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139 lines
5.8 KiB
Markdown
139 lines
5.8 KiB
Markdown
# Bucket Versioning Design Guide [](https://slack.min.io) [](https://hub.docker.com/r/minio/minio/)
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## Description of `xl.meta`
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`xl.meta` is a new self describing backend format used by MinIO to support AWS S3 compatible versioning.
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This file is the source of truth for each `version` at rest. `xl.meta` is a msgpack file serialized from a
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well defined data structure. To understand `xl.meta` here are the few things to start with
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`xl.meta` carries first 8 bytes an XL header which describes the current format and the format version,
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allowing the unmarshaller's to automatically use the right data structures to parse the subsequent content in the stream.
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### v1.0
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| Entry | Encoding | Content
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| ----------|-------------|----------------------------------------
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| xlHeader | [4]byte | `'X', 'L', '2', ' '`
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| xlVersion | [4]byte | `'1', ' ', ' ', ' '`
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| xlMetaV2 | msgp object | All versions as single messagepack object
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| [EOF] | |
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### v1.1+
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Version 1.1 added inline data, which will be placed after the metadata.
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Therefore, the metadata is wrapped as a binary array for easy skipping.
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| Entry | Encoding | Content
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| ---------------|----------------|----------------------------------------
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| xlHeader | [4]byte | `'X', 'L', '2', ' '`
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| xlVersionMajor | uint16 | Major xl-meta version.
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| xlVersionMinor | uint16 | Minor xl-meta version.
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| xlMetaV2 | msgp bin array | Bin array with serialized metadata
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| crc | msgp uint | Lower 32 bits of 64 bit xxhash of previous array contents (v1.2+ only)
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| inline data | binary | Inline data if any, see Inline Data section for encoding.
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| [EOF] | |
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## v1.0-v1.2 Versions
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`xl.meta` carries three types of object entries which designate the type of version object stored.
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- ObjectType (default)
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- LegacyObjectType (preserves existing deployments and older xl.json format)
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- DeleteMarker (a versionId to capture the DELETE sequences implemented primarily for AWS spec compatibility)
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A sample msgpack-JSON `xl.meta`, you can debug the content inside `xl.meta` using [xl-meta.go](https://github.com/minio/minio/tree/master/docs/debugging#decoding-metadata) program.
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```json
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{
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"Versions": [
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{
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"Type": 1,
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"V2Obj": {
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"ID": "KWUs8S+8RZq4Vp5TWy6KFg==",
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"DDir": "X3pDAFu8Rjyft7QD6t7W5g==",
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"EcAlgo": 1,
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"EcM": 2,
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"EcN": 2,
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"EcBSize": 10485760,
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"EcIndex": 3,
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"EcDist": [3, 4, 1, 2],
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"CSumAlgo": 1,
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"PartNums": [1],
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"PartETags": [""],
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"PartSizes": [314],
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"PartASizes": [282],
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"Size": 314,
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"MTime": 1591820730,
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"MetaSys": {
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"X-Minio-Internal-Server-Side-Encryption-S3-Kms-Key-Id": "bXktbWluaW8ta2V5",
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"X-Minio-Internal-Server-Side-Encryption-S3-Kms-Sealed-Key": "ZXlKaFpXRmtJam9pUVVWVExUSTFOaTFIUTAwdFNFMUJReTFUU0VFdE1qVTJJaXdpYVhZaU9pSkJMMVZzZFVnelZYVjZSR2N6UkhGWUwycEViRmRCUFQwaUxDSnViMjVqWlNJNklpdE9lbkJXVWtseFlWSlNVa2t2UVhNaUxDSmllWFJsY3lJNklrNDBabVZsZG5WU1NWVnRLMFoyUWpBMVlYTk9aMU41YVhoU1RrNUpkMDlhTkdKa2RuaGpLMjFuVDNnMFFYbFJhbE15V0hkU1pEZzNRMk54ZUN0SFFuSWlmUT09",
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"X-Minio-Internal-Server-Side-Encryption-Seal-Algorithm": "REFSRXYyLUhNQUMtU0hBMjU2",
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"X-Minio-Internal-Server-Side-Encryption-Iv": "bW5YRDhRUGczMVhkc2pJT1V1UVlnbWJBcndIQVhpTUN1dnVBS0QwNUVpaz0=",
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"X-Minio-Internal-Server-Side-Encryption-S3-Sealed-Key": "SUFBZkFPeUo5ZHVVSEkxYXFLU0NSRkJTTnM0QkVJNk9JWU1QcFVTSXFhK2dHVThXeE9oSHJCZWwwdnRvTldUNE8zS1BtcWluR0cydmlNNFRWa0N0Mmc9PQ=="
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},
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"MetaUsr": {
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"content-type": "application/octet-stream",
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"etag": "20000f00f58c508b40720270929bd90e9f07b9bd78fb605e5432a67635fc34722e4fc53b1d5fab9ff8400eb9ded4fba2"
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}
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}
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}
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]
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}
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```
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### v1.3+ versions
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Version 1.3 introduces changes to help with [faster metadata reads and updates](https://blog.min.io/minio-versioning-metadata-deep-dive/)
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| Entry | Encoding | Content
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| ----------------|-----------------------------|----------------------------------------
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| xlHeaderVersion | msgp uint | header version identifier
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| xlMetaVersion | msgp uint | metadata version identifier
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| versions | msgp int | Number of versions following
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| header_1 | msgp bin array | Header of version 1
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| metadata_1 | msgp bin array | Metadata of version 1
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| ...header_n | msgp bin array | Header of last version
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| ...metadata_n | msgp bin array | Metadata of last version
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Each header contains a mspg array (tuple) encoded object:
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xlHeaderVersion version == 1:
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```
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//msgp:tuple xlMetaV2VersionHeader
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type xlMetaV2VersionHeader struct {
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VersionID [16]byte // Version UUID, raw.
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ModTime int64 // Unix nanoseconds.
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Signature [4]byte // Signature of metadata.
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Type uint8 // Type if the version
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Flags uint8
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}
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```
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The following flags are defined:
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```
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const (
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FreeVersion = 1 << 0
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UsesDataDir = 1 << 1
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InlineData = 1 << 2
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)
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```
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The "Metadata" section contains a single version, encoded in similar fashion as each version in the `Versions` array
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of the previous version.
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## Inline Data
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Inline data is optional. If no inline data is present, it is encoded as 0 bytes.
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| Entry | Encoding | Content
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| --------------------|-----------------------------|----------------------------------------
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| xlMetaInlineDataVer | byte | version identifier
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| id -> data | msgp map[string][]byte | Map of string id -> byte content
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Currently only xlMetaInlineDataVer == 1 exists.
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The ID is the string encoded Version ID of which the data corresponds.
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