I have a Standard website in Azure with a small instance, (1 core and 1.75 GB memory). It seems to be coping fine and handling the requests smoothly, although I am expecting a lot more within the week.
It is unclear though under what circumstances I should be looking to scale the instance size to the next level ie to Medium. (Besides MemoryWorkingSet of course, rather obvious :))
ie. Will moving up to a Medium instance resolve high CPU time ?
What other telltales should I be watching for ?
I am NOT comfortable scaling the number of instances to more than one at the moment until I resolve some cache issues.
I think the key point I am trying to understand is the link between the metrics provided and the means of scaling available regardless of it being scaled horizontally or vertically.
I am trying to keep the average response time as low as possible as the number of users that interact with the website increase.
Which of the other metrics will alert me when the load on the server is getting to its limits & I will need to scale Vertically ?
The idea behind scaling in Azure is to scale horizontally, i.e. add more instances. Azure can do this for you automatically. If you can't add more instances, Azure can't do the scaling for you automatically.
You can move to Medium instance, overall capacity will increase, but it is impossible to say what your application will require under heavy load. I suggest you run profiler and load test to find out the weak parts of your app and improve these before you have an actual increase in useage.
Related
I'm relatively new to JavaFX and have written a small applet which launches a number of (typically between 3 and 10) sub-processes. Each process has a dedicated tab displaying current status and a large TextArea where the process output is appended to. For simplicity all tabs are generated on startup.
javafx.application.Platform.runLater(() -> logTextArea.appendText(line)))
The applet works fine when workloads on sub-processes are low-moderate (not many logs), but starts to freeze when sub-processes are heavily used and generate a decent amount of logging output (a good few hundreds of lines per second in total).
I looked into binding the TextArea to the output, but my understanding is it effectively calls the Platform.runLater() method so there will still be hundreds of calls to JavaFX application thread per second.
Batching logging outputs isn't an ideal solution either because I'd like to keep the displayed log as real-time as possible.
The only solution which I think might solve the problem seems to be dynamic loading of individual tabs. This would definitely prevent unnecessary calls to update logging textareas that aren't currently visible, but before I go ahead to make the changes, I'd like to get some helpful advice from you here. Thanks!
Thanks for all your suggestions. Finally got around to implementing a fix today.
The issue was fixed by using a buffer coupled with a secondary check for time lapse (maximum 20 lines or 100 ms).
In addition, I also implemented rolling output to limit the total process output to 1,000 lines.
Thanks again for your invaluable contribution!
I have 19 websites running on Azure Standard Websites, with the instance size set to Small.
Right now I can't scale out to multiple instances (or use auto scale) because some of these sites are legacy sites that won't play nice across multiple sites.
The sites running now are fairly basic, but there are 3 sites that are growing fast, and I don't want to have them all bogged down because of the small instance, but I also don't want to pay for a large instance if I don't have to.
How to know when I should scale up to a medium or large instance?
There doesn't seem to be any way to see CPU load in the portal, only CPU time.
Instead of scale up, you need to scale out. you can set CPU metric and set the number if instances you need for that metric -
I'm using open source Torque 3d game engine for the avia simulator project.
I need to generate single image from the several IG (image generator) PCs.Each IG displays has its own view camera with certain angle offset and get the info about the current position from the server via LAN.
I've already setup multi IG system.
Network connection is robust (less than <1 ms)
Frame rate is good as well - about 70 FPS on each IG.
However while moving the whole picture looks broken because some IG are updating their views faster than others.
I'm looking for the solution that will make the IG update simultaneously. Maybe some kind of precise time synchronization algorithms that make different PC connected via LAN act as one.
I had a much simpler problem, but my approach might help you.
You've got to run clocks on all your machines with, say, a 15 millisecond tick. Each image needs to be generated correctly for a specific tick and marked with its tick ID time. The display machine can check its own clock, determine the specific tick number (time) for which it should display, grab the images for that specific time, and display them.
(To have the right mindset to think about this, imagine your network is really bad and think about one IG delivering 1000 images ahead of the current display tick while another is 5 ticks behind. Write for this sort of system and the results will look really good on the one you have.)
Ideally you want your display running a bit behind the IGs so you always have a full set of images for the current tick. I had a client-server setup and slowed the display (client) timer down if it came close to missing updates and sped it up if it was getting too far behind. You have to synchronize all your IG machines, so it might be better to have the master clock on the display and have it send messages to speed up any IG machine that's getting behind. (You may not have the variable network delays I had, but it's best to plan for them.)
The key is that each image must be made at a particular time, that the display include only images for the time being displayed, and that the composite images appear right when they should (every 15 milliseconds, on the millisecond). Also, do not depend on your network or even your machines to do anything in a timely manner. Use feedback to keep everything synched.
Addition On Feedback:
Say the last image for the frame at time T arrives 5ms after time T by the display computer's time (real time). If you display the frame for time T at T plus 10 ms, no one will notice the lag and you'll have plenty of time to assemble the images. Using a constant (10 ms) delay might work for you, especially if you make it big enough. It may be the way to go if you always run with the exact same network.
But you are depending on all your IG machines being precisely synchronized for real time, taking no more than a certain amount of time to produce their image, and delivering their image to the display machine all in predictable lengths of time.
What I'd suggest is have your display machine determine the delay based on the time stamps on the images it receives. It would want to increase the delay if it isn't getting the images it needs in time, and decrease it if all the IG's are running several images ahead of what the display needs. (You might want to ignore the occasional really late image. You have to decide which is more annoying: images that are out-of-date, a display that is running noticably behind time, or a display that noticably speeds up and slows down.)
In my original answer I was suggesting some kind of feedback from the display to keep the IG machines running on time, but that may be overkill: your computer's clocks are probably good enough for that.
Very generally, when any two processes have to coordinate over time, it's best if they talk to each other to stay in step (feedback) rather than each stick to a carefully timed schedule.
Does anybody have any hints as to how to approach writing an ASP.net app that needs to have a guaranteed response time?
When under high load that would normally cause us to exceed our desired response time, we want to throw out an appropriate number of requests, so that the rest of the requests can return before the max response time. Throwing out requests based on exceeding a fixed req/s is not viable, as there are other external factors that will control response time that cause the max rps we can safely support to fiarly drastically drift and fluctuate over time.
Its ok if a few requests take a little too long, but we'd like the great majority of them to meet the required response time window. We want to "throw out" the minimal or near minimal number of requests so that we can process the rest of the requests in the allotted response time.
It should account for ASP.Net queuing time, ideally the network request time but that is less important.
We'd also love to do adaptive work, like make a db call if we have plenty of time, but do some computations if we're shorter on time.
Thanks!
SLAs with a guaranteed response time require a bit of work.
First off you need to spend a lot of time profiling your application. You want to understand exactly how it behaves under various load scenarios: light, medium, heavy, crushing.. When doing this profiling step it is going to be critical that it's done on the exact same hardware / software configuration that production uses. Results from one set of hardware have no bearing on results from an even slightly different set of hardware. This isn't just about the servers either; I'm talking routers, switches, cable lengths, hard drives (make/model), everything. Even BIOS revisions on the machines, RAID controllers and any other device in the loop.
While profiling make sure the types of work loads represent an actual slice of what you are going to see. Obviously there are certain load mixes which will execute faster than others.
I'm not entirely sure what you mean by "throw out an appropriate number of requests". That sounds like you want to drop those requests... which sounds wrong on a number of levels. Doing this usually kills an SLA as being an "outage".
Next, you are going to have to actively monitor your servers for load. If load levels get within a certain percentage of your max then you need to add more hardware to increase capacity.
Another thing, monitoring result times internally is only part of it. You'll need to monitor them from various external locations as well depending on where your clients are.
And that's just about your application. There are other forces at work such as your connection to the Internet. You will need multiple providers with active failover in case one goes down... Or, if possible, go with a solid cloud provider.
Yes, in the last mvcConf one of the speakers compares the performance of various view engines for ASP.NET MVC. I think it was Steven Smith's presentation that did the comparison, but I'm not 100% sure.
You have to keep in mind, however, that ASP.NET will really only play a very minor role in the performance of your app; DB is likely to be your biggest bottle neck.
Hope the video helps.
I am working on a client proposal and they will need to upgrade their network infrastructure to support hosting an ASP.NET application. Essentially, I need to estimate peak usage for a system with a known quantity of users (currently 250). A simple answer like "you'll need a dedicated T1 line" would probably suffice, but I'd like to have data to back it up.
Another question referenced NetLimiter, which looks pretty slick for getting a sense of what's being used.
My general thought is that I'll fire the web app up and use the system like I would anticipate it be used at the customer, really at a leisurely pace, over a certain time span, and then multiply the bandwidth usage by the number of users and divide by the time.
This doesn't seem very scientific. It may be good enough for a proposal, but I'd like to see if there's a better way.
I know there are load tools available for testing web application performance, but it seems like these would not accurately simulate peak user load for bandwidth testing purposes (too much at once).
The platform is Windows/ASP.NET and the application is hosted within SharePoint (MOSS 2007).
In lieu of a good reporting tool for bandwidth usage, you can always do a rough guesstimate.
N = Number of page views in busiest hour
P = Average Page size
(N * P) /3600) = Average traffic per second.
The server itself will have a lot more internal traffic for probably db server/NAS/etc. But outward facing that should give you a very rough idea on utilization. Obviously you will need to far surpass the above value as you never want to be 100% utilized, and to allow for other traffic.
I would also not suggest using an arbitrary number like 250 users. Use the heaviest production day/hour as a reference. Double and triple if you like, but that will give you the expected distribution of user behavior if you have good log files/user auditing. It will help make your guesstimate more accurate.
As another commenter pointed out, a data center is a good idea, when redundancy and bandwidth availability become are a concern. Your needs may vary, but do not dismiss the suggestion lightly.
There are several additional questions that need to be asked here.
Is it 250 total users, or 250 concurrent users? If concurrent, is that 250 peak, or 250 typically? If it's 250 total users, are they all expected to use it at the same time (eg, an intranet site, where people must use it as part of their job), or is it more of a community site where they may or may not use it? I assume the way you've worded this that it is 250 total users, but that still doesn't tell enough about the site to make an estimate.
If it's a community or "normal" internet site, it will also depend on the usage - eg, are people really going to be using this intensely, or is it something that some users will simply log into once, and then forget? This can be a tough question from your perspective, since you will want to assume the former, but if you spend a lot of money on network infrastructure and no one ends up using it, it can be a very bad thing.
What is the site doing? At the low end of the spectrum, there is a "typical" web application, where you have reasonable size (say, 1-2k) pages and a handful of images. A bit more intense is a site that has a lot of media - eg, flickr style image browsing. At the upper end is a site with a lot of downloads - streaming movies, or just large files or datasets being downloaded.
This is getting a bit outside the threshold of your question, but another thing to look at is the future of the site: is the usage going to possibly double in the next year, or month? Be wary of locking into a long term contract with something like a T1 or fiber connection, without having some way to upgrade.
Another question is reliability - do you need redundancy in connections? It can cost a lot up front, but there are ways to do multi-homed connections where you can balance access across a couple of links, and then just use one (albeit with reduced capacity) in the event of failure.
Another option to consider, which effectively lets you completely avoid this entire question, is to just host the application in a datacenter. You pay a relatively low monthly fee (low compared to the cost of a dedicated high-quality connection), and you get as much bandwidth as you need (eg, most hosting plans will give you something like 500GB transfer a month, to start with - and some will just give you unlimited). The datacenter is also going to be more reliable than anything you can build (short of your own 6+ figure datacenter) because they have redundant internet, power backup, redundant cooling, fire protection, physical security.. and they have people that manage all of this for you, so you never have to deal with it.