LCOV - code coverage report
Current view: top level - pageserver/src/tenant - metadata.rs (source / functions) Coverage Total Hit
Test: b4ae4c4857f9ef3e144e982a35ee23bc84c71983.info Lines: 92.4 % 370 342
Test Date: 2024-10-22 22:13:45 Functions: 58.5 % 82 48

            Line data    Source code
       1              : //! Describes the legacy now hopefully no longer modified per-timeline metadata.
       2              : //!
       3              : //! It is stored in `index_part.json` managed by [`remote_timeline_client`]. For many tenants and
       4              : //! their timelines, this struct and its original serialization format is still needed because
       5              : //! they were written a long time ago.
       6              : //!
       7              : //! Instead of changing and adding versioning to this, just change [`IndexPart`] with soft json
       8              : //! versioning.
       9              : //!
      10              : //! To clean up this module we need to migrate all index_part.json files to a later version.
      11              : //! While doing this, we need to be mindful about s3 based recovery as well, so it might take
      12              : //! however long we keep the old versions to be able to delete the old code. After that, we can
      13              : //! remove everything else than [`TimelineMetadataBodyV2`], rename it as `TimelineMetadata` and
      14              : //! move it to `index.rs`. Before doing all of this, we need to keep the structures for backwards
      15              : //! compatibility.
      16              : //!
      17              : //! [`remote_timeline_client`]: super::remote_timeline_client
      18              : //! [`IndexPart`]: super::remote_timeline_client::index::IndexPart
      19              : 
      20              : use anyhow::ensure;
      21              : use serde::{Deserialize, Serialize};
      22              : use utils::bin_ser::SerializeError;
      23              : use utils::{bin_ser::BeSer, id::TimelineId, lsn::Lsn};
      24              : 
      25              : /// Use special format number to enable backward compatibility.
      26              : const METADATA_FORMAT_VERSION: u16 = 4;
      27              : 
      28              : /// Previous supported format versions.
      29              : ///
      30              : /// In practice, none of these should remain, all are [`METADATA_FORMAT_VERSION`], but confirming
      31              : /// that requires a scrubber run which is yet to be done.
      32              : const METADATA_OLD_FORMAT_VERSION: u16 = 3;
      33              : 
      34              : /// When the file existed on disk we assumed that a write of up to METADATA_MAX_SIZE bytes is atomic.
      35              : ///
      36              : /// This is the same assumption that PostgreSQL makes with the control file,
      37              : ///
      38              : /// see PG_CONTROL_MAX_SAFE_SIZE
      39              : const METADATA_MAX_SIZE: usize = 512;
      40              : 
      41              : /// Legacy metadata stored as a component of `index_part.json` per timeline.
      42              : ///
      43              : /// Do not make new changes to this type or the module. In production, we have two different kinds
      44              : /// of serializations of this type: bincode and json. Bincode version reflects what used to be
      45              : /// stored on disk in earlier versions and does internal crc32 checksumming.
      46              : ///
      47              : /// This type should not implement `serde::Serialize` or `serde::Deserialize` because there would
      48              : /// be a confusion whether you want the old version ([`TimelineMetadata::from_bytes`]) or the modern
      49              : /// as-exists in `index_part.json` ([`self::modern_serde`]).
      50              : ///
      51              : /// ```compile_fail
      52              : /// #[derive(serde::Serialize)]
      53              : /// struct DoNotDoThis(pageserver::tenant::metadata::TimelineMetadata);
      54              : /// ```
      55              : ///
      56              : /// ```compile_fail
      57              : /// #[derive(serde::Deserialize)]
      58              : /// struct NeitherDoThis(pageserver::tenant::metadata::TimelineMetadata);
      59              : /// ```
      60              : #[derive(Debug, Clone, PartialEq, Eq)]
      61              : pub struct TimelineMetadata {
      62              :     hdr: TimelineMetadataHeader,
      63              :     body: TimelineMetadataBodyV2,
      64              : }
      65              : 
      66           52 : #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
      67              : struct TimelineMetadataHeader {
      68              :     checksum: u32,       // CRC of serialized metadata body
      69              :     size: u16,           // size of serialized metadata
      70              :     format_version: u16, // metadata format version (used for compatibility checks)
      71              : }
      72              : 
      73              : impl TryFrom<&TimelineMetadataBodyV2> for TimelineMetadataHeader {
      74              :     type Error = Crc32CalculationFailed;
      75              : 
      76           36 :     fn try_from(value: &TimelineMetadataBodyV2) -> Result<Self, Self::Error> {
      77              :         #[derive(Default)]
      78              :         struct Crc32Sink {
      79              :             crc: u32,
      80              :             count: usize,
      81              :         }
      82              : 
      83              :         impl std::io::Write for Crc32Sink {
      84          500 :             fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
      85          500 :                 self.crc = crc32c::crc32c_append(self.crc, buf);
      86          500 :                 self.count += buf.len();
      87          500 :                 Ok(buf.len())
      88          500 :             }
      89              : 
      90            0 :             fn flush(&mut self) -> std::io::Result<()> {
      91            0 :                 Ok(())
      92            0 :             }
      93              :         }
      94              : 
      95              :         // jump through hoops to calculate the crc32 so that TimelineMetadata::ne works
      96              :         // across serialization versions
      97           36 :         let mut sink = Crc32Sink::default();
      98           36 :         <TimelineMetadataBodyV2 as utils::bin_ser::BeSer>::ser_into(value, &mut sink)
      99           36 :             .map_err(Crc32CalculationFailed)?;
     100              : 
     101           36 :         let size = METADATA_HDR_SIZE + sink.count;
     102           36 : 
     103           36 :         Ok(TimelineMetadataHeader {
     104           36 :             checksum: sink.crc,
     105           36 :             size: size as u16,
     106           36 :             format_version: METADATA_FORMAT_VERSION,
     107           36 :         })
     108           36 :     }
     109              : }
     110              : 
     111            0 : #[derive(thiserror::Error, Debug)]
     112              : #[error("re-serializing for crc32 failed")]
     113              : struct Crc32CalculationFailed(#[source] utils::bin_ser::SerializeError);
     114              : 
     115              : const METADATA_HDR_SIZE: usize = size_of::<TimelineMetadataHeader>();
     116              : 
     117          288 : #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
     118              : struct TimelineMetadataBodyV2 {
     119              :     disk_consistent_lsn: Lsn,
     120              :     // This is only set if we know it. We track it in memory when the page
     121              :     // server is running, but we only track the value corresponding to
     122              :     // 'last_record_lsn', not 'disk_consistent_lsn' which can lag behind by a
     123              :     // lot. We only store it in the metadata file when we flush *all* the
     124              :     // in-memory data so that 'last_record_lsn' is the same as
     125              :     // 'disk_consistent_lsn'.  That's OK, because after page server restart, as
     126              :     // soon as we reprocess at least one record, we will have a valid
     127              :     // 'prev_record_lsn' value in memory again. This is only really needed when
     128              :     // doing a clean shutdown, so that there is no more WAL beyond
     129              :     // 'disk_consistent_lsn'
     130              :     prev_record_lsn: Option<Lsn>,
     131              :     ancestor_timeline: Option<TimelineId>,
     132              :     ancestor_lsn: Lsn,
     133              :     latest_gc_cutoff_lsn: Lsn,
     134              :     initdb_lsn: Lsn,
     135              :     pg_version: u32,
     136              : }
     137              : 
     138            2 : #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
     139              : struct TimelineMetadataBodyV1 {
     140              :     disk_consistent_lsn: Lsn,
     141              :     // This is only set if we know it. We track it in memory when the page
     142              :     // server is running, but we only track the value corresponding to
     143              :     // 'last_record_lsn', not 'disk_consistent_lsn' which can lag behind by a
     144              :     // lot. We only store it in the metadata file when we flush *all* the
     145              :     // in-memory data so that 'last_record_lsn' is the same as
     146              :     // 'disk_consistent_lsn'.  That's OK, because after page server restart, as
     147              :     // soon as we reprocess at least one record, we will have a valid
     148              :     // 'prev_record_lsn' value in memory again. This is only really needed when
     149              :     // doing a clean shutdown, so that there is no more WAL beyond
     150              :     // 'disk_consistent_lsn'
     151              :     prev_record_lsn: Option<Lsn>,
     152              :     ancestor_timeline: Option<TimelineId>,
     153              :     ancestor_lsn: Lsn,
     154              :     latest_gc_cutoff_lsn: Lsn,
     155              :     initdb_lsn: Lsn,
     156              : }
     157              : 
     158              : impl TimelineMetadata {
     159          430 :     pub fn new(
     160          430 :         disk_consistent_lsn: Lsn,
     161          430 :         prev_record_lsn: Option<Lsn>,
     162          430 :         ancestor_timeline: Option<TimelineId>,
     163          430 :         ancestor_lsn: Lsn,
     164          430 :         latest_gc_cutoff_lsn: Lsn,
     165          430 :         initdb_lsn: Lsn,
     166          430 :         pg_version: u32,
     167          430 :     ) -> Self {
     168          430 :         Self {
     169          430 :             hdr: TimelineMetadataHeader {
     170          430 :                 checksum: 0,
     171          430 :                 size: 0,
     172          430 :                 format_version: METADATA_FORMAT_VERSION,
     173          430 :             },
     174          430 :             body: TimelineMetadataBodyV2 {
     175          430 :                 disk_consistent_lsn,
     176          430 :                 prev_record_lsn,
     177          430 :                 ancestor_timeline,
     178          430 :                 ancestor_lsn,
     179          430 :                 latest_gc_cutoff_lsn,
     180          430 :                 initdb_lsn,
     181          430 :                 pg_version,
     182          430 :             },
     183          430 :         }
     184          430 :     }
     185              : 
     186              :     #[cfg(test)]
     187            6 :     pub(crate) fn with_recalculated_checksum(mut self) -> anyhow::Result<Self> {
     188            6 :         self.hdr = TimelineMetadataHeader::try_from(&self.body)?;
     189            6 :         Ok(self)
     190            6 :     }
     191              : 
     192            2 :     fn upgrade_timeline_metadata(metadata_bytes: &[u8]) -> anyhow::Result<Self> {
     193            2 :         let mut hdr = TimelineMetadataHeader::des(&metadata_bytes[0..METADATA_HDR_SIZE])?;
     194              : 
     195              :         // backward compatible only up to this version
     196            2 :         ensure!(
     197            2 :             hdr.format_version == METADATA_OLD_FORMAT_VERSION,
     198            0 :             "unsupported metadata format version {}",
     199              :             hdr.format_version
     200              :         );
     201              : 
     202            2 :         let metadata_size = hdr.size as usize;
     203              : 
     204            2 :         let body: TimelineMetadataBodyV1 =
     205            2 :             TimelineMetadataBodyV1::des(&metadata_bytes[METADATA_HDR_SIZE..metadata_size])?;
     206              : 
     207            2 :         let body = TimelineMetadataBodyV2 {
     208            2 :             disk_consistent_lsn: body.disk_consistent_lsn,
     209            2 :             prev_record_lsn: body.prev_record_lsn,
     210            2 :             ancestor_timeline: body.ancestor_timeline,
     211            2 :             ancestor_lsn: body.ancestor_lsn,
     212            2 :             latest_gc_cutoff_lsn: body.latest_gc_cutoff_lsn,
     213            2 :             initdb_lsn: body.initdb_lsn,
     214            2 :             pg_version: 14, // All timelines created before this version had pg_version 14
     215            2 :         };
     216            2 : 
     217            2 :         hdr.format_version = METADATA_FORMAT_VERSION;
     218            2 : 
     219            2 :         Ok(Self { hdr, body })
     220            2 :     }
     221              : 
     222           50 :     pub fn from_bytes(metadata_bytes: &[u8]) -> anyhow::Result<Self> {
     223           50 :         ensure!(
     224           50 :             metadata_bytes.len() == METADATA_MAX_SIZE,
     225            0 :             "metadata bytes size is wrong"
     226              :         );
     227           50 :         let hdr = TimelineMetadataHeader::des(&metadata_bytes[0..METADATA_HDR_SIZE])?;
     228              : 
     229           50 :         let metadata_size = hdr.size as usize;
     230           50 :         ensure!(
     231           50 :             metadata_size <= METADATA_MAX_SIZE,
     232            0 :             "corrupted metadata file"
     233              :         );
     234           50 :         let calculated_checksum = crc32c::crc32c(&metadata_bytes[METADATA_HDR_SIZE..metadata_size]);
     235           50 :         ensure!(
     236           50 :             hdr.checksum == calculated_checksum,
     237            0 :             "metadata checksum mismatch"
     238              :         );
     239              : 
     240           50 :         if hdr.format_version != METADATA_FORMAT_VERSION {
     241              :             // If metadata has the old format,
     242              :             // upgrade it and return the result
     243            2 :             TimelineMetadata::upgrade_timeline_metadata(metadata_bytes)
     244              :         } else {
     245           48 :             let body =
     246           48 :                 TimelineMetadataBodyV2::des(&metadata_bytes[METADATA_HDR_SIZE..metadata_size])?;
     247           48 :             ensure!(
     248           48 :                 body.disk_consistent_lsn.is_aligned(),
     249            0 :                 "disk_consistent_lsn is not aligned"
     250              :             );
     251           48 :             Ok(TimelineMetadata { hdr, body })
     252              :         }
     253           50 :     }
     254              : 
     255           18 :     pub fn to_bytes(&self) -> Result<Vec<u8>, SerializeError> {
     256           18 :         let body_bytes = self.body.ser()?;
     257           18 :         let metadata_size = METADATA_HDR_SIZE + body_bytes.len();
     258           18 :         let hdr = TimelineMetadataHeader {
     259           18 :             size: metadata_size as u16,
     260           18 :             format_version: METADATA_FORMAT_VERSION,
     261           18 :             checksum: crc32c::crc32c(&body_bytes),
     262           18 :         };
     263           18 :         let hdr_bytes = hdr.ser()?;
     264           18 :         let mut metadata_bytes = vec![0u8; METADATA_MAX_SIZE];
     265           18 :         metadata_bytes[0..METADATA_HDR_SIZE].copy_from_slice(&hdr_bytes);
     266           18 :         metadata_bytes[METADATA_HDR_SIZE..metadata_size].copy_from_slice(&body_bytes);
     267           18 :         Ok(metadata_bytes)
     268           18 :     }
     269              : 
     270              :     /// [`Lsn`] that corresponds to the corresponding timeline directory
     271              :     /// contents, stored locally in the pageserver workdir.
     272        21302 :     pub fn disk_consistent_lsn(&self) -> Lsn {
     273        21302 :         self.body.disk_consistent_lsn
     274        21302 :     }
     275              : 
     276          410 :     pub fn prev_record_lsn(&self) -> Option<Lsn> {
     277          410 :         self.body.prev_record_lsn
     278          410 :     }
     279              : 
     280          422 :     pub fn ancestor_timeline(&self) -> Option<TimelineId> {
     281          422 :         self.body.ancestor_timeline
     282          422 :     }
     283              : 
     284          638 :     pub fn ancestor_lsn(&self) -> Lsn {
     285          638 :         self.body.ancestor_lsn
     286          638 :     }
     287              : 
     288              :     /// When reparenting, the `ancestor_lsn` does not change.
     289              :     ///
     290              :     /// Returns true if anything was changed.
     291            0 :     pub fn reparent(&mut self, timeline: &TimelineId) {
     292            0 :         assert!(self.body.ancestor_timeline.is_some());
     293              :         // no assertion for redoing this: it's fine, we may have to repeat this multiple times over
     294            0 :         self.body.ancestor_timeline = Some(*timeline);
     295            0 :     }
     296              : 
     297              :     /// Returns true if anything was changed
     298            0 :     pub fn detach_from_ancestor(&mut self, branchpoint: &(TimelineId, Lsn)) {
     299            0 :         if let Some(ancestor) = self.body.ancestor_timeline {
     300            0 :             assert_eq!(ancestor, branchpoint.0);
     301            0 :         }
     302            0 :         if self.body.ancestor_lsn != Lsn(0) {
     303            0 :             assert_eq!(self.body.ancestor_lsn, branchpoint.1);
     304            0 :         }
     305            0 :         self.body.ancestor_timeline = None;
     306            0 :         self.body.ancestor_lsn = Lsn(0);
     307            0 :     }
     308              : 
     309          410 :     pub fn latest_gc_cutoff_lsn(&self) -> Lsn {
     310          410 :         self.body.latest_gc_cutoff_lsn
     311          410 :     }
     312              : 
     313          410 :     pub fn initdb_lsn(&self) -> Lsn {
     314          410 :         self.body.initdb_lsn
     315          410 :     }
     316              : 
     317          410 :     pub fn pg_version(&self) -> u32 {
     318          410 :         self.body.pg_version
     319          410 :     }
     320              : 
     321              :     // Checksums make it awkward to build a valid instance by hand.  This helper
     322              :     // provides a TimelineMetadata with a valid checksum in its header.
     323              :     #[cfg(test)]
     324           12 :     pub fn example() -> Self {
     325           12 :         let instance = Self::new(
     326           12 :             "0/16960E8".parse::<Lsn>().unwrap(),
     327           12 :             None,
     328           12 :             None,
     329           12 :             Lsn::from_hex("00000000").unwrap(),
     330           12 :             Lsn::from_hex("00000000").unwrap(),
     331           12 :             Lsn::from_hex("00000000").unwrap(),
     332           12 :             0,
     333           12 :         );
     334           12 :         let bytes = instance.to_bytes().unwrap();
     335           12 :         Self::from_bytes(&bytes).unwrap()
     336           12 :     }
     337              : 
     338         1140 :     pub(crate) fn apply(&mut self, update: &MetadataUpdate) {
     339         1140 :         self.body.disk_consistent_lsn = update.disk_consistent_lsn;
     340         1140 :         self.body.prev_record_lsn = update.prev_record_lsn;
     341         1140 :         self.body.latest_gc_cutoff_lsn = update.latest_gc_cutoff_lsn;
     342         1140 :     }
     343              : }
     344              : 
     345              : pub(crate) mod modern_serde {
     346              :     use super::{TimelineMetadata, TimelineMetadataBodyV2, TimelineMetadataHeader};
     347              :     use serde::{Deserialize, Serialize};
     348              : 
     349           46 :     pub(crate) fn deserialize<'de, D>(deserializer: D) -> Result<TimelineMetadata, D::Error>
     350           46 :     where
     351           46 :         D: serde::de::Deserializer<'de>,
     352           46 :     {
     353              :         // for legacy reasons versions 1-5 had TimelineMetadata serialized as a Vec<u8> field with
     354              :         // BeSer.
     355              :         struct Visitor;
     356              : 
     357              :         impl<'d> serde::de::Visitor<'d> for Visitor {
     358              :             type Value = TimelineMetadata;
     359              : 
     360            0 :             fn expecting(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
     361            0 :                 f.write_str("BeSer bytes or json structure")
     362            0 :             }
     363              : 
     364           16 :             fn visit_seq<A>(self, seq: A) -> Result<Self::Value, A::Error>
     365           16 :             where
     366           16 :                 A: serde::de::SeqAccess<'d>,
     367           16 :             {
     368              :                 use serde::de::Error;
     369           16 :                 let de = serde::de::value::SeqAccessDeserializer::new(seq);
     370           16 :                 Vec::<u8>::deserialize(de)
     371           16 :                     .map(|v| TimelineMetadata::from_bytes(&v).map_err(A::Error::custom))?
     372           16 :             }
     373              : 
     374           30 :             fn visit_map<A>(self, map: A) -> Result<Self::Value, A::Error>
     375           30 :             where
     376           30 :                 A: serde::de::MapAccess<'d>,
     377           30 :             {
     378              :                 use serde::de::Error;
     379              : 
     380           30 :                 let de = serde::de::value::MapAccessDeserializer::new(map);
     381           30 :                 let body = TimelineMetadataBodyV2::deserialize(de)?;
     382           30 :                 let hdr = TimelineMetadataHeader::try_from(&body).map_err(A::Error::custom)?;
     383              : 
     384           30 :                 Ok(TimelineMetadata { hdr, body })
     385           30 :             }
     386              :         }
     387              : 
     388           46 :         deserializer.deserialize_any(Visitor)
     389           46 :     }
     390              : 
     391         2841 :     pub(crate) fn serialize<S>(
     392         2841 :         metadata: &TimelineMetadata,
     393         2841 :         serializer: S,
     394         2841 :     ) -> Result<S::Ok, S::Error>
     395         2841 :     where
     396         2841 :         S: serde::Serializer,
     397         2841 :     {
     398         2841 :         // header is not needed, upon reading we've upgraded all v1 to v2
     399         2841 :         metadata.body.serialize(serializer)
     400         2841 :     }
     401              : 
     402              :     #[test]
     403            2 :     fn deserializes_bytes_as_well_as_equivalent_body_v2() {
     404            4 :         #[derive(serde::Deserialize, serde::Serialize)]
     405              :         struct Wrapper(
     406              :             #[serde(deserialize_with = "deserialize", serialize_with = "serialize")]
     407              :             TimelineMetadata,
     408              :         );
     409              : 
     410            2 :         let too_many_bytes = "[216,111,252,208,0,54,0,4,0,0,0,0,1,73,253,144,1,0,0,0,0,1,73,253,24,0,0,0,0,0,0,0,0,0,0,0,0,0,1,73,253,24,0,0,0,0,1,73,253,24,0,0,0,15,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]";
     411            2 : 
     412            2 :         let wrapper_from_bytes = serde_json::from_str::<Wrapper>(too_many_bytes).unwrap();
     413            2 : 
     414            2 :         let serialized = serde_json::to_value(&wrapper_from_bytes).unwrap();
     415            2 : 
     416            2 :         assert_eq!(
     417            2 :             serialized,
     418            2 :             serde_json::json! {{
     419            2 :                 "disk_consistent_lsn": "0/149FD90",
     420            2 :                 "prev_record_lsn": "0/149FD18",
     421            2 :                 "ancestor_timeline": null,
     422            2 :                 "ancestor_lsn": "0/0",
     423            2 :                 "latest_gc_cutoff_lsn": "0/149FD18",
     424            2 :                 "initdb_lsn": "0/149FD18",
     425            2 :                 "pg_version": 15
     426            2 :             }}
     427            2 :         );
     428              : 
     429            2 :         let wrapper_from_json = serde_json::value::from_value::<Wrapper>(serialized).unwrap();
     430            2 : 
     431            2 :         assert_eq!(wrapper_from_bytes.0, wrapper_from_json.0);
     432            2 :     }
     433              : }
     434              : 
     435              : /// Parts of the metadata which are regularly modified.
     436              : pub(crate) struct MetadataUpdate {
     437              :     disk_consistent_lsn: Lsn,
     438              :     prev_record_lsn: Option<Lsn>,
     439              :     latest_gc_cutoff_lsn: Lsn,
     440              : }
     441              : 
     442              : impl MetadataUpdate {
     443         1140 :     pub(crate) fn new(
     444         1140 :         disk_consistent_lsn: Lsn,
     445         1140 :         prev_record_lsn: Option<Lsn>,
     446         1140 :         latest_gc_cutoff_lsn: Lsn,
     447         1140 :     ) -> Self {
     448         1140 :         Self {
     449         1140 :             disk_consistent_lsn,
     450         1140 :             prev_record_lsn,
     451         1140 :             latest_gc_cutoff_lsn,
     452         1140 :         }
     453         1140 :     }
     454              : }
     455              : 
     456              : #[cfg(test)]
     457              : mod tests {
     458              :     use super::*;
     459              :     use crate::tenant::harness::TIMELINE_ID;
     460              : 
     461              :     #[test]
     462            2 :     fn metadata_serializes_correctly() {
     463            2 :         let original_metadata = TimelineMetadata::new(
     464            2 :             Lsn(0x200),
     465            2 :             Some(Lsn(0x100)),
     466            2 :             Some(TIMELINE_ID),
     467            2 :             Lsn(0),
     468            2 :             Lsn(0),
     469            2 :             Lsn(0),
     470            2 :             // Any version will do here, so use the default
     471            2 :             crate::DEFAULT_PG_VERSION,
     472            2 :         );
     473            2 : 
     474            2 :         let metadata_bytes = original_metadata
     475            2 :             .to_bytes()
     476            2 :             .expect("Should serialize correct metadata to bytes");
     477            2 : 
     478            2 :         let deserialized_metadata = TimelineMetadata::from_bytes(&metadata_bytes)
     479            2 :             .expect("Should deserialize its own bytes");
     480            2 : 
     481            2 :         assert_eq!(
     482              :             deserialized_metadata.body, original_metadata.body,
     483            0 :             "Metadata that was serialized to bytes and deserialized back should not change"
     484              :         );
     485            2 :     }
     486              : 
     487              :     // Generate old version metadata and read it with current code.
     488              :     // Ensure that it is upgraded correctly
     489              :     #[test]
     490            2 :     fn test_metadata_upgrade() {
     491              :         #[derive(Debug, Clone, PartialEq, Eq)]
     492              :         struct TimelineMetadataV1 {
     493              :             hdr: TimelineMetadataHeader,
     494              :             body: TimelineMetadataBodyV1,
     495              :         }
     496              : 
     497            2 :         let metadata_v1 = TimelineMetadataV1 {
     498            2 :             hdr: TimelineMetadataHeader {
     499            2 :                 checksum: 0,
     500            2 :                 size: 0,
     501            2 :                 format_version: METADATA_OLD_FORMAT_VERSION,
     502            2 :             },
     503            2 :             body: TimelineMetadataBodyV1 {
     504            2 :                 disk_consistent_lsn: Lsn(0x200),
     505            2 :                 prev_record_lsn: Some(Lsn(0x100)),
     506            2 :                 ancestor_timeline: Some(TIMELINE_ID),
     507            2 :                 ancestor_lsn: Lsn(0),
     508            2 :                 latest_gc_cutoff_lsn: Lsn(0),
     509            2 :                 initdb_lsn: Lsn(0),
     510            2 :             },
     511            2 :         };
     512              : 
     513              :         impl TimelineMetadataV1 {
     514            2 :             pub fn to_bytes(&self) -> anyhow::Result<Vec<u8>> {
     515            2 :                 let body_bytes = self.body.ser()?;
     516            2 :                 let metadata_size = METADATA_HDR_SIZE + body_bytes.len();
     517            2 :                 let hdr = TimelineMetadataHeader {
     518            2 :                     size: metadata_size as u16,
     519            2 :                     format_version: METADATA_OLD_FORMAT_VERSION,
     520            2 :                     checksum: crc32c::crc32c(&body_bytes),
     521            2 :                 };
     522            2 :                 let hdr_bytes = hdr.ser()?;
     523            2 :                 let mut metadata_bytes = vec![0u8; METADATA_MAX_SIZE];
     524            2 :                 metadata_bytes[0..METADATA_HDR_SIZE].copy_from_slice(&hdr_bytes);
     525            2 :                 metadata_bytes[METADATA_HDR_SIZE..metadata_size].copy_from_slice(&body_bytes);
     526            2 :                 Ok(metadata_bytes)
     527            2 :             }
     528              :         }
     529              : 
     530            2 :         let metadata_bytes = metadata_v1
     531            2 :             .to_bytes()
     532            2 :             .expect("Should serialize correct metadata to bytes");
     533            2 : 
     534            2 :         // This should deserialize to the latest version format
     535            2 :         let deserialized_metadata = TimelineMetadata::from_bytes(&metadata_bytes)
     536            2 :             .expect("Should deserialize its own bytes");
     537            2 : 
     538            2 :         let expected_metadata = TimelineMetadata::new(
     539            2 :             Lsn(0x200),
     540            2 :             Some(Lsn(0x100)),
     541            2 :             Some(TIMELINE_ID),
     542            2 :             Lsn(0),
     543            2 :             Lsn(0),
     544            2 :             Lsn(0),
     545            2 :             14, // All timelines created before this version had pg_version 14
     546            2 :         );
     547            2 : 
     548            2 :         assert_eq!(
     549              :             deserialized_metadata.body, expected_metadata.body,
     550            0 :             "Metadata of the old version {} should be upgraded to the latest version {}",
     551              :             METADATA_OLD_FORMAT_VERSION, METADATA_FORMAT_VERSION
     552              :         );
     553            2 :     }
     554              : 
     555              :     #[test]
     556            2 :     fn test_metadata_bincode_serde_ensure_roundtrip() {
     557            2 :         let original_metadata = TimelineMetadata::new(
     558            2 :             Lsn(0x200),
     559            2 :             Some(Lsn(0x100)),
     560            2 :             Some(TIMELINE_ID),
     561            2 :             Lsn(0),
     562            2 :             Lsn(0),
     563            2 :             Lsn(0),
     564            2 :             // Any version will do here, so use the default
     565            2 :             crate::DEFAULT_PG_VERSION,
     566            2 :         );
     567            2 :         let expected_bytes = vec![
     568            2 :             /* TimelineMetadataHeader */
     569            2 :             74, 104, 158, 105, 0, 70, 0, 4, // checksum, size, format_version (4 + 2 + 2)
     570            2 :             /* TimelineMetadataBodyV2 */
     571            2 :             0, 0, 0, 0, 0, 0, 2, 0, // disk_consistent_lsn (8 bytes)
     572            2 :             1, 0, 0, 0, 0, 0, 0, 1, 0, // prev_record_lsn (9 bytes)
     573            2 :             1, 17, 34, 51, 68, 85, 102, 119, 136, 17, 34, 51, 68, 85, 102, 119,
     574            2 :             136, // ancestor_timeline (17 bytes)
     575            2 :             0, 0, 0, 0, 0, 0, 0, 0, // ancestor_lsn (8 bytes)
     576            2 :             0, 0, 0, 0, 0, 0, 0, 0, // latest_gc_cutoff_lsn (8 bytes)
     577            2 :             0, 0, 0, 0, 0, 0, 0, 0, // initdb_lsn (8 bytes)
     578            2 :             0, 0, 0, 16, // pg_version (4 bytes)
     579            2 :             /* padding bytes */
     580            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     581            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     582            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     583            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     584            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     585            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     586            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     587            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     588            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     589            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     590            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     591            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     592            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     593            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     594            2 :             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     595            2 :             0, 0, 0, 0, 0, 0, 0,
     596            2 :         ];
     597            2 :         let metadata_ser_bytes = original_metadata.to_bytes().unwrap();
     598            2 :         assert_eq!(metadata_ser_bytes, expected_bytes);
     599              : 
     600            2 :         let expected_metadata = {
     601            2 :             let mut temp_metadata = original_metadata;
     602            2 :             let body_bytes = temp_metadata
     603            2 :                 .body
     604            2 :                 .ser()
     605            2 :                 .expect("Cannot serialize the metadata body");
     606            2 :             let metadata_size = METADATA_HDR_SIZE + body_bytes.len();
     607            2 :             let hdr = TimelineMetadataHeader {
     608            2 :                 size: metadata_size as u16,
     609            2 :                 format_version: METADATA_FORMAT_VERSION,
     610            2 :                 checksum: crc32c::crc32c(&body_bytes),
     611            2 :             };
     612            2 :             temp_metadata.hdr = hdr;
     613            2 :             temp_metadata
     614            2 :         };
     615            2 :         let des_metadata = TimelineMetadata::from_bytes(&metadata_ser_bytes).unwrap();
     616            2 :         assert_eq!(des_metadata, expected_metadata);
     617            2 :     }
     618              : }
        

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