Fix linting issues in telemetry implementation

- Fix no-plusplus errors: replace ++ and -- with += 1 and -= 1
- Fix global-require errors: move require() calls to imports
- Fix no-unused-vars errors: remove or mark unused variables
- Fix no-await-in-loop: add eslint-disable for intentional retry logic
- Fix no-lonely-if: refactor nested if statements
- Fix default-case: add default case to switch statements
- Fix no-promise-executor-return: wrap setTimeout in arrow function

All linting errors resolved. Only 14 warnings remain for unnamed test functions.

Author: samikshya-db

coverage/coverage-summary.json

@@ -1,5 +1,6 @@
 import thrift from 'thrift';
 import Int64 from 'node-int64';
+import os from 'os';
 
 import { EventEmitter } from 'events';
 import TCLIService from '../thrift/TCLIService';
@@ -77,10 +78,15 @@ export default class DBSQLClient extends EventEmitter implements IDBSQLClient, I
 
   // Telemetry components (instance-based, NOT singletons)
   private host?: string;
+
   private featureFlagCache?: FeatureFlagCache;
+
   private telemetryClientProvider?: TelemetryClientProvider;
+
   private telemetryEmitter?: TelemetryEventEmitter;
+
   private telemetryAggregator?: MetricsAggregator;
+
   private circuitBreakerRegistry?: CircuitBreakerRegistry;
 
   private static getDefaultLogger(): IDBSQLLogger {
@@ -197,7 +203,7 @@ export default class DBSQLClient extends EventEmitter implements IDBSQLClient, I
       driverName: '@databricks/sql',
       nodeVersion: process.version,
       platform: process.platform,
-      osVersion: require('os').release(),
+      osVersion: os.release(),
 
       // Feature flags
       cloudFetchEnabled: this.config.useCloudFetch ?? false,
@@ -239,7 +245,7 @@ export default class DBSQLClient extends EventEmitter implements IDBSQLClient, I
       this.telemetryEmitter = new TelemetryEventEmitter(this);
 
       // Get or create telemetry client for this host (increments refCount)
-      const telemetryClient = this.telemetryClientProvider.getOrCreateClient(this.host);
+      this.telemetryClientProvider.getOrCreateClient(this.host);
 
       // Create circuit breaker registry and exporter
       this.circuitBreakerRegistry = new CircuitBreakerRegistry(this);

generated_task_specs.json

@@ -34,6 +34,7 @@ import { definedOrError } from './utils';
 import { OperationChunksIterator, OperationRowsIterator } from './utils/OperationIterator';
 import HiveDriverError from './errors/HiveDriverError';
 import IClientContext from './contracts/IClientContext';
+import ExceptionClassifier from './telemetry/ExceptionClassifier';
 
 interface DBSQLOperationConstructorOptions {
   handle: TOperationHandle;
@@ -79,7 +80,9 @@ export default class DBSQLOperation implements IOperation {
 
   // Telemetry tracking fields
   private startTime: number = Date.now();
+
   private pollCount: number = 0;
+
   private sessionId?: string;
 
   constructor({ handle, directResults, context, sessionId }: DBSQLOperationConstructorOptions) {
@@ -236,7 +239,7 @@ export default class DBSQLOperation implements IOperation {
     }
 
     // Track poll count for telemetry
-    this.pollCount++;
+    this.pollCount += 1;
 
     const driver = await this.context.getDriver();
     const response = await driver.getOperationStatus({
@@ -504,7 +507,7 @@ export default class DBSQLOperation implements IOperation {
    */
   private emitStatementStart(): void {
     try {
-      const telemetryEmitter = (this.context as any).telemetryEmitter;
+      const {telemetryEmitter} = (this.context as any);
       if (!telemetryEmitter) {
         return;
       }
@@ -525,8 +528,8 @@ export default class DBSQLOperation implements IOperation {
    */
   private emitStatementComplete(): void {
     try {
-      const telemetryEmitter = (this.context as any).telemetryEmitter;
-      const telemetryAggregator = (this.context as any).telemetryAggregator;
+      const {telemetryEmitter} = (this.context as any);
+      const {telemetryAggregator} = (this.context as any);
       if (!telemetryEmitter || !telemetryAggregator) {
         return;
       }
@@ -557,13 +560,12 @@ export default class DBSQLOperation implements IOperation {
    */
   private emitErrorEvent(error: Error): void {
     try {
-      const telemetryEmitter = (this.context as any).telemetryEmitter;
+      const {telemetryEmitter} = (this.context as any);
       if (!telemetryEmitter) {
         return;
       }
 
-      // Import ExceptionClassifier at runtime to avoid circular dependencies
-      const ExceptionClassifier = require('./telemetry/ExceptionClassifier').default;
+      // Classify the exception
       const isTerminal = ExceptionClassifier.isTerminal(error);
 
       telemetryEmitter.emitError({

lib/DBSQLClient.ts

@@ -113,7 +113,8 @@ export default class CloudFetchResultHandler implements IResultsProvider<ArrowBa
     this.logDownloadMetrics(link.fileLink, result.byteLength, downloadTimeMs);
 
     // Emit cloudfetch.chunk telemetry event
-    this.emitCloudFetchChunk(this.chunkIndex++, downloadTimeMs, result.byteLength);
+    this.emitCloudFetchChunk(this.chunkIndex, downloadTimeMs, result.byteLength);
+    this.chunkIndex += 1;
 
     return {
       batches: [Buffer.from(result)],
@@ -144,7 +145,7 @@ export default class CloudFetchResultHandler implements IResultsProvider<ArrowBa
         return;
       }
 
-      const telemetryEmitter = (this.context as any).telemetryEmitter;
+      const {telemetryEmitter} = (this.context as any);
       if (!telemetryEmitter) {
         return;
       }

lib/DBSQLOperation.ts

@@ -61,9 +61,13 @@ export const DEFAULT_CIRCUIT_BREAKER_CONFIG: CircuitBreakerConfig = {
  */
 export class CircuitBreaker {
   private state: CircuitBreakerState = CircuitBreakerState.CLOSED;
+
   private failureCount = 0;
+
   private successCount = 0;
+
   private nextAttempt?: Date;
+
   private readonly config: CircuitBreakerConfig;
 
   constructor(
@@ -138,7 +142,7 @@ export class CircuitBreaker {
     this.failureCount = 0;
 
     if (this.state === CircuitBreakerState.HALF_OPEN) {
-      this.successCount++;
+      this.successCount += 1;
       logger.log(
         LogLevel.debug,
         `Circuit breaker success in HALF_OPEN (${this.successCount}/${this.config.successThreshold})`
@@ -160,7 +164,7 @@ export class CircuitBreaker {
   private onFailure(): void {
     const logger = this.context.getLogger();
 
-    this.failureCount++;
+    this.failureCount += 1;
     this.successCount = 0; // Reset success count on failure
 
     logger.log(

lib/result/CloudFetchResultHandler.ts

@@ -14,12 +14,12 @@
  * limitations under the License.
  */
 
+import fetch, { Response } from 'node-fetch';
 import IClientContext from '../contracts/IClientContext';
 import { LogLevel } from '../contracts/IDBSQLLogger';
 import { TelemetryMetric, DEFAULT_TELEMETRY_CONFIG } from './types';
 import { CircuitBreakerRegistry } from './CircuitBreaker';
 import ExceptionClassifier from './ExceptionClassifier';
-import fetch, { Response } from 'node-fetch';
 
 /**
  * Databricks telemetry log format for export.
@@ -77,7 +77,9 @@ interface DatabricksTelemetryPayload {
  */
 export default class DatabricksTelemetryExporter {
   private circuitBreaker;
+
   private readonly userAgent: string;
+
   private fetchFn: typeof fetch;
 
   constructor(
@@ -90,7 +92,6 @@ export default class DatabricksTelemetryExporter {
     this.fetchFn = fetchFunction || fetch;
 
     // Get driver version for user agent
-    const config = context.getConfig();
     this.userAgent = `databricks-sql-nodejs/${this.getDriverVersion()}`;
   }
 
@@ -131,7 +132,8 @@ export default class DatabricksTelemetryExporter {
 
     let lastError: Error | null = null;
 
-    for (let attempt = 0; attempt <= maxRetries; attempt++) {
+    /* eslint-disable no-await-in-loop */
+    for (let attempt = 0; attempt <= maxRetries; attempt += 1) {
       try {
         await this.exportInternal(metrics);
         return; // Success
@@ -157,7 +159,7 @@ export default class DatabricksTelemetryExporter {
         }
 
         // Calculate backoff with exponential + jitter (100ms - 1000ms)
-        const baseDelay = Math.min(100 * Math.pow(2, attempt), 1000);
+        const baseDelay = Math.min(100 * 2**attempt, 1000);
         const jitter = Math.random() * 100;
         const delay = baseDelay + jitter;
 
@@ -169,6 +171,7 @@ export default class DatabricksTelemetryExporter {
         await this.sleep(delay);
       }
     }
+    /* eslint-enable no-await-in-loop */
 
     // Should not reach here, but just in case
     if (lastError) {
@@ -200,10 +203,8 @@ export default class DatabricksTelemetryExporter {
       `Exporting ${metrics.length} telemetry metrics to ${authenticatedExport ? 'authenticated' : 'unauthenticated'} endpoint`
     );
 
-    // Get connection provider for auth headers (if authenticated)
-    const connectionProvider = await this.context.getConnectionProvider();
-
     // Make HTTP POST request
+    // Note: In production, auth headers would be added via connectionProvider
     const response: Response = await this.fetchFn(endpoint, {
       method: 'POST',
       headers: {
@@ -301,6 +302,8 @@ export default class DatabricksTelemetryExporter {
    * Sleep for the specified number of milliseconds.
    */
   private sleep(ms: number): Promise<void> {
-    return new Promise((resolve) => setTimeout(resolve, ms));
+    return new Promise((resolve) => {
+      setTimeout(resolve, ms);
+    });
   }
 }

lib/telemetry/CircuitBreaker.ts

@@ -34,7 +34,9 @@ export interface FeatureFlagContext {
  */
 export default class FeatureFlagCache {
   private contexts: Map<string, FeatureFlagContext>;
+
   private readonly CACHE_DURATION_MS = 15 * 60 * 1000; // 15 minutes
+
   private readonly FEATURE_FLAG_NAME = 'databricks.partnerplatform.clientConfigsFeatureFlags.enableTelemetryForNodeJs';
 
   constructor(private context: IClientContext) {
@@ -54,7 +56,7 @@ export default class FeatureFlagCache {
       };
       this.contexts.set(host, ctx);
     }
-    ctx.refCount++;
+    ctx.refCount += 1;
     return ctx;
   }
 
@@ -65,7 +67,7 @@ export default class FeatureFlagCache {
   releaseContext(host: string): void {
     const ctx = this.contexts.get(host);
     if (ctx) {
-      ctx.refCount--;
+      ctx.refCount -= 1;
       if (ctx.refCount <= 0) {
         this.contexts.delete(host);
       }
@@ -105,8 +107,10 @@ export default class FeatureFlagCache {
    * Fetches feature flag from server.
    * This is a placeholder implementation that returns false.
    * Real implementation would fetch from server using connection provider.
+   * @param _host The host to fetch feature flag for (unused in placeholder implementation)
    */
-  private async fetchFeatureFlag(host: string): Promise<boolean> {
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  private async fetchFeatureFlag(_host: string): Promise<boolean> {
     // Placeholder implementation
     // Real implementation would use:
     // const connectionProvider = await this.context.getConnectionProvider();

lib/telemetry/DatabricksTelemetryExporter.ts

@@ -60,9 +60,13 @@ interface StatementTelemetryDetails {
  */
 export default class MetricsAggregator {
   private statementMetrics: Map<string, StatementTelemetryDetails> = new Map();
+
   private pendingMetrics: TelemetryMetric[] = [];
+
   private flushTimer: NodeJS.Timeout | null = null;
+
   private batchSize: number;
+
   private flushIntervalMs: number;
 
   constructor(
@@ -171,12 +175,10 @@ export default class MetricsAggregator {
 
       // Flush immediately for terminal errors
       this.flush();
-    } else {
+    } else if (event.statementId) {
       // Retryable error - buffer until statement complete
-      if (event.statementId) {
-        const details = this.getOrCreateStatementDetails(event);
-        details.errors.push(event);
-      }
+      const details = this.getOrCreateStatementDetails(event);
+      details.errors.push(event);
     }
   }
 
@@ -201,12 +203,16 @@ export default class MetricsAggregator {
         break;
 
       case TelemetryEventType.CLOUDFETCH_CHUNK:
-        details.chunkCount++;
+        details.chunkCount += 1;
         details.bytesDownloaded += event.bytes ?? 0;
         if (event.compressed !== undefined) {
           details.compressionEnabled = event.compressed;
         }
         break;
+
+      default:
+        // Unknown event type - ignore
+        break;
     }
   }
 

lib/telemetry/FeatureFlagCache.ts

@@ -67,7 +67,7 @@ class TelemetryClientProvider {
     }
 
     // Increment reference count
-    holder.refCount++;
+    holder.refCount += 1;
     logger.log(
       LogLevel.debug,
       `TelemetryClient reference count for ${host}: ${holder.refCount}`
@@ -92,7 +92,7 @@ class TelemetryClientProvider {
     }
 
     // Decrement reference count
-    holder.refCount--;
+    holder.refCount -= 1;
     logger.log(
       LogLevel.debug,
       `TelemetryClient reference count for ${host}: ${holder.refCount}`