有人恨MongoDB嗎?

jieforest發表於2012-09-28
MongoDB
For a guaranteed surge of traffic and to hit the Hacker News homepage, all you need to do is write about why you hate MongoDB and/or migrated to some other database. We’ve been using it to power our server monitoring service, Server Density, for over 3 years now and so with experience, many of the problems cited in these posts seem like basic mistakes in deployment and understanding.

With any product, if you decide to deploy it to production you need to be sure you fully understand its architecture and scaling profile. This is even more important with newer products like MongoDB because there is less community knowledge and understanding. This is partly the responsibility of the developers using those tools but also the responsibility of the vendor to ensure that major gotchas are highlighted.

When we originally switched to MongoDB back in 2009 one of the plus points was the detailed documentation. It’s even more detailed now and there is a large project underway rewriting the existing wiki docs. 10gen, the company behind MongoDB, also run huge numbers of conferences around the world so others can share knowledge, offer commercial training, free webinars and recently announced free online courses.

However, there seem to have been quite a few “don’t use MongoDB” posts over the last few months so is there actually a real problem with MongoDB itself?

Let’s take a look at a few of them to see what the issues were:

I’ll Give MongoDB Another Try. In Ten Years – 24 Sept 2012

Headline problem: Deployed on 32 bit server so was limited to 2GB database. Writes were being silently discarded.
Mistake: Deployed to 32 bit servers without knowledge of the limit. Did not use safe writes and didn’t check for errors after writes.

Comments: The 32 bit limit is noted (perhaps it should be a warning) on the download page but the main problem was the author did not know when writes started to fail. MongoDB uses unsafe writes by default in the sense that from the driver, you do not know if the write has succeeded without a further call to getLastError. This is because one of the often cited use cases for MongoDB is fast writes, which is achieved by fire and forget queries.

There has been much discussion about whether this is a sensible default and here we’ve seen someone caught out by this. I’ve spoken to quite a few people who didn’t understand this so if it isn’t to be changed, the documentation should highlight it. The PHP docs do thisbut the quick start tutorials for Ruby and Python don’t. With 10gen controlling all official drivers, this inconsistence could be rectified.

Many suggest this default is a good way to get favourable benchmarks but there are no official ones so I don’t think that’s relevant.

來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/301743/viewspace-745312/，如需轉載，請註明出處，否則將追究法律責任。

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