// serviceLookup is used to handle a service query func (d *DNSServer) serviceLookup(network, datacenter, service, tag string, req, resp *dns.Msg) { // Make an RPC request args := structs.ServiceSpecificRequest{ Datacenter: datacenter, ServiceName: service, ServiceTag: tag, TagFilter: tag != "", QueryOptions: structs.QueryOptions{AllowStale: d.config.AllowStale}, } var out structs.IndexedCheckServiceNodes RPC: if err := d.agent.RPC("Health.ServiceNodes", &args, &out); err != nil { d.logger.Printf("[ERR] dns: rpc error: %v", err) resp.SetRcode(req, dns.RcodeServerFailure) return } // Verify that request is not too stale, redo the request if args.AllowStale && out.LastContact > d.config.MaxStale { args.AllowStale = false d.logger.Printf("[WARN] dns: Query results too stale, re-requesting") goto RPC } // If we have no nodes, return not found! if len(out.Nodes) == 0 { resp.SetRcode(req, dns.RcodeNameError) return } // Determine the TTL var ttl time.Duration if d.config.ServiceTTL != nil { var ok bool ttl, ok = d.config.ServiceTTL[service] if !ok { ttl = d.config.ServiceTTL["*"] } } // Filter out any service nodes due to health checks out.Nodes = d.filterServiceNodes(out.Nodes) // Perform a random shuffle shuffleServiceNodes(out.Nodes) // If the network is not TCP, restrict the number of responses if network != "tcp" && len(out.Nodes) > maxServiceResponses { out.Nodes = out.Nodes[:maxServiceResponses] // Flag that there are more records to return in the UDP response if d.config.EnableTruncate == true { resp.Truncated = true } } // Add various responses depending on the request qType := req.Question[0].Qtype d.serviceNodeRecords(out.Nodes, req, resp, ttl) if qType == dns.TypeSRV { d.serviceSRVRecords(datacenter, out.Nodes, req, resp, ttl) } }