replaces network startup

engine/verification/requester/requester.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/opentracing/opentracing-go"
 	"github.com/rs/zerolog"
+	"github.com/rs/zerolog/log"
 	"golang.org/x/exp/rand"
 
 	"github.com/onflow/flow-go/engine"
@@ -48,6 +49,7 @@ type Engine struct {
 	unit  *engine.Unit
 	state protocol.State  // used to check the last sealed height.
 	con   network.Conduit // used to send the chunk data request, and receive the response.
+	net   module.Network
 
 	// monitoring
 	tracer  module.Tracer
@@ -86,14 +88,9 @@ func New(log zerolog.Logger,
 		pendingRequests:  pendingRequests,
 		reqUpdaterFunc:   reqUpdaterFunc,
 		reqQualifierFunc: reqQualifierFunc,
+		net:              net,
 	}
 
-	con, err := net.Register(engine.RequestChunks, e)
-	if err != nil {
-		return nil, fmt.Errorf("could not register chunk data pack provider engine: %w", err)
-	}
-	e.con = con
-
 	return e, nil
 }
 
@@ -134,10 +131,19 @@ func (e *Engine) Process(originID flow.Identifier, event interface{}) error {
 // Ready initializes the engine and returns a channel that is closed when the initialization is done.
 func (e *Engine) Ready() <-chan struct{} {
 	if e.handler == nil {
+		// we should crash the node with fatal-level log if handler is missing
 		e.log.Fatal().Msg("could not start requester engine with missing chunk data pack handler")
 	}
 
+	con, err := e.net.Register(engine.RequestChunks, e)
+	if err != nil {
+		// we should crash the node with fatal-level log if network module is missing
+		log.Fatal().Err(err).Msg("could not register requester engine on network")
+	}
+	e.con = con
+
 	delay := time.Duration(0)
+
 	// run a periodic check to retry requesting chunk data packs.
 	// if onTimer takes longer than retryInterval, the next call will be blocked until the previous
 	// call has finished.