feat: sync Cloudflare DNS records with Traefik container hosts

Create a record for each Host(...) in running containers' Traefik router
labels, tagged with a configurable comment and optional tags, and delete
owned records once their host has been down for DELETE_AFTER.

config_test.go

@@ -0,0 +1,99 @@
+package main
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+func envOf(m map[string]string) func(string) string {
+	return func(k string) string { return m[k] }
+}
+
+func requiredEnv() map[string]string {
+	return map[string]string{
+		"CF_API_TOKEN": "token",
+		"CF_ZONE_ID":   "zone",
+		"DOMAIN":       "Example.com.",
+		"TARGET":       "192.0.2.10",
+	}
+}
+
+func TestLoadConfigDefaults(t *testing.T) {
+	c, err := LoadConfig(envOf(requiredEnv()))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if c.Domain != "example.com" || c.RecordType != "A" || c.TTL != 1 || c.Proxied || c.DryRun {
+		t.Fatalf("unexpected config: %+v", c)
+	}
+	if c.Comment != "managed by traefik-cloudflare-dns" {
+		t.Fatalf("comment = %q", c.Comment)
+	}
+	if c.DeleteAfter != time.Hour || c.ResyncInterval != time.Minute {
+		t.Fatalf("durations = %v, %v", c.DeleteAfter, c.ResyncInterval)
+	}
+	if c.DockerHost != "unix:///var/run/docker.sock" {
+		t.Fatalf("docker host = %q", c.DockerHost)
+	}
+}
+
+func TestLoadConfigMissing(t *testing.T) {
+	_, err := LoadConfig(envOf(map[string]string{"DOMAIN": "example.com"}))
+	if err == nil || !strings.Contains(err.Error(), "CF_API_TOKEN, CF_ZONE_ID, TARGET") {
+		t.Fatalf("err = %v", err)
+	}
+}
+
+func TestLoadConfigRecordType(t *testing.T) {
+	for target, want := range map[string]string{
+		"192.0.2.10":        "A",
+		"2001:db8::1":       "AAAA",
+		"Host.Example.net.": "CNAME",
+	} {
+		env := requiredEnv()
+		env["TARGET"] = target
+		c, err := LoadConfig(envOf(env))
+		if err != nil {
+			t.Fatal(err)
+		}
+		if c.RecordType != want {
+			t.Errorf("TARGET %q: type %s, want %s", target, c.RecordType, want)
+		}
+	}
+}
+
+func TestLoadConfigOptional(t *testing.T) {
+	env := requiredEnv()
+	env["RECORD_COMMENT"] = "created by the jp companion"
+	env["RECORD_TAGS"] = "managed-by:traefik-cloudflare-dns, server:jp"
+	env["PROXIED"] = "true"
+	env["DELETE_AFTER"] = "30m"
+	env["DRY_RUN"] = "1"
+	c, err := LoadConfig(envOf(env))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if c.Comment != "created by the jp companion" || !c.Proxied || !c.DryRun || c.DeleteAfter != 30*time.Minute {
+		t.Fatalf("unexpected config: %+v", c)
+	}
+	if len(c.Tags) != 2 || c.Tags[1] != "server:jp" {
+		t.Fatalf("tags = %v", c.Tags)
+	}
+}
+
+func TestLoadConfigInvalid(t *testing.T) {
+	for name, kv := range map[string][2]string{
+		"bad tag":      {"RECORD_TAGS", "nocolon"},
+		"bad bool":     {"PROXIED", "maybe"},
+		"bad duration": {"DELETE_AFTER", "soon"},
+		"line break":   {"RECORD_COMMENT", "a\nb"},
+		"zero resync":  {"RESYNC_INTERVAL", "0s"},
+	} {
+		env := requiredEnv()
+		env[kv[0]] = kv[1]
+		if _, err := LoadConfig(envOf(env)); err == nil {
+			t.Errorf("%s: expected an error", name)
+		}
+	}
+}