Thought Garage

I work in a company where we develop software for Wireless carriers and all our software is expected to provide service availability at 99.999% (Five Nines). That means just about 5  minutes outage for an entire year. And its really a big deal if that target is missed (and result in hefty penalties). And as consumers of a telephone service or a cell phone we expect that cell phone works all the time. You never know when we need it.

On the web though its a different story. For many services we are quite fine with outages now and then. Unless you are a business consumer and your business depends on having an internet portal up and running all the time ( like Dell.com or Amazon.com), an outage normally doesn’t affect anything. We regularly see ‘Maintenance or Scheduled Outage’ Notifications on most web applications and we thank them for the notice.

As per Gmail’s official blog, Gmail service availability is at 99.9%, which means about one and half a minute per day outage or about 45 minutes outage in a month or about 9 hours outage for an entire year.

Gmail web interface was down yesterday for about 100 minutes due to overload issues. And I am pretty sure, most of us are not even aware of that. But Google appeared to make a big deal about it and  trying to make sure it won’t happen again.

Here is what happened:

This morning (Pacific Time) we took a small fraction of Gmail’s servers offline to perform routine upgrades. This isn’t in itself a problem — we do this all the time, and Gmail’s web interface runs in many locations and just sends traffic to other locations when one is offline.

However, as we now know, we had slightly underestimated the load which some recent changes (ironically, some designed to improve service availability) placed on the request routers — servers which direct web queries to the appropriate Gmail server for response. At about 12:30 pm Pacific a few of the request routers became overloaded and in effect told the rest of the system "stop sending us traffic, we’re too slow!". This transferred the load onto the remaining request routers, causing a few more of them to also become overloaded, and within minutes nearly all of the request routers were overloaded. As a result, people couldn’t access Gmail via the web interface because their requests couldn’t be routed to a Gmail server. IMAP/POP access and mail processing continued to work normally because these requests don’t use the same routers.

While Google has fixed the issue by bringing in more servers up, one of their action plan to modify overload control intrigued me.

“if many request routers are overloaded simultaneously, they all should just get slower instead of refusing to accept traffic and shifting their load”

In most Telecom software applications the approach we take in times of overload is to continue all the calls that are already setup without any impact (like no degradation of voice quality) and refuse setting up any newer calls until overload is subdued. In most cases, you may hear an announcement like ‘network busy. try after some time’.

I am not sure during Gmail outage, each and every user on the web interface is affected or only a handful of users that trying to login during that time were affected. If each and every user is affected, I think Google must try to fix the problem in a way not to affect already logged in users and refuse all new logins. That way, only a handful will be affected.

It appears, Google want to affect everybody with delayed responses instead of refusing service to some. Isn’t it refusing some with a proper message is better than making everybody feel that Gmail is slower. For people like me, the perception of Slow response is much bigger deal than outage for a few minutes. I don’t want to spend 10 minutes to access and send an email. I am quite fine to do that after 10 minutes.

Google announced Gmail offline access yesterday, I read on the web different interpretations of what it is and what it means for your offline email activities like checking and composing emails even when offline.

Well, if you are currently using Outlook or any other desktop counter parts, there is nothing new on the table. Gmail was one of the first providers to provide free POP/IMAP access. So if you have outlook or any other desktop email application, you could readily access Gmail and compose emails while offline. This functionality was not new.

This new offer is for those who do not use any desktop email client applications like outlook but only use Gmail in a browser.  Gmail with the help of Google gears now can download all email and store in the browser add-on (gears) to provide offline access to your emails. It will even allow you to compose an email and send it when connected to the Internet.

This functionality as such is nothing special if you already accessing Gmail with a client application. But if you prefer an alternative from Google, then this will be for you.

Google is very well known for this. Gmail now comes with a custom time. That means you can send an email as if you had sent it in the past. Not only that, you can request such a way that the email will be marked as ‘read’ by the recipient. AAHHaaaa!

I am about cry ‘cheating’ cheating. Instead, I realized, today is April 1st.  Wonderful, Googlers !!

How do I use it?

Just click "Set custom time" from the Compose view. Any email you send to the past appears in the proper chronological order in your recipient’s inbox. You can opt for it to show up read or unread by selecting the appropriate option.

Is there a limit to how far back I can send email?

Yes. You’ll only be able to send email back until April 1, 2004, the day we launched Gmail. If we were to let you send an email from Gmail before Gmail existed, well, that would be like hanging out with your parents before you were born — crazy talk.

How does it work?

Gmail utilizes an e-flux capacitor to resolve issues of causality (see Grandfather Paradox).

How come I only get ten?

Our researchers have concluded that allowing each person more than ten pre-dated emails per year would cause people to lose faith in the accuracy of time, thus rendering the feature useless.

Their findings:

N = Total emails sent
P = Probability that user believes the time stamp
φ = The Golden Ratio
L = Average life expectancy

Gmail: Google’s approach to email