What happens behind the scenes when we type www.google.com in a browser? (2015)

https://github.com/vasanthk/how-web-works

by MrXOR • 7 years ago

259 71 7 years ago

github.com

MrXOR• 7 years ago

Another similar context:

https://github.com/alex/what-happens-when

https://news.ycombinator.com/item?id=8902105

https://news.ycombinator.com/item?id=9189096

0815test• 7 years ago

Doesn't it depend on the browser? Does Google Chrome still do that thing where if you fire the browser up and then type www.google.com in it, it actually searches Google for that string and returns a results page, instead of just browsing there?

pedrocx486• 7 years ago

Doesn't happen to me, at least didn't happen in a while.

chromeguy66• 7 years ago

The behaviour of the URL bar is modifiable in most modern browsers. The default on most is automatic detection of URLs - if something looks like an URL, it's treated like one and if it doesn't, it searches your search engine of choice.

jimmaswell3• 7 years ago

I would've liked to see ps/2 keyboards gone over. I still use one.

notyourwork2• 7 years ago

Do you plug it into a USB port or a ps/2 port on motherboard?

jimmaswell3• 7 years ago

The motherboard.

tingol• 7 years ago

Could you expand on why? Just curious.

jimmaswell3• 7 years ago

I bought it at a yard sale ~10 years ago and it still works

EE84M3i• 7 years ago

I think this would be better if it had more details about font rendering and layout engines.

jdbernard• 7 years ago

I agree. We should fork it, flesh out those details and submit a pull request. :)

unixpickle• 7 years ago

Of course, google in particular is behind a very complex distributed network. Distributed DBs are mentioned, but it would be cool to know more about how web requests are distributed and routed in this system.

notyourwork2• 7 years ago

It most likely depends on what resource you are referring to. If its a search query that will differ drastically from a gmail request. Therefore, its really case specific in monolithic companies with distributed and decentralized architecture.

devonkim2• 7 years ago

You could start with the Maglev paper but I’m not sure if that’s still in production use there https://ai.google/research/pubs/pub44824

ibdkhb• 7 years ago

I did this years ago so it might be different now, but I blocked google.com and some subdomains at the firewall, found a document hosted on google docs (google.com domain) link in google.co.uk search result, clicked it and instead of the link failing due to it being blocked at the firewall, a google.se (swedish) server started sending the ip traffic for the blocked document to come down. I never tried blocking google.se and then repeating to see what other google domain would send the document next, but its clear Google have written their own routing to get information around some restrictions beit deliberate or misconfigured. Its also an excellent way to probe what servers have blocks in place or not, ie censorship. Its also pretty much instant rerouting ie subsecond, so their ability to pass instructions to other servers in a timely manner is obvious. I wonder if their servers are using swarm intelligence in area's or not? They did custom build their own machines, which would have given them the opportunity to tear up the rule book some what.

mandeepj• 7 years ago

relevant - https://www.google.com/search/howsearchworks/?fg=1

RyanShook2• 7 years ago

A lot is written about the algorithms and search results from Google but I haven’t seen much on crawling and indexing. I imagine there are multiple teams in Google who help maintain the integrity and completeness of their indexes but would love to know more about it considering it might be the largest single repository of knowledge.

shereadsthenews2• 7 years ago

I believe email is significantly larger than the web. Wouldn't that be your largest repo of knowledge, in aggregate?

turtles3• 7 years ago

In the TLS handshake: "The server generates its own hash, and then decrypts the client-sent hash to verify that it matches"

The server decrypts a hash? But thats not how hashes work.

goochtek• 7 years ago

It should read "then compares the generated hash to the hash that was received from the client to verify that it matches"

Or something along those lines.

turtles3• 7 years ago

I assume the reason for doing this is to confirm the symmetric key now in use is known between both parties?

sowbug2• 7 years ago

The client encrypts its hash before sending it to the server. Thus the server must decrypt it to compare it to the one it generated.

tristanperry2• 7 years ago

Hashes are one-way, so cannot be decrypted. The server can _compare_ the results of a hash (by doing the hash itself, and comparing the results), though.

tialaramex2• 7 years ago

Most of that description is outdated and/or wrong. Probably this HN article should say (2015).

But yes, of course you can decrypt an encrypted hash, this way you get back the plain hash.

The client calculates a hash, it _encrypts_ that hash, and sends it to the server, the server _decrypts_ it, and then can verify that it has the same calculation.

The reason this is done is that it can detect a situation in which the client and server were persuaded to arrive at the same results by different means, whereupon they should abort the connection. The mechanism in TLS 1.2 and earlier was not very good, a better one is included in TLS 1.3 but alas last I looked it is disabled in popular browsers because it's incompatible with yet more middlebox crapware from "security" companies.

0xEFF• 7 years ago

Do you find this an useful interview question in 2019? What is or isn’t useful about the answer from candidates?

Blackthorn• 7 years ago

I do. If a candidate is a frontend developer and can't tell me anything beyond the absolute basics of how http works, that spells trouble.

owenmarshall2• 7 years ago

I like it, especially for interviewing for ops/devops/sre/whatever we say today.

It’s a good warm up question because pretty much any answer is right, and it quickly lets the candidate get to their comfort zone. It is also amenable to be simplified or tweaked - if the candidate doesn’t know much about CDNs or layer 7 load balancing or whatever, you just move past them. And you can change some of the parameters to be sure the candidate isn’t just memorizing the answer sheet.

It can also give a strong signal where the candidate’s knowledge is weak: if you talk to me at length about Apache throwing read syscalls to pull files from the disk but quickly gloss over the networking bits, that might indicate you don’t know them well.

GauntletWizard• 7 years ago

This is precisely what I use it for, and precisely why I like answering it. I will talk in detail about the bits I know, smell bullshit (and look up answers) in the bits I don't, and it gives me an answer to candidates depth in all of them. Backend devs will talk about search and set theory algorithms. SREs will talk protocols. Networking guys will talk layer3-7. Everyone has their own style, and it's certainly the most informative in determining where to prove next.

A good candidate had breadth and depth of knowledge. This one question shows breadth and tells you where to find depth. It doesn't work as well for pure frontend people, but only barely - I almost expect frontend people to understand interrupts and syscalls on that end.

irq113• 7 years ago

This question is now burnt. Nobody should be using it. (In reality, it was burnt a long time ago, but it’s crispy and black now.)

If you do use it, you’re merely selecting for people who have read posts like this on HN and reddit. Candidates who have memorized any of this will look vastly superior to those who haven’t.

It’s telling that there are already two sibling comments who are arguing that this is a good question - explains a lot about why technical interviews suck.

brokenmachine• 7 years ago

Just the fact those people are interested enough to read HN/Reddit for their own sake can't be a bad thing though.

I'm not an employer but I know I'd rather my workmates were the kind of people who are actually interested in computers enough to read about them for pleasure, not just those "straight by the book" types.

owenmarshall2• 7 years ago

I agree, technical interviews suck, and I’d be happy if my technical interviewer skills reached “average” ;-)

But I’m still doing them and my employer won’t let me stop - so help me refine a bit. What question(s) would you like to see interviews ask more?

fivre• 7 years ago

You notably do not provide any better alternative. Show me some other technical question that can surface useful information about a candidate's knowledge in a typical 30-minute interview.

The question is good because it both involves something most everyone does on a daily basis while providing a wide range of possible areas to explore further: there isn't any single "correct" answer that's possible to cover in a short time, but what candidates do tell you probably indicates what they're most familiar with.

Candidates prepping for this question isn't much of an issue since (a) most simply don't and (b) there's always room to go further into a specific part of the transaction.

AndrewStephens• 7 years ago

I love a good reductionist deep dive into things we use everyday. This is a great overview to a wide range of topics.

I wrote something similar a couple of years ago[0] which skips the keyboard and display but goes further into the world of IP packet transmission (and HTTP/2). The parent link is better written though.

[0] https://sheep.horse/2017/10/how_you_are_reading_this_page.ht...

ryanf3232• 7 years ago

Very comprehensive. However, it is missing how the client machine will ARP the gateway for the MAC address if it is not in its tables.

mizzao• 7 years ago

Perhaps you should submit a PR on the repo?

ryanf3232• 7 years ago

I should and I will

jamesmcintyre• 7 years ago

I worked with the guy who wrote this repo. He's one of the smartest, nicest, and genuinely curious guys I know.

He also ran teams and his leadership style was very humble and encouraging in a workplace that was, at times, the opposite.

So glad to see he's still publishing awesome content like this.

Be sure to check out some of his other popular repos, great stuff!

mayakumar• 7 years ago

I roger that. His name is `Vasanth Krishnamoorthy`. I still have the good fortune of working with him in `WalmartLabs`. Extremely talented, multi-faceted, curious and above all a wonderful human being. I have learnt plenty through my interactions with him and am still learning from him :-). I am serendipitously lucky to have met him in my life.

techslave2• 7 years ago

i invented this question circa 2009. i have to assume, one of many that independently invented it.

in my version, it’s not “what is behind the scenes “, it’s “tell me everything you can in as much detail as you like, what has to happen to visit www.google.com”. of course in 2009 google had only just become google.com.

shereadsthenews2• 7 years ago

I've noticed that when anyone claims to have invented something on HN, they get voted down. But I have no reason to doubt it. Please tell us more about how you came to use this question, and why you think it wasn't in circulation before that. I know someone asked me this in an interview in 2010, so it was in wider use by then.

toast03• 7 years ago

Edit: rewritten without snark

I was interviewed on this in 2004 for Yahoo! although the hostname in question was different.

macintux• 7 years ago

You mean 1999 perhaps?

techslave2• 7 years ago

ARGH! too late to edit. of course i meant 1999 not 2009.

beamatronic• 7 years ago

I used to work with some guys from Taos Consulting. They asked a similar interview question. “What happens when you ping Google”. Your answer was expected to take at least 3 hours.

yread• 7 years ago

I also got asked a similar question in a an interview (as a programmer) and I answered it well and they hired me. But I think it's an absolutely terrible question for judging whether a person will be a good hire.

tianshuo• 7 years ago

This is almost the same open-ended interview questions I've used for many years, works a charm because it filters the engineers from the chaff (who just copy-pastes code from the internet w/o understanding why)

mrunkel2• 7 years ago

Me too. This gives a quick insight into what the applicant knows and what they are interested in.

This is usually one of the three questions I require as part of an application.

The other two are a technical question tailored for the position and the third a 'throwaway' that the applicant answer as they see fit. In the past it's been things like "What is the airspeed of an unladen swallow? (European or African)"

dev_north_east• 7 years ago

"What is the airspeed of an unladen swallow? (European or African)"

What are you expecting to get from something like that?

maaaats• 7 years ago

Yeah, if you don't understand how the browser has implemented lexical analysis, it surely means you only copy paste code /s

davidmr• 7 years ago

That seems like an uncharitable conclusion. I think most people worth hiring (in an interview where that question is asked) should be able to expound at some length on at least some part of the process. What part of the process they spend the most time talking about is an interesting window into their experience.

amelius• 7 years ago

If only we knew!

fouronnes3• 7 years ago

It's amazing how detailed this is, and yet there are still steps missing!

xurukefi• 7 years ago

The most amazing part about this is that regardless of how much more details one would want to put into it, it is probably practically infeasible to make it complete. It's a wonderful example to demonstrate the importance of the concept of abstraction in CS.

vinayms• 7 years ago

The main problem with these kinds of exposition topics is that the steps involved are quite dense. By that I mean something like density of real numbers; between any two real numbers there are any number of real numbers. Then, the writer just chooses to expand on those steps that they are comfortable with, or the ones that get more eyeballs. I mean, why not explain how signal travels across various media like air, underwater cables, to and from satellite etc?

Now, don't get me wrong, I am not saying this is useless. I am just saying that if one chooses to give a 30k feet perspective, they had better stay there and not bounce between 40K and 10K.

bgravinz• 7 years ago

I’m not seeing not sticking to 30k is really detrimental to how most people would likely consume a doc like this, which would probably be to sample various parts to find what they’re interested in and then dig in.

tempguy9999• 7 years ago

I would most politely wish to note that one is tended to read documents. One should rarely consume them unless in the spirit of espionage.

Equally, in the comfort of one's own parlour, one may listen to one's wireless. Not 'consume', as was once heard.

The butler informs me on this occasion that I am correct. I bow to him in this. Uncommonly sharp fellow.

And so to the Drone's Club, where literature, wireless nor dolly birds are permitted.

theandrewbailey• 7 years ago

I remember an interview where I answered a similarly in-depth question about what happens when you load a file, from file system traversal, down to the heads moving across the platter (because almost no one used SSDs in 2009).

What happens behind the scenes when we type www.google.com in a browser? (2015)

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