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Phase D: Automated DNS registration via MCNS

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Add DNSRegistrar that creates/updates/deletes A records in MCNS
during deploy and stop. When a service has routes, the agent ensures
an A record exists in the configured zone pointing to the node's
address. On stop, the record is removed.

- Add MCNSConfig to agent config (server_url, ca_cert, token_path,
  zone, node_addr) with defaults and env overrides
- Add DNSRegistrar (internal/agent/dns.go): REST client for MCNS
  record CRUD, nil-receiver safe
- Wire into deploy flow (EnsureRecord after route registration)
- Wire into stop flow (RemoveRecord before container stop)
- 7 new tests, make all passes with 0 issues

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Kyle Isom
2026-03-27 14:33:41 -07:00
parent e4d131021e
commit 9d9ad6588e
7 changed files with 608 additions and 0 deletions
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33
internal/config/agent.go
View File

@@ -16,6 +16,7 @@ type AgentConfig struct {
Agent AgentSettings `toml:"agent"`
MCProxy MCProxyConfig `toml:"mcproxy"`
Metacrypt MetacryptConfig `toml:"metacrypt"`
MCNS MCNSConfig `toml:"mcns"`
Monitor MonitorConfig `toml:"monitor"`
Log LogConfig `toml:"log"`
}
@@ -40,6 +41,26 @@ type MetacryptConfig struct {
TokenPath string `toml:"token_path"`
}
// MCNSConfig holds the MCNS DNS integration settings for automated
// DNS record registration. If ServerURL is empty, DNS registration
// is disabled.
type MCNSConfig struct {
// ServerURL is the MCNS API base URL (e.g. "https://localhost:28443").
ServerURL string `toml:"server_url"`
// CACert is the path to the CA certificate for verifying MCNS's TLS.
CACert string `toml:"ca_cert"`
// TokenPath is the path to the MCIAS service token file.
TokenPath string `toml:"token_path"`
// Zone is the DNS zone for service records. Defaults to "svc.mcp.metacircular.net".
Zone string `toml:"zone"`
// NodeAddr is the IP address to register as the A record value.
NodeAddr string `toml:"node_addr"`
}
// MCProxyConfig holds the mc-proxy connection settings.
type MCProxyConfig struct {
// Socket is the path to the mc-proxy gRPC admin API Unix socket.
@@ -177,6 +198,9 @@ func applyAgentDefaults(cfg *AgentConfig) {
if cfg.Metacrypt.Issuer == "" {
cfg.Metacrypt.Issuer = "infra"
}
if cfg.MCNS.Zone == "" {
cfg.MCNS.Zone = "svc.mcp.metacircular.net"
}
}
func applyAgentEnvOverrides(cfg *AgentConfig) {
@@ -213,6 +237,15 @@ func applyAgentEnvOverrides(cfg *AgentConfig) {
if v := os.Getenv("MCP_AGENT_METACRYPT_TOKEN_PATH"); v != "" {
cfg.Metacrypt.TokenPath = v
}
if v := os.Getenv("MCP_AGENT_MCNS_SERVER_URL"); v != "" {
cfg.MCNS.ServerURL = v
}
if v := os.Getenv("MCP_AGENT_MCNS_TOKEN_PATH"); v != "" {
cfg.MCNS.TokenPath = v
}
if v := os.Getenv("MCP_AGENT_MCNS_NODE_ADDR"); v != "" {
cfg.MCNS.NodeAddr = v
}
}
func validateAgentConfig(cfg *AgentConfig) error {

80
internal/config/config_test.go
View File

@@ -171,6 +171,11 @@ func TestLoadAgentConfig(t *testing.T) {
if cfg.Metacrypt.Issuer != "infra" {
t.Fatalf("metacrypt.issuer default: got %q, want infra", cfg.Metacrypt.Issuer)
}
// MCNS defaults when section is omitted.
if cfg.MCNS.Zone != "svc.mcp.metacircular.net" {
t.Fatalf("mcns.zone default: got %q, want svc.mcp.metacircular.net", cfg.MCNS.Zone)
}
}
func TestCLIConfigValidation(t *testing.T) {
@@ -521,6 +526,81 @@ node_name = "rift"
}
}
func TestAgentConfigMCNS(t *testing.T) {
cfgStr := `
[server]
grpc_addr = "0.0.0.0:9444"
tls_cert = "/srv/mcp/cert.pem"
tls_key = "/srv/mcp/key.pem"
[database]
path = "/srv/mcp/mcp.db"
[mcias]
server_url = "https://mcias.metacircular.net:8443"
service_name = "mcp-agent"
[agent]
node_name = "rift"
[mcns]
server_url = "https://localhost:28443"
ca_cert = "/srv/mcp/certs/metacircular-ca.pem"
token_path = "/srv/mcp/metacrypt-token"
zone = "custom.zone"
node_addr = "10.0.0.1"
`
path := writeTempConfig(t, cfgStr)
cfg, err := LoadAgentConfig(path)
if err != nil {
t.Fatalf("load: %v", err)
}
if cfg.MCNS.ServerURL != "https://localhost:28443" {
t.Fatalf("mcns.server_url: got %q", cfg.MCNS.ServerURL)
}
if cfg.MCNS.CACert != "/srv/mcp/certs/metacircular-ca.pem" {
t.Fatalf("mcns.ca_cert: got %q", cfg.MCNS.CACert)
}
if cfg.MCNS.Zone != "custom.zone" {
t.Fatalf("mcns.zone: got %q", cfg.MCNS.Zone)
}
if cfg.MCNS.NodeAddr != "10.0.0.1" {
t.Fatalf("mcns.node_addr: got %q", cfg.MCNS.NodeAddr)
}
}
func TestAgentConfigMCNSEnvOverrides(t *testing.T) {
minimal := `
[server]
grpc_addr = "0.0.0.0:9444"
tls_cert = "/srv/mcp/cert.pem"
tls_key = "/srv/mcp/key.pem"
[database]
path = "/srv/mcp/mcp.db"
[mcias]
server_url = "https://mcias.metacircular.net:8443"
service_name = "mcp-agent"
[agent]
node_name = "rift"
`
t.Setenv("MCP_AGENT_MCNS_SERVER_URL", "https://override:28443")
t.Setenv("MCP_AGENT_MCNS_TOKEN_PATH", "/override/token")
t.Setenv("MCP_AGENT_MCNS_NODE_ADDR", "10.0.0.99")
path := writeTempConfig(t, minimal)
cfg, err := LoadAgentConfig(path)
if err != nil {
t.Fatalf("load: %v", err)
}
if cfg.MCNS.ServerURL != "https://override:28443" {
t.Fatalf("mcns.server_url: got %q", cfg.MCNS.ServerURL)
}
if cfg.MCNS.TokenPath != "/override/token" {
t.Fatalf("mcns.token_path: got %q", cfg.MCNS.TokenPath)
}
if cfg.MCNS.NodeAddr != "10.0.0.99" {
t.Fatalf("mcns.node_addr: got %q", cfg.MCNS.NodeAddr)
}
}
func TestDurationParsing(t *testing.T) {
tests := []struct {
input string