Thrift Package for Go

API Documentation: http://godoc.org/github.com/samuel/go-thrift

License

3-clause BSD. See LICENSE file.

Overview

So why another thrift package? While the existing one (thrift4go) works well, my philosophy is that interfaces should match the language. Most Thrift libraries try to match the API of the original which makes them awkward to use in other languages.

As an example, Go already has the idea of a thrift transport in the ReadWriteCloser interfaces.

Another design decision was to keep the generated code as terse as possible. The generator only creates a struct and the encoding/decoding is done through reflection. Annotations are used to set thrift ID for a field and options such as 'required'.

Example struct:

type User struct {
    Id        int64    `thrift:"1,required"`
    Name      string   `thrift:"2"`
    PostCount int32    `thrift:"3,keepempty"`
    Flags     []string `thrift:"4"`
    SomeSet   []string `thrift:"5,set"`
}

Types

Most types map directly to the native Go types, but there are some quirks and limitations.

• Go supports a more limited set of types for map keys than Thrift

• To use a set define the field as []type and provide a tag of "set":

    StringSet []string `thrift:"1,set"`
  

• Unsigned types aren't supported. Thrift only has signed types. Could encode/decode unsigned types as their signed counterparts, but I decided against that for now.

• []byte get encoded/decoded as a string because the Thrift binary type is the same as string on the wire.

RPC

The standard Go net/rpc package is used to provide RPC. Although, one incompatibility is the net/rpc's use of ServiceName.Method for naming RPC methods. To get around this the Thrift ServerCodec prefixes method names with "Thrift".

Transport

There are no specific transport "classes" as there are in most Thrift libraries. Instead, the standard io.ReadWriteCloser is used as the interface. If the value also implements the thrift.Flusher interface then Flush() error is called after protocol.WriteMessageEnd.

Framed transport is supported by wrapping a value implementing io.ReadWriteCloser with thrift.NewFramedReadWriteCloser(value)

One-way requests

Client

One-way request support needs to be enabled on the RPC codec explicitly. The reason they're not allowed by default is because the Go RPC package doesn't actually support one-way requests. To get around this requires a rather janky hack of using channels to track pending requests in the codec and faking responses.

Server

One-way requests aren't yet implemented on the server side.

Parser & Code Generator

The "parser" subdirectory contains a Thrift IDL parser, and "generator" contains a Go code generator. It could be extended to include other languages.

How to use the generator:

$ go install github.com/samuel/go-thrift/generator

$ generator --help
Usage of parsimony: [options] inputfile outputfile
  -go.binarystring=false: Always use string for binary instead of []byte
  -go.json.enumnum=false: For JSON marshal enums by number instead of name
  -go.packagename="": Override the package name
  -go.pointers=false: Make all fields pointers

$ mkdir $GOPATH/src/cassandra
$ generator cassandra.thrift $GOPATH/cassandra/thrift.go

# Then can import "cassandra"

TODO

• "extends" for services
• default values (is it worth it? maybe just annotations?)