First implementation of K2V (#293)

**Specification:**

View spec at [this URL](https://git.deuxfleurs.fr/Deuxfleurs/garage/src/branch/k2v/doc/drafts/k2v-spec.md)

- [x] Specify the structure of K2V triples
- [x] Specify the DVVS format used for causality detection
- [x] Specify the K2V index (just a counter of number of values per partition key)
- [x] Specify single-item endpoints: ReadItem, InsertItem, DeleteItem
- [x] Specify index endpoint: ReadIndex
- [x] Specify multi-item endpoints: InsertBatch, ReadBatch, DeleteBatch
- [x] Move to JSON objects instead of tuples
- [x] Specify endpoints for polling for updates on single values (PollItem)

**Implementation:**

- [x] Table for K2V items, causal contexts
- [x] Indexing mechanism and table for K2V index
- [x] Make API handlers a bit more generic
- [x] K2V API endpoint
- [x] K2V API router
- [x] ReadItem
- [x] InsertItem
- [x] DeleteItem
- [x] PollItem
- [x] ReadIndex
- [x] InsertBatch
- [x] ReadBatch
- [x] DeleteBatch

**Testing:**

- [x] Just a simple Python script that does some requests to check visually that things are going right (does not contain parsing of results or assertions on returned values)
- [x] Actual tests:
  - [x] Adapt testing framework
  - [x] Simple test with InsertItem + ReadItem
  - [x] Test with several Insert/Read/DeleteItem + ReadIndex
  - [x] Test all combinations of return formats for ReadItem
  - [x] Test with ReadBatch, InsertBatch, DeleteBatch
  - [x] Test with PollItem
  - [x] Test error codes
- [ ] Fix most broken stuff
  - [x] test PollItem broken randomly
  - [x] when invalid causality tokens are given, errors should be 4xx not 5xx

**Improvements:**

- [x] Descending range queries
  - [x] Specify
  - [x] Implement
  - [x] Add test
- [x] Batch updates to index counter
- [x] Put K2V behind `k2v` feature flag

Co-authored-by: Alex Auvolat <alex@adnab.me>
Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/293
Co-authored-by: Alex <alex@adnab.me>
Co-committed-by: Alex <alex@adnab.me>

1 files changed, 207 insertions, 0 deletions

diff --git a/src/model/s3/version_table.rs b/src/model/s3/version_table.rs
new file mode 100644
index 00000000..ad096772
--- /dev/null
+++ b/src/model/s3/version_table.rs
@@ -0,0 +1,207 @@
+use serde::{Deserialize, Serialize};
+use std::sync::Arc;
+
+use garage_util::background::BackgroundRunner;
+use garage_util::data::*;
+
+use garage_table::crdt::*;
+use garage_table::replication::TableShardedReplication;
+use garage_table::*;
+
+use crate::s3::block_ref_table::*;
+
+use garage_model_050::version_table as old;
+
+/// A version of an object
+#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
+pub struct Version {
+	/// UUID of the version, used as partition key
+	pub uuid: Uuid,
+
+	// Actual data: the blocks for this version
+	// In the case of a multipart upload, also store the etags
+	// of individual parts and check them when doing CompleteMultipartUpload
+	/// Is this version deleted
+	pub deleted: crdt::Bool,
+	/// list of blocks of data composing the version
+	pub blocks: crdt::Map<VersionBlockKey, VersionBlock>,
+	/// Etag of each part in case of a multipart upload, empty otherwise
+	pub parts_etags: crdt::Map<u64, String>,
+
+	// Back link to bucket+key so that we can figure if
+	// this was deleted later on
+	/// Bucket in which the related object is stored
+	pub bucket_id: Uuid,
+	/// Key in which the related object is stored
+	pub key: String,
+}
+
+impl Version {
+	pub fn new(uuid: Uuid, bucket_id: Uuid, key: String, deleted: bool) -> Self {
+		Self {
+			uuid,
+			deleted: deleted.into(),
+			blocks: crdt::Map::new(),
+			parts_etags: crdt::Map::new(),
+			bucket_id,
+			key,
+		}
+	}
+
+	pub fn has_part_number(&self, part_number: u64) -> bool {
+		let case1 = self
+			.parts_etags
+			.items()
+			.binary_search_by(|(k, _)| k.cmp(&part_number))
+			.is_ok();
+		let case2 = self
+			.blocks
+			.items()
+			.binary_search_by(|(k, _)| k.part_number.cmp(&part_number))
+			.is_ok();
+		case1 || case2
+	}
+}
+
+#[derive(PartialEq, Eq, Clone, Copy, Debug, Serialize, Deserialize)]
+pub struct VersionBlockKey {
+	/// Number of the part
+	pub part_number: u64,
+	/// Offset of this sub-segment in its part
+	pub offset: u64,
+}
+
+impl Ord for VersionBlockKey {
+	fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+		self.part_number
+			.cmp(&other.part_number)
+			.then(self.offset.cmp(&other.offset))
+	}
+}
+
+impl PartialOrd for VersionBlockKey {
+	fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+		Some(self.cmp(other))
+	}
+}
+
+/// Informations about a single block
+#[derive(PartialEq, Eq, Ord, PartialOrd, Clone, Copy, Debug, Serialize, Deserialize)]
+pub struct VersionBlock {
+	/// Blake2 sum of the block
+	pub hash: Hash,
+	/// Size of the block
+	pub size: u64,
+}
+
+impl AutoCrdt for VersionBlock {
+	const WARN_IF_DIFFERENT: bool = true;
+}
+
+impl Entry<Uuid, EmptyKey> for Version {
+	fn partition_key(&self) -> &Uuid {
+		&self.uuid
+	}
+	fn sort_key(&self) -> &EmptyKey {
+		&EmptyKey
+	}
+	fn is_tombstone(&self) -> bool {
+		self.deleted.get()
+	}
+}
+
+impl Crdt for Version {
+	fn merge(&mut self, other: &Self) {
+		self.deleted.merge(&other.deleted);
+
+		if self.deleted.get() {
+			self.blocks.clear();
+			self.parts_etags.clear();
+		} else {
+			self.blocks.merge(&other.blocks);
+			self.parts_etags.merge(&other.parts_etags);
+		}
+	}
+}
+
+pub struct VersionTable {
+	pub background: Arc<BackgroundRunner>,
+	pub block_ref_table: Arc<Table<BlockRefTable, TableShardedReplication>>,
+}
+
+impl TableSchema for VersionTable {
+	const TABLE_NAME: &'static str = "version";
+
+	type P = Uuid;
+	type S = EmptyKey;
+	type E = Version;
+	type Filter = DeletedFilter;
+
+	fn updated(&self, old: Option<&Self::E>, new: Option<&Self::E>) {
+		let block_ref_table = self.block_ref_table.clone();
+		let old = old.cloned();
+		let new = new.cloned();
+
+		self.background.spawn(async move {
+			if let (Some(old_v), Some(new_v)) = (old, new) {
+				// Propagate deletion of version blocks
+				if new_v.deleted.get() && !old_v.deleted.get() {
+					let deleted_block_refs = old_v
+						.blocks
+						.items()
+						.iter()
+						.map(|(_k, vb)| BlockRef {
+							block: vb.hash,
+							version: old_v.uuid,
+							deleted: true.into(),
+						})
+						.collect::<Vec<_>>();
+					block_ref_table.insert_many(&deleted_block_refs[..]).await?;
+				}
+			}
+			Ok(())
+		})
+	}
+
+	fn matches_filter(entry: &Self::E, filter: &Self::Filter) -> bool {
+		filter.apply(entry.deleted.get())
+	}
+
+	fn try_migrate(bytes: &[u8]) -> Option<Self::E> {
+		let old = rmp_serde::decode::from_read_ref::<_, old::Version>(bytes).ok()?;
+
+		let blocks = old
+			.blocks
+			.items()
+			.iter()
+			.map(|(k, v)| {
+				(
+					VersionBlockKey {
+						part_number: k.part_number,
+						offset: k.offset,
+					},
+					VersionBlock {
+						hash: Hash::try_from(v.hash.as_slice()).unwrap(),
+						size: v.size,
+					},
+				)
+			})
+			.collect::<crdt::Map<_, _>>();
+
+		let parts_etags = old
+			.parts_etags
+			.items()
+			.iter()
+			.map(|(k, v)| (*k, v.clone()))
+			.collect::<crdt::Map<_, _>>();
+
+		Some(Version {
+			uuid: Hash::try_from(old.uuid.as_slice()).unwrap(),
+			deleted: crdt::Bool::new(old.deleted.get()),
+			blocks,
+			parts_etags,
+			bucket_id: blake2sum(old.bucket.as_bytes()),
+			key: old.key,
+		})
+	}
+}