ytclone

Copy static tables, files, YSON documents, and directories between YTsaurus and S3, preserving schemas and portable attributes.

Restoring from S3 requires a yt-s3-v2 archive created by ytclone. Earlier archive formats are rejected; re-export the source to a new S3 prefix.

Installation

pip install ytclone

Requires CPython 3.10+ on Linux x86_64 with glibc or macOS ARM64 (Apple Silicon).

Also available as standalone downloads and Docker images.

Quick start

Configure access to YTsaurus and S3:

export YT_PROXY="https://yt.example.com"
export YT_TOKEN="..."
export AWS_ACCESS_KEY_ID="..."
export AWS_SECRET_ACCESS_KEY="..."
export AWS_DEFAULT_REGION="us-east-1"

The S3 bucket must already exist. For an S3-compatible service, also set S3_ENDPOINT to its URL. Use AWS_SESSION_TOKEN for temporary credentials.

Copy to S3:

ytclone //home/analytics/events s3://my-bucket/export --log-file export.log

The full YT path is appended to the S3 prefix: this command stores events at s3://my-bucket/export/home/analytics/events/.

Restore to YTsaurus:

ytclone s3://my-bucket/export/home/analytics/events \
  //home/analytics/events_copy --log-file restore.log

The restore destination is used exactly as given: the children of events go directly under //home/analytics/events_copy. With --log-file, progress appears on the console and detailed logs are appended to the file.

Repeated runs

Rerun the command after an interruption or source update. Completed, unchanged nodes are skipped; other nodes are copied again. An unfinished table, file, or document restarts from the beginning.

Source data is never deleted. Destination nodes absent from the source are kept. Use a separate S3 prefix for each source cluster.

Parallel export

Use --max-streams to export large tables through several streams, or ytclone-parallel for multiple copy processes. Both apply to YT → S3; restore with ytclone.

Table format and compression

Both export commands now request Zstandard-compressed table data from the YT proxy by default. They remove the z-zstd_<level> transport container and upload its standard Zstandard frames without local decompression or recompression. Files and documents continue to use local Zstandard compression.

The initial supported combinations are --table-format yson (the default) or --table-format skiff, with --compression zstd and --compression-level 3. For example:

ytclone //home/analytics/events s3://my-bucket/skiff-export \
  --table-format skiff --compression-level 3 --log-file export.log

Each table's manifest records its wire format and schema. Restore selects them automatically, so no format option is needed. Skiff keeps complex values and columns outside the declared schema in its YSON catch-all field. Schemas, unsigned integers, binary strings and nulls are preserved.

The deprecated --yt-zstd-passthrough export option is accepted as a no-op; omitting it now gives the same table compression behavior. Unsupported proxy compression fails explicitly, without falling back to local table compression. Proxy blocks may compress less efficiently than a continuous local stream. Use fresh destination prefixes when comparing formats or compression levels; repeated unchanged copies are skipped. Changing a table's format or compression level forces a fresh export of that table. Existing v2 YSON archives remain readable, but upgrading from local table compression causes a one-time table re-export. Use this version or newer to restore newly written manifests; older readers do not understand the added format metadata.

Before you copy

• Dynamic tables are skipped and reported; links are unsupported.
• One current archive version. Failed uploads keep the previous copy available. Updates publish first, then try to delete the old copy. No history is kept.
• Permissions are not copied. ACLs, ownership, and account settings are excluded. Replacing an existing YT table, file, or document recreates the node, so its previous settings are not preserved either.
• Consistency is per node. A directory tree is not a single point-in-time snapshot.
• Concurrent exports can fail on conflicts. Updating an archive during restore can also fail the restore; rerun it. Concurrent restores to the same YT nodes are unsupported.
• S3 must support atomic conditional writes. See update and recovery details for rollback and cleanup behavior.

Documentation

Run ytclone --help or ytclone-parallel --help for all command-line options.

• User guide: paths, configuration, progress, retries, and parallel export.
• Architecture: archive format, change detection, and execution diagrams.
• Contributing: installation from source, development, and tests.

License: MIT.