Improve indices metadata error handling (#232913)

## Summary

- Enhanced `IndicesMetadataService` to gracefully handle receiver
errors.
- Added comprehensive test coverage for `MetadataReceiver` including
edge cases for null/undefined responses, empty results, and ES client
errors.
- Updated existing tests in `IndicesMetadataService` to reflect new
error handling behavior.

Author: szaffarano

x-pack/platform/plugins/private/indices_metadata/server/lib/services/indices_metadata.test.ts

@@ -583,8 +583,72 @@ describe('Indices Metadata - IndicesMetadataService', () => {
     it('should handle receiver errors during publishIndicesMetadata', async () => {
       const error = new Error('Elasticsearch error');
       receiver.getIndices.mockRejectedValue(error);
+      receiver.getDataStreams.mockResolvedValue(mockDataStreams);
+      receiver.getIndexTemplatesStats.mockResolvedValue(mockIndexTemplates);
+
+      await service['publishIndicesMetadata'](); // eslint-disable-line dot-notation
+
+      expect(logger.error).toHaveBeenCalledWith('Error fetching indices metadata', { error });
+      expect(logger.debug).toHaveBeenCalledWith(
+        'Skipping indices metadata publish due to fetch errors'
+      );
+      expect(sender.reportEBT).not.toHaveBeenCalled();
+    });
+
+    it('should handle partial receiver errors during publishIndicesMetadata', async () => {
+      const error = new Error('DataStream error');
+      receiver.getIndices.mockResolvedValue(mockIndexSettings);
+      receiver.getDataStreams.mockRejectedValue(error);
+      receiver.getIndexTemplatesStats.mockResolvedValue(mockIndexTemplates);
+
+      await service['publishIndicesMetadata'](); // eslint-disable-line dot-notation
+
+      expect(logger.error).toHaveBeenCalledWith('Error fetching indices metadata', { error });
+      expect(logger.debug).toHaveBeenCalledWith(
+        'Skipping indices metadata publish due to fetch errors'
+      );
+      expect(sender.reportEBT).not.toHaveBeenCalled();
+    });
+
+    it('should handle all receiver methods failing during publishIndicesMetadata', async () => {
+      const indicesError = new Error('Indices error');
+      const dataStreamError = new Error('DataStream error');
+      const templatesError = new Error('Templates error');
+
+      receiver.getIndices.mockRejectedValue(indicesError);
+      receiver.getDataStreams.mockRejectedValue(dataStreamError);
+      receiver.getIndexTemplatesStats.mockRejectedValue(templatesError);
 
-      await expect(service['publishIndicesMetadata']()).rejects.toThrow('Elasticsearch error'); // eslint-disable-line dot-notation
+      await service['publishIndicesMetadata'](); // eslint-disable-line dot-notation
+
+      expect(logger.error).toHaveBeenCalledWith('Error fetching indices metadata', {
+        error: indicesError,
+      });
+      expect(logger.debug).toHaveBeenCalledWith(
+        'Skipping indices metadata publish due to fetch errors'
+      );
+      expect(sender.reportEBT).not.toHaveBeenCalled();
+    });
+
+    it('should continue processing when receiver methods return empty results', async () => {
+      receiver.getIndices.mockResolvedValue([]);
+      receiver.getDataStreams.mockResolvedValue([]);
+      receiver.getIndexTemplatesStats.mockResolvedValue([]);
+      receiver.getIndicesStats.mockImplementation(async function* () {
+        // yield nothing
+      });
+      receiver.isIlmStatsAvailable.mockResolvedValue(false);
+      receiver.getIlmsPolicies.mockImplementation(async function* () {
+        // yield nothing
+      });
+
+      await service['publishIndicesMetadata'](); // eslint-disable-line dot-notation
+
+      expect(receiver.getIndices).toHaveBeenCalled();
+      expect(receiver.getDataStreams).toHaveBeenCalled();
+      expect(receiver.getIndexTemplatesStats).toHaveBeenCalled();
+      expect(sender.reportEBT).toHaveBeenCalledTimes(5); // datastreams, indices settings, indices stats, ILM policies (empty), templates
+      expect(logger.debug).toHaveBeenCalledWith('ILM explain API is not available');
     });
 
     it('should handle sender errors during publishDatastreamsStats', () => {

x-pack/platform/plugins/private/indices_metadata/server/lib/services/indices_metadata.ts

@@ -103,7 +103,19 @@ export class IndicesMetadataService {
       this.receiver.getIndices(),
       this.receiver.getDataStreams(),
       this.receiver.getIndexTemplatesStats(),
-    ]);
+    ]).catch((error) => {
+      this.logger.error('Error fetching indices metadata', { error });
+      return [undefined, undefined, undefined];
+    });
+
+    if (
+      indicesSettings === undefined ||
+      dataStreams === undefined ||
+      indexTemplates === undefined
+    ) {
+      this.logger.debug('Skipping indices metadata publish due to fetch errors');
+      return;
+    }
 
     const indices = indicesSettings.map((index) => index.index_name);