103 lines
3.7 KiB
Go
103 lines
3.7 KiB
Go
// Copyright 2015 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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/*
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Package rpc provides access to the exported methods of an object across a network
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or other I/O connection. After creating a server instance objects can be registered,
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making it visible from the outside. Exported methods that follow specific
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conventions can be called remotely. It also has support for the publish/subscribe
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pattern.
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Methods that satisfy the following criteria are made available for remote access:
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- object must be exported
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- method must be exported
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- method returns 0, 1 (response or error) or 2 (response and error) values
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- method argument(s) must be exported or builtin types
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- method returned value(s) must be exported or builtin types
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An example method:
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func (s *CalcService) Div(a, b int) (int, error)
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When the returned error isn't nil the returned integer is ignored and the error is
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send back to the client. Otherwise the returned integer is send back to the client.
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The server offers the ServeCodec method which accepts a ServerCodec instance. It will
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read requests from the codec, process the request and sends the response back to the
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client using the codec. The server can execute requests concurrently. Responses
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can be send back to the client out of order.
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An example server which uses the JSON codec:
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type CalculatorService struct {}
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func (s *CalculatorService) Add(a, b int) int {
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return a + b
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}
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func (s *CalculatorService Div(a, b int) (int, error) {
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if b == 0 {
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return 0, errors.New("divide by zero")
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}
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return a/b, nil
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}
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calculator := new(CalculatorService)
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server := NewServer()
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server.RegisterName("calculator", calculator")
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l, _ := net.ListenUnix("unix", &net.UnixAddr{Net: "unix", Name: "/tmp/calculator.sock"})
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for {
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c, _ := l.AcceptUnix()
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codec := v2.NewJSONCodec(c)
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go server.ServeCodec(codec)
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}
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The package also supports the publish subscribe pattern through the use of subscriptions.
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A method that is considered eligible for notifications must satisfy the following criteria:
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- object must be exported
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- method must be exported
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- method argument(s) must be exported or builtin types
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- method must return the tuple Subscription, error
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An example method:
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func (s *BlockChainService) Head() (Subscription, error) {
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sub := s.bc.eventMux.Subscribe(ChainHeadEvent{})
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return v2.NewSubscription(sub), nil
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}
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This method will push all raised ChainHeadEvents to subscribed clients. If the client is only
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interested in every N'th block it is possible to add a criteria.
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func (s *BlockChainService) HeadFiltered(nth uint64) (Subscription, error) {
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sub := s.bc.eventMux.Subscribe(ChainHeadEvent{})
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criteria := func(event interface{}) bool {
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chainHeadEvent := event.(ChainHeadEvent)
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if chainHeadEvent.Block.NumberU64() % nth == 0 {
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return true
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}
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return false
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}
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return v2.NewSubscriptionFiltered(sub, criteria), nil
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}
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Subscriptions are deleted when:
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- the user sends an unsubscribe request
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- the connection which was used to create the subscription is closed
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*/
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package rpc
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