iExec documentation

Appearance

ChatGPT Ask in ChatGPT

📤 Outputs ​

Your iApp must generate outputs that users can retrieve and decrypt. Understanding how to structure your outputs, create the required metadata, and follow best practices is essential for building effective privacy-preserving applications.

This guide covers how to generate outputs from your iApp and ensure they can be properly retrieved by users.

Creating Outputs ​

Your iApp must generate outputs in the IEXEC_OUT directory. Every iApp must create a computed.json file with metadata about the computation.

Basic Output Structure ​

python
import os
import json

# Get output directory
iexec_out = os.environ['IEXEC_OUT']

# Create your result file
result_data = {
    "analysis": "positive sentiment",
    "confidence": 0.92,
    "processed_at": "2024-01-15T10:30:00Z"
}

# Save main result
with open(f"{iexec_out}/result.json", 'w') as f:
    json.dump(result_data, f)

# REQUIRED: Create `computed.json` metadata
computed_metadata = {
    "deterministic-output-path": f"{iexec_out}/result.json",
    "execution-timestamp": "2024-01-15T10:30:00Z",
    "app-version": "1.0.0"
}

with open(f"{iexec_out}/computed.json", 'w') as f:
    json.dump(computed_metadata, f)
javascript
const fs = require('fs');
const path = require('path');

// Get output directory
const iexecOut = process.env.IEXEC_OUT;

// Create your result file
const resultData = {
  analysis: 'positive sentiment',
  confidence: 0.92,
  processed_at: '2024-01-15T10:30:00Z',
};

// Save main result
fs.writeFileSync(
  path.join(iexecOut, 'result.json'),
  JSON.stringify(resultData, null, 2)
);

// REQUIRED: Create computed.json metadata
const computedMetadata = {
  'deterministic-output-path': path.join(iexecOut, 'result.json'),
  'execution-timestamp': '2024-01-15T10:30:00Z',
  'app-version': '1.0.0',
};

fs.writeFileSync(
  path.join(iexecOut, 'computed.json'),
  JSON.stringify(computedMetadata, null, 2)
);

Output Best Practices ​

  1. Always create computed.json - This is mandatory
  2. Use descriptive filenames - analysis_result.json, not output.txt
  3. Include metadata - Timestamps, versions, parameters used
  4. Structure your data - Use JSON for structured results
  5. Keep files reasonable - Large outputs increase retrieval time and may hit memory limits
  6. Memory awareness - TEE enclave memory is limited, avoid generating multi-GB outputs

Example: Multi-file Output ​

python
import os
import json

iexec_out = os.environ['IEXEC_OUT']

# Create multiple output files
summary = {"total_processed": 1000, "success_rate": 0.95}
with open(f"{iexec_out}/summary.json", 'w') as f:
    json.dump(summary, f)

# Create a detailed report
with open(f"{iexec_out}/detailed_report.txt", 'w') as f:
    f.write("Detailed analysis results...\n")

# Create visualization data
chart_data = {"labels": ["A", "B", "C"], "values": [10, 20, 30]}
with open(f"{iexec_out}/chart_data.json", 'w') as f:
    json.dump(chart_data, f)

# Required metadata file
computed = {
    "deterministic-output-path": f"{iexec_out}/summary.json",
    "additional-files": [
        f"{iexec_out}/detailed_report.txt",
        f"{iexec_out}/chart_data.json"
    ]
}
with open(f"{iexec_out}/computed.json", 'w') as f:
    json.dump(computed, f)

What's Next? ​

You now understand how to generate proper outputs from your iApp!

Continue building with these guides: