Perform a dry-run Ingress create to verify subdomain does not exist (#27)

Author: FluxCapacitor2

backend/src/service/helper/deploymentConfig.ts

@@ -26,6 +26,7 @@ import {
   RepositoryNotFoundError,
   ValidationError,
 } from "../common/errors.ts";
+import { canCreateIngress } from "../isSubdomainAvailable.ts";
 
 type GitWorkloadConfig = components["schemas"]["WorkloadConfigOptions"] & {
   source: "git";
@@ -364,8 +365,16 @@ export class DeploymentConfigService {
     }
 
     const appWithSubdomain = await this.appRepo.getAppBySubdomain(subdomain);
-    if (appWithSubdomain && appWithSubdomain.id !== existingAppId) {
-      throw new ValidationError("Subdomain is in use");
+    if (appWithSubdomain) {
+      if (appWithSubdomain.id !== existingAppId) {
+        throw new ValidationError(
+          "Subdomain is in use by another AnvilOps app",
+        );
+      }
+    } else {
+      if (!(await canCreateIngress(subdomain))) {
+        throw new ValidationError("Subdomain is in use");
+      }
     }
   }
 }

backend/src/service/isSubdomainAvailable.ts

@@ -1,14 +1,51 @@
+import { ApiException } from "@kubernetes/client-node";
 import { db } from "../db/index.ts";
+import { svcK8s } from "../lib/cluster/kubernetes.ts";
+import { createIngressConfig } from "../lib/cluster/resources/ingress.ts";
+import { env } from "../lib/env.ts";
+import { isRFC1123 } from "../lib/validate.ts";
 import { ValidationError } from "./common/errors.ts";
 
 export async function isSubdomainAvailable(subdomain: string) {
-  if (
-    subdomain.length > 54 ||
-    subdomain.match(/^[a-z0-9](?:[a-z0-9-]*[a-z0-9])?$/) === null
-  ) {
+  if (!isRFC1123(subdomain)) {
     throw new ValidationError("Invalid subdomain.");
   }
 
-  const appUsingSubdomain = await db.app.getAppBySubdomain(subdomain);
-  return appUsingSubdomain === null;
+  const [appUsingSubdomain, ingressDryRun] = await Promise.all([
+    db.app.getAppBySubdomain(subdomain),
+    canCreateIngress(subdomain),
+  ]);
+
+  return appUsingSubdomain === null && ingressDryRun;
+}
+
+/**
+ * Does a dry-run of creating an Ingress with the specified subdomain.
+ * @returns true if the dry-run succeeded, or false if it failed due to a request error (4xx), which indicates that the subdomain is probably taken.
+ */
+export async function canCreateIngress(subdomain: string) {
+  const config = createIngressConfig({
+    createIngress: true,
+    name: "anvilops-ingress-probe",
+    namespace: env.CURRENT_NAMESPACE,
+    port: 80,
+    serviceName: "anvilops-ingress-probe",
+    subdomain: subdomain,
+    servicePort: 80,
+  });
+
+  try {
+    await svcK8s["KubernetesObjectApi"].create(
+      config,
+      undefined,
+      /* dryRun = */ "All",
+    );
+    return true;
+  } catch (err) {
+    if (err instanceof ApiException && err.code >= 400 && err.code < 500) {
+      // The dry-run failed. This is probably due to an existing Ingress using the subdomain and path that we want to reserve.
+      return false;
+    }
+    throw err;
+  }
 }