Hands-On Software Engineering with Golang

The gateway

The gateway service is nothing more than a wrapper on top of a gRPC client. The interesting bit of its implementation is the CollectQuotes method, which is what our main package will invoke to begin a new trace:

func (gw *Gateway) CollectQuotes(ctx context.Context, SKU string) (map[string]float64, error) {
    span, ctx := opentracing.StartSpanFromContext(ctx, "CollectQuotes")
    defer span.Finish()

    res, err := gw.client.GetQuote(ctx, &proto.QuotesRequest{SKU: SKU})
    if err != nil {
        return nil, err
    }

    quoteMap := make(map[string]float64, len(res.Quotes))
    for _, quote := range res.Quotes {
        quoteMap[quote.Vendor] = quote.Price
    }
    return quoteMap, nil
}

Here, we use StartSpanFromContext to create a new named span and embed its trace details ...