gets cached it won't be personalized.
Is there a way to make use of all the DMS features with proxy cache turned on? If not, how do you handle this problem for high-traffic sites - is it buying more Content Delivery servers to carry the load, or extending current server with better hardware (RAM, CPU, bandwidth)?
You might try moving away from your proxy caching for some pages, or even all.
There's no reason not to use a CDN for static assets and media library assets, so stick with that
Leverage Sitecore's built-in html cache for sublayouts/renderings - there are quite a few options for caching
Use Sitecore's Debug feature to track down the slowest components on your site
Consider using indexes instead of doing "fast" or Sitecore queries
Don't do descendants query "//*" (I often see this when calculating selected state for navigation - hint: go the other way, calculate the ancestors of the current page)
#jammykam wrote an excellent answer on this over here.
John West wrote a great blog post on this also, though a bit older.
Good luck!
I've been wondering about this myself.
I have been thinking of implementing an ajax web service that:
- talks to the DMS and returns JSON
- allows you to render the personalised components client side
- allows you to trigger anlaytics events
I have been googling around and I haven't found anyone that has done it and published the information yet. The only place I have found something similar is actually in the mobile sdk, but I haven't had a chance to delve into it yet.
I have also not been able to use proxy server caching and DMS together successfully. For extremely high loads, I have recommended to clients to follow the standard optimization and scaling guidelines, especially architecting for proper Sitecore sublayout and layout caching for as much of the site as possible. With that caching done, follow it up by distributing across multiple Content Delivery nodes with load balancing to help support high volume with personalization at the same time.
I've heard that other CMS's with personalization use a javascript approach to load the personalized content on the client-side, but I would be worried about losing track of the analytics data that is gathered when personalized content is loaded and interacted with.
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I was asked this question once at an interview:
"Suppose you own a website where the server is at some remote location. One day, some user calls/emails you saying the site is abominably slow. How would you identify why the site is slow? Also, when you check the website yourself as any user would (using your browser), the site behaves just fine."
I could think of only one thing (which was shot down):
Check the server logs to analyse incoming traffic. Maybe a DoS attack or exceptionally high traffic. Interviewer told me to assume the server has normal traffic and no DoS.
I was kind of lost because I had never thought of this problem. I have almost no idea how running a server/website works. So if someone could highlight a few approaches, it would be nice.
While googling around, I could find only this relevant, wonderful article. That article is kind of too technical for me now, but I'm slowly breaking it down and understanding it.
Since you already said when you check the site yourself the speed is fine, this means that (at least for the pages you checked) there is nothing wrong with the server and it can serve those pages at a good speed. What you should be figuring out at this point is what the difference is between you and the user that reports your site is slow. It might be a lot of different things:
Is the user using a slow network connection (mobile for example)?
Does the user experience the same problems with other websites hosted at the same webhoster? If so, this could indicate a network problem. Normally this could also indicate a resource problem at the webserver, but in that case the site would also be slow for you.
If neither of the above leads to an answer, you could assume that the connection to the server and the server itself are fine. This means the problem must be in the users device. Find out which browser/OS he uses and try to replicate the problem. If that fails find out if he uses any antivirus or similar software that might cause problems.
This is a great tool to find the speed of web pages and tells you what makes it slow: https://developers.google.com/speed/pagespeed/insights
I think one of the important thing that is missing from above answers is the server location, which can play a vital in web performance.
When someone is saying that it is taking a longer time to open a web page that means high latency. High latency can be caused due to server location.
Let's assume as you are the owner of the web page then the server and client are co-located, so it will have a low latency.
But, now if client is across the border, then latency time will increase drastically. And hence a slow perfomance.
Another factor is caching which drastically affects the latency time.
Taking the example of facebook, they have server all over the world to reduce the latency time (and also to provide several other advantages) and they use huge caching system to cache their hot data (trending topics) whereas cold data (old data) are stored in hard disk so it takes a longer time to load an older photo or post.
So, a user might would have complained about this as they were trying load up some cold data.
I can think of these few reasons (first two are already mentioned above):
High Latency due to location of client
Server memory might need to be increased
Number of service calls from the page.
If a service could be down at the time of complaint, it could prevent page from loading.
The server load might be too high at the time of the poor experience. The server might need to increase the resources (e.g. adding another server/web server to the cluster).
Check if there was any background job running on the server at that time.
It is important to check the logs and schedules of the batch jobs to determine what all was running at that time.
Hope this help.
Normally the user takes the page loading time as a measure to find out that the site is slow. But if you really want to know that what is taking the maximum time the you can open the browser debugger by pressing f12. if your browser is chrome the click on network and see what calls your application is making and which are taking maximum time. If you are using Firefox the you need to install firebug. If you have that, then again press f12 and click on Net.
One reason could be the role of the user is different of your role. You might be having suppose an administrator privilege (some thing like super user role) and the code might be just allowing everything for such role that means it does not really do much of conditional checking to see what is allowed or not. Some times, it's a considerable over ahead to get all the privileges of the user and have the conditions checking, how course depends how how the authorization is implemented. That means, the page might be really slow for specific roles. Hence, you should find out the roles of the user and see if that is a reason.
Obviously an issue with the connection of the person connecting to your site OR it's possible it was a temporary issue and by the time you checked your site, everything was dandy. You could check your logs or ask your host if there was an issue at the time the slow down occured.
This is usually a memory issue and it can be resolved by increasing the Heap Size of the Web Server hosting the application. In case the application is running on Weblogic Server. Heap size can be increased in "setEnv" file located in Application Home.
Goodluck!
Michael Orebe
Though your question is quite clear, web site optimisation is a very extensive subject.
The majority of the popular web developing frameworks are for some reason, extremely processor inefficient.
The old fashioned way of developing n-tier web applications is still very relevant and is still considered to be best practice according the W3C. If you take a little time to read the source code structure of the most popular web developing frameworks you will see that they run much more code at the server than is necessary.
This may seem a bit of a simple answer but, the less code you run at the server and the more code you run at the client the faster your servers will work.
Sometimes contrasting framework code against the old fashioned way is the best way to get an understanding of this. Here is a link to a fully working mini web application which represents W3C best practices and runs the minimum amount of code at the server and the maximum amount of code at the client: http://developersfound.com/W3C_MVC_EX.zip this codebases is also MVC compliant.
This codebase comes with a MySQL database dump, php and client side code. To see this code in action you will need to restore the SQL dump to a MySQL instance (sql dump came from MySQL 8 Community) and add the user and schema permissions that are found in the php file (conn_include.php); setting the user to have execute permissions on the schema.
If you contrast this code base against all of the most popular web frameworks, it will really open your eyes to just how inefficient these frameworks are. The popular PHP frameworks that claim to be MVC frameworks aren’t actually MVC compliant at all. This is because they rely on embedding PHP tags inside HTML tags or visa-versa (considered very bad practice according the W3C). Also most popular node frameworks run way more code at the server than is necessary. Embedded tags also stop asynchronous calls from working properly unless the framework supports AJAX dumps such as Yii 2.
Two of the most important rules to follow with MVC compliance is: never embed server side tags (such as PHP tags) in HTML tags or visa-versa (unless there is a very good excuse such as SEO) and religiously never write code to run at the server if it can be run at the client. Also true MVC is based on tier separation, where as the MVC frameworks are based on code separation. True MVC compliance is very processor efficient. Don’t get me wrong MVC frameworks are very useful for a lot of things, but if you’re developing a site that is going to get millions of hits, they are quite useless, or at least they will drive your cloud bills so high that it will really eat into your company’s profits.
In summary frameworks don’t give much control over what code runs at the client or server and are very inefficient but you can get prototypes up and running quicker with less code.
In contrast the old fashioned way takes a bit more elbow grease but you have complete control over what runs at the server and what runs at the client.
As an additional bit of advice for optimisation avoid using pass-through queries and triggers and instead opt for stored procedures. Historically stored procedures weren’t invented at the time MVC was present as a paradigm but it definitely increases separation of concerns between the tiers and is much more processor efficient.
Hope this advice helps.
Web applications frameworks such as sinatra (ruby), play (scala), lift (scala) produces a web server listening to a specific port.
I know there are some reasons like security, clustering and, in some cases, performance, that may lead me to use an apache web server in front of my web application one.
Do you have any reasons for this from your experience?
Part of any web application is fully standardized and commoditized functionality. The mature web servers like nginx or apache can do the following things. They can do the following things in a way that is very likely more correct, more efficient, more stable, more secure, more familiar to sysadmins, and more easy to configure than anything you could rewrite in your application server.
Serve static files such as HTML, images, CSS, javascript, fonts, etc
Handle virtual hosting (multiple domains on a single IP address)
URL rewriting
hostname rewriting/redirecting
TLS termination (thanks #emt14)
compression (thanks #JacobusR)
A separate web server provides the ability to serve a "down for maintenance" page while your application server restarts or crashes
Reverse proxies can provide load balancing and fault tolerance for you application framework
Web servers have built-in and tested mechanisms for binding to privileged ports (below 1024) as root and then executing as a non-privileged user. Most web application frameworks do not do this by default.
Mature web servers are battle hardened and stable. By stable, I mean that they quite literally almost never crash. Your web application is almost certainly far less stable. This gives you the ability to at least serve a pretty error page to the user saying your application is down instead of the web browser just displaying a generic "could not connect" error.
Anecdotal case in point: nginx handles attack that would otherwise DoS node.js: http://blog.nodejs.org/2013/10/22/cve-2013-4450-http-server-pipeline-flood-dos/
And just in case you want the semi-official answer from Isaac Schluetter at the Airbnb tech talk on January 30, 2013 around 40 minutes in he addresses the question of whether node is stable & secure enough to serve connections directly to the Internet. His answer is essentially "yes" it is fine. So you can do it and you will probably be fine from a stability and security standpoint (assuming you are using cluster to handle unexpected termination of an app server process), but as detailed above the reality of current operations is that still almost everybody runs node behind a separate web server or reverse proxy/cache.
I would add:
ssl handling
for some servers like apache lots of modules (i.e.
ntml/kerberos authentication)
Web servers are much better for some things compared to your application, like serving static.
Quite often the frameworks do everything you need, but sometimes, adding a layer on top of that can give you seemingly free functionality like compression, security, session management, load balancing, etc. Still, adding a web server may also introduce security issues, for example, chances are your web server security may be compromised easier than Lift by itself. Also, some of the web frameworks are extremely scalable and may even be hampered by an ill chosen web server.
In summary, if you require web server like functionality that is not provided by the framework, then a web server may be a very good option, but keep in mind that it's one more thing to configure properly and update regularly with security patches, etc.
If for example, you just need encryption, or compression, then you may find that adding the correct library or plug-in to your framework may do just that (and only that)
With a proxy http server, the framework doesn't need to keep an http connection open for giving the computed content and can then start serving some other request. It acts as a buffer.
It's an issue of reinventing the wheel. Most frameworks will give you a development environment but for production it's usually good practice to use a commercial/open source project that is able to deal with all issues that arise during production.
Guys building a Framework will have the framework to concentrate on whilst guys building a server are doing just the same(perfecting).
I have reasonable experience to manage my own server, so gogrid style management is not a problem. But seems mosso is a tag cheaper somewhat- except the very difficult to access compute cycles terms. Anyone could share about this would be very welcomed.
Well, even at the current moment as correct answer is marked GoGrid choice, I think I need to share my experience with GoGrid.
It's been several weeks after we broke our commitment with them and I think I'm pretty calm now to write cons for them.
1) Images. We were trying to use Windows 2008 images and those were pretty old. To be up to date, you need to install 80+ updates and that takes a while. But that's not the worst thing. Worst thing is, that default image hdd size is 20gb and that was not enough to complete windows updating, at least in automatic way (not talking about installing additional software). There's no way to increase image size, so you need to make all kinds of workarounds (for example disable virtual memory, when installing).
2) Support. It's not fanatic. I would call it robotic. Although live chat is working, at least we were unable to solve by live chat most of the problems, because live chat support personel would always forward request to upper level, which is not accessible through live chat. Another thing is, that as I understood, engineers, that have real knowledge and access to infrastructure don't work at night and in weekends (I was working from Europe, so I had completely different time zone).
3) Service Level Agreement. You need to be careful about small print (for example I've missed that rule 1hour of non working is compensated 100x was working only for one month bill), but there are things, that are not mentioned - for example I was told, that SLA terms do not work for cloud storage, although I think you won't find this mentioned in SLA.
4) Reaction time. Although in SLA they say, that will solve any issue in two hours, we couldn't get solution in 10 days. Problem was clear: network speed between gogrid server instances, also between instance and cloud storage was 10-15kbps (measured using several tools, such as netio and etc., tested several instances and so on). That wasn't because they forgot or smth., we were checking status at various levels every day. My management talked with VP of technology or something and he promised that problem will be solved in nearest time, several days passed and no solution was proposed. And some of the emails about how they are investigating problem made me laugh.
5) Internet speeds. Sometimes they were really good (I've measured 550mbps download speed), but sometimes they are terrible (upload up to 0.05mbps).
If someone thinks, that this is some kind of competitors posting, I have chat and email logs about mentioned issues, also screen shots of internet speed tests and could provide under request.
Ok, and one good thing about their service - you can use several IP addresses on one instance (what our current hosting provider - Amazon EC2 is unable to do).
Stay away from GoGrid !
I don't have any experience with Mosso, but I do have (unfortunately) VERY bad experience with GoGrid.
As other people mentioned, their support is horrible. Most times you will get a live chat person that really is no help at all - doesn't really know their system or how it works so he can't really help with any problem beyond restarting your server.
Another issue is their performance which is at best unreliable and at worst just not there. Starting from I/O which can drop to < 1mb/s (measured by a few tools) - ranging to network connections that are very slow - load balancers which do not spread the load (2 servers on RoundRobin get 70/30)
Not to mention a very buggy portal - new server picks a free ip, which I am then told is in use...and not by me - even though I have the whole range "assigned" to me -
new cases which are saved without the text - buttons which say "upgrade to a new plan" but do nothing... etc... etc...
Their billing department which is not responsive and you have to argue about everything (why am I paying $0.5/gb traffic when the site states $0.29 ?????)
I have been using them for about a year now - and that's only because I don't have the time to move. Hopefully I will be able to get the hell out of there in a month.
As you can tell, I am very very frustrated with them. I know it's my fault I didn't run away sooner, but I really didn't expect such a low level of service and quality.
beware....
Yoav.
Mosso has way better service though, and the clients stay happy. The only issue I have experienced with them ever was installing DNN (which is a pain period) and a single client machine refused to allow for FTP access to their site... but again, Mosso techs did everything they could to get it going.
It's simple, Mosso is just like a "reseller" hosting. They provide you everything whitelabel from billing to control panel then you sell it back to customers.
If you are developer, I recommend you choose GoGrid. Firstly, Mosso doesn't provide SSH access. Secondly, if you are RoR/Mongrel user, you are capped to limited RAM (unless you pay extra in addition to $100). Moreover, GoGrid allows you to choose server image (CentOS, Redhat, Windows) with some out-of-the-box support for RoR and LAMP.
Somemore, GoGrid provides you initial credits ($50 or $95 if you use MS-WEBFWRD) for you to try out before actually paying for it.
Mosso does not give you Admin control over the "servers" anymore...
Disclosure: I am the Technology Evangelist for GoGrid.
I wanted to address some of the points above by #Giedrius and #Yoav. I'm sorry if your experience was lower than expected. We have and continue to make dramatic improvements and upgrades to both our product features as well as our service. That being said, I want to answer a few points that you listed above, specifically:
1) Images - Do note that the HD size (persistent storage) is tied to the RAM allocation. Our base images for the lowest RAM allocation (512 MB) is now 30 GBs. Also, because some users experienced some performance issues with low allocations of RAM on Windows servers, we have set a minimum allocation of 1 GB or higher for most Windows instances. Also, all of our Windows 2008 instances now have SP2 on them: wiki.gogrid.com/wiki/index.php/Server_Images#Windows_2008_Server
2) Support - We are always working on making our support team and processes even better. Remember that there are several public clouds that charge for support, something we don't do. Yes, it is available 24/7/365 and you are correct that there are typically more support personnel available during business hours (that is the norm for many companies). Be we are here to help 24x7. Also, every GoGrid account gets a dedicated service team which consists of a variety of personnel from our organization (acct mgmt, tech support, billing, etc.)
3) SLA - We offer one of the most robust SLAs in the marketplace. Also, Cloud Storage IS in fact covered in our SLA under Section VI here: www.gogrid.com/legal/sla.php .
4) Reaction time - I do not believe that we ever state in the SLA that any issue will be "resolved" within 2 hours. I doubt that ANY hosting provider can offer that, simply because of the nature of hosting and the complexity therein. We will acknowledge and respond to tickets (as stated within the SLA) within 2 hours or 30 minutes depending on the nature of the ticket. I'm sorry if that isn't clear so please let me know where it can be better explained.
5) Internet speeds - we have multiple bandwidth providers for our datacenter. It is not typical that there is latency, jitter or slow transfer speeds. If a situation is encountered where the speeds are not what you expect, I encourage you to open a support ticket so that we can investigate.
6) I/O - recently we have been benchmarked by an independent 3rd party, CloudHarmony.com, as having the best I/O of cloud providers: http://blog.cloudharmony.com/2010/06/disk-io-benchmarking-in-cloud.html
7) Network Connections - see #5 above
8) Load Balancers - if you are encountering balancing issues, we encourage you to report it. Details on our LB can be found on the wiki: wiki.gogrid.com/wiki/index.php/(F5)_Load_Balancer
9) Portal - We continue to make optimizations to the web portal including recently launching a "list view" for customers with larger environments. If the portal is "misbehaving", I recommend clearing your cache and using the latest browser version (I personally use Chrome and Firefox regularly on the portal w/o issue). Alternatively, you could use the API to manage your GoGrid infrastructure.
10) Transfer Plan - A few months ago, we released some new RAM and Transfer Plans. It seems that you are still on the old Transfer plan if you have $0.50/GB instead of $0.29. We don't automatically change customers' plans without their permission. So I recommend that you upgrade your plan to enjoy the new pricing.
Hope that helps answer the questions/concerns. I didn't mean for it to be a sales pitch (as I'm not a sales guy) but I wanted to be sure that other readers had "the other side of the story."
Please contact me should you have any questions: michael[at]gogrid.com
Thanks!
-Michael