Fix telemetry PR review comments from #325

Three fixes addressing review feedback:

1. Fix documentation typo (sreekanth-db comment)
   - DatabricksTelemetryExporter.ts:94
   - Changed "TelemetryFrontendLog" to "DatabricksTelemetryLog"

2. Add proxy support (jadewang-db comment)
   - DatabricksTelemetryExporter.ts:exportInternal()
   - Get HTTP agent from connection provider
   - Pass agent to fetch for proxy support
   - Follows same pattern as CloudFetchResultHandler and DBSQLSession
   - Supports http/https/socks proxies with authentication

3. Fix flush timer to prevent rate limiting (sreekanth-db comment)
   - MetricsAggregator.ts:flush()
   - Reset timer after manual flushes (batch size, terminal errors)
   - Ensures consistent 30s spacing between exports
   - Prevents rapid successive flushes (e.g., batch at 25s, timer at 30s)

All changes follow existing driver patterns and maintain backward compatibility.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: samikshya-db

lib/telemetry/DatabricksTelemetryExporter.ts

@@ -91,7 +91,7 @@ interface DatabricksTelemetryLog {
 interface DatabricksTelemetryPayload {
   uploadTime: number;
   items: string[]; // Always empty - required field
-  protoLogs: string[]; // JSON-stringified TelemetryFrontendLog objects
+  protoLogs: string[]; // JSON-stringified DatabricksTelemetryLog objects
 }
 
 /**
@@ -237,7 +237,11 @@ export default class DatabricksTelemetryExporter {
     // Get authentication headers if using authenticated endpoint
     const authHeaders = authenticatedExport ? await this.context.getAuthHeaders() : {};
 
-    // Make HTTP POST request with authentication
+    // Get agent with proxy settings (same pattern as CloudFetchResultHandler and DBSQLSession)
+    const connectionProvider = await this.context.getConnectionProvider();
+    const agent = await connectionProvider.getAgent();
+
+    // Make HTTP POST request with authentication and proxy support
     const response: Response = await this.fetchFn(endpoint, {
       method: 'POST',
       headers: {
@@ -246,6 +250,7 @@ export default class DatabricksTelemetryExporter {
         'User-Agent': this.userAgent,
       },
       body: JSON.stringify(payload),
+      agent, // Include agent for proxy support
     });
 
     if (!response.ok) {

lib/telemetry/MetricsAggregator.ts

@@ -337,8 +337,10 @@ export default class MetricsAggregator {
 
   /**
    * Flush all pending metrics to exporter. Never throws.
+   *
+   * @param resetTimer If true, resets the flush timer after flushing (default: true)
    */
-  flush(): void {
+  flush(resetTimer: boolean = true): void {
     const logger = this.context.getLogger();
 
     try {
@@ -351,6 +353,12 @@ export default class MetricsAggregator {
 
       // Export metrics (exporter.export never throws)
       this.exporter.export(metricsToExport);
+
+      // Reset timer to avoid rapid successive flushes (e.g., batch flush at 25s then timer flush at 30s)
+      // This ensures consistent spacing between exports and helps avoid rate limiting
+      if (resetTimer) {
+        this.startFlushTimer();
+      }
     } catch (error: any) {
       // CRITICAL: All exceptions swallowed and logged at debug level ONLY
       logger.log(LogLevel.debug, `MetricsAggregator.flush error: ${error.message}`);
@@ -369,7 +377,8 @@ export default class MetricsAggregator {
       }
 
       this.flushTimer = setInterval(() => {
-        this.flush();
+        // Don't reset timer when flush is triggered by the timer itself
+        this.flush(false);
       }, this.flushIntervalMs);
 
       // Prevent timer from keeping Node.js process alive
@@ -398,8 +407,8 @@ export default class MetricsAggregator {
         this.completeStatement(statementId);
       }
 
-      // Final flush
-      this.flush();
+      // Final flush - don't reset timer since we're closing
+      this.flush(false);
     } catch (error: any) {
       // CRITICAL: All exceptions swallowed and logged at debug level ONLY
       logger.log(LogLevel.debug, `MetricsAggregator.close error: ${error.message}`);