Fix gpu detector in localTrainingService (#1068)

src/nni_manager/training_service/local/gpuScheduler.ts

@@ -105,12 +105,16 @@ class GPUScheduler {
     }
 
     private async updateGPUSummary(): Promise<void> {
-        const cmdresult: cpp.childProcessPromise.Result =
-            await execTail(path.join(this.gpuMetricCollectorScriptFolder, 'gpu_metrics'));
-        if (cmdresult && cmdresult.stdout) {
-            this.gpuSummary = <GPUSummary>JSON.parse(cmdresult.stdout);
-        } else {
-            this.log.error('Could not get gpu metrics information!');
+        let gpuMetricPath = path.join(this.gpuMetricCollectorScriptFolder, 'gpu_metrics');
+        if (fs.existsSync(gpuMetricPath)) {
+            const cmdresult: cpp.childProcessPromise.Result = await execTail(gpuMetricPath);
+            if (cmdresult && cmdresult.stdout) {
+                this.gpuSummary = <GPUSummary>JSON.parse(cmdresult.stdout);
+            } else {
+                this.log.error('Could not get gpu metrics information!');
+            }
+        } else{
+            this.log.warning('gpu_metrics file does not exist!')
         }
     }
 }