Since the link in the summary is broken, this is the facebook blog post.
Post contents: Early today Facebook was down or unreachable for many of you for approximately 2.5 hours. This is the worst outage we’ve had in over four years, and we wanted to first of all apologize for it. We also wanted to provide much more technical detail on what happened and share one big lesson learned.
The key flaw that caused this outage to be so severe was an unfortunate handling of an error condition. An automated system for verifying configuration values ended up causing much more damage than it fixed.
The intent of the automated system is to check for configuration values that are invalid in the cache and replace them with updated values from the persistent store. This works well for a transient problem with the cache, but it doesn’t work when the persistent store is invalid.
Today we made a change to the persistent copy of a configuration value that was interpreted as invalid. This meant that every single client saw the invalid value and attempted to fix it. Because the fix involves making a query to a cluster of databases, that cluster was quickly overwhelmed by hundreds of thousands of queries a second.
To make matters worse, every time a client got an error attempting to query one of the databases it interpreted it as an invalid value, and deleted the corresponding cache key. This meant that even after the original problem had been fixed, the stream of queries continued. As long as the databases failed to service some of the requests, they were causing even more requests to themselves. We had entered a feedback loop that didn’t allow the databases to recover.
The way to stop the feedback cycle was quite painful - we had to stop all traffic to this database cluster, which meant turning off the site. Once the databases had recovered and the root cause had been fixed, we slowly allowed more people back onto the site.
This got the site back up and running today, and for now we’ve turned off the system that attempts to correct configuration values. We’re exploring new designs for this configuration system following design patterns of other systems at Facebook that deal more gracefully with feedback loops and transient spikes.
We apologize again for the site outage, and we want you to know that we take the performance and reliability of Facebook very seriously.
Researchers at Rensselaer Polytechnic Institute produced "paper batteries" on nanocomposite paper with an energy density of about 13Wh/kg back in 2007. You can see the paper here.
Shouldn't it be possible to triangulate the position based on signal strength from multiple points, and just locate the tower, break in and see what the hardware attached to the transmitter does?
The update isn't failing. You are safely restoring the software, but the baseband of the phone is upgrade as part of the iOS 4 update. So the 'failure' you are seeing is when the 3.1.3 software detects a baseband version that, to it, doesn't exist. This link spells it out for you.
I know, right. Surely, if they can ship bananas to New York from South America and they're still green, then they can ship this cacao husk stuff to Delaware.
The genetically engineered, seedless, under-ripe when picked bananas you mean?
It's nice they've developed a way to transfer data at ridiculous speeds, but it does the average user no good as long as we're using mechanical hard drives. Even a "mere" 1 gigabit network connection outstrips the ability of spinning platters to absorb it. I guess this Light Peak thing is aimed at the server market then?
That's not really a fair analysis. HD video is often stored compressed, but needs to be transferred at full resolution uncompressed to the display medium. The DVI spec supports 3.96Gbit/s. HDMI even goes up to 10.2Gbit/s. There are plenty of other examples where a high-bandwidth transport will be useful.
If you own the device, you can do this, too? Would it not make sense for Apple to be the owner of the prototype device and thus possess the ability to do the mobileme remote wipe? See MobileMe - Find Your iPhone, particularly the "Protect your privacy with Remote Wipe" section.
It seems to me that if you can design an algorithm to verify how humans interact with a computer, it should be relatively trivial to engineer an algorithm that mimics this interaction?
Thanks for all the replies so far, the reason I ask what will look best on a resume is with the economy the way it is, I've begun to wonder what combination of education and experience will give me the most opportunities down the road.
I am an excellent programmer, but working 9-5 in a cubicle writing code scares me and does not seem like a good way to spend the next 30+ years of my life.
That being said, I have done some freelance web design and web database application development and really enjoyed it. I have also worked in various environments doing IT work and found it alright.
So further complicating the issue, (and no offense to people who have a BS or MS in IT) but I often hear that IT degrees are for people who couldn't make it in Computer Science. So does going from a competitive CS program to an IT program look like this?
I don't know how graduate school works. I'm not worried about being miserable at school. I can do anything for one year. It's after school that I'm most concerned with.
And finally, regarding staying here at the same Uni for graduate work, I had never really thought of leaving. A big part of that, however, is I have worked really hard while here and will be completing my B.S. in a total of 3 years. I will still have quite a bit of scholarship money that may be applied to my graduate work if I stay here.
Well, particularly for those small devices it would seem that they would still require stepdown circuitry--likely a transformer. It just won't require rectification and smoothing.
I wouldn't expect TV/Movie content to go DRM free anytime soon. Apple doesn't have the market power there that it does with the music industry and studios have no reason to listen to them.
You may upgrade your library for $.30/song.
Could this mean that there could some day be the potential for crafting a virus, with the intent of infecting another virus to potentially destroy it? Something like this would probably have the potential to do more harm than good, but maybe this is a new way to look at potential treatments?
Slashdot Mirror
What a feat, a simple cheesy iPhone app that has pilots quaking in their boots.
Do not click parent link. Goatse. I need to wash my eyes out.
Since the link in the summary is broken, this is the facebook blog post.
Post contents:
Early today Facebook was down or unreachable for many of you for approximately 2.5 hours. This is the worst outage we’ve had in over four years, and we wanted to first of all apologize for it. We also wanted to provide much more technical detail on what happened and share one big lesson learned.
The key flaw that caused this outage to be so severe was an unfortunate handling of an error condition. An automated system for verifying configuration values ended up causing much more damage than it fixed.
The intent of the automated system is to check for configuration values that are invalid in the cache and replace them with updated values from the persistent store. This works well for a transient problem with the cache, but it doesn’t work when the persistent store is invalid.
Today we made a change to the persistent copy of a configuration value that was interpreted as invalid. This meant that every single client saw the invalid value and attempted to fix it. Because the fix involves making a query to a cluster of databases, that cluster was quickly overwhelmed by hundreds of thousands of queries a second.
To make matters worse, every time a client got an error attempting to query one of the databases it interpreted it as an invalid value, and deleted the corresponding cache key. This meant that even after the original problem had been fixed, the stream of queries continued. As long as the databases failed to service some of the requests, they were causing even more requests to themselves. We had entered a feedback loop that didn’t allow the databases to recover.
The way to stop the feedback cycle was quite painful - we had to stop all traffic to this database cluster, which meant turning off the site. Once the databases had recovered and the root cause had been fixed, we slowly allowed more people back onto the site.
This got the site back up and running today, and for now we’ve turned off the system that attempts to correct configuration values. We’re exploring new designs for this configuration system following design patterns of other systems at Facebook that deal more gracefully with feedback loops and transient spikes.
We apologize again for the site outage, and we want you to know that we take the performance and reliability of Facebook very seriously.
Researchers at Rensselaer Polytechnic Institute produced "paper batteries" on nanocomposite paper with an energy density of about 13Wh/kg back in 2007. You can see the paper here.
Shouldn't it be possible to triangulate the position based on signal strength from multiple points, and just locate the tower, break in and see what the hardware attached to the transmitter does?
What's the rationale behind not putting a blower on all cars? Seems like a good idea and not that unreasonable...
Install it in your car then. Don't even suggest putting it in mine.
whoooooosh.
The update isn't failing. You are safely restoring the software, but the baseband of the phone is upgrade as part of the iOS 4 update. So the 'failure' you are seeing is when the 3.1.3 software detects a baseband version that, to it, doesn't exist. This link spells it out for you.
A more informative video can be found here with one of the engineers describing its function while it plays back some old recordings.
I know, right. Surely, if they can ship bananas to New York from South America and they're still green, then they can ship this cacao husk stuff to Delaware.
The genetically engineered, seedless, under-ripe when picked bananas you mean?
This guy is forgetting that we live in a (sort of) democracy. How would a democracy where the people aren't educated work?
Most likely remarkably similar to how it works today with the largely (under)educated populace.
It's nice they've developed a way to transfer data at ridiculous speeds, but it does the average user no good as long as we're using mechanical hard drives. Even a "mere" 1 gigabit network connection outstrips the ability of spinning platters to absorb it. I guess this Light Peak thing is aimed at the server market then?
That's not really a fair analysis. HD video is often stored compressed, but needs to be transferred at full resolution uncompressed to the display medium. The DVI spec supports 3.96Gbit/s. HDMI even goes up to 10.2Gbit/s. There are plenty of other examples where a high-bandwidth transport will be useful.
If you own the device, you can do this, too? Would it not make sense for Apple to be the owner of the prototype device and thus possess the ability to do the mobileme remote wipe? See MobileMe - Find Your iPhone, particularly the "Protect your privacy with Remote Wipe" section.
You should be aware that with those data plans, there is no contract and you can opt-in and opt-out right from the device.
Novell Zenworks is a kluge of hack after hack and in my experience, less than reliable. ...sorry to say.
Unlikely, seeing as the gas giant planets don't have surfaces.
The sun is a planet?
It seems to me that if you can design an algorithm to verify how humans interact with a computer, it should be relatively trivial to engineer an algorithm that mimics this interaction?
Maybe someone smarter than I could clarify?
Damn it! Where's my chair?
I assure you, people come to me if they need to cheat. Programming is not a problem.
Thanks for all the replies so far, the reason I ask what will look best on a resume is with the economy the way it is, I've begun to wonder what combination of education and experience will give me the most opportunities down the road.
I am an excellent programmer, but working 9-5 in a cubicle writing code scares me and does not seem like a good way to spend the next 30+ years of my life.
That being said, I have done some freelance web design and web database application development and really enjoyed it. I have also worked in various environments doing IT work and found it alright.
So further complicating the issue, (and no offense to people who have a BS or MS in IT) but I often hear that IT degrees are for people who couldn't make it in Computer Science. So does going from a competitive CS program to an IT program look like this?
I don't know how graduate school works. I'm not worried about being miserable at school. I can do anything for one year. It's after school that I'm most concerned with.
And finally, regarding staying here at the same Uni for graduate work, I had never really thought of leaving. A big part of that, however, is I have worked really hard while here and will be completing my B.S. in a total of 3 years. I will still have quite a bit of scholarship money that may be applied to my graduate work if I stay here.
Again, thank you all so much.
Well, particularly for those small devices it would seem that they would still require stepdown circuitry--likely a transformer. It just won't require rectification and smoothing.
I wouldn't expect TV/Movie content to go DRM free anytime soon. Apple doesn't have the market power there that it does with the music industry and studios have no reason to listen to them. You may upgrade your library for $.30/song.
Sounds like a job for Clippy.
I think you meant software is like a city... houses, roads, bridges... and tubes.
Could this mean that there could some day be the potential for crafting a virus, with the intent of infecting another virus to potentially destroy it? Something like this would probably have the potential to do more harm than good, but maybe this is a new way to look at potential treatments?
MathML is pretty full featured. Equations are stored in a standardized XML format. http://www.w3.org/Math/