Peter (IMC), I think the official word is that we have “over 10,000 PCs” at Google. That stat is a few years old, but that’s the official word, so I that’s what I’ll stick with.

Eddie, normally we use PBs for talking between servers, so I’m not aware of any code to do LDAP with pbuffers. Google tends to use C++ for lots of production machines because we want to wring the most performance from things. There might be JavaScript-to-pbuffer code, but I’m not aware of any. My guess is that we might look to the open-source community for Ruby support; there are people that use Ruby at Google, but it’s not as common as Python/C++/Java is at Google.

Does this support routing a newer version of a message through an older server? If an V2 server sends a V2 objects to a V1 server which routes the object on to another V2 server. Does this final server get a V2 object or a V1 object?

Steve Brewer, great question. Yonatan Zunger answered exactly this question in his post. I’ll quote the relevant bit:

If the protocol deserializer comes across a tag number which isn’t in its copy of the protocol definition, it will just keep it as uninterpreted data and pass it along when it reserializes the proto. So if you have three servers, and A sends a message to B which processes it and then sends it on to C, and you want to add a new field which A uses to communicate something to C, you don’t need to update the B server; it will just pass the updated protocol message along to C. I can’t even begin to tell you how much more pleasant this can make your life.

Some pointers from that post include progress on protocol buffers (sometimes called pbuffers) in Haskell and Perl:
http://hackage.haskell.org/cgi-bin/hackage-scripts/package/protocol-buffers-0.0.5
http://groups.google.com/group/protobuf-perl

Other fellow Googlers have weighed in here:
http://scottkirkwood.blogspot.com/2008/07/google-opensources-protocol-buffers.html

http://zunger.livejournal.com/164024.html

This sounds like it would make that kind of distributed serving of data more efficient.

afewtips.com

This is completely unrelated, but I just thought I’d mention your blog fails both the XHTML and CSS validation tests you have linked at the bottom of every page.