Hands-On Software Engineering with Golang

The aggregator service

The next service that we will be implementing is the Aggregator type. As shown in the following code snippet, it stores a vendor ID, a list of provider addresses to query, and a list of gRPC clients for those addresses:

type Aggregator struct {
    vendorID      string
    providerAddrs []string
    clients       []proto.QuoteServiceClient
}

func NewAggregator(vendorID string, providerAddrs []string) *Aggregator {
    return &Aggregator{
        vendorID:      vendorID,
        providerAddrs: providerAddrs,
    }
}

The gRPC clients are lazily created when the Serve method is invoked:

func (a *Aggregator) Serve(ctx context.Context) (string, error) { tracer := tracer.MustGetTracer(a.vendorID) tracerClientOpt := grpc.WithUnaryInterceptor(otgrpc.OpenTracingClientInterceptor(tracer)) ...