feat: add S3 model upload support

- Add upload_to_s3 function to handler
- Save trained BERT models to S3 when credentials provided
- Save LoRA adapters to S3 when credentials provided
- Input params: s3_bucket, s3_prefix, aws_access_key_id, aws_secret_access_key, aws_region

components/runpod_trainer/handler.py

@@ -3,13 +3,49 @@ RunPod Serverless Handler for DDI Model Training
 
 Supports both BERT-style classification and LLM fine-tuning with LoRA.
 Uses 176K real DrugBank DDI samples with drug names.
+Saves trained models to S3.
 """
 import os
 import json
 import runpod
+import boto3
+from datetime import datetime
 from typing import Dict, Any, List, Optional
 
 
+def upload_to_s3(local_path: str, s3_bucket: str, s3_prefix: str, aws_credentials: Dict) -> str:
+    """Upload a directory to S3 and return the S3 URI."""
+    import tarfile
+    import tempfile
+    
+    # Create tar.gz of the model directory
+    timestamp = datetime.utcnow().strftime("%Y%m%d_%H%M%S")
+    tar_name = f"model_{timestamp}.tar.gz"
+    tar_path = os.path.join(tempfile.gettempdir(), tar_name)
+    
+    print(f"Creating archive: {tar_path}")
+    with tarfile.open(tar_path, "w:gz") as tar:
+        tar.add(local_path, arcname="model")
+    
+    # Upload to S3
+    s3_client = boto3.client(
+        's3',
+        aws_access_key_id=aws_credentials.get('aws_access_key_id'),
+        aws_secret_access_key=aws_credentials.get('aws_secret_access_key'),
+        region_name=aws_credentials.get('aws_region', 'us-east-1')
+    )
+    
+    s3_key = f"{s3_prefix}/{tar_name}"
+    print(f"Uploading to s3://{s3_bucket}/{s3_key}")
+    
+    s3_client.upload_file(tar_path, s3_bucket, s3_key)
+    
+    # Cleanup
+    os.remove(tar_path)
+    
+    return f"s3://{s3_bucket}/{s3_key}"
+
+
 # DDI severity labels
 DDI_SEVERITY = {
     1: "minor",
@@ -229,10 +265,31 @@ def train_llm_lora(job_input: Dict[str, Any]) -> Dict[str, Any]:
         
         print(f"Training complete! Loss: {metrics['train_loss']:.4f}")
         
+        # Save LoRA adapter to S3 if credentials provided
+        s3_uri = None
+        s3_bucket = job_input.get('s3_bucket')
+        if s3_bucket:
+            save_dir = os.path.join(work_dir, 'lora_adapter')
+            print(f"Saving LoRA adapter to {save_dir}...")
+            model.save_pretrained(save_dir)
+            tokenizer.save_pretrained(save_dir)
+            
+            aws_creds = {
+                'aws_access_key_id': job_input.get('aws_access_key_id'),
+                'aws_secret_access_key': job_input.get('aws_secret_access_key'),
+                'aws_region': job_input.get('aws_region', 'us-east-1'),
+            }
+            model_short = model_name.split('/')[-1]
+            s3_prefix = job_input.get('s3_prefix', f'ddi-models/lora-{model_short}')
+            s3_uri = upload_to_s3(save_dir, s3_bucket, s3_prefix, aws_creds)
+            metrics['s3_uri'] = s3_uri
+            print(f"LoRA adapter uploaded to {s3_uri}")
+        
         return {
             'status': 'success',
             'metrics': metrics,
-            'message': f'Gemma 3 fine-tuned on {len(raw_data):,} real DrugBank DDI samples'
+            'model_uri': s3_uri,
+            'message': f'LLM fine-tuned on {len(raw_data):,} real DrugBank DDI samples'
         }
         
     except Exception as e:
@@ -357,7 +414,26 @@ def train_bert_classifier(job_input: Dict[str, Any]) -> Dict[str, Any]:
                 'eval_f1_weighted': float(eval_result['eval_f1_weighted']),
             })
         
-        return {'status': 'success', 'metrics': metrics, 'message': 'BERT classifier trained on DrugBank data'}
+        # Save model to S3 if credentials provided
+        s3_uri = None
+        s3_bucket = job_input.get('s3_bucket')
+        if s3_bucket:
+            save_dir = os.path.join(work_dir, 'saved_model')
+            print(f"Saving model to {save_dir}...")
+            trainer.save_model(save_dir)
+            tokenizer.save_pretrained(save_dir)
+            
+            aws_creds = {
+                'aws_access_key_id': job_input.get('aws_access_key_id'),
+                'aws_secret_access_key': job_input.get('aws_secret_access_key'),
+                'aws_region': job_input.get('aws_region', 'us-east-1'),
+            }
+            s3_prefix = job_input.get('s3_prefix', 'ddi-models/bert')
+            s3_uri = upload_to_s3(save_dir, s3_bucket, s3_prefix, aws_creds)
+            metrics['s3_uri'] = s3_uri
+            print(f"Model uploaded to {s3_uri}")
+        
+        return {'status': 'success', 'metrics': metrics, 'model_uri': s3_uri, 'message': 'BERT classifier trained on DrugBank data'}
         
     except Exception as e:
         import traceback