cloudflare-r2:multipart-init

R2 Multipart Upload Setup

Initialize and implement multipart upload workflow for handling large files (>100MB) with chunking, error recovery, and progress tracking.

Required Information

1. File size (in MB): {{file_size}}
2. Object key (destination path): {{key}}
3. Part size (5-100 MB, recommended 10MB): {{part_size}}
4. Content type: {{content_type}}

What This Command Does

1. Calculates optimal part size based on file size
2. Shows createMultipartUpload code for initialization
3. Generates part upload loop with retry logic
4. Provides completion/abort handlers
5. Adds progress tracking for user feedback

Multipart Upload Constraints

• Minimum part size: 5 MB (except last part)
• Maximum part size: 100 MB
• Maximum parts: 10,000 parts per upload
• Part numbers: 1 to 10,000 (1-based indexing)

Part Size Calculator

function calculatePartSize(fileSizeMB: number): number {
  const MIN_PART_SIZE = 5 * 1024 * 1024;  // 5MB
  const MAX_PART_SIZE = 100 * 1024 * 1024; // 100MB
  const MAX_PARTS = 10000;

  const fileSize = fileSizeMB * 1024 * 1024;
  const recommendedSize = Math.ceil(fileSize / MAX_PARTS);

  if (recommendedSize < MIN_PART_SIZE) {
    return MIN_PART_SIZE;
  } else if (recommendedSize > MAX_PART_SIZE) {
    return MAX_PART_SIZE;
  } else {
    return recommendedSize;
  }
}

// Example: 500MB file = 10MB parts (50 parts)
// Example: 50GB file = 10MB parts (5000 parts)

Complete Implementation

import { Hono } from 'hono';

type Bindings = {
  MY_BUCKET: R2Bucket;
};

const app = new Hono<{ Bindings: Bindings }>();

// Step 1: Initialize multipart upload
app.post('/multipart/create', async (c) => {
  const { key, contentType } = await c.req.json();

  const multipart = await c.env.MY_BUCKET.createMultipartUpload(key, {
    httpMetadata: {
      contentType: contentType || 'application/octet-stream',
    },
    customMetadata: {
      uploadedAt: new Date().toISOString(),
    },
  });

  return c.json({
    uploadId: multipart.uploadId,
    key: multipart.key,
  });
});

// Step 2: Upload individual parts
app.put('/multipart/upload-part', async (c) => {
  const { uploadId, key, partNumber } = await c.req.json();
  const data = await c.req.arrayBuffer();

  // Validate part number (1-10000)
  if (partNumber < 1 || partNumber > 10000) {
    return c.json({ error: 'Invalid part number' }, 400);
  }

  const multipart = c.env.MY_BUCKET.resumeMultipartUpload(key, uploadId);
  const uploadedPart = await multipart.uploadPart(partNumber, data);

  return c.json({
    partNumber,
    etag: uploadedPart.etag,
  });
});

// Step 3: Complete multipart upload
app.post('/multipart/complete', async (c) => {
  const { uploadId, key, parts } = await c.req.json();

  const multipart = c.env.MY_BUCKET.resumeMultipartUpload(key, uploadId);

  // parts = [{ partNumber: 1, etag: 'abc' }, { partNumber: 2, etag: 'def' }, ...]
  const object = await multipart.complete(parts);

  return c.json({
    success: true,
    key: object.key,
    size: object.size,
    etag: object.httpEtag,
  });
});

// Step 4: Abort multipart upload (cleanup)
app.delete('/multipart/abort', async (c) => {
  const { uploadId, key } = await c.req.json();

  const multipart = c.env.MY_BUCKET.resumeMultipartUpload(key, uploadId);
  await multipart.abort();

  return c.json({ success: true, message: 'Upload aborted' });
});

export default app;