dockerdiscovery: support sub rules for frontend rule

Author: joonas-fi

pkg/erdiscovery/dockerdiscovery/traefikannotations.go

@@ -63,11 +63,21 @@ func traefikAnnotationsToApp(service Service) (*erconfig.Application, error) {
 	}
 
 	frontend, err := func() (erconfig.Frontend, error) {
+		parsed, err := parseTraefikFrontendRule(frontendRule)
+		if err != nil {
+			return erconfig.Frontend{}, err
+		}
+
+		opts := []erconfig.FrontendOpt{}
+		if parsed.PathPrefix != "" {
+			opts = append(opts, erconfig.PathPrefix(parsed.PathPrefix))
+		}
+
 		switch {
-		case strings.HasPrefix(frontendRule, "Host:"):
-			return erconfig.SimpleHostnameFrontend(frontendRule[len("Host:"):]), nil
-		case strings.HasPrefix(frontendRule, "HostRegexp:"):
-			return erconfig.RegexpHostnameFrontend(frontendRule[len("HostRegexp:"):]), nil
+		case parsed.Host != "":
+			return erconfig.SimpleHostnameFrontend(parsed.Host, opts...), nil
+		case parsed.HostRegexp != "":
+			return erconfig.RegexpHostnameFrontend(parsed.HostRegexp, opts...), nil
 		default:
 			return erconfig.Frontend{}, fmt.Errorf("unsupported frontend rule: %s", frontendRule)
 		}
@@ -137,3 +147,33 @@ func traefikAnnotationsToApp(service Service) (*erconfig.Application, error) {
 
 	return &app, nil
 }
+
+type traefikFrontendRule struct {
+	Host       string `json:",omitempty"` // `Host:...` rule
+	PathPrefix string `json:",omitempty"` // `PathPrefix:...` rule
+	HostRegexp string `json:",omitempty"` // `HostRegexp:...` rule
+}
+
+// https://doc.traefik.io/traefik/v1.7/user-guide/examples/#using-labels-in-docker-composeyml
+func parseTraefikFrontendRule(rule string) (traefikFrontendRule, error) {
+	parsed := traefikFrontendRule{}
+
+	// `Host:example.com;PathPrefix:/admin/`
+	// => `["Host:example.com", "PathPrefix:/admin/"]`
+	subRules := strings.Split(rule, ";")
+
+	for _, subRule := range subRules {
+		switch {
+		case strings.HasPrefix(subRule, "Host:"):
+			parsed.Host = subRule[len("Host:"):]
+		case strings.HasPrefix(subRule, "PathPrefix:"):
+			parsed.PathPrefix = subRule[len("PathPrefix:"):]
+		case strings.HasPrefix(subRule, "HostRegexp:"):
+			parsed.HostRegexp = subRule[len("HostRegexp:"):]
+		default:
+			return parsed, fmt.Errorf("unsupported rule: '%s'", subRule)
+		}
+	}
+
+	return parsed, nil
+}

pkg/erdiscovery/dockerdiscovery/traefikannotations_test.go

@@ -159,6 +159,28 @@ func TestTraefikAnnotationsToApp(t *testing.T) {
       }
     }
   }
+}`),
+		mkTestCase("multiple_subrules", ip101, labels{
+			"traefik.frontend.rule": "Host:example.com;PathPrefix:/admin/",
+			"edgerouter.auth":       "public",
+		}, `{
+  "id": "multiple_subrules",
+  "frontends": [
+    {
+      "kind": "hostname",
+      "hostname": "example.com",
+      "path_prefix": "/admin/"
+    }
+  ],
+  "backend": {
+    "kind": "reverse_proxy",
+    "reverse_proxy_opts": {
+      "origins": [
+        "http://192.168.1.101:80"
+      ],
+      "pass_host_header": true
+    }
+  }
 }`),
 	}
 
@@ -174,3 +196,11 @@ func TestTraefikAnnotationsToApp(t *testing.T) {
 		})
 	}
 }
+
+func TestParseSubRules(t *testing.T) {
+	rule, err := parseTraefikFrontendRule("Host:example.com;PathPrefix:/admin/")
+	assert.Ok(t, err)
+	asJSON, err := json.Marshal(rule)
+	assert.Ok(t, err)
+	assert.EqualString(t, string(asJSON), `{"Host":"example.com","PathPrefix":"/admin/"}`)
+}