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use old metadata format by default (for a week)
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@skyzh
skyzh committed May 9, 2024
1 parent 21f3984 commit 396b9cf
Showing 1 changed file with 122 additions and 23 deletions.
145 changes: 122 additions & 23 deletions pageserver/src/tenant/metadata.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,12 +14,26 @@ use utils::bin_ser::SerializeError;
use utils::{bin_ser::BeSer, id::TimelineId, lsn::Lsn};

/// Use special format number to enable backward compatibility.
///
/// Currently, we are in the transition period between bodyv3 and bodyv2. We will keep
/// both formats available for a week, and then auto-upgrade everything to v3.
///
/// The version is distinguished by the header format number. We always use bodyv3 as
/// the in-memory representation of the data. If the header format is the old one, the
/// body will be serialized using bincode. Otherwise, it will be serialized using JSON,
/// which is the default method for bodyv3.
const METADATA_FORMAT_VERSION: u16 = 5;

/// Previous supported format versions.
const METADATA_OLD_FORMAT_VERSION_V2: u16 = 4;
const METADATA_OLD_FORMAT_VERSION_V1: u16 = 3;

/// We assume that a write of up to METADATA_MAX_SIZE bytes is atomic.
///
/// This is the same assumption that PostgreSQL makes with the control file,
/// see PG_CONTROL_MAX_SAFE_SIZE
const METADATA_MAX_SIZE: usize = 512;

/// Metadata stored on disk for each timeline
///
/// The fields correspond to the values we hold in memory, in Timeline.
Expand Down Expand Up @@ -113,7 +127,7 @@ impl TimelineMetadata {
hdr: TimelineMetadataHeader {
checksum: 0,
size: 0,
format_version: METADATA_FORMAT_VERSION,
format_version: METADATA_OLD_FORMAT_VERSION_V2, // Default to the old format v2
},
body: TimelineMetadataBodyV3 {
disk_consistent_lsn,
Expand Down Expand Up @@ -148,7 +162,7 @@ impl TimelineMetadata {
pg_version: body.pg_version,
};

hdr.format_version = METADATA_FORMAT_VERSION;
hdr.format_version = METADATA_OLD_FORMAT_VERSION_V2; // DO NOT auto-upgrade
body
}
METADATA_OLD_FORMAT_VERSION_V1 => {
Expand Down Expand Up @@ -203,19 +217,38 @@ impl TimelineMetadata {
}

pub fn to_bytes(&self) -> Result<Vec<u8>, SerializeError> {
let body_bytes =
serde_json::to_vec(&self.body).map_err(|e| SerializeError::BadInput(e.into()))?;
let metadata_size = METADATA_HDR_SIZE + body_bytes.len();
let hdr = TimelineMetadataHeader {
size: metadata_size as u16,
format_version: METADATA_FORMAT_VERSION,
checksum: crc32c::crc32c(&body_bytes),
};
let hdr_bytes = hdr.ser()?;
let mut metadata_bytes = Vec::new();
metadata_bytes.extend(hdr_bytes);
metadata_bytes.extend(body_bytes);
Ok(metadata_bytes)
match self.hdr.format_version {
METADATA_OLD_FORMAT_VERSION_V2 => {
let body_bytes = self.body.ser()?;
let metadata_size = METADATA_HDR_SIZE + body_bytes.len();
let hdr = TimelineMetadataHeader {
size: metadata_size as u16,
format_version: METADATA_OLD_FORMAT_VERSION_V2,
checksum: crc32c::crc32c(&body_bytes),
};
let hdr_bytes = hdr.ser()?;
let mut metadata_bytes = vec![0u8; METADATA_MAX_SIZE];
metadata_bytes[0..METADATA_HDR_SIZE].copy_from_slice(&hdr_bytes);
metadata_bytes[METADATA_HDR_SIZE..metadata_size].copy_from_slice(&body_bytes);
Ok(metadata_bytes)
}
METADATA_FORMAT_VERSION => {
let body_bytes = serde_json::to_vec(&self.body)
.map_err(|e| SerializeError::BadInput(e.into()))?;
let metadata_size = METADATA_HDR_SIZE + body_bytes.len();
let hdr = TimelineMetadataHeader {
size: metadata_size as u16,
format_version: METADATA_FORMAT_VERSION,
checksum: crc32c::crc32c(&body_bytes),
};
let hdr_bytes = hdr.ser()?;
let mut metadata_bytes = Vec::new();
metadata_bytes.extend(hdr_bytes);
metadata_bytes.extend(body_bytes);
Ok(metadata_bytes)
}
_ => unreachable!(),
}
}

/// [`Lsn`] that corresponds to the corresponding timeline directory
Expand Down Expand Up @@ -340,9 +373,6 @@ mod tests {
use super::*;
use crate::tenant::harness::TIMELINE_ID;

// Previous limit on maximum metadata size
const METADATA_MAX_SIZE: usize = 512;

#[test]
fn metadata_serializes_correctly() {
let original_metadata = TimelineMetadata::new(
Expand Down Expand Up @@ -440,6 +470,7 @@ mod tests {
// Generate old version metadata and read it with current code.
// Ensure that it is upgraded correctly
#[test]
#[ignore]
fn test_metadata_upgrade_v2() {
#[derive(Debug, Clone, PartialEq, Eq)]
struct TimelineMetadataV2 {
Expand Down Expand Up @@ -507,12 +538,12 @@ mod tests {
}

#[test]
fn test_roundtrip_metadata_v3() {
let metadata_v3 = TimelineMetadata {
fn test_roundtrip_metadata_v2() {
let metadata_v2 = TimelineMetadata {
hdr: TimelineMetadataHeader {
checksum: 0,
size: 0,
format_version: METADATA_FORMAT_VERSION,
format_version: METADATA_OLD_FORMAT_VERSION_V2,
},
body: TimelineMetadataBodyV3 {
disk_consistent_lsn: Lsn(0x200),
Expand All @@ -525,7 +556,7 @@ mod tests {
},
};

let metadata_bytes = metadata_v3
let metadata_bytes = metadata_v2
.to_bytes()
.expect("Should serialize correct metadata to bytes");

Expand All @@ -547,7 +578,75 @@ mod tests {
}

#[test]
fn test_encode_regression() {
fn test_encode_regression_v2() {
let mut original_metadata = TimelineMetadata::new(
Lsn(0x200),
Some(Lsn(0x100)),
Some(TIMELINE_ID),
Lsn(0),
Lsn(0),
Lsn(0),
// Any version will do here, so use the default
crate::DEFAULT_PG_VERSION,
);
original_metadata.hdr.format_version = METADATA_OLD_FORMAT_VERSION_V2;

let expected_bytes = vec![
/* bincode length encoding bytes */
0, 0, 0, 0, 0, 0, 2, 0, // 8 bytes for the length of the serialized vector
/* TimelineMetadataHeader */
4, 37, 101, 34, 0, 70, 0, 4, // checksum, size, format_version (4 + 2 + 2)
/* TimelineMetadataBodyV2 */
0, 0, 0, 0, 0, 0, 2, 0, // disk_consistent_lsn (8 bytes)
1, 0, 0, 0, 0, 0, 0, 1, 0, // prev_record_lsn (9 bytes)
1, 17, 34, 51, 68, 85, 102, 119, 136, 17, 34, 51, 68, 85, 102, 119,
136, // ancestor_timeline (17 bytes)
0, 0, 0, 0, 0, 0, 0, 0, // ancestor_lsn (8 bytes)
0, 0, 0, 0, 0, 0, 0, 0, // latest_gc_cutoff_lsn (8 bytes)
0, 0, 0, 0, 0, 0, 0, 0, // initdb_lsn (8 bytes)
0, 0, 0, 15, // pg_version (4 bytes)
/* padding bytes */
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0,
];
let metadata_ser_bytes = original_metadata.ser().unwrap();
assert_eq!(metadata_ser_bytes, expected_bytes);

let expected_metadata = {
let mut temp_metadata = original_metadata;
let body_bytes = temp_metadata
.body
.ser()
.expect("Cannot serialize the metadata body");
let metadata_size = METADATA_HDR_SIZE + body_bytes.len();
let hdr = TimelineMetadataHeader {
size: metadata_size as u16,
format_version: METADATA_OLD_FORMAT_VERSION_V2,
checksum: crc32c::crc32c(&body_bytes),
};
temp_metadata.hdr = hdr;
temp_metadata
};
let des_metadata = TimelineMetadata::des(&metadata_ser_bytes).unwrap();
assert_eq!(des_metadata, expected_metadata);
}

#[test]
fn test_encode_regression_v3() {
let metadata_v3 = TimelineMetadata {
hdr: TimelineMetadataHeader {
checksum: 0,
Expand Down

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