github.com/darrenli6/fabric-sdk-example@v0.0.0-20220109053535-94b13b56df8c/events/consumer/consumer.go

/*
Copyright IBM Corp. 2016 All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

		 http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package consumer

import (
	"errors"
	"fmt"
	"io"
	"sync"
	"time"

	"golang.org/x/net/context"
	"google.golang.org/grpc"

	"github.com/hyperledger/fabric/common/flogging"
	"github.com/hyperledger/fabric/core/comm"
	mspmgmt "github.com/hyperledger/fabric/msp/mgmt"
	ehpb "github.com/hyperledger/fabric/protos/peer"
	"github.com/hyperledger/fabric/protos/utils"
)

var consumerLogger = flogging.MustGetLogger("eventhub_consumer")

//EventsClient holds the stream and adapter for consumer to work with
type EventsClient struct {
	sync.RWMutex
	peerAddress string
	regTimeout  time.Duration
	stream      ehpb.Events_ChatClient
	adapter     EventAdapter
}

//NewEventsClient Returns a new grpc.ClientConn to the configured local PEER.
func NewEventsClient(peerAddress string, regTimeout time.Duration, adapter EventAdapter) (*EventsClient, error) {
	var err error
	if regTimeout < 100*time.Millisecond {
		regTimeout = 100 * time.Millisecond
		err = fmt.Errorf("regTimeout >= 0, setting to 100 msec")
	} else if regTimeout > 60*time.Second {
		regTimeout = 60 * time.Second
		err = fmt.Errorf("regTimeout > 60, setting to 60 sec")
	}
	return &EventsClient{sync.RWMutex{}, peerAddress, regTimeout, nil, adapter}, err
}

//newEventsClientConnectionWithAddress Returns a new grpc.ClientConn to the configured local PEER.
func newEventsClientConnectionWithAddress(peerAddress string) (*grpc.ClientConn, error) {
	if comm.TLSEnabled() {
		return comm.NewClientConnectionWithAddress(peerAddress, true, true, comm.InitTLSForPeer())
	}
	return comm.NewClientConnectionWithAddress(peerAddress, true, false, nil)
}

func (ec *EventsClient) send(emsg *ehpb.Event) error {
	ec.Lock()
	defer ec.Unlock()

	// obtain the default signing identity for this peer; it will be used to sign the event
	localMsp := mspmgmt.GetLocalMSP()
	if localMsp == nil {
		return errors.New("nil local MSP manager")
	}

	signer, err := localMsp.GetDefaultSigningIdentity()
	if err != nil {
		return fmt.Errorf("could not obtain the default signing identity, err %s", err)
	}

	//pass the signer's cert to Creator
	signerCert, err := signer.Serialize()
	if err != nil {
		return fmt.Errorf("fail to serialize the default signing identity, err %s", err)
	}
	emsg.Creator = signerCert

	signedEvt, err := utils.GetSignedEvent(emsg, signer)
	if err != nil {
		return fmt.Errorf("could not sign outgoing event, err %s", err)
	}

	return ec.stream.Send(signedEvt)
}

// RegisterAsync - registers interest in a event and doesn't wait for a response
func (ec *EventsClient) RegisterAsync(ies []*ehpb.Interest) error {
	creator, err := getCreatorFromLocalMSP()
	if err != nil {
		return fmt.Errorf("error getting creator from MSP: %s", err)
	}
	emsg := &ehpb.Event{Event: &ehpb.Event_Register{Register: &ehpb.Register{Events: ies}}, Creator: creator}

	if err = ec.send(emsg); err != nil {
		consumerLogger.Errorf("error on Register send %s\n", err)
	}
	return err
}

// register - registers interest in a event
func (ec *EventsClient) register(ies []*ehpb.Interest) error {
	var err error
	if err = ec.RegisterAsync(ies); err != nil {
		return err
	}

	regChan := make(chan struct{})
	go func() {
		defer close(regChan)
		in, inerr := ec.stream.Recv()
		if inerr != nil {
			err = inerr
			return
		}
		switch in.Event.(type) {
		case *ehpb.Event_Register:
		case nil:
			err = fmt.Errorf("invalid nil object for register")
		default:
			err = fmt.Errorf("invalid registration object")
		}
	}()
	select {
	case <-regChan:
	case <-time.After(ec.regTimeout):
		err = fmt.Errorf("timeout waiting for registration")
	}
	return err
}

// UnregisterAsync - Unregisters interest in a event and doesn't wait for a response
func (ec *EventsClient) UnregisterAsync(ies []*ehpb.Interest) error {
	creator, err := getCreatorFromLocalMSP()
	if err != nil {
		return fmt.Errorf("error getting creator from MSP: %s", err)
	}
	emsg := &ehpb.Event{Event: &ehpb.Event_Unregister{Unregister: &ehpb.Unregister{Events: ies}}, Creator: creator}

	if err = ec.send(emsg); err != nil {
		err = fmt.Errorf("error on unregister send %s\n", err)
	}

	return err
}

// Recv receives next event - use when client has not called Start
func (ec *EventsClient) Recv() (*ehpb.Event, error) {
	in, err := ec.stream.Recv()
	if err == io.EOF {
		// read done.
		if ec.adapter != nil {
			ec.adapter.Disconnected(nil)
		}
		return nil, err
	}
	if err != nil {
		if ec.adapter != nil {
			ec.adapter.Disconnected(err)
		}
		return nil, err
	}
	return in, nil
}
func (ec *EventsClient) processEvents() error {
	defer ec.stream.CloseSend()
	for {
		in, err := ec.stream.Recv()
		if err == io.EOF {
			// read done.
			if ec.adapter != nil {
				ec.adapter.Disconnected(nil)
			}
			return nil
		}
		if err != nil {
			if ec.adapter != nil {
				ec.adapter.Disconnected(err)
			}
			return err
		}
		if ec.adapter != nil {
			cont, err := ec.adapter.Recv(in)
			if !cont {
				return err
			}
		}
	}
}

//Start establishes connection with Event hub and registers interested events with it
func (ec *EventsClient) Start() error {
	conn, err := newEventsClientConnectionWithAddress(ec.peerAddress)
	if err != nil {
		return fmt.Errorf("could not create client conn to %s:%s", ec.peerAddress, err)
	}

	ies, err := ec.adapter.GetInterestedEvents()
	if err != nil {
		return fmt.Errorf("error getting interested events:%s", err)
	}

	if len(ies) == 0 {
		return fmt.Errorf("must supply interested events")
	}

	serverClient := ehpb.NewEventsClient(conn)
	ec.stream, err = serverClient.Chat(context.Background())
	if err != nil {
		return fmt.Errorf("could not create client conn to %s:%s", ec.peerAddress, err)
	}

	if err = ec.register(ies); err != nil {
		return err
	}

	go ec.processEvents()

	return nil
}

//Stop terminates connection with event hub
func (ec *EventsClient) Stop() error {
	if ec.stream == nil {
		// in case the steam/chat server has not been established earlier, we assume that it's closed, successfully
		return nil
	}
	return ec.stream.CloseSend()
}

func getCreatorFromLocalMSP() ([]byte, error) {
	localMsp := mspmgmt.GetLocalMSP()
	if localMsp == nil {
		return nil, errors.New("nil local MSP manager")
	}
	signer, err := localMsp.GetDefaultSigningIdentity()
	if err != nil {
		return nil, fmt.Errorf("could not obtain the default signing identity, err %s", err)
	}
	creator, err := signer.Serialize()
	if err != nil {
		return nil, fmt.Errorf("error serializing the signer: %s", err)
	}
	return creator, nil
}