Goodbye global lock – MongoDB 2.0 vs 2.2

http://blog.serverdensity.com/2012/05/23/goodbye-global-lock-mongodb-2-0-vs-2-2/

by bsg75 • 14 years ago

79 34 14 years ago

blog.serverdensity.com

facorreia• 14 years ago

Damn, when I glanced upon the title I thought it was about Python's GIL.

slurgfest• 14 years ago

What actual use case do you have that CPython's GIL is affecting in any serious way? And if you do have a real case which somehow requires the removal of the GIL, why don't you just use Jython, which has no GIL and recently released an implementation of Python 2.7?

Mavrik• 14 years ago

Um, pretty much all parallelizable CPU number crunching (data mining algorithms, computer vision etc.) which aren't covered in C code. Those are especially problematic, since they're usually coupled with numpy and simillar libraries not supported on other Python implementations - including Jython.

mitchellh2• 14 years ago

They've moved from a _process_ level lock to a _database_ level lock. Let's take a moment to golf clap their mediocrity. golf clap

Use a real database.

scottostler• 14 years ago

If you take a look at the benchmarks further down the page, the real improvement seems to be that mongo does a better job of yielding during page faults. That provides an improvement even with a single database.

bsg756• 14 years ago

I am a Real Database(tm) person, but I will give them some credit for:

"Nevertheless, a major focus for the upcoming 2.2 release has been removing the global lock and introducing database level locking as an initial step towards collection level locking and potentially even more granular concurrency in future releases."

This stuff is hard to get right, and why RDBMS' are simultaneously maligned as "old tech", yet are still the most dependable database mechanisms available.

It seems like the successful(popular) "NoSQL" engines will eventually reinvent many RDBMS wheels - at least in the cases where they are aiming to be replacements.

nknight• 14 years ago

> It seems like the successful(popular) "NoSQL" engines will eventually reinvent many RDBMS wheels.

The wheels in question aren't RDBMS wheels, they're just generic database wheels. The backlash against RDBMSs wasn't because of implementation details like this, it was because of the baggage of relational structures in general, and SQL in particular.

The "reinvention" of these wheels is occurring now because non-relational databases are maturing now.

mitchellh2• 14 years ago

I don't claim that it is easy, especially with an RDBMS. Actually, given the few courses I took in university on database design, I know its very non-trivial.

But MongoDB is not an RDBMS. There are no joins, so a query can only touch one collection (table) at a time anyways, so at least in that regards its much easier than an RDBMS.

shubber• 14 years ago

It seems like Mongo in particular is reinventing the RDBMS wheel entirely, except with a frustrating JSON query language. The benchmark blog post a couple of days ago versus an out-of-the-box Postgres deploy (i.e. memory crippled) was not very impressive.

And look: they've implemented clusters - by pushing a Slony equivalent into the DB itself.

Please forgive my bile - I was a little nonplussed with Mongo, and now I have to use it for a client. Now I'm a lot nonplussed.

sausagefeet• 14 years ago

AFAIK, the locking in Mongo has more to do with them using memory mapped files than anything else. Other DB's, like Riak, do not have this problem. But perhaps someone can prove me wrong.

DenisM• 14 years ago

No need to be snarky, but I certainly share your general sentiment:

http://news.ycombinator.com/item?id=3412386

taligent4• 14 years ago

And they've indicated that in the next stable release they will have collection level locking. All moving towards sub collection locking.

It is a relatively new database and they trying to make changes in small increments to ensure they don't break anything.

Seems prudent to me.

tinyjoe• 14 years ago

Not that new, and with that much funding they received. They're just being lazy.

scorpioxy• 14 years ago

"10gen do not provide official benchmarks because they tend to be irrelevant to real world usage."

Anybody else thing this sentence is silly? I definitely do not base my judgement on a tool off its artificial benchmarks but I do check them to see if an upgrade is worth it or not. Irrelevant or not, please publish them.

I'm a mongo user(for offline analytics) so any improvement in performance will be good.

Karunamon• 14 years ago

>Anybody else thing this sentence is silly?

Not really. It's a lose/lose proposition to publish benchmarks, especially on something that's so environment and dataset dependent. Either real world performance is way below the benchmark leading to all kinds of storm and strife, or way above and then you lose credibility and people wondered why you bother anyways.

timmyd• 14 years ago

i guess then in some respects - its funny how correct Adam was in his comments

http://www.quora.com/Quora-Infrastructure/Why-does-Quora-use...

peterbe• 14 years ago

Well done 10gen peeps! Keep up the good work. You deserve all the credit you can get. There's still a lot of work to do to catch up with established RDBMSes but you're definitely getting a bunch of things right already today.

onetwothreefour• 14 years ago

These posts (the one about 20ms for a memcached lookup especially) make me doubt the technical prowess of the entire ServerDensity staff, and thereby stopping me from ever considering this product.

Goodbye global lock – MongoDB 2.0 vs 2.2

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