This really needs to be handled in the application since protobuf has no
idea which fields are expendable or can be truncated. What I was trying to
suggest earlier was to construct many Req protobufs and serialize those
individually. i.e., instead of 1 Req proto with 1,000,000 page ids,
construct 1000 Req protos, each containing 1000 page ids. You can serialize
each of those individually, stopping when you hit your memory budget.
That being said, I would suggest redesigning your protocol so that you don't
have to construct enormous messages. It sounds like what you really want is
something like the streaming functionality in the rpc service - rather than
sending one large protobuf you would want to stream each page id.
On Thu, Jun 3, 2010 at 6:27 AM, dirlt <dirtysalt1...@gmail.com> wrote:
> 3ku for you relply:).For the first one,I think your answer is quite
> clear.
>
> But to the second one,en,I want to produce the serialization of Req.
>
> Let me explain again:). assume my application is like this:
> 0.server app wants to send 1,000,000 pageids to client
> 1.if server app sends 1,000,000 pages id and serialize it, it will
> cost 1GB memory
>
> 2.but server app can just allocate 100MB memory. So obviously server
> app can't send all pageids[1,000,000] to client
>
> 3.meanwhile the server app's protobuf is very clever. It[protobuf] can
> calculate that "if server app has 100MB, it can just hold 10,000
> pageids at most". So protobuf tells server that "Hi server,if you just
> have 100MB memory,I can only hold 10,000 pageids"
>
> 4.so the server app knows it,so app just serialize 10,000 pageids into
> memory instead of 1,000,000 pageids.
>
> I hope I clarify it now.. If the protobuf doesn't implement it, do you
> have any idea about it?.
>
>
> On Jun 3, 12:40 am, Jason Hsueh <jas...@google.com> wrote:
> > On Tue, Jun 1, 2010 at 6:21 AM, bnh <baoneng...@gmail.com> wrote:
> > > I'm using a protobuf as the protocol for a distributed system.But now
> > > I
> > > have some questions about protobuf
> >
> > > a.Whether protobuf provides the inteface for user-defined allocator
> > > because sometimes I find 'malloc' cost too much? I've tried TCmalloc,
> > > but I think I can optimize the memory allocation according to my
> > > application.
> >
> > No, there are no hooks for providing an allocator. You'd need to override
> > malloc the way TCmalloc does if you want to use your own allocator.
> >
> >
> >
> >
> >
> > > b.Whethere protobuf provides a way to serialize a class/object
> > > partially[Or do you have some ideas about it]? Because my application
> > > is
> > > very sensitive of memory usage.. Such as a class
> >
> > > class Req{
> > > int userid;
> > > vector<PageID> pageid;
> > > };
> >
> > > I want to pack 1000 pageids into the Req. But if I pack all of them,
> > > the
> > > Req's size is about 1GB [hypothetically]. But I just have 100MB
> > > memory,
> > > so I just plan to pack pageids as many as possible until the memory
> > > usage of Req is about 100MB. ['serialize object partially according to
> > > memory usage'].
> >
> > Are you talking about producing the serialization of Req, with a large
> > number of PageIds, or parsing such a serialization into an in-memory
> object?
> > For the former, you can serialize in smaller pieces, and just concatenate
> > the serializations:
> http://code.google.com/apis/protocolbuffers/docs/encoding.html#optional
> > For the latter, there is no way for you to tell the parser to stop
> parsing
> > when memory usage reaches a certain limit. However, you can do this
> yourself
> > if you split the serialization into multiple pieces.
> >
> >
> >
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