On May 29, 2012, at 23:26 , msrobo wrote:
> According to the documentation, it's recommended that the message size
> be <= 1 Megabyte. I've searched around for the reason for this
> recommendation, but I can't seem to find anything. Based on some basic
> benchmarking serializing/unserializing messages ranging from a few KB
> to more than 1MB in C++ there doesn't seem to be a drastic increase in
> time. More specifically, it doesn't seem to be performance driven in a
> C++ application.

I think the main motivation is that there is no way to "seek" inside a protocol 
buffer, and you must load the entire thing into memory in one go. Hence when 
you get really large messages, you may need to allocate huge amounts of memory 
(the memory for the serialized buffer, and the memory for the entire protocol 
buffer object).

1 MB is just a recommendation, but there are also some internal default limits 
set to 64 MB for "security" issues: If you parse an enormous message, it 
requires allocating a ton of RAM. Hence the limits can prevent servers from 
running out of memory. If you have huge messages, you'll need to call the 
appropriate APIs to change the limits.




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