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1/14/2014
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Dropbox Takes Blame For Cloud Outage

Post-mortem analysis says Friday's cloud service outage was caused by bad script in routine maintenance update.

Deadly Downtime: The Worst Network Outages Of 2013
Deadly Downtime: The Worst Network Outages Of 2013
(click image for larger view and for slideshow)

Dropbox says it knows how to avoid the type of outage that struck its service Friday: In the future, it will check the state of its servers before making additions to their code.

That will prevent an operating system update from being applied to a running production server, a process that usually results in the server shutting down. Enterprise users who rely on Dropbox for offsite storage already understand the principle. Some may be wondering whether Dropbox has the operational smarts to be relied upon for the long term.

Dropbox was trying to upgrade some servers' operating systems Friday evening in "a routine maintenance episode" when a buggy script caused some of the updates to be applied to production servers, a move that resulted in the maintenance effort being anything but routine. Dropbox customers experienced a 2.5-hour loss of access to the service, with some services out for much of the weekend.

Dropbox uses thousands of database servers to store pictures, documents, and other complex user data. Each database system includes a master database server and two slaves, an approach that leaves two copies of the data intact in case of a server hardware failure. The maintenance script appears to have launched new servers on running database servers.

"A subtle bug in the script caused the command to reinstall a small number of active machines. Unfortunately, some master-slave pairs were impacted which resulted in the site going down," wrote Akhil Gupta, head of infrastructure, in a post-mortem blog Sunday.

[Some cloud customers are getting fed up with outages. See Amazon Cloud Outage Causes Customer To Leave.]

Dropbox went off the air abruptly Friday between 5:30 and 6:00 p.m. Pacific time. For two hours, Dropbox's site remained dark, then reappeared at 8:00 p.m., according to user observations posted to Twitter and other sites. Users were able to log in again starting about 8:30 p.m. PT.

It wasn't clear from Gupta's post mortem how many servers had been directly affected; at one point he referred to "a handful." Gupta assured customers, "Your files were never at risk during the outage. These databases do not contain file data. We use them to provide some of our features (for example, photo album sharing, camera uploads, and some API features)."

On the other hand, operation of some of the paired master/slave database systems appear to have been entirely lost, something that a cloud operation tries at all times to avoid. Normally, if a master system is lost, its operations are taken offline long enough for the two slaves to create a third copy of the data and appoint one of the three as the new master.

(Source: Wikipedia.)
(Source: Wikipedia.)

Gupta explained in the blog, "To restore service as fast as possible, we performed the recovery from our backups." This suggests that Dropbox had to load stored copies of database systems to get its production systems running again.

"We were able to restore most functionality within 3 hours," he wrote, "but the large size of some of our databases slowed recovery, and it took until 4:40 p.m. PT [Sunday] for core service to fully return," Gupta wrote. This was at least 46 hours and 40 minutes after the outage began. Dropbox Photo Lab service was still being worked on after 48 hours.

Two-and-a-half hours into the outage, Dropbox responded to rumors and denied that its site had been hacked. At 8:30 p.m. Friday, the company tweeted: "Dropbox site is back up! Claims of leaked user info are a hoax. The outage was caused during internal maintenance. Thanks for your patience!"

One Twitter user agreed: "Dropbox not hacked, just stupid."

Gupta's post mortem took forthright responsibility for the outage, admitting Dropbox caused it with the faulty operating system upgrade script. It reassured users about their data, while explaining why it had taken so long to bring all services back online. But the fact that master/slave systems seem to have gone down together in "a routine maintenance episode" is not fully explained. If the operating system upgrade were staged so that only one of three database servers was changed at a time, two systems would have remained intact and recovery would have been faster.

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jemison288
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jemison288,
User Rank: Ninja
1/15/2014 | 1:43:01 PM
Re: Really? Has anyone looked at Amazon's outage history?
You can't compare Dropbox's internal database servers with Amazon running Infrastructure-as-a-Service for thousands (tens? hundreds? of thousands) of customers. They're not equivalent; Dropbox's internal database servers shouldn't go down like they did.  Amazon has *never* had an internal database failure like Dropbox had here, and Amazon does a heck of a lot more than Dropbox does.


Running database servers so they don't go down is a well-understood and known problem.  Running patches on production servers is verbotem and shouldn't happen.  This is reminiscent of Dropbox's security issues (allowing anyone to access anyone else's account for more than 4 hours; employees putting Dropbox customer information into an employee Dropbox); it makes it look like Dropbox has a lazy culture toward security and operational integrity.
Stratustician
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Stratustician,
User Rank: Ninja
1/15/2014 | 11:38:38 AM
Really? Has anyone looked at Amazon's outage history?
In all fairness, as a service, Dropbox has been pretty reliable.  Sure, it's suffered from the odd glitch, but the reality is that these technologies are still managed by humans, and we make errors.  I'd understand if a) you were running critical databases in Dropbox (hopefully not) or b) it was a paid service (most of us using the free version).

Let's compare it to the wonderful track record of the Amazon AWS folks.  Suddenly Dropbox doesn't seem too bad, does it?

Good for Dropbox to be upfront with the cause. For users to call them stupid is overreacting a bit I think, mistakes happen. Show me someone who hasn't accidentally glitched something and I'll happily tip my hat to their pure awesomeness.
Charlie Babcock
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Charlie Babcock,
User Rank: Author
1/14/2014 | 3:19:45 PM
Dropbox damage should have been limited, wasn't
In response to Number 6, I would have to agree that DropBox has a good record, but if you look at the Twitter comments on the outage, you can see doubt creeping into some of its users' confidence in their offsite storage supplier. And on one important point, the explanation for the outage is not an explanation. The updating of the operating system in some database master/slave combinations resulted in all three systems being lost. They then had to be reconstructed from backup, as I read the explanation. Any one who reads this differently is welcome to explain a different interpretation. But my position is, this isn't supposed to happen in the cloud. The cloud software allows for, and compensates for the failure of any one component and the service as a whole keeps running. The damage from what went wrong at Dropbox should have been contained, but it wasn't.  
avaya
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avaya,
User Rank: Apprentice
1/14/2014 | 3:19:22 PM
Re: Responsibility, yes, but not transparency
I gotta agree with your assesment.
avaya
100%
0%
avaya,
User Rank: Apprentice
1/14/2014 | 3:18:15 PM
Re: Responsibility, yes, but not transparency
All your files are just one subtle bug away :). The postmortem explanation is not through and internal controls seem to be lacking. Overwriting a production server or handful of servers doesnt happen even in rookie tech firms.

Also, it is hard to believe the pranksters timed the hoax perfectly.  How do they know the unplanned maintenance schedule or is it pure coincidence? Many unanswered questions here.

 
pat.white
IW Pick
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pat.white,
User Rank: Apprentice
1/14/2014 | 2:44:16 PM
Re: Responsibility, yes, but not transparency
I'd actually offer, in the industry Dropbox is known for being extremely cautious and thorough. They make very slow, deliberate updates to their products when things are perfect. This seems a bit out of character for them, and I personally wonder if they're feeling pressure to move faster as the competition with Box heats up.
Number 6
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Number 6,
User Rank: Moderator
1/14/2014 | 2:23:22 PM
Shocking! Dropbox Not Perfect!
"Some may be wondering whether Dropbox has the operational smarts to be relied upon for the long term."

As opposed to all those other suppliers upon which we rely that have never, ever committed a mistake in their existence? 

And "Some?" Who exactly has raised this question? It's easy to write "some say" followed by an overly broad assertion made only by the author without backing it up (pun not intended).
cbabcock
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cbabcock,
User Rank: Strategist
1/14/2014 | 1:06:01 PM
Responsibility, yes, but not transparency
Dropbox is taking responsibilty here for a human programming error, but the explanation falls well short of transparency.
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