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rpcbus.go
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rpcbus.go
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// This Source Code Form is subject to the terms of the MIT License.
// If a copy of the MIT License was not distributed with this
// file, you can obtain one at https://opensource.org/licenses/MIT.
//
// Copyright (c) DUSK NETWORK. All rights reserved.
package rpcbus
import (
"bytes"
"errors"
"fmt"
"sync"
"time"
"github.com/dusk-network/dusk-blockchain/pkg/p2p/wire/topics"
)
// ErrMethodNotExists is returned when calling an unregistered method.
type ErrMethodNotExists struct {
topic topics.Topic
}
// Error obeys the error interface.
func (e *ErrMethodNotExists) Error() string {
return fmt.Sprintf("method not registered: %s", e.topic)
}
var (
// ErrRequestTimeout is returned when request timeout-ed.
ErrRequestTimeout = errors.New("timeout-ed request")
// ErrMethodExists is returned when method is already registered.
ErrMethodExists = errors.New("method exists already")
// ErrInvalidRequestChan is returned method is bound to nil chan.
ErrInvalidRequestChan = errors.New("invalid request channel")
// DefaultTimeout is used when 0 timeout is set on calling a method.
DefaultTimeout = 5 * time.Second
)
// RPCBus is a request–response mechanism for internal communication between node
// components/subsystems. Under the hood this is long-polling method based on
// "chan chan" technique.
type RPCBus struct {
mu sync.RWMutex
registry map[topics.Topic]chan<- Request
}
// Request is the request object forwarded to the RPC endpoint.
type Request struct {
Params interface{}
RespChan chan Response
}
// Response is the response to the request forwarded to the RPC endpoint.
type Response struct {
Resp interface{}
Err error
}
// EmptyRequest returns a Request instance with no parameters.
func EmptyRequest() Request {
return NewRequest(bytes.Buffer{})
}
// NewRequest builds a new request with params. It creates the response channel
// under the hood.
func NewRequest(p interface{}) Request {
return Request{
Params: p,
RespChan: make(chan Response, 1),
}
}
// NewResponse builds a new response.
func NewResponse(p interface{}, err error) Response {
return Response{
Resp: p,
Err: err,
}
}
// New creates an RPCBus instance.
func New() *RPCBus {
return &RPCBus{
registry: make(map[topics.Topic]chan<- Request),
}
}
// Register registers a method and binds it to a handler channel. methodName
// must be unique per node instance. If not, returns err.
func (bus *RPCBus) Register(t topics.Topic, req chan<- Request) error {
bus.mu.Lock()
defer bus.mu.Unlock()
if req == nil {
return ErrInvalidRequestChan
}
if _, ok := bus.registry[t]; ok {
return ErrMethodExists
}
bus.registry[t] = req
return nil
}
// Deregister removes a handler channel from a method.
func (bus *RPCBus) Deregister(t topics.Topic) {
bus.mu.Lock()
defer bus.mu.Unlock()
delete(bus.registry, t)
}
// Call runs a long-polling technique to request from the method Consumer to
// run the corresponding procedure and return a result or timeout.
func (bus *RPCBus) Call(t topics.Topic, req Request, timeOut time.Duration) (interface{}, error) {
reqChan, err := bus.getReqChan(t)
if err != nil {
return bytes.Buffer{}, err
}
if timeOut <= 0 {
timeOut = DefaultTimeout
}
return bus.callTimeout(reqChan, req, timeOut)
}
func (bus *RPCBus) callTimeout(reqChan chan<- Request, req Request, timeOut time.Duration) (interface{}, error) {
timer := time.NewTimer(timeOut)
select {
case reqChan <- req:
case <-timer.C:
return bytes.Buffer{}, ErrRequestTimeout
}
if !timer.Stop() {
<-timer.C
}
timer.Reset(timeOut)
var resp Response
select {
case resp = <-req.RespChan:
case <-timer.C:
return bytes.Buffer{}, ErrRequestTimeout
}
if !timer.Stop() {
<-timer.C
}
return resp.Resp, resp.Err
}
//nolint
func (bus *RPCBus) callNoTimeout(reqChan chan<- Request, req Request) (interface{}, error) {
reqChan <- req
resp := <-req.RespChan
return resp.Resp, resp.Err
}
func (bus *RPCBus) getReqChan(t topics.Topic) (chan<- Request, error) {
bus.mu.RLock()
defer bus.mu.RUnlock()
if reqChan, ok := bus.registry[t]; ok {
return reqChan, nil
}
return nil, &ErrMethodNotExists{t}
}
// Close the RPCBus by resetting the registry.
func (bus *RPCBus) Close() {
bus.mu.Lock()
defer bus.mu.Unlock()
// Channels should be closed only by the goroutines/components
// that make them
// Reset registry
bus.registry = make(map[topics.Topic]chan<- Request)
}