rpc

Documentation

Overview

Package rpc contains RPC-related structs shared between many components.

Index

• type Unused
  • func (u *Unused) UnmarshalBson(buf *bytes.Buffer, kind byte)

Types

type Unused

type Unused struct{}

Unused is a placeholder type for args and reply values that aren't used. For example, a server might declare a method without args or reply:

func (s *Server) SomeMethod(ctx *Context, args *rpc.Unused, reply *rpc.Unused)

The client would then call it like this:

client.rpcCall("SomeMethod", &rpc.Unused{}, &rpc.Unused{}, waitTime)

Using Unused ensures that, when the server doesn't care about a value, it will silently ignore any value that is passed. With previous placeholder values, such as strings, certain values might result in panics in the BSON library.

If a method declared with Unused as its args or reply is changed to accept a real struct, old clients will encode an empty struct, which will be silently ignored by the new servers. New clients talking to old servers will send the real struct, which will be silently ignored. This allows args or replies to be added to existing methods that previously did not use them.

func (*Unused) UnmarshalBson

func (u *Unused) UnmarshalBson(buf *bytes.Buffer, kind byte)

UnmarshalBson skips over an encoded Unused in a backward-compatible way. Previous versions of Unused would BSON-encode a naked string value, which bson.EncodeSimple() would encode as a document with a field named bson.MAGICTAG. Here we skip over any document or sub-document without looking for the special MAGICTAG field name.