feature: storage check reads the test file back

hasura/metadata/actions.graphql

@@ -788,6 +788,10 @@ type Query {
   telemetryStats(includeSelf: Boolean): TelemetryStats!
 }
 
+type Mutation {
+  testDownload: TestDownloadResponse
+}
+
 type Mutation {
   testUpload: TestUploadResponse
 }
@@ -1380,6 +1384,10 @@ type TelemetryStats {
   countries: [TelemetryCountryCount!]!
 }
 
+type TestDownloadResponse {
+  error: String
+}
+
 type TestUploadResponse {
   error: String
 }

hasura/metadata/actions.yaml

@@ -1113,6 +1113,13 @@ actions:
       forward_client_headers: true
     permissions:
       - role: administrator
+  - name: testDownload
+    definition:
+      kind: synchronous
+      handler: '{{HASURA_GRAPHQL_ACTIONS_HOOK}}'
+      forward_client_headers: true
+    permissions:
+      - role: administrator
   - name: testUpload
     definition:
       kind: synchronous
@@ -2066,6 +2073,7 @@ custom_types:
     - name: TelemetryUtilityTypeCount
     - name: TelemetryUtilitySourceCount
     - name: TelemetryStats
+    - name: TestDownloadResponse
     - name: TestUploadResponse
     - name: GetTestUploadResponse
     - name: ApiKeyResponse

src/s3/s3.controller.ts

@@ -52,6 +52,35 @@ export class S3Controller {
     }
   }
 
+  // Reads back the file testUpload wrote, the way a download is served: through
+  // a presigned link. The browser can't do this itself, since most buckets
+  // don't allow the panel's site to read them directly.
+  @HasuraAction()
+  public async testDownload() {
+    try {
+      const response = await fetch(
+        await this.s3.getPresignedUrl("hello.txt", undefined, 60, "get"),
+      );
+
+      if (!response.ok) {
+        throw new Error(`${response.status} ${response.statusText}`);
+      }
+
+      if (!(await response.text()).startsWith("world")) {
+        throw new Error(
+          "the test file came back different from what was written",
+        );
+      }
+
+      return {};
+    } catch (error) {
+      this.logger.error(`Failed to download file from S3: ${error.message}`);
+      return {
+        error: error.message,
+      };
+    }
+  }
+
   @HasuraAction()
   public async getTestUploadLink() {
     try {