110 lines
4.3 KiB
Go
110 lines
4.3 KiB
Go
// Copyright 2015 The go-ethereum Authors
|
|
// This file is part of the go-ethereum library.
|
|
//
|
|
// The go-ethereum library is free software: you can redistribute it and/or modify
|
|
// it under the terms of the GNU Lesser General Public License as published by
|
|
// the Free Software Foundation, either version 3 of the License, or
|
|
// (at your option) any later version.
|
|
//
|
|
// The go-ethereum library is distributed in the hope that it will be useful,
|
|
// but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
// GNU Lesser General Public License for more details.
|
|
//
|
|
// You should have received a copy of the GNU Lesser General Public License
|
|
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
|
|
|
|
/*
|
|
Package rpc implements bi-directional JSON-RPC 2.0 on multiple transports.
|
|
|
|
It provides access to the exported methods of an object across a network or other I/O
|
|
connection. After creating a server or client instance, objects can be registered to make
|
|
them visible as 'services'. Exported methods that follow specific conventions can be
|
|
called remotely. It also has support for the publish/subscribe pattern.
|
|
|
|
# RPC Methods
|
|
|
|
Methods that satisfy the following criteria are made available for remote access:
|
|
|
|
- method must be exported
|
|
- method returns 0, 1 (response or error) or 2 (response and error) values
|
|
|
|
An example method:
|
|
|
|
func (s *CalcService) Add(a, b int) (int, error)
|
|
|
|
When the returned error isn't nil the returned integer is ignored and the error is sent
|
|
back to the client. Otherwise the returned integer is sent back to the client.
|
|
|
|
Optional arguments are supported by accepting pointer values as arguments. E.g. if we want
|
|
to do the addition in an optional finite field we can accept a mod argument as pointer
|
|
value.
|
|
|
|
func (s *CalcService) Add(a, b int, mod *int) (int, error)
|
|
|
|
This RPC method can be called with 2 integers and a null value as third argument. In that
|
|
case the mod argument will be nil. Or it can be called with 3 integers, in that case mod
|
|
will be pointing to the given third argument. Since the optional argument is the last
|
|
argument the RPC package will also accept 2 integers as arguments. It will pass the mod
|
|
argument as nil to the RPC method.
|
|
|
|
The server offers the ServeCodec method which accepts a ServerCodec instance. It will read
|
|
requests from the codec, process the request and sends the response back to the client
|
|
using the codec. The server can execute requests concurrently. Responses can be sent back
|
|
to the client out of order.
|
|
|
|
An example server which uses the JSON codec:
|
|
|
|
type CalculatorService struct {}
|
|
|
|
func (s *CalculatorService) Add(a, b int) int {
|
|
return a + b
|
|
}
|
|
|
|
func (s *CalculatorService) Div(a, b int) (int, error) {
|
|
if b == 0 {
|
|
return 0, errors.New("divide by zero")
|
|
}
|
|
return a/b, nil
|
|
}
|
|
|
|
calculator := new(CalculatorService)
|
|
server := NewServer()
|
|
server.RegisterName("calculator", calculator)
|
|
l, _ := net.ListenUnix("unix", &net.UnixAddr{Net: "unix", Name: "/tmp/calculator.sock"})
|
|
server.ServeListener(l)
|
|
|
|
# Subscriptions
|
|
|
|
The package also supports the publish subscribe pattern through the use of subscriptions.
|
|
A method that is considered eligible for notifications must satisfy the following
|
|
criteria:
|
|
|
|
- method must be exported
|
|
- first method argument type must be context.Context
|
|
- method must have return types (rpc.Subscription, error)
|
|
|
|
An example method:
|
|
|
|
func (s *BlockChainService) NewBlocks(ctx context.Context) (rpc.Subscription, error) {
|
|
...
|
|
}
|
|
|
|
When the service containing the subscription method is registered to the server, for
|
|
example under the "blockchain" namespace, a subscription is created by calling the
|
|
"blockchain_subscribe" method.
|
|
|
|
Subscriptions are deleted when the user sends an unsubscribe request or when the
|
|
connection which was used to create the subscription is closed. This can be initiated by
|
|
the client and server. The server will close the connection for any write error.
|
|
|
|
For more information about subscriptions, see https://github.com/ethereum/go-ethereum/wiki/RPC-PUB-SUB.
|
|
|
|
# Reverse Calls
|
|
|
|
In any method handler, an instance of rpc.Client can be accessed through the
|
|
ClientFromContext method. Using this client instance, server-to-client method calls can be
|
|
performed on the RPC connection.
|
|
*/
|
|
package rpc
|