chore: generate sites in Caddyfile from x-ports alongside caddy.json

internal/machine/caddyconfig/caddyfile.go

@@ -1,17 +1,122 @@
 package caddyconfig
 
 import (
+	"bytes"
 	"fmt"
+	"log/slog"
+	"net"
+	"strconv"
+	"strings"
+	"text/template"
 
 	"github.com/psviderski/uncloud/pkg/api"
 )
 
-func GenerateCaddyfile(containers []api.ServiceContainer, verifyResponse string) (string, error) {
-	return fmt.Sprintf(`http:// {
-	handle %s {
-		respond "%s" 200
+const caddyfileTemplate = `http:// {
+	handle {{.VerifyPath}} {
+		respond "{{.VerifyResponse}}" 200
 	}
 	log
 }
-`, VerifyPath, verifyResponse), nil
+
+(common_proxy) {
+	# Retry failed requests up to lb_retries times against other available upstreams.
+	lb_retries 3
+	# Upstreams are marked unhealthy for fail_duration after a failed request (passive health checking).
+	fail_duration 30s
+}
+{{- range $hostname, $upstreams := .HTTPHostUpstreams}}
+
+http://{{$hostname}} {
+	reverse_proxy {
+		to {{join $upstreams " "}}
+		import common_proxy
+	}
+	log
+}{{end}}
+{{- range $hostname, $upstreams := .HTTPSHostUpstreams}}
+
+https://{{$hostname}} {
+	reverse_proxy {
+		to {{join $upstreams " "}}
+		import common_proxy
+	}
+	log
+}{{end}}
+`
+
+func GenerateCaddyfile(containers []api.ServiceContainer, verifyResponse string) (string, error) {
+	httpHostUpstreams, httpsHostUpstreams := httpUpstreamsFromContainers(containers)
+
+	funcs := template.FuncMap{"join": strings.Join}
+	tmpl, err := template.New("Caddyfile").Funcs(funcs).Parse(caddyfileTemplate)
+	if err != nil {
+		return "", fmt.Errorf("failed to parse Caddyfile template: %w", err)
+	}
+
+	data := struct {
+		VerifyPath         string
+		VerifyResponse     string
+		HTTPHostUpstreams  map[string][]string
+		HTTPSHostUpstreams map[string][]string
+	}{
+		VerifyPath:         VerifyPath,
+		VerifyResponse:     verifyResponse,
+		HTTPHostUpstreams:  httpHostUpstreams,
+		HTTPSHostUpstreams: httpsHostUpstreams,
+	}
+
+	var buf bytes.Buffer
+	if err = tmpl.Execute(&buf, data); err != nil {
+		return "", fmt.Errorf("failed to execute Caddyfile template: %w", err)
+	}
+
+	return buf.String(), nil
+}
+
+// httpUpstreamsFromContainers extracts upstreams for HTTP and HTTPS protocols from the published ports of the provided
+// service containers.
+func httpUpstreamsFromContainers(containers []api.ServiceContainer) (map[string][]string, map[string][]string) {
+	// Maps hostnames to lists of upstreams (container IP:port pairs).
+	httpHostUpstreams := make(map[string][]string)
+	httpsHostUpstreams := make(map[string][]string)
+	for _, ctr := range containers {
+		if !ctr.Healthy() {
+			continue
+		}
+
+		ip := ctr.UncloudNetworkIP()
+		if !ip.IsValid() {
+			// Container is not connected to the uncloud Docker network (could be host network).
+			continue
+		}
+		log := slog.With("container", ctr.ID)
+
+		ports, err := ctr.ServicePorts()
+		if err != nil {
+			log.Error("Failed to parse service ports for container.", "err", err)
+			continue
+		}
+
+		for _, port := range ports {
+			if port.Mode != api.PortModeIngress {
+				continue
+			}
+
+			switch port.Protocol {
+			case api.ProtocolHTTP:
+				upstream := net.JoinHostPort(ip.String(), strconv.Itoa(int(port.ContainerPort)))
+				httpHostUpstreams[port.Hostname] = append(httpHostUpstreams[port.Hostname], upstream)
+			case api.ProtocolHTTPS:
+				upstream := net.JoinHostPort(ip.String(), strconv.Itoa(int(port.ContainerPort)))
+				httpsHostUpstreams[port.Hostname] = append(httpsHostUpstreams[port.Hostname], upstream)
+			default:
+				// TODO: implement L4 ingress routing for TCP and UDP.
+				log.Error("Unsupported protocol for ingress port.", "port", port)
+				continue
+			}
+		}
+	}
+
+	return httpHostUpstreams, httpsHostUpstreams
 }