Feat : Multiple download functionality

docs/howto/asyncDownloadMultiple.md

@@ -0,0 +1,186 @@
+## Asynchronous Multiple File Downloads
+
+The Gen3 SDK provides an optimized asynchronous download method `async_download_multiple` for efficiently downloading large numbers of files with high throughput and memory efficiency.
+
+## Overview
+
+The `async_download_multiple` method implements a hybrid architecture combining:
+
+- **Multiprocessing**: Multiple Python subprocesses for CPU utilization
+- **Asyncio**: High I/O concurrency within each process
+- **Queue-based memory management**: Efficient handling of large file sets
+- **Just-in-time presigned URL generation**: Optimized authentication flow
+
+## Architecture
+
+### Concurrency Model
+
+The implementation uses a three-tier architecture:
+
+1. **Producer Thread**: Feeds GUIDs to worker processes via bounded queues
+2. **Worker Processes**: Multiple Python subprocesses with asyncio event loops
+3. **Queue System**: Memory-efficient streaming of work items
+
+```python
+# Architecture overview
+Producer Thread → Input Queue → Worker Processes → Output Queue → Results
+     (1)           (configurable)   (configurable)    (configurable)   (Final)
+```
+
+### Key Features
+
+- **Memory Efficiency**: Bounded queues prevent memory explosion with large file sets
+- **True Parallelism**: Multiprocessing bypasses Python GIL limitations
+- **High Concurrency**: Configurable concurrent downloads per process
+- **Resume Support**: Skip completed files with `--skip-completed` flag
+- **Progress Tracking**: Real-time progress bars and detailed reporting
+
+## Usage
+
+### Command Line Interface
+
+Download multiple files using a manifest:
+
+```bash
+gen3 --endpoint my-commons.org --auth credentials.json download-multiple \
+    --manifest files.json \
+    --download-path ./downloads \
+    --max-concurrent-requests 10 \
+    --filename-format original \
+    --skip-completed \
+    --no-prompt
+```
+
+### Python API
+
+The `async_download_multiple` method is available in the `Gen3File` class for programmatic use. Refer to the Python SDK documentation for the complete API reference.
+
+## Parameters
+
+For detailed parameter information and current default values, run:
+
+```bash
+gen3 download-multiple --help
+```
+
+The command supports various options for customizing download behavior, including concurrency settings, file naming strategies, and progress controls.
+
+## Performance Characteristics
+
+### Throughput Optimization
+
+The method is optimized for high-throughput scenarios:
+
+- **Concurrent Downloads**: Configurable number of simultaneous downloads
+- **Memory Usage**: Bounded by queue sizes (typically < 100MB)
+- **CPU Utilization**: Leverages multiple CPU cores
+- **Network Efficiency**: Just-in-time presigned URL generation
+
+### Scalability
+
+Performance scales with:
+
+- **File Count**: Linear time complexity with constant memory usage
+- **File Size**: Independent of individual file sizes
+- **Network Bandwidth**: Limited by available bandwidth and concurrent connections
+- **System Resources**: Scales with available CPU cores and memory
+
+## Error Handling
+
+### Robust Error Recovery
+
+The implementation includes comprehensive error handling:
+
+- **Network Failures**: Automatic retry with exponential backoff
+- **Authentication Errors**: Token refresh and retry
+- **File System Errors**: Graceful handling of permission and space issues
+- **Process Failures**: Automatic worker process restart
+
+### Result Reporting
+
+The method returns a structured result object containing lists of succeeded, failed, and skipped downloads with detailed information about each operation.
+
+## Best Practices
+
+### Configuration Recommendations
+
+For optimal performance, adjust the concurrency and process settings based on your specific use case:
+
+- **Small files**: Use higher concurrent request limits
+- **Large files**: Use lower concurrent request limits to avoid overwhelming the system
+- **High-bandwidth networks**: Increase the number of worker processes
+- **Limited memory**: Reduce queue sizes to manage memory usage
+
+
+## Comparison with Synchronous Downloads
+
+### Performance Advantages
+
+| Metric             | Synchronous                  | Asynchronous                 |
+| ------------------ | ---------------------------- | ---------------------------- |
+| Memory Usage       | O(n) - grows with file count | O(1) - bounded by queue size |
+| CPU Utilization    | Single core                  | Multiple cores               |
+| Network Efficiency | Sequential                   | Parallel                     |
+| Scalability        | Limited by GIL               | Scales with CPU cores        |
+
+## Troubleshooting
+
+### Common Issues
+
+**Slow Downloads:**
+
+- Check network bandwidth and server limits
+- Reduce concurrent request limits if server is overwhelmed
+
+**Memory Issues:**
+
+- Reduce queue sizes and batch sizes
+- Lower the number of worker processes if system memory is limited
+- Monitor system memory usage during downloads
+
+**Authentication Errors:**
+
+- Verify credentials file is valid and not expired
+- Check endpoint URL is correct
+- Ensure proper permissions for target files
+
+**Process Failures:**
+
+- Check system resources (CPU, memory, file descriptors)
+- Verify network connectivity to Gen3 commons
+- Review logs for specific error messages
+
+### Debugging
+
+Enable verbose logging for detailed debugging:
+
+```bash
+gen3 -vv --endpoint my-commons.org --auth credentials.json download-multiple \
+    --manifest files.json \
+    --download-path ./downloads
+```
+
+## Examples
+
+### Basic Usage
+
+```bash
+# Download files with default settings
+gen3 --endpoint data.commons.io --auth creds.json download-multiple \
+    --manifest my_files.json \
+    --download-path ./data
+```
+
+### High-Performance Configuration
+
+```bash
+# Optimized for high-throughput downloads
+gen3 --endpoint data.commons.io --auth creds.json download-multiple \
+    --manifest large_dataset.json \
+    --download-path ./large_downloads \
+    --max-concurrent-requests 8 \
+    --no-progress \
+    --skip-completed
+```
+
+**Note**: The specific values shown in examples (like `--max-concurrent-requests 8`) are for demonstration only. For current parameter options and default values, always refer to the command line help: `gen3 download-multiple --help`

gen3/cli/__main__.py

@@ -15,6 +15,7 @@
 import gen3.cli.drs_pull as drs_pull
 import gen3.cli.users as users
 import gen3.cli.wrap as wrap
+import gen3.cli.download as download
 import gen3
 from gen3 import logging as sdklogging
 from gen3.cli import nih
@@ -142,6 +143,8 @@ def main(
 main.add_command(objects.objects)
 main.add_command(drs_pull.drs_pull)
 main.add_command(file.file)
+main.add_command(download.download_single, name="download-single")
+main.add_command(download.download_multiple, name="download-multiple")
 main.add_command(nih.nih)
 main.add_command(users.users)
 main.add_command(wrap.run)