Rclone S3 Timestamp Module

This module preserves file modification times when Sync Engine uses the S3 backend with rclone serve s3. It applies automatically when the S3 backend is selected.

Modification Time

Sync Engine stores mtime in milliseconds, while rclone interprets x-amz-meta-mtime as Unix seconds. The module converts the header on the wire, in both directions: uploads convert milliseconds to seconds (for example, 1700000123456 to 1700000123.456), and downloads convert seconds back to milliseconds.

Conversion applies only to parsable values: uploads convert only values shaped like Sync Engine timestamps (13-digit milliseconds); downloads convert only numeric values. When rclone serve s3 loses its in-memory metadata after a server restart and omits x-amz-meta-mtime, the S3 backend recovers the time from Last-Modified on its own.

Encryption

When encryption is enabled, its wrapper (priority 7919) encrypts metadata before the S3 backend turns it into x-amz-meta-* headers. The encrypted mtime is non-numeric, so this module leaves it unchanged; encryption restores the millisecond value on read.

Implementation

The module registers a remote request middleware at priority 307, outside the S3 SigV4 middleware (304) so request signatures cover the converted value, and inside the retry middleware (2000) so every attempt converts from the original parameters. The middleware rebuilds requests and responses instead of mutating them, leaving every other header untouched.