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>

6 files changed, 1541 insertions, 0 deletions

diff --git a/src/garage/tests/k2v/batch.rs b/src/garage/tests/k2v/batch.rs
new file mode 100644
index 00000000..1182a298
--- /dev/null
+++ b/src/garage/tests/k2v/batch.rs
@@ -0,0 +1,525 @@
+use std::collections::HashMap;
+
+use crate::common;
+
+use assert_json_diff::assert_json_eq;
+use serde_json::json;
+
+use super::json_body;
+use hyper::Method;
+
+#[tokio::test]
+async fn test_batch() {
+	let ctx = common::context();
+	let bucket = ctx.create_bucket("test-k2v-batch");
+
+	let mut values = HashMap::new();
+	values.insert("a", "initial test 1");
+	values.insert("b", "initial test 2");
+	values.insert("c", "initial test 3");
+	values.insert("d.1", "initial test 4");
+	values.insert("d.2", "initial test 5");
+	values.insert("e", "initial test 6");
+	let mut ct = HashMap::new();
+
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.body(
+			format!(
+				r#"[
+	{{"pk": "root", "sk": "a", "ct": null, "v": "{}"}},
+	{{"pk": "root", "sk": "b", "ct": null, "v": "{}"}},
+	{{"pk": "root", "sk": "c", "ct": null, "v": "{}"}},
+	{{"pk": "root", "sk": "d.1", "ct": null, "v": "{}"}},
+	{{"pk": "root", "sk": "d.2", "ct": null, "v": "{}"}},
+	{{"pk": "root", "sk": "e", "ct": null, "v": "{}"}}
+		]"#,
+				base64::encode(values.get(&"a").unwrap()),
+				base64::encode(values.get(&"b").unwrap()),
+				base64::encode(values.get(&"c").unwrap()),
+				base64::encode(values.get(&"d.1").unwrap()),
+				base64::encode(values.get(&"d.2").unwrap()),
+				base64::encode(values.get(&"e").unwrap()),
+			)
+			.into_bytes(),
+		)
+		.method(Method::POST)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+
+	for sk in ["a", "b", "c", "d.1", "d.2", "e"] {
+		let res = ctx
+			.k2v
+			.request
+			.builder(bucket.clone())
+			.path("root")
+			.query_param("sort_key", Some(sk))
+			.signed_header("accept", "*/*")
+			.send()
+			.await
+			.unwrap();
+		assert_eq!(res.status(), 200);
+		assert_eq!(
+			res.headers().get("content-type").unwrap().to_str().unwrap(),
+			"application/octet-stream"
+		);
+		ct.insert(
+			sk,
+			res.headers()
+				.get("x-garage-causality-token")
+				.unwrap()
+				.to_str()
+				.unwrap()
+				.to_string(),
+		);
+		let res_body = hyper::body::to_bytes(res.into_body())
+			.await
+			.unwrap()
+			.to_vec();
+		assert_eq!(res_body, values.get(sk).unwrap().as_bytes());
+	}
+
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.query_param("search", Option::<&str>::None)
+		.body(
+			br#"[
+	{"partitionKey": "root"},
+	{"partitionKey": "root", "start": "c"},
+	{"partitionKey": "root", "start": "c", "reverse": true, "end": "a"},
+	{"partitionKey": "root", "limit": 1},
+	{"partitionKey": "root", "prefix": "d"}
+		]"#
+			.to_vec(),
+		)
+		.method(Method::POST)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	let json_res = json_body(res).await;
+	assert_json_eq!(
+		json_res,
+		json!([
+			{
+				"partitionKey": "root",
+				"prefix": null,
+				"start": null,
+				"end": null,
+				"limit": null,
+				"reverse": false,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "a", "ct": ct.get("a").unwrap(), "v": [base64::encode(values.get("a").unwrap())]},
+				  {"sk": "b", "ct": ct.get("b").unwrap(), "v": [base64::encode(values.get("b").unwrap())]},
+				  {"sk": "c", "ct": ct.get("c").unwrap(), "v": [base64::encode(values.get("c").unwrap())]},
+				  {"sk": "d.1", "ct": ct.get("d.1").unwrap(), "v": [base64::encode(values.get("d.1").unwrap())]},
+				  {"sk": "d.2", "ct": ct.get("d.2").unwrap(), "v": [base64::encode(values.get("d.2").unwrap())]},
+				  {"sk": "e", "ct": ct.get("e").unwrap(), "v": [base64::encode(values.get("e").unwrap())]}
+				],
+				"more": false,
+				"nextStart": null,
+			},
+			{
+				"partitionKey": "root",
+				"prefix": null,
+				"start": "c",
+				"end": null,
+				"limit": null,
+				"reverse": false,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "c", "ct": ct.get("c").unwrap(), "v": [base64::encode(values.get("c").unwrap())]},
+				  {"sk": "d.1", "ct": ct.get("d.1").unwrap(), "v": [base64::encode(values.get("d.1").unwrap())]},
+				  {"sk": "d.2", "ct": ct.get("d.2").unwrap(), "v": [base64::encode(values.get("d.2").unwrap())]},
+				  {"sk": "e", "ct": ct.get("e").unwrap(), "v": [base64::encode(values.get("e").unwrap())]}
+				],
+				"more": false,
+				"nextStart": null,
+			},
+			{
+				"partitionKey": "root",
+				"prefix": null,
+				"start": "c",
+				"end": "a",
+				"limit": null,
+				"reverse": true,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "c", "ct": ct.get("c").unwrap(), "v": [base64::encode(values.get("c").unwrap())]},
+				  {"sk": "b", "ct": ct.get("b").unwrap(), "v": [base64::encode(values.get("b").unwrap())]},
+				],
+				"more": false,
+				"nextStart": null,
+			},
+			{
+				"partitionKey": "root",
+				"prefix": null,
+				"start": null,
+				"end": null,
+				"limit": 1,
+				"reverse": false,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "a", "ct": ct.get("a").unwrap(), "v": [base64::encode(values.get("a").unwrap())]}
+				],
+				"more": true,
+				"nextStart": "b",
+			},
+			{
+				"partitionKey": "root",
+				"prefix": "d",
+				"start": null,
+				"end": null,
+				"limit": null,
+				"reverse": false,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "d.1", "ct": ct.get("d.1").unwrap(), "v": [base64::encode(values.get("d.1").unwrap())]},
+				  {"sk": "d.2", "ct": ct.get("d.2").unwrap(), "v": [base64::encode(values.get("d.2").unwrap())]}
+				],
+				"more": false,
+				"nextStart": null,
+			},
+		])
+	);
+
+	// Insert some new values
+	values.insert("c'", "new test 3");
+	values.insert("d.1'", "new test 4");
+	values.insert("d.2'", "new test 5");
+
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.body(
+			format!(
+				r#"[
+	{{"pk": "root", "sk": "b", "ct": "{}", "v": null}},
+	{{"pk": "root", "sk": "c", "ct": null, "v": "{}"}},
+	{{"pk": "root", "sk": "d.1", "ct": "{}", "v": "{}"}},
+	{{"pk": "root", "sk": "d.2", "ct": null, "v": "{}"}}
+		]"#,
+				ct.get(&"b").unwrap(),
+				base64::encode(values.get(&"c'").unwrap()),
+				ct.get(&"d.1").unwrap(),
+				base64::encode(values.get(&"d.1'").unwrap()),
+				base64::encode(values.get(&"d.2'").unwrap()),
+			)
+			.into_bytes(),
+		)
+		.method(Method::POST)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+
+	for sk in ["b", "c", "d.1", "d.2"] {
+		let res = ctx
+			.k2v
+			.request
+			.builder(bucket.clone())
+			.path("root")
+			.query_param("sort_key", Some(sk))
+			.signed_header("accept", "*/*")
+			.send()
+			.await
+			.unwrap();
+		if sk == "b" {
+			assert_eq!(res.status(), 204);
+		} else {
+			assert_eq!(res.status(), 200);
+		}
+		ct.insert(
+			sk,
+			res.headers()
+				.get("x-garage-causality-token")
+				.unwrap()
+				.to_str()
+				.unwrap()
+				.to_string(),
+		);
+	}
+
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.query_param("search", Option::<&str>::None)
+		.body(
+			br#"[
+	{"partitionKey": "root"},
+	{"partitionKey": "root", "prefix": "d"},
+	{"partitionKey": "root", "prefix": "d.", "end": "d.2"},
+	{"partitionKey": "root", "prefix": "d.", "limit": 1},
+	{"partitionKey": "root", "prefix": "d.", "start": "d.2", "limit": 1},
+	{"partitionKey": "root", "prefix": "d.", "reverse": true},
+	{"partitionKey": "root", "prefix": "d.", "start": "d.2", "reverse": true},
+	{"partitionKey": "root", "prefix": "d.", "limit": 2}
+		]"#
+			.to_vec(),
+		)
+		.method(Method::POST)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	let json_res = json_body(res).await;
+	assert_json_eq!(
+		json_res,
+		json!([
+			{
+				"partitionKey": "root",
+				"prefix": null,
+				"start": null,
+				"end": null,
+				"limit": null,
+				"reverse": false,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "a", "ct": ct.get("a").unwrap(), "v": [base64::encode(values.get("a").unwrap())]},
+				  {"sk": "c", "ct": ct.get("c").unwrap(), "v": [base64::encode(values.get("c").unwrap()), base64::encode(values.get("c'").unwrap())]},
+				  {"sk": "d.1", "ct": ct.get("d.1").unwrap(), "v": [base64::encode(values.get("d.1'").unwrap())]},
+				  {"sk": "d.2", "ct": ct.get("d.2").unwrap(), "v": [base64::encode(values.get("d.2").unwrap()), base64::encode(values.get("d.2'").unwrap())]},
+				  {"sk": "e", "ct": ct.get("e").unwrap(), "v": [base64::encode(values.get("e").unwrap())]}
+				],
+				"more": false,
+				"nextStart": null,
+			},
+			{
+				"partitionKey": "root",
+				"prefix": "d",
+				"start": null,
+				"end": null,
+				"limit": null,
+				"reverse": false,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "d.1", "ct": ct.get("d.1").unwrap(), "v": [base64::encode(values.get("d.1'").unwrap())]},
+				  {"sk": "d.2", "ct": ct.get("d.2").unwrap(), "v": [base64::encode(values.get("d.2").unwrap()), base64::encode(values.get("d.2'").unwrap())]},
+				],
+				"more": false,
+				"nextStart": null,
+			},
+			{
+				"partitionKey": "root",
+				"prefix": "d.",
+				"start": null,
+				"end": "d.2",
+				"limit": null,
+				"reverse": false,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "d.1", "ct": ct.get("d.1").unwrap(), "v": [base64::encode(values.get("d.1'").unwrap())]},
+				],
+				"more": false,
+				"nextStart": null,
+			},
+			{
+				"partitionKey": "root",
+				"prefix": "d.",
+				"start": null,
+				"end": null,
+				"limit": 1,
+				"reverse": false,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "d.1", "ct": ct.get("d.1").unwrap(), "v": [base64::encode(values.get("d.1'").unwrap())]},
+				],
+				"more": true,
+				"nextStart": "d.2",
+			},
+			{
+				"partitionKey": "root",
+				"prefix": "d.",
+				"start": "d.2",
+				"end": null,
+				"limit": 1,
+				"reverse": false,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "d.2", "ct": ct.get("d.2").unwrap(), "v": [base64::encode(values.get("d.2").unwrap()), base64::encode(values.get("d.2'").unwrap())]},
+				],
+				"more": false,
+				"nextStart": null,
+			},
+			{
+				"partitionKey": "root",
+				"prefix": "d.",
+				"start": null,
+				"end": null,
+				"limit": null,
+				"reverse": true,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "d.2", "ct": ct.get("d.2").unwrap(), "v": [base64::encode(values.get("d.2").unwrap()), base64::encode(values.get("d.2'").unwrap())]},
+				  {"sk": "d.1", "ct": ct.get("d.1").unwrap(), "v": [base64::encode(values.get("d.1'").unwrap())]},
+				],
+				"more": false,
+				"nextStart": null,
+			},
+			{
+				"partitionKey": "root",
+				"prefix": "d.",
+				"start": "d.2",
+				"end": null,
+				"limit": null,
+				"reverse": true,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "d.2", "ct": ct.get("d.2").unwrap(), "v": [base64::encode(values.get("d.2").unwrap()), base64::encode(values.get("d.2'").unwrap())]},
+				  {"sk": "d.1", "ct": ct.get("d.1").unwrap(), "v": [base64::encode(values.get("d.1'").unwrap())]},
+				],
+				"more": false,
+				"nextStart": null,
+			},
+			{
+				"partitionKey": "root",
+				"prefix": "d.",
+				"start": null,
+				"end": null,
+				"limit": 2,
+				"reverse": false,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "d.1", "ct": ct.get("d.1").unwrap(), "v": [base64::encode(values.get("d.1'").unwrap())]},
+				  {"sk": "d.2", "ct": ct.get("d.2").unwrap(), "v": [base64::encode(values.get("d.2").unwrap()), base64::encode(values.get("d.2'").unwrap())]},
+				],
+				"more": false,
+				"nextStart": null,
+			},
+		])
+	);
+
+	// Test DeleteBatch
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.query_param("delete", Option::<&str>::None)
+		.body(
+			br#"[
+	{"partitionKey": "root", "start": "a", "end": "c"},
+	{"partitionKey": "root", "prefix": "d"}
+		]"#
+			.to_vec(),
+		)
+		.method(Method::POST)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	let json_res = json_body(res).await;
+	assert_json_eq!(
+		json_res,
+		json!([
+			{
+				"partitionKey": "root",
+				"prefix": null,
+				"start": "a",
+				"end": "c",
+				"singleItem": false,
+				"deletedItems": 1,
+			},
+			{
+				"partitionKey": "root",
+				"prefix": "d",
+				"start": null,
+				"end": null,
+				"singleItem": false,
+				"deletedItems": 2,
+			},
+		])
+	);
+
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.query_param("search", Option::<&str>::None)
+		.body(
+			br#"[
+	{"partitionKey": "root"},
+	{"partitionKey": "root", "reverse": true}
+		]"#
+			.to_vec(),
+		)
+		.method(Method::POST)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	let json_res = json_body(res).await;
+	assert_json_eq!(
+		json_res,
+		json!([
+			{
+				"partitionKey": "root",
+				"prefix": null,
+				"start": null,
+				"end": null,
+				"limit": null,
+				"reverse": false,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "c", "ct": ct.get("c").unwrap(), "v": [base64::encode(values.get("c").unwrap()), base64::encode(values.get("c'").unwrap())]},
+				  {"sk": "e", "ct": ct.get("e").unwrap(), "v": [base64::encode(values.get("e").unwrap())]}
+				],
+				"more": false,
+				"nextStart": null,
+			},
+			{
+				"partitionKey": "root",
+				"prefix": null,
+				"start": null,
+				"end": null,
+				"limit": null,
+				"reverse": true,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "e", "ct": ct.get("e").unwrap(), "v": [base64::encode(values.get("e").unwrap())]},
+				  {"sk": "c", "ct": ct.get("c").unwrap(), "v": [base64::encode(values.get("c").unwrap()), base64::encode(values.get("c'").unwrap())]},
+				],
+				"more": false,
+				"nextStart": null,
+			},
+		])
+	);
+}
diff --git a/src/garage/tests/k2v/errorcodes.rs b/src/garage/tests/k2v/errorcodes.rs
new file mode 100644
index 00000000..2fcc45bc
--- /dev/null
+++ b/src/garage/tests/k2v/errorcodes.rs
@@ -0,0 +1,141 @@
+use crate::common;
+
+use hyper::Method;
+
+#[tokio::test]
+async fn test_error_codes() {
+	let ctx = common::context();
+	let bucket = ctx.create_bucket("test-k2v-error-codes");
+
+	// Regular insert should work (code 200)
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.method(Method::PUT)
+		.path("root")
+		.query_param("sort_key", Some("test1"))
+		.body(b"Hello, world!".to_vec())
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+
+	// Insert with trash causality token: invalid request
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.method(Method::PUT)
+		.path("root")
+		.query_param("sort_key", Some("test1"))
+		.signed_header("x-garage-causality-token", "tra$sh")
+		.body(b"Hello, world!".to_vec())
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 400);
+
+	// Search without partition key: invalid request
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.query_param("search", Option::<&str>::None)
+		.body(
+			br#"[
+	{},
+		]"#
+			.to_vec(),
+		)
+		.method(Method::POST)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 400);
+
+	// Search with start that is not in prefix: invalid request
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.query_param("search", Option::<&str>::None)
+		.body(
+			br#"[
+	{"partition_key": "root", "prefix": "a", "start": "bx"},
+		]"#
+			.to_vec(),
+		)
+		.method(Method::POST)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 400);
+
+	// Search with invalid json: 400
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.query_param("search", Option::<&str>::None)
+		.body(
+			br#"[
+	{"partition_key": "root"
+		]"#
+			.to_vec(),
+		)
+		.method(Method::POST)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 400);
+
+	// Batch insert with invalid causality token: 400
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.body(
+			br#"[
+	{"pk": "root", "sk": "a", "ct": "tra$h", "v": "aGVsbG8sIHdvcmxkCg=="}
+		]"#
+			.to_vec(),
+		)
+		.method(Method::POST)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 400);
+
+	// Batch insert with invalid data: 400
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.body(
+			br#"[
+	{"pk": "root", "sk": "a", "ct": null, "v": "aGVsbG8sIHdvcmx$Cg=="}
+		]"#
+			.to_vec(),
+		)
+		.method(Method::POST)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 400);
+
+	// Poll with invalid causality token: 400
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("test1"))
+		.query_param("causality_token", Some("tra$h"))
+		.query_param("timeout", Some("10"))
+		.signed_header("accept", "application/octet-stream")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 400);
+}
diff --git a/src/garage/tests/k2v/item.rs b/src/garage/tests/k2v/item.rs
new file mode 100644
index 00000000..bf2b01f8
--- /dev/null
+++ b/src/garage/tests/k2v/item.rs
@@ -0,0 +1,719 @@
+use crate::common;
+
+use assert_json_diff::assert_json_eq;
+use serde_json::json;
+
+use super::json_body;
+use hyper::Method;
+
+#[tokio::test]
+async fn test_items_and_indices() {
+	let ctx = common::context();
+	let bucket = ctx.create_bucket("test-k2v-item-and-index");
+
+	// ReadIndex -- there should be nothing
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.send()
+		.await
+		.unwrap();
+	let res_body = json_body(res).await;
+	assert_json_eq!(
+		res_body,
+		json!({
+			"prefix": null,
+			"start": null,
+			"end": null,
+			"limit": null,
+			"reverse": false,
+			"partitionKeys": [],
+			"more": false,
+			"nextStart": null
+		})
+	);
+
+	let content2_len = "_: hello universe".len();
+	let content3_len = "_: concurrent value".len();
+
+	for (i, sk) in ["a", "b", "c", "d"].iter().enumerate() {
+		let content = format!("{}: hello world", sk).into_bytes();
+		let content2 = format!("{}: hello universe", sk).into_bytes();
+		let content3 = format!("{}: concurrent value", sk).into_bytes();
+
+		// Put initially, no causality token
+		let res = ctx
+			.k2v
+			.request
+			.builder(bucket.clone())
+			.path("root")
+			.query_param("sort_key", Some(sk))
+			.body(content.clone())
+			.method(Method::PUT)
+			.send()
+			.await
+			.unwrap();
+		assert_eq!(res.status(), 200);
+
+		// Get value back
+		let res = ctx
+			.k2v
+			.request
+			.builder(bucket.clone())
+			.path("root")
+			.query_param("sort_key", Some(sk))
+			.signed_header("accept", "*/*")
+			.send()
+			.await
+			.unwrap();
+		assert_eq!(res.status(), 200);
+		assert_eq!(
+			res.headers().get("content-type").unwrap().to_str().unwrap(),
+			"application/octet-stream"
+		);
+		let ct = res
+			.headers()
+			.get("x-garage-causality-token")
+			.unwrap()
+			.to_str()
+			.unwrap()
+			.to_string();
+		let res_body = hyper::body::to_bytes(res.into_body())
+			.await
+			.unwrap()
+			.to_vec();
+		assert_eq!(res_body, content);
+
+		// ReadIndex -- now there should be some stuff
+		let res = ctx
+			.k2v
+			.request
+			.builder(bucket.clone())
+			.send()
+			.await
+			.unwrap();
+		let res_body = json_body(res).await;
+		assert_json_eq!(
+			res_body,
+			json!({
+				"prefix": null,
+				"start": null,
+				"end": null,
+				"limit": null,
+				"reverse": false,
+				"partitionKeys": [
+				{
+					"pk": "root",
+					"entries": i+1,
+					"conflicts": i,
+					"values": i+i+1,
+					"bytes": i*(content2.len() + content3.len()) + content.len(),
+				}
+				],
+				"more": false,
+				"nextStart": null
+			})
+		);
+
+		// Put again, this time with causality token
+		let res = ctx
+			.k2v
+			.request
+			.builder(bucket.clone())
+			.path("root")
+			.query_param("sort_key", Some(sk))
+			.signed_header("x-garage-causality-token", ct.clone())
+			.body(content2.clone())
+			.method(Method::PUT)
+			.send()
+			.await
+			.unwrap();
+		assert_eq!(res.status(), 200);
+
+		// Get value back
+		let res = ctx
+			.k2v
+			.request
+			.builder(bucket.clone())
+			.path("root")
+			.query_param("sort_key", Some(sk))
+			.signed_header("accept", "*/*")
+			.send()
+			.await
+			.unwrap();
+		assert_eq!(res.status(), 200);
+		assert_eq!(
+			res.headers().get("content-type").unwrap().to_str().unwrap(),
+			"application/octet-stream"
+		);
+		let res_body = hyper::body::to_bytes(res.into_body())
+			.await
+			.unwrap()
+			.to_vec();
+		assert_eq!(res_body, content2);
+
+		// ReadIndex -- now there should be some stuff
+		let res = ctx
+			.k2v
+			.request
+			.builder(bucket.clone())
+			.send()
+			.await
+			.unwrap();
+		let res_body = json_body(res).await;
+		assert_json_eq!(
+			res_body,
+			json!({
+				"prefix": null,
+				"start": null,
+				"end": null,
+				"limit": null,
+				"reverse": false,
+				"partitionKeys": [
+				{
+					"pk": "root",
+					"entries": i+1,
+					"conflicts": i,
+					"values": i+i+1,
+					"bytes": i*content3.len() + (i+1)*content2.len(),
+				}
+				],
+				"more": false,
+				"nextStart": null
+			})
+		);
+
+		// Put again with same CT, now we have concurrent values
+		let res = ctx
+			.k2v
+			.request
+			.builder(bucket.clone())
+			.path("root")
+			.query_param("sort_key", Some(sk))
+			.signed_header("x-garage-causality-token", ct.clone())
+			.body(content3.clone())
+			.method(Method::PUT)
+			.send()
+			.await
+			.unwrap();
+		assert_eq!(res.status(), 200);
+
+		// Get value back
+		let res = ctx
+			.k2v
+			.request
+			.builder(bucket.clone())
+			.path("root")
+			.query_param("sort_key", Some(sk))
+			.signed_header("accept", "*/*")
+			.send()
+			.await
+			.unwrap();
+		assert_eq!(res.status(), 200);
+		assert_eq!(
+			res.headers().get("content-type").unwrap().to_str().unwrap(),
+			"application/json"
+		);
+		let res_json = json_body(res).await;
+		assert_json_eq!(
+			res_json,
+			[base64::encode(&content2), base64::encode(&content3)]
+		);
+
+		// ReadIndex -- now there should be some stuff
+		let res = ctx
+			.k2v
+			.request
+			.builder(bucket.clone())
+			.send()
+			.await
+			.unwrap();
+		let res_body = json_body(res).await;
+		assert_json_eq!(
+			res_body,
+			json!({
+				"prefix": null,
+				"start": null,
+				"end": null,
+				"limit": null,
+				"reverse": false,
+				"partitionKeys": [
+				{
+					"pk": "root",
+					"entries": i+1,
+					"conflicts": i+1,
+					"values": 2*(i+1),
+					"bytes": (i+1)*(content2.len() + content3.len()),
+				}
+				],
+				"more": false,
+				"nextStart": null
+			})
+		);
+	}
+
+	// Now delete things
+	for (i, sk) in ["a", "b", "c", "d"].iter().enumerate() {
+		// Get value back (we just need the CT)
+		let res = ctx
+			.k2v
+			.request
+			.builder(bucket.clone())
+			.path("root")
+			.query_param("sort_key", Some(sk))
+			.signed_header("accept", "*/*")
+			.send()
+			.await
+			.unwrap();
+		assert_eq!(res.status(), 200);
+		let ct = res
+			.headers()
+			.get("x-garage-causality-token")
+			.unwrap()
+			.to_str()
+			.unwrap()
+			.to_string();
+
+		// Delete it
+		let res = ctx
+			.k2v
+			.request
+			.builder(bucket.clone())
+			.method(Method::DELETE)
+			.path("root")
+			.query_param("sort_key", Some(sk))
+			.signed_header("x-garage-causality-token", ct)
+			.send()
+			.await
+			.unwrap();
+		assert_eq!(res.status(), 204);
+
+		// ReadIndex -- now there should be some stuff
+		let res = ctx
+			.k2v
+			.request
+			.builder(bucket.clone())
+			.send()
+			.await
+			.unwrap();
+		let res_body = json_body(res).await;
+		if i < 3 {
+			assert_json_eq!(
+				res_body,
+				json!({
+					"prefix": null,
+					"start": null,
+					"end": null,
+					"limit": null,
+					"reverse": false,
+					"partitionKeys": [
+					{
+						"pk": "root",
+						"entries": 3-i,
+						"conflicts": 3-i,
+						"values": 2*(3-i),
+						"bytes": (3-i)*(content2_len + content3_len),
+					}
+					],
+					"more": false,
+					"nextStart": null
+				})
+			);
+		} else {
+			assert_json_eq!(
+				res_body,
+				json!({
+					"prefix": null,
+					"start": null,
+					"end": null,
+					"limit": null,
+					"reverse": false,
+					"partitionKeys": [],
+					"more": false,
+					"nextStart": null
+				})
+			);
+		}
+	}
+}
+
+#[tokio::test]
+async fn test_item_return_format() {
+	let ctx = common::context();
+	let bucket = ctx.create_bucket("test-k2v-item-return-format");
+
+	let single_value = b"A single value".to_vec();
+	let concurrent_value = b"A concurrent value".to_vec();
+
+	// -- Test with a single value --
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.body(single_value.clone())
+		.method(Method::PUT)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+
+	// f0: either
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.signed_header("accept", "*/*")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	assert_eq!(
+		res.headers().get("content-type").unwrap().to_str().unwrap(),
+		"application/octet-stream"
+	);
+	let ct = res
+		.headers()
+		.get("x-garage-causality-token")
+		.unwrap()
+		.to_str()
+		.unwrap()
+		.to_string();
+	let res_body = hyper::body::to_bytes(res.into_body())
+		.await
+		.unwrap()
+		.to_vec();
+	assert_eq!(res_body, single_value);
+
+	// f1: not specified
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	assert_eq!(
+		res.headers().get("content-type").unwrap().to_str().unwrap(),
+		"application/json"
+	);
+	let res_body = json_body(res).await;
+	assert_json_eq!(res_body, json!([base64::encode(&single_value)]));
+
+	// f2: binary
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.signed_header("accept", "application/octet-stream")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	assert_eq!(
+		res.headers().get("content-type").unwrap().to_str().unwrap(),
+		"application/octet-stream"
+	);
+	let res_body = hyper::body::to_bytes(res.into_body())
+		.await
+		.unwrap()
+		.to_vec();
+	assert_eq!(res_body, single_value);
+
+	// f3: json
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.signed_header("accept", "application/json")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	assert_eq!(
+		res.headers().get("content-type").unwrap().to_str().unwrap(),
+		"application/json"
+	);
+	let res_body = json_body(res).await;
+	assert_json_eq!(res_body, json!([base64::encode(&single_value)]));
+
+	// -- Test with a second, concurrent value --
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.body(concurrent_value.clone())
+		.method(Method::PUT)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+
+	// f0: either
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.signed_header("accept", "*/*")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	assert_eq!(
+		res.headers().get("content-type").unwrap().to_str().unwrap(),
+		"application/json"
+	);
+	let res_body = json_body(res).await;
+	assert_json_eq!(
+		res_body,
+		json!([
+			base64::encode(&single_value),
+			base64::encode(&concurrent_value)
+		])
+	);
+
+	// f1: not specified
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	assert_eq!(
+		res.headers().get("content-type").unwrap().to_str().unwrap(),
+		"application/json"
+	);
+	let res_body = json_body(res).await;
+	assert_json_eq!(
+		res_body,
+		json!([
+			base64::encode(&single_value),
+			base64::encode(&concurrent_value)
+		])
+	);
+
+	// f2: binary
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.signed_header("accept", "application/octet-stream")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 409); // CONFLICT
+
+	// f3: json
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.signed_header("accept", "application/json")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	assert_eq!(
+		res.headers().get("content-type").unwrap().to_str().unwrap(),
+		"application/json"
+	);
+	let res_body = json_body(res).await;
+	assert_json_eq!(
+		res_body,
+		json!([
+			base64::encode(&single_value),
+			base64::encode(&concurrent_value)
+		])
+	);
+
+	// -- Delete first value, concurrently with second insert --
+	// -- (we now have a concurrent value and a deletion) --
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.method(Method::DELETE)
+		.signed_header("x-garage-causality-token", ct)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 204);
+
+	// f0: either
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.signed_header("accept", "*/*")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	assert_eq!(
+		res.headers().get("content-type").unwrap().to_str().unwrap(),
+		"application/json"
+	);
+	let res_body = json_body(res).await;
+	assert_json_eq!(res_body, json!([base64::encode(&concurrent_value), null]));
+
+	// f1: not specified
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	assert_eq!(
+		res.headers().get("content-type").unwrap().to_str().unwrap(),
+		"application/json"
+	);
+	let ct = res
+		.headers()
+		.get("x-garage-causality-token")
+		.unwrap()
+		.to_str()
+		.unwrap()
+		.to_string();
+	let res_body = json_body(res).await;
+	assert_json_eq!(res_body, json!([base64::encode(&concurrent_value), null]));
+
+	// f2: binary
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.signed_header("accept", "application/octet-stream")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 409); // CONFLICT
+
+	// f3: json
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.signed_header("accept", "application/json")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	assert_eq!(
+		res.headers().get("content-type").unwrap().to_str().unwrap(),
+		"application/json"
+	);
+	let res_body = json_body(res).await;
+	assert_json_eq!(res_body, json!([base64::encode(&concurrent_value), null]));
+
+	// -- Delete everything --
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.method(Method::DELETE)
+		.signed_header("x-garage-causality-token", ct)
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 204);
+
+	// f0: either
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.signed_header("accept", "*/*")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 204); // NO CONTENT
+
+	// f1: not specified
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	assert_eq!(
+		res.headers().get("content-type").unwrap().to_str().unwrap(),
+		"application/json"
+	);
+	let res_body = json_body(res).await;
+	assert_json_eq!(res_body, json!([null]));
+
+	// f2: binary
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.signed_header("accept", "application/octet-stream")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 204); // NO CONTENT
+
+	// f3: json
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("v1"))
+		.signed_header("accept", "application/json")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+	assert_eq!(
+		res.headers().get("content-type").unwrap().to_str().unwrap(),
+		"application/json"
+	);
+	let res_body = json_body(res).await;
+	assert_json_eq!(res_body, json!([null]));
+}
diff --git a/src/garage/tests/k2v/mod.rs b/src/garage/tests/k2v/mod.rs
new file mode 100644
index 00000000..a009460e
--- /dev/null
+++ b/src/garage/tests/k2v/mod.rs
@@ -0,0 +1,18 @@
+pub mod batch;
+pub mod errorcodes;
+pub mod item;
+pub mod poll;
+pub mod simple;
+
+use hyper::{Body, Response};
+
+pub async fn json_body(res: Response<Body>) -> serde_json::Value {
+	let res_body: serde_json::Value = serde_json::from_slice(
+		&hyper::body::to_bytes(res.into_body())
+			.await
+			.unwrap()
+			.to_vec()[..],
+	)
+	.unwrap();
+	res_body
+}
diff --git a/src/garage/tests/k2v/poll.rs b/src/garage/tests/k2v/poll.rs
new file mode 100644
index 00000000..70dc0410
--- /dev/null
+++ b/src/garage/tests/k2v/poll.rs
@@ -0,0 +1,98 @@
+use hyper::Method;
+use std::time::Duration;
+
+use crate::common;
+
+#[tokio::test]
+async fn test_poll() {
+	let ctx = common::context();
+	let bucket = ctx.create_bucket("test-k2v-poll");
+
+	// Write initial value
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.method(Method::PUT)
+		.path("root")
+		.query_param("sort_key", Some("test1"))
+		.body(b"Initial value".to_vec())
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+
+	// Retrieve initial value to get its causality token
+	let res2 = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("test1"))
+		.signed_header("accept", "application/octet-stream")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res2.status(), 200);
+	let ct = res2
+		.headers()
+		.get("x-garage-causality-token")
+		.unwrap()
+		.to_str()
+		.unwrap()
+		.to_string();
+
+	let res2_body = hyper::body::to_bytes(res2.into_body())
+		.await
+		.unwrap()
+		.to_vec();
+	assert_eq!(res2_body, b"Initial value");
+
+	// Start poll operation
+	let poll = {
+		let bucket = bucket.clone();
+		let ct = ct.clone();
+		tokio::spawn(async move {
+			let ctx = common::context();
+			ctx.k2v
+				.request
+				.builder(bucket.clone())
+				.path("root")
+				.query_param("sort_key", Some("test1"))
+				.query_param("causality_token", Some(ct))
+				.query_param("timeout", Some("10"))
+				.signed_header("accept", "application/octet-stream")
+				.send()
+				.await
+		})
+	};
+
+	// Write new value that supersedes initial one
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.method(Method::PUT)
+		.path("root")
+		.query_param("sort_key", Some("test1"))
+		.signed_header("x-garage-causality-token", ct)
+		.body(b"New value".to_vec())
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+
+	// Check poll finishes with correct value
+	let poll_res = tokio::select! {
+		_ = tokio::time::sleep(Duration::from_secs(10)) => panic!("poll did not terminate in time"),
+		res = poll => res.unwrap().unwrap(),
+	};
+
+	assert_eq!(poll_res.status(), 200);
+
+	let poll_res_body = hyper::body::to_bytes(poll_res.into_body())
+		.await
+		.unwrap()
+		.to_vec();
+	assert_eq!(poll_res_body, b"New value");
+}
diff --git a/src/garage/tests/k2v/simple.rs b/src/garage/tests/k2v/simple.rs
new file mode 100644
index 00000000..ae9a8674
--- /dev/null
+++ b/src/garage/tests/k2v/simple.rs
@@ -0,0 +1,40 @@
+use crate::common;
+
+use hyper::Method;
+
+#[tokio::test]
+async fn test_simple() {
+	let ctx = common::context();
+	let bucket = ctx.create_bucket("test-k2v-simple");
+
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.method(Method::PUT)
+		.path("root")
+		.query_param("sort_key", Some("test1"))
+		.body(b"Hello, world!".to_vec())
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+
+	let res2 = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("test1"))
+		.signed_header("accept", "application/octet-stream")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res2.status(), 200);
+
+	let res2_body = hyper::body::to_bytes(res2.into_body())
+		.await
+		.unwrap()
+		.to_vec();
+	assert_eq!(res2_body, b"Hello, world!");
+}