Spanner: Google's Globally-Distributed Database

http://research.google.com/archive/spanner.html

by SriniK • 14 years ago

258 55 14 years ago

research.google.com

lsb• 14 years ago

Interestingly, the data storage seems similar to Rich Hickey's Datomic: "data is versioned, and each version is automatically timestamped with its commit time; old versions of data are subject to conﬁgurable garbage-collection policies; and applications can read data at old timestamps."

tdg• 14 years ago

That's exactly like BigTable[1]. It makes sense that they built on top of that.

[1] http://static.googleusercontent.com/external_content/untrust...

akkartik2• 14 years ago

But you can mutate bigtable cells. Datomic seems dramatically different in that respect.

nnythm• 14 years ago

MVCC has been around for at least thirty years, but it's interesting that we have seen more databases with this feature recently.

linuxhansl4• 14 years ago

Almost all databases use it in form or the other.

PostgreSQL uses it, Oracle uses it, MySQL (innodb) uses it, Apache HBase uses it, the list goes on and on...

sedachv2• 14 years ago

Timestamp versioning is one of the oldest (1978) ideas in distributed systems: http://patricklogan.blogspot.ca/2007/09/naming-and-synchroni...

pwpwp• 14 years ago

Transactions don't scale. They really need to use NoSQL.

Evbn2• 14 years ago

Did you read the first page? BigTable has no trnsanctions, and scales, but is a pain for apps that need consistency. Spanner adds transactions for apps that need it, at scale, charging a tax in the form of latency.

Using two different clock technogies per node (GPS and atomic!) and light speed networking helps make this manageable.

Fault-tolerant time!

zaphar2• 14 years ago

We read about this at work at google a few months ago in a reading group. (perks of the job) And we spent almost the entire time talking about the timestamps. It is perhaps the most important piece of this paper. Fault tolerant time is right.

ChuckMcM2• 14 years ago

This was an interesting project at Google, it started when I was there, and it was breaking things when I left. It is too bad that Ken Thompson didn't get at least acknowledged for his role in making it happen.

I don't think it will be as influential as the original GFS was but its an important piece of work that folks should study.

Locke16893• 14 years ago

No, I think it's critical. I worked on one of the first services to ever use Spanner when I was an intern. Lock-free read transactions is a game changer. Short answer -- if your database system can't do lock-free reads, your database is broken. That one feature allows one to do some incredible performance optimizations.

theotherone• 14 years ago

Elaborate?

linuxhansl4• 14 years ago

>if your database system can't do lock-free reads, your database is broken

Yep.

bgentry• 14 years ago

I would also be interested in a longer, elaborated answer.

eluos• 14 years ago

"non-blocking reads in the past"

Sounds like google's finally invented time travel.

zwischenzug• 14 years ago

What _exactly_ is a lock-free read transaction? Is it different to reading in a MVCC system?

luriel2• 14 years ago

> It is too bad that Ken Thompson didn't get at least acknowledged for his role in making it happen.

Interesting, can you say more about this?

Is he not mentioned because officially he is part of the Go team?

enneff2• 14 years ago

Ken sat near Jeff, Sanjay, and co while they were designing Spanner, and he regularly consults in an informal capacity on people's projects. I wasn't there, but it wouldn't surprise me at all if Ken's unique insight contributed to Spanner's design.

ChuckMcM2• 14 years ago

When I was in the platforms group looking at storage issues the Spanner requirements had a lot of commentary from Ken in them, so much so that I thought it was his idea/project until someone corrected me a bit later. That was why I was surprised he wasn't acknowledged, from where I sat it seemed like he was one of the architects of the effort. Apparently that wasn't the case.

linuxhansl4• 14 years ago

I work on HBase (the Apache version of BigTable). It makes me sad to see how far ahead Google is compared to the rest of the world. :)

The notion of uncertain time is ingenious.

zaphar2• 14 years ago

I think that's more a factor of Google's scaling needs vs the rest of the world. We needed to invent it first so we did.

state• 14 years ago

That's a nice way to put it. That's exactly why these inventions are so interesting: they seem give insight in to problems of another order of magnitude.

DonnyV• 14 years ago

At least they understand by sharing this information it moves the technology forward. You don't see a lot of other big companies doing that.

moondowner• 14 years ago

Another research publcation from Google that's more-than-worth reading.

These just pile up, I must find time and get my hands on them...

hellooo• 14 years ago

Is spanner written in cc or java?

kaib• 14 years ago

kleiba• 14 years ago

Interestingly, "Spanner" is German for "voyeur". Coming from Google it's almost kind of ironic.

dmayle• 14 years ago

Even more interesting, "Spanner" is English for "something that spans", as in a database spanning the world.

Maybe it's a bit snarky, but I really don't see how you can read into something like that. It reminds me of the following Jack Handy quote:

Maybe in order to understand mankind, we have to look at the word itself: "Mankind". Basically, it's made up of two separate words - "mank" and "ind". What do these words mean? It's a mystery, and that's why so is mankind. - Jack Handy

huxley• 14 years ago

A spanner is also British English for what North Americans call a wrench.

linuxhansl4• 14 years ago

Another observation that struck me when I read this (and after reading the percolator and megastore papers) is how there is a convergence of the "traditional" relational DB world and the "new NoSQL" world. Relational Databases are becoming more scalable, partially with new technology, partially by shedding features in some scenarios. And the NoSQL stores, are becoming less so (it was really about "NoSQL" anyway, but that's a different story). All of these stores have layers or features that bring closer to the traditional SQL/relational model.

Spanner appears to strike a nice middle ground.

Nitramp• 14 years ago

I think the major contribution in this paper is how to do consistent snapshot reads in a distributed system without a common reference clock, i.e. the use of True Time.

Many databases use some sort of MVCC, but they operate on a single node or in a closely connected cluster. This paper shows how to achieve the same properties in a system spanning continents.

tete• 14 years ago

Fun fact: Spanner means voyeur in German slang.

Anyway, looks like a very exciting project. One could come up with so many applications.

sudhirj• 14 years ago

This looks like the High-Replicaiton datastore which is now the default in App Engine - Paxos replication, a choice between strong and eventual consistency and tablet sharding. Interesting that they've already built it and it's available for everyone to use.

Spanner: Google's Globally-Distributed Database

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