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, 337 insertions, 0 deletions

diff --git a/src/model/s3/object_table.rs b/src/model/s3/object_table.rs
new file mode 100644
index 00000000..3d9a89f7
--- /dev/null
+++ b/src/model/s3/object_table.rs
@@ -0,0 +1,337 @@
+use serde::{Deserialize, Serialize};
+use std::collections::BTreeMap;
+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::version_table::*;
+
+use garage_model_050::object_table as old;
+
+/// An object
+#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
+pub struct Object {
+	/// The bucket in which the object is stored, used as partition key
+	pub bucket_id: Uuid,
+
+	/// The key at which the object is stored in its bucket, used as sorting key
+	pub key: String,
+
+	/// The list of currenty stored versions of the object
+	versions: Vec<ObjectVersion>,
+}
+
+impl Object {
+	/// Initialize an Object struct from parts
+	pub fn new(bucket_id: Uuid, key: String, versions: Vec<ObjectVersion>) -> Self {
+		let mut ret = Self {
+			bucket_id,
+			key,
+			versions: vec![],
+		};
+		for v in versions {
+			ret.add_version(v)
+				.expect("Twice the same ObjectVersion in Object constructor");
+		}
+		ret
+	}
+
+	/// Adds a version if it wasn't already present
+	#[allow(clippy::result_unit_err)]
+	pub fn add_version(&mut self, new: ObjectVersion) -> Result<(), ()> {
+		match self
+			.versions
+			.binary_search_by(|v| v.cmp_key().cmp(&new.cmp_key()))
+		{
+			Err(i) => {
+				self.versions.insert(i, new);
+				Ok(())
+			}
+			Ok(_) => Err(()),
+		}
+	}
+
+	/// Get a list of currently stored versions of `Object`
+	pub fn versions(&self) -> &[ObjectVersion] {
+		&self.versions[..]
+	}
+}
+
+/// Informations about a version of an object
+#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
+pub struct ObjectVersion {
+	/// Id of the version
+	pub uuid: Uuid,
+	/// Timestamp of when the object was created
+	pub timestamp: u64,
+	/// State of the version
+	pub state: ObjectVersionState,
+}
+
+/// State of an object version
+#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
+pub enum ObjectVersionState {
+	/// The version is being received
+	Uploading(ObjectVersionHeaders),
+	/// The version is fully received
+	Complete(ObjectVersionData),
+	/// The version uploaded containded errors or the upload was explicitly aborted
+	Aborted,
+}
+
+impl Crdt for ObjectVersionState {
+	fn merge(&mut self, other: &Self) {
+		use ObjectVersionState::*;
+		match other {
+			Aborted => {
+				*self = Aborted;
+			}
+			Complete(b) => match self {
+				Aborted => {}
+				Complete(a) => {
+					a.merge(b);
+				}
+				Uploading(_) => {
+					*self = Complete(b.clone());
+				}
+			},
+			Uploading(_) => {}
+		}
+	}
+}
+
+/// Data stored in object version
+#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
+pub enum ObjectVersionData {
+	/// The object was deleted, this Version is a tombstone to mark it as such
+	DeleteMarker,
+	/// The object is short, it's stored inlined
+	Inline(ObjectVersionMeta, #[serde(with = "serde_bytes")] Vec<u8>),
+	/// The object is not short, Hash of first block is stored here, next segments hashes are
+	/// stored in the version table
+	FirstBlock(ObjectVersionMeta, Hash),
+}
+
+impl AutoCrdt for ObjectVersionData {
+	const WARN_IF_DIFFERENT: bool = true;
+}
+
+/// Metadata about the object version
+#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
+pub struct ObjectVersionMeta {
+	/// Headers to send to the client
+	pub headers: ObjectVersionHeaders,
+	/// Size of the object
+	pub size: u64,
+	/// etag of the object
+	pub etag: String,
+}
+
+/// Additional headers for an object
+#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
+pub struct ObjectVersionHeaders {
+	/// Content type of the object
+	pub content_type: String,
+	/// Any other http headers to send
+	pub other: BTreeMap<String, String>,
+}
+
+impl ObjectVersion {
+	fn cmp_key(&self) -> (u64, Uuid) {
+		(self.timestamp, self.uuid)
+	}
+
+	/// Is the object version currently being uploaded
+	pub fn is_uploading(&self) -> bool {
+		matches!(self.state, ObjectVersionState::Uploading(_))
+	}
+
+	/// Is the object version completely received
+	pub fn is_complete(&self) -> bool {
+		matches!(self.state, ObjectVersionState::Complete(_))
+	}
+
+	/// Is the object version available (received and not a tombstone)
+	pub fn is_data(&self) -> bool {
+		match self.state {
+			ObjectVersionState::Complete(ObjectVersionData::DeleteMarker) => false,
+			ObjectVersionState::Complete(_) => true,
+			_ => false,
+		}
+	}
+}
+
+impl Entry<Uuid, String> for Object {
+	fn partition_key(&self) -> &Uuid {
+		&self.bucket_id
+	}
+	fn sort_key(&self) -> &String {
+		&self.key
+	}
+	fn is_tombstone(&self) -> bool {
+		self.versions.len() == 1
+			&& self.versions[0].state
+				== ObjectVersionState::Complete(ObjectVersionData::DeleteMarker)
+	}
+}
+
+impl Crdt for Object {
+	fn merge(&mut self, other: &Self) {
+		// Merge versions from other into here
+		for other_v in other.versions.iter() {
+			match self
+				.versions
+				.binary_search_by(|v| v.cmp_key().cmp(&other_v.cmp_key()))
+			{
+				Ok(i) => {
+					self.versions[i].state.merge(&other_v.state);
+				}
+				Err(i) => {
+					self.versions.insert(i, other_v.clone());
+				}
+			}
+		}
+
+		// Remove versions which are obsolete, i.e. those that come
+		// before the last version which .is_complete().
+		let last_complete = self
+			.versions
+			.iter()
+			.enumerate()
+			.rev()
+			.find(|(_, v)| v.is_complete())
+			.map(|(vi, _)| vi);
+
+		if let Some(last_vi) = last_complete {
+			self.versions = self.versions.drain(last_vi..).collect::<Vec<_>>();
+		}
+	}
+}
+
+pub struct ObjectTable {
+	pub background: Arc<BackgroundRunner>,
+	pub version_table: Arc<Table<VersionTable, TableShardedReplication>>,
+}
+
+#[derive(Clone, Copy, Debug, Serialize, Deserialize)]
+pub enum ObjectFilter {
+	IsData,
+	IsUploading,
+}
+
+impl TableSchema for ObjectTable {
+	const TABLE_NAME: &'static str = "object";
+
+	type P = Uuid;
+	type S = String;
+	type E = Object;
+	type Filter = ObjectFilter;
+
+	fn updated(&self, old: Option<&Self::E>, new: Option<&Self::E>) {
+		let version_table = self.version_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 old versions
+				for v in old_v.versions.iter() {
+					let newly_deleted = match new_v
+						.versions
+						.binary_search_by(|nv| nv.cmp_key().cmp(&v.cmp_key()))
+					{
+						Err(_) => true,
+						Ok(i) => {
+							new_v.versions[i].state == ObjectVersionState::Aborted
+								&& v.state != ObjectVersionState::Aborted
+						}
+					};
+					if newly_deleted {
+						let deleted_version =
+							Version::new(v.uuid, old_v.bucket_id, old_v.key.clone(), true);
+						version_table.insert(&deleted_version).await?;
+					}
+				}
+			}
+			Ok(())
+		})
+	}
+
+	fn matches_filter(entry: &Self::E, filter: &Self::Filter) -> bool {
+		match filter {
+			ObjectFilter::IsData => entry.versions.iter().any(|v| v.is_data()),
+			ObjectFilter::IsUploading => entry.versions.iter().any(|v| v.is_uploading()),
+		}
+	}
+
+	fn try_migrate(bytes: &[u8]) -> Option<Self::E> {
+		let old_obj = rmp_serde::decode::from_read_ref::<_, old::Object>(bytes).ok()?;
+		Some(migrate_object(old_obj))
+	}
+}
+
+// vvvvvvvv migration code, stupid stuff vvvvvvvvvvvv
+// (we just want to change bucket into bucket_id by hashing it)
+
+fn migrate_object(o: old::Object) -> Object {
+	let versions = o
+		.versions()
+		.iter()
+		.cloned()
+		.map(migrate_object_version)
+		.collect();
+	Object {
+		bucket_id: blake2sum(o.bucket.as_bytes()),
+		key: o.key,
+		versions,
+	}
+}
+
+fn migrate_object_version(v: old::ObjectVersion) -> ObjectVersion {
+	ObjectVersion {
+		uuid: Uuid::try_from(v.uuid.as_slice()).unwrap(),
+		timestamp: v.timestamp,
+		state: match v.state {
+			old::ObjectVersionState::Uploading(h) => {
+				ObjectVersionState::Uploading(migrate_object_version_headers(h))
+			}
+			old::ObjectVersionState::Complete(d) => {
+				ObjectVersionState::Complete(migrate_object_version_data(d))
+			}
+			old::ObjectVersionState::Aborted => ObjectVersionState::Aborted,
+		},
+	}
+}
+
+fn migrate_object_version_headers(h: old::ObjectVersionHeaders) -> ObjectVersionHeaders {
+	ObjectVersionHeaders {
+		content_type: h.content_type,
+		other: h.other,
+	}
+}
+
+fn migrate_object_version_data(d: old::ObjectVersionData) -> ObjectVersionData {
+	match d {
+		old::ObjectVersionData::DeleteMarker => ObjectVersionData::DeleteMarker,
+		old::ObjectVersionData::Inline(m, b) => {
+			ObjectVersionData::Inline(migrate_object_version_meta(m), b)
+		}
+		old::ObjectVersionData::FirstBlock(m, h) => ObjectVersionData::FirstBlock(
+			migrate_object_version_meta(m),
+			Hash::try_from(h.as_slice()).unwrap(),
+		),
+	}
+}
+
+fn migrate_object_version_meta(m: old::ObjectVersionMeta) -> ObjectVersionMeta {
+	ObjectVersionMeta {
+		headers: migrate_object_version_headers(m.headers),
+		size: m.size,
+		etag: m.etag,
+	}
+}