Aspir8 and resolving service endpoints in kubernetes with DNS SRV

[rzikm]

The Readme for Microsoft.Extensions.ServiceDiscovery.Dns mentions

When deploying to Kubernetes, the DNS SRV service endpoint provider can be used to resolve endpoints. For example, the following resource definition will result in a DNS SRV record being created for an endpoint named "default" and an endpoint named "dashboard", both on the service named "basket".

apiVersion: v1
kind: Service
metadata:
  name: basket
spec:
  selector:
    name: basket-service
  clusterIP: None
  ports:
  - name: default
    port: 8080
  - name: dashboard
    port: 8888

However, when using Aspir8 to generate kubernetes deployments (for example in the TestShop project), I get

---
apiVersion: v1
kind: Service
metadata:
  name: basketservice
spec:
  type: ClusterIP
  selector:
    app: basketservice
  ports:
    - name: http
      port: 8080
      targetPort: 8080
    - name: https
      port: 8443
      targetPort: 8443

Notice that the name of the 8080 port is http instead of default, meaning that DNS SRV resolution will attempt to resolve _default._tcp._basketservice and fail (because there is no "default" port). So the options app developer has are either:

• manually fixup the generated yaml - and risk it being overwritten on next aspirate generate invocation
• fix all references in code to http://_http.basketservice - which does not work well if I want to do local deployment via dotnet run in AppHost folder.

Furthermore, reading the comments and code:

aspire/src/Microsoft.Extensions.ServiceDiscovery.Dns/DnsSrvServiceEndpointProviderFactory.cs

Lines 25 to 44 in 15db8a1

	// If a default namespace is not specified, then this provider will attempt to infer the namespace from the service name, but only when running inside Kubernetes.
	// Kubernetes DNS spec: https://github.com/kubernetes/dns/blob/master/docs/specification.md
	// SRV records are available for headless services with named ports.
	// They take the form $"_{portName}._{protocol}.{serviceName}.{namespace}.{suffix}"
	// The suffix (after the service name) can be parsed from /etc/resolv.conf
	// Otherwise, the namespace can be read from /var/run/secrets/kubernetes.io/serviceaccount/namespace and combined with an assumed suffix of "svc.cluster.local".
	// The protocol is assumed to be "tcp".
	// The portName is the name of the port in the service definition. If the serviceName parses as a URI, we use the scheme as the port name, otherwise "default".
	if (string.IsNullOrWhiteSpace(_querySuffix))
	{
	DnsServiceEndpointProviderBase.Log.NoDnsSuffixFound(logger, query.ToString()!);
	provider = default;
	return false;
	}
	var portName = query.EndpointName ?? "default";
	var srvQuery = $"_{portName}._tcp.{query.ServiceName}.{_querySuffix}";
	provider = new DnsSrvServiceEndpointProvider(query, srvQuery, hostName: query.ServiceName, options, logger, resolver, timeProvider);
	return true;
	}

Specifically note the last sentece: "If serviceName parses as a URI, we use scheme as the port name, otherwise "default""

Bu there is no corresponding code in ServiceEndpointQuery parsing code

aspire/src/Microsoft.Extensions.ServiceDiscovery.Abstractions/ServiceEndpointQuery.cs

Lines 36 to 76 in 22d5ec4

	public static bool TryParse(string input, [NotNullWhen(true)] out ServiceEndpointQuery? query)
	{
	ArgumentException.ThrowIfNullOrEmpty(input);
	bool hasScheme;
	if (!input.Contains("://", StringComparison.InvariantCulture)
	&& Uri.TryCreate($"fakescheme://{input}", default, out var uri))
	{
	hasScheme = false;
	}
	else if (Uri.TryCreate(input, default, out uri))
	{
	hasScheme = true;
	}
	else
	{
	query = null;
	return false;
	}
	var uriHost = uri.Host;
	var segmentSeparatorIndex = uriHost.IndexOf('.');
	string host;
	string? endpointName = null;
	if (uriHost.StartsWith('_') && segmentSeparatorIndex > 1 && uriHost[^1] != '.')
	{
	endpointName = uriHost[1..segmentSeparatorIndex];
	// Skip the endpoint name, including its prefix ('_') and suffix ('.').
	host = uriHost[(segmentSeparatorIndex + 1)..];
	}
	else
	{
	host = uriHost;
	}
	// Allow multiple schemes to be separated by a '+', eg. "https+http://host:port".
	var schemes = hasScheme ? uri.Scheme.Split('+') : [];
	query = new(input, schemes, host, endpointName);
	return true;
	}

Given the comments in the first code snippet, I would expect referencing http://basketservice to lead to resolving via SRV query for _http._tcp.basketservice. On the other hand, it is not so clear what should happen with http+https://basketservice.