Add a K2V client library and CLI (#303)

lib.rs could use getting split in modules, but I'm not sure how exactly

Co-authored-by: trinity-1686a <trinity@deuxfleurs.fr>
Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/303
Co-authored-by: trinity-1686a <trinity.pointard@gmail.com>
Co-committed-by: trinity-1686a <trinity.pointard@gmail.com>

3 files changed, 1054 insertions, 0 deletions

diff --git a/src/k2v-client/src/bin/k2v-cli.rs b/src/k2v-client/src/bin/k2v-cli.rs
new file mode 100644
index 00000000..38c39361
--- /dev/null
+++ b/src/k2v-client/src/bin/k2v-cli.rs
@@ -0,0 +1,466 @@
+use k2v_client::*;
+
+use garage_util::formater::format_table;
+
+use rusoto_core::credential::AwsCredentials;
+use rusoto_core::Region;
+
+use clap::{Parser, Subcommand};
+
+/// K2V command line interface
+#[derive(Parser, Debug)]
+#[clap(author, version, about, long_about = None)]
+struct Args {
+	/// Name of the region to use
+	#[clap(short, long, env = "AWS_REGION", default_value = "garage")]
+	region: String,
+	/// Url of the endpoint to connect to
+	#[clap(short, long, env = "K2V_ENDPOINT")]
+	endpoint: String,
+	/// Access key ID
+	#[clap(short, long, env = "AWS_ACCESS_KEY_ID")]
+	key_id: String,
+	/// Access key ID
+	#[clap(short, long, env = "AWS_SECRET_ACCESS_KEY")]
+	secret: String,
+	/// Bucket name
+	#[clap(short, long, env = "K2V_BUCKET")]
+	bucket: String,
+	#[clap(subcommand)]
+	command: Command,
+}
+
+#[derive(Subcommand, Debug)]
+enum Command {
+	/// Insert a single value
+	Insert {
+		/// Partition key to insert to
+		partition_key: String,
+		/// Sort key to insert to
+		sort_key: String,
+		/// Causality of the insertion
+		#[clap(short, long)]
+		causality: Option<String>,
+		/// Value to insert
+		#[clap(flatten)]
+		value: Value,
+	},
+	/// Read a single value
+	Read {
+		/// Partition key to read from
+		partition_key: String,
+		/// Sort key to read from
+		sort_key: String,
+		/// Output formating
+		#[clap(flatten)]
+		output_kind: ReadOutputKind,
+	},
+	/// Delete a single value
+	Delete {
+		/// Partition key to delete from
+		partition_key: String,
+		/// Sort key to delete from
+		sort_key: String,
+		/// Causality information
+		#[clap(short, long)]
+		causality: String,
+	},
+	/// List partition keys
+	ReadIndex {
+		/// Output formating
+		#[clap(flatten)]
+		output_kind: BatchOutputKind,
+		/// Output only partition keys matching this filter
+		#[clap(flatten)]
+		filter: Filter,
+	},
+	/// Read a range of sort keys
+	ReadRange {
+		/// Partition key to read from
+		partition_key: String,
+		/// Output formating
+		#[clap(flatten)]
+		output_kind: BatchOutputKind,
+		/// Output only sort keys matching this filter
+		#[clap(flatten)]
+		filter: Filter,
+	},
+	/// Delete a range of sort keys
+	DeleteRange {
+		/// Partition key to delete from
+		partition_key: String,
+		/// Output formating
+		#[clap(flatten)]
+		output_kind: BatchOutputKind,
+		/// Delete only sort keys matching this filter
+		#[clap(flatten)]
+		filter: Filter,
+	},
+}
+
+/// Where to read a value from
+#[derive(Parser, Debug)]
+#[clap(group = clap::ArgGroup::new("value").multiple(false).required(true))]
+struct Value {
+	/// Read value from a file. use - to read from stdin
+	#[clap(short, long, group = "value")]
+	file: Option<String>,
+	/// Read a base64 value from commandline
+	#[clap(short, long, group = "value")]
+	b64: Option<String>,
+	/// Read a raw (UTF-8) value from the commandline
+	#[clap(short, long, group = "value")]
+	text: Option<String>,
+}
+
+impl Value {
+	async fn to_data(&self) -> Result<Vec<u8>, Error> {
+		if let Some(ref text) = self.text {
+			Ok(text.as_bytes().to_vec())
+		} else if let Some(ref b64) = self.b64 {
+			base64::decode(b64).map_err(|_| Error::Message("invalid base64 input".into()))
+		} else if let Some(ref path) = self.file {
+			use tokio::io::AsyncReadExt;
+			if path == "-" {
+				let mut file = tokio::io::stdin();
+				let mut vec = Vec::new();
+				file.read_to_end(&mut vec).await?;
+				Ok(vec)
+			} else {
+				let mut file = tokio::fs::File::open(path).await?;
+				let mut vec = Vec::new();
+				file.read_to_end(&mut vec).await?;
+				Ok(vec)
+			}
+		} else {
+			unreachable!("Value must have one option set")
+		}
+	}
+}
+
+#[derive(Parser, Debug)]
+#[clap(group = clap::ArgGroup::new("output-kind").multiple(false).required(false))]
+struct ReadOutputKind {
+	/// Base64 output. Conflicts are line separated, first line is causality token
+	#[clap(short, long, group = "output-kind")]
+	b64: bool,
+	/// Raw output. Conflicts generate error, causality token is not returned
+	#[clap(short, long, group = "output-kind")]
+	raw: bool,
+	/// Human formated output
+	#[clap(short = 'H', long, group = "output-kind")]
+	human: bool,
+	/// JSON formated output
+	#[clap(short, long, group = "output-kind")]
+	json: bool,
+}
+
+impl ReadOutputKind {
+	fn display_output(&self, val: CausalValue) -> ! {
+		use std::io::Write;
+		use std::process::exit;
+
+		if self.json {
+			let stdout = std::io::stdout();
+			serde_json::to_writer_pretty(stdout, &val).unwrap();
+			exit(0);
+		}
+
+		if self.raw {
+			let mut val = val.value;
+			if val.len() != 1 {
+				eprintln!(
+					"Raw mode can only read non-concurent values, found {} values, expected 1",
+					val.len()
+				);
+				exit(1);
+			}
+			let val = val.pop().unwrap();
+			match val {
+				K2vValue::Value(v) => {
+					std::io::stdout().write_all(&v).unwrap();
+					exit(0);
+				}
+				K2vValue::Tombstone => {
+					eprintln!("Expected value, found tombstone");
+					exit(2);
+				}
+			}
+		}
+
+		let causality: String = val.causality.into();
+		if self.b64 {
+			println!("{}", causality);
+			for val in val.value {
+				match val {
+					K2vValue::Value(v) => {
+						println!("{}", base64::encode(&v))
+					}
+					K2vValue::Tombstone => {
+						println!();
+					}
+				}
+			}
+			exit(0);
+		}
+
+		// human
+		println!("causality: {}", causality);
+		println!("values:");
+		for val in val.value {
+			match val {
+				K2vValue::Value(v) => {
+					if let Ok(string) = std::str::from_utf8(&v) {
+						println!("  utf-8: {}", string);
+					} else {
+						println!("  base64: {}", base64::encode(&v));
+					}
+				}
+				K2vValue::Tombstone => {
+					println!("  tombstone");
+				}
+			}
+		}
+		exit(0);
+	}
+}
+
+#[derive(Parser, Debug)]
+#[clap(group = clap::ArgGroup::new("output-kind").multiple(false).required(false))]
+struct BatchOutputKind {
+	/// Human formated output
+	#[clap(short = 'H', long, group = "output-kind")]
+	human: bool,
+	/// JSON formated output
+	#[clap(short, long, group = "output-kind")]
+	json: bool,
+}
+
+/// Filter for batch operations
+#[derive(Parser, Debug)]
+#[clap(group = clap::ArgGroup::new("filter").multiple(true).required(true))]
+struct Filter {
+	/// Match only keys starting with this prefix
+	#[clap(short, long, group = "filter")]
+	prefix: Option<String>,
+	/// Match only keys lexicographically after this key (including this key itself)
+	#[clap(short, long, group = "filter")]
+	start: Option<String>,
+	/// Match only keys lexicographically before this key (excluding this key)
+	#[clap(short, long, group = "filter")]
+	end: Option<String>,
+	/// Only match the first X keys
+	#[clap(short, long)]
+	limit: Option<u64>,
+	/// Return keys in reverse order
+	#[clap(short, long)]
+	reverse: bool,
+	/// Return only keys where conflict happened
+	#[clap(short, long)]
+	conflicts_only: bool,
+	/// Also include keys storing only tombstones
+	#[clap(short, long)]
+	tombstones: bool,
+	/// Return any key
+	#[clap(short, long, group = "filter")]
+	all: bool,
+}
+
+impl Filter {
+	fn k2v_filter(&self) -> k2v_client::Filter<'_> {
+		k2v_client::Filter {
+			start: self.start.as_deref(),
+			end: self.end.as_deref(),
+			prefix: self.prefix.as_deref(),
+			limit: self.limit,
+			reverse: self.reverse,
+		}
+	}
+}
+
+#[tokio::main]
+async fn main() -> Result<(), Error> {
+	let args = Args::parse();
+
+	let region = Region::Custom {
+		name: args.region,
+		endpoint: args.endpoint,
+	};
+
+	let creds = AwsCredentials::new(args.key_id, args.secret, None, None);
+
+	let client = K2vClient::new(region, args.bucket, creds, None)?;
+
+	match args.command {
+		Command::Insert {
+			partition_key,
+			sort_key,
+			causality,
+			value,
+		} => {
+			client
+				.insert_item(
+					&partition_key,
+					&sort_key,
+					value.to_data().await?,
+					causality.map(Into::into),
+				)
+				.await?;
+		}
+		Command::Delete {
+			partition_key,
+			sort_key,
+			causality,
+		} => {
+			client
+				.delete_item(&partition_key, &sort_key, causality.into())
+				.await?;
+		}
+		Command::Read {
+			partition_key,
+			sort_key,
+			output_kind,
+		} => {
+			let res = client.read_item(&partition_key, &sort_key).await?;
+			output_kind.display_output(res);
+		}
+		Command::ReadIndex {
+			output_kind,
+			filter,
+		} => {
+			if filter.conflicts_only || filter.tombstones {
+				return Err(Error::Message(
+					"conlicts-only and tombstones are invalid for read-index".into(),
+				));
+			}
+			let res = client.read_index(filter.k2v_filter()).await?;
+			if output_kind.json {
+				let values = res
+					.items
+					.into_iter()
+					.map(|(k, v)| {
+						let mut value = serde_json::to_value(v).unwrap();
+						value
+							.as_object_mut()
+							.unwrap()
+							.insert("sort_key".to_owned(), k.into());
+						value
+					})
+					.collect::<Vec<_>>();
+				let json = serde_json::json!({
+					"next_key": res.next_start,
+					"values": values,
+				});
+
+				let stdout = std::io::stdout();
+				serde_json::to_writer_pretty(stdout, &json).unwrap();
+			} else {
+				if let Some(next) = res.next_start {
+					println!("next key: {}", next);
+				}
+
+				let mut to_print = Vec::new();
+				to_print.push(format!("key:\tentries\tconflicts\tvalues\tbytes"));
+				for (k, v) in res.items {
+					to_print.push(format!(
+						"{}\t{}\t{}\t{}\t{}",
+						k, v.entries, v.conflicts, v.values, v.bytes
+					));
+				}
+				format_table(to_print);
+			}
+		}
+		Command::ReadRange {
+			partition_key,
+			output_kind,
+			filter,
+		} => {
+			let op = BatchReadOp {
+				partition_key: &partition_key,
+				filter: filter.k2v_filter(),
+				conflicts_only: filter.conflicts_only,
+				tombstones: filter.tombstones,
+				single_item: false,
+			};
+			let mut res = client.read_batch(&[op]).await?;
+			let res = res.pop().unwrap();
+			if output_kind.json {
+				let values = res
+					.items
+					.into_iter()
+					.map(|(k, v)| {
+						let mut value = serde_json::to_value(v).unwrap();
+						value
+							.as_object_mut()
+							.unwrap()
+							.insert("sort_key".to_owned(), k.into());
+						value
+					})
+					.collect::<Vec<_>>();
+				let json = serde_json::json!({
+					"next_key": res.next_start,
+					"values": values,
+				});
+
+				let stdout = std::io::stdout();
+				serde_json::to_writer_pretty(stdout, &json).unwrap();
+			} else {
+				if let Some(next) = res.next_start {
+					println!("next key: {}", next);
+				}
+				for (key, values) in res.items {
+					println!("key: {}", key);
+					let causality: String = values.causality.into();
+					println!("causality: {}", causality);
+					for value in values.value {
+						match value {
+							K2vValue::Value(v) => {
+								if let Ok(string) = std::str::from_utf8(&v) {
+									println!("  value(utf-8): {}", string);
+								} else {
+									println!("  value(base64): {}", base64::encode(&v));
+								}
+							}
+							K2vValue::Tombstone => {
+								println!("  tombstone");
+							}
+						}
+					}
+				}
+			}
+		}
+		Command::DeleteRange {
+			partition_key,
+			output_kind,
+			filter,
+		} => {
+			let op = BatchDeleteOp {
+				partition_key: &partition_key,
+				prefix: filter.prefix.as_deref(),
+				start: filter.start.as_deref(),
+				end: filter.end.as_deref(),
+				single_item: false,
+			};
+			if filter.reverse
+				|| filter.conflicts_only
+				|| filter.tombstones
+				|| filter.limit.is_some()
+			{
+				return Err(Error::Message(
+					"limit, conlicts-only, reverse and tombstones are invalid for delete-range"
+						.into(),
+				));
+			}
+
+			let res = client.delete_batch(&[op]).await?;
+
+			if output_kind.json {
+				println!("{}", res[0]);
+			} else {
+				println!("deleted {} keys", res[0]);
+			}
+		}
+	}
+
+	Ok(())
+}
diff --git a/src/k2v-client/src/error.rs b/src/k2v-client/src/error.rs
new file mode 100644
index 00000000..62357934
--- /dev/null
+++ b/src/k2v-client/src/error.rs
@@ -0,0 +1,22 @@
+use std::borrow::Cow;
+
+use thiserror::Error;
+
+/// Errors returned by this crate
+#[derive(Error, Debug)]
+pub enum Error {
+	#[error("received invalid response: {0}")]
+	InvalidResponse(Cow<'static, str>),
+	#[error("not found")]
+	NotFound,
+	#[error("io error: {0}")]
+	IoError(#[from] std::io::Error),
+	#[error("rusoto tls error: {0}")]
+	RusotoTls(#[from] rusoto_core::request::TlsError),
+	#[error("rusoto http error: {0}")]
+	RusotoHttp(#[from] rusoto_core::HttpDispatchError),
+	#[error("deserialization error: {0}")]
+	Deserialization(#[from] serde_json::Error),
+	#[error("{0}")]
+	Message(Cow<'static, str>),
+}
diff --git a/src/k2v-client/src/lib.rs b/src/k2v-client/src/lib.rs
new file mode 100644
index 00000000..ba1cd6ea
--- /dev/null
+++ b/src/k2v-client/src/lib.rs
@@ -0,0 +1,566 @@
+use std::collections::BTreeMap;
+use std::time::Duration;
+
+use http::header::{ACCEPT, CONTENT_LENGTH, CONTENT_TYPE};
+use http::status::StatusCode;
+use http::HeaderMap;
+
+use rusoto_core::{ByteStream, DispatchSignedRequest, HttpClient};
+use rusoto_credential::AwsCredentials;
+use rusoto_signature::region::Region;
+use rusoto_signature::signature::SignedRequest;
+use serde::de::Error as DeError;
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+
+use tokio::io::AsyncReadExt;
+
+mod error;
+
+pub use error::Error;
+
+const DEFAULT_TIMEOUT: Duration = Duration::from_secs(5);
+const DEFAULT_POLL_TIMEOUT: Duration = Duration::from_secs(300);
+const SERVICE: &str = "k2v";
+const GARAGE_CAUSALITY_TOKEN: &str = "X-Garage-Causality-Token";
+
+/// Client used to query a K2V server.
+pub struct K2vClient {
+	region: Region,
+	bucket: String,
+	creds: AwsCredentials,
+	client: HttpClient,
+}
+
+impl K2vClient {
+	/// Create a new K2V client.
+	pub fn new(
+		region: Region,
+		bucket: String,
+		creds: AwsCredentials,
+		user_agent: Option<String>,
+	) -> Result<Self, Error> {
+		let mut client = HttpClient::new()?;
+		if let Some(ua) = user_agent {
+			client.local_agent_prepend(ua);
+		} else {
+			client.local_agent_prepend(format!("k2v/{}", env!("CARGO_PKG_VERSION")));
+		}
+		Ok(K2vClient {
+			region,
+			bucket,
+			creds,
+			client,
+		})
+	}
+
+	/// Perform a ReadItem request, reading the value(s) stored for a single pk+sk.
+	pub async fn read_item(
+		&self,
+		partition_key: &str,
+		sort_key: &str,
+	) -> Result<CausalValue, Error> {
+		let mut req = SignedRequest::new(
+			"GET",
+			SERVICE,
+			&self.region,
+			&format!("/{}/{}", self.bucket, partition_key),
+		);
+		req.add_param("sort_key", sort_key);
+		req.add_header(ACCEPT, "application/octet-stream, application/json");
+
+		let res = self.dispatch(req, None).await?;
+
+		let causality = res
+			.causality_token
+			.ok_or_else(|| Error::InvalidResponse("missing causality token".into()))?;
+
+		if res.status == StatusCode::NO_CONTENT {
+			return Ok(CausalValue {
+				causality,
+				value: vec![K2vValue::Tombstone],
+			});
+		}
+
+		match res.content_type.as_deref() {
+			Some("application/octet-stream") => Ok(CausalValue {
+				causality,
+				value: vec![K2vValue::Value(res.body)],
+			}),
+			Some("application/json") => {
+				let value = serde_json::from_slice(&res.body)?;
+				Ok(CausalValue { causality, value })
+			}
+			Some(ct) => Err(Error::InvalidResponse(
+				format!("invalid content type: {}", ct).into(),
+			)),
+			None => Err(Error::InvalidResponse("missing content type".into())),
+		}
+	}
+
+	/// Perform a PollItem request, waiting for the value(s) stored for a single pk+sk to be
+	/// updated.
+	pub async fn poll_item(
+		&self,
+		partition_key: &str,
+		sort_key: &str,
+		causality: CausalityToken,
+		timeout: Option<Duration>,
+	) -> Result<Option<CausalValue>, Error> {
+		let timeout = timeout.unwrap_or(DEFAULT_POLL_TIMEOUT);
+
+		let mut req = SignedRequest::new(
+			"GET",
+			SERVICE,
+			&self.region,
+			&format!("/{}/{}", self.bucket, partition_key),
+		);
+		req.add_param("sort_key", sort_key);
+		req.add_param("causality_token", &causality.0);
+		req.add_param("timeout", &timeout.as_secs().to_string());
+		req.add_header(ACCEPT, "application/octet-stream, application/json");
+
+		let res = self.dispatch(req, Some(timeout + DEFAULT_TIMEOUT)).await?;
+
+		let causality = res
+			.causality_token
+			.ok_or_else(|| Error::InvalidResponse("missing causality token".into()))?;
+
+		if res.status == StatusCode::NOT_MODIFIED {
+			return Ok(None);
+		}
+
+		if res.status == StatusCode::NO_CONTENT {
+			return Ok(Some(CausalValue {
+				causality,
+				value: vec![K2vValue::Tombstone],
+			}));
+		}
+
+		match res.content_type.as_deref() {
+			Some("application/octet-stream") => Ok(Some(CausalValue {
+				causality,
+				value: vec![K2vValue::Value(res.body)],
+			})),
+			Some("application/json") => {
+				let value = serde_json::from_slice(&res.body)?;
+				Ok(Some(CausalValue { causality, value }))
+			}
+			Some(ct) => Err(Error::InvalidResponse(
+				format!("invalid content type: {}", ct).into(),
+			)),
+			None => Err(Error::InvalidResponse("missing content type".into())),
+		}
+	}
+
+	/// Perform an InsertItem request, inserting a value for a single pk+sk.
+	pub async fn insert_item(
+		&self,
+		partition_key: &str,
+		sort_key: &str,
+		value: Vec<u8>,
+		causality: Option<CausalityToken>,
+	) -> Result<(), Error> {
+		let mut req = SignedRequest::new(
+			"PUT",
+			SERVICE,
+			&self.region,
+			&format!("/{}/{}", self.bucket, partition_key),
+		);
+		req.add_param("sort_key", sort_key);
+		req.set_payload(Some(value));
+
+		if let Some(causality) = causality {
+			req.add_header(GARAGE_CAUSALITY_TOKEN, &causality.0);
+		}
+
+		self.dispatch(req, None).await?;
+		Ok(())
+	}
+
+	/// Perform a DeleteItem request, deleting the value(s) stored for a single pk+sk.
+	pub async fn delete_item(
+		&self,
+		partition_key: &str,
+		sort_key: &str,
+		causality: CausalityToken,
+	) -> Result<(), Error> {
+		let mut req = SignedRequest::new(
+			"DELETE",
+			SERVICE,
+			&self.region,
+			&format!("/{}/{}", self.bucket, partition_key),
+		);
+		req.add_param("sort_key", sort_key);
+		req.add_header(GARAGE_CAUSALITY_TOKEN, &causality.0);
+
+		self.dispatch(req, None).await?;
+		Ok(())
+	}
+
+	/// Perform a ReadIndex request, listing partition key which have at least one associated
+	/// sort key, and which matches the filter.
+	pub async fn read_index(
+		&self,
+		filter: Filter<'_>,
+	) -> Result<PaginatedRange<PartitionInfo>, Error> {
+		let mut req =
+			SignedRequest::new("GET", SERVICE, &self.region, &format!("/{}", self.bucket));
+		filter.insert_params(&mut req);
+
+		let res = self.dispatch(req, None).await?;
+
+		let resp: ReadIndexResponse = serde_json::from_slice(&res.body)?;
+
+		let items = resp
+			.partition_keys
+			.into_iter()
+			.map(|ReadIndexItem { pk, info }| (pk, info))
+			.collect();
+
+		Ok(PaginatedRange {
+			items,
+			next_start: resp.next_start,
+		})
+	}
+
+	/// Perform an InsertBatch request, inserting multiple values at once. Note: this operation is
+	/// *not* atomic: it is possible for some sub-operations to fails and others to success. In
+	/// that case, failure is reported.
+	pub async fn insert_batch(&self, operations: &[BatchInsertOp<'_>]) -> Result<(), Error> {
+		let mut req =
+			SignedRequest::new("POST", SERVICE, &self.region, &format!("/{}", self.bucket));
+
+		let payload = serde_json::to_vec(operations)?;
+		req.set_payload(Some(payload));
+		self.dispatch(req, None).await?;
+		Ok(())
+	}
+
+	/// Perform a ReadBatch request, reading multiple values or range of values at once.
+	pub async fn read_batch(
+		&self,
+		operations: &[BatchReadOp<'_>],
+	) -> Result<Vec<PaginatedRange<CausalValue>>, Error> {
+		let mut req =
+			SignedRequest::new("POST", SERVICE, &self.region, &format!("/{}", self.bucket));
+		req.add_param("search", "");
+
+		let payload = serde_json::to_vec(operations)?;
+		req.set_payload(Some(payload));
+		let res = self.dispatch(req, None).await?;
+
+		let resp: Vec<BatchReadResponse> = serde_json::from_slice(&res.body)?;
+
+		Ok(resp
+			.into_iter()
+			.map(|e| PaginatedRange {
+				items: e
+					.items
+					.into_iter()
+					.map(|BatchReadItem { sk, ct, v }| {
+						(
+							sk,
+							CausalValue {
+								causality: ct,
+								value: v,
+							},
+						)
+					})
+					.collect(),
+				next_start: e.next_start,
+			})
+			.collect())
+	}
+
+	/// Perform a DeleteBatch request, deleting mutiple values or range of values at once, without
+	/// providing causality information.
+	pub async fn delete_batch(&self, operations: &[BatchDeleteOp<'_>]) -> Result<Vec<u64>, Error> {
+		let mut req =
+			SignedRequest::new("POST", SERVICE, &self.region, &format!("/{}", self.bucket));
+		req.add_param("delete", "");
+
+		let payload = serde_json::to_vec(operations)?;
+		req.set_payload(Some(payload));
+		let res = self.dispatch(req, None).await?;
+
+		let resp: Vec<BatchDeleteResponse> = serde_json::from_slice(&res.body)?;
+
+		Ok(resp.into_iter().map(|r| r.deleted_items).collect())
+	}
+
+	async fn dispatch(
+		&self,
+		mut req: SignedRequest,
+		timeout: Option<Duration>,
+	) -> Result<Response, Error> {
+		req.sign(&self.creds);
+		let mut res = self
+			.client
+			.dispatch(req, Some(timeout.unwrap_or(DEFAULT_TIMEOUT)))
+			.await?;
+
+		let causality_token = res
+			.headers
+			.remove(GARAGE_CAUSALITY_TOKEN)
+			.map(CausalityToken);
+		let content_type = res.headers.remove(CONTENT_TYPE);
+
+		let body = match res.status {
+			StatusCode::OK => read_body(&mut res.headers, res.body).await?,
+			StatusCode::NO_CONTENT => Vec::new(),
+			StatusCode::NOT_FOUND => return Err(Error::NotFound),
+			StatusCode::NOT_MODIFIED => Vec::new(),
+			_ => {
+				return Err(Error::InvalidResponse(
+					format!("invalid error code: {}", res.status).into(),
+				))
+			}
+		};
+
+		Ok(Response {
+			body,
+			status: res.status,
+			causality_token,
+			content_type,
+		})
+	}
+}
+
+async fn read_body(headers: &mut HeaderMap<String>, body: ByteStream) -> Result<Vec<u8>, Error> {
+	let body_len = headers
+		.get(CONTENT_LENGTH)
+		.and_then(|h| h.parse().ok())
+		.unwrap_or(0);
+	let mut res = Vec::with_capacity(body_len);
+	body.into_async_read().read_to_end(&mut res).await?;
+	Ok(res)
+}
+
+/// An opaque token used to convey causality between operations.
+#[derive(Debug, Clone, PartialEq, Eq, Deserialize, Serialize)]
+#[serde(transparent)]
+pub struct CausalityToken(String);
+
+impl From<String> for CausalityToken {
+	fn from(v: String) -> Self {
+		CausalityToken(v)
+	}
+}
+
+impl From<CausalityToken> for String {
+	fn from(v: CausalityToken) -> Self {
+		v.0
+	}
+}
+
+/// A value in K2V. can be either a binary value, or a tombstone.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum K2vValue {
+	Tombstone,
+	Value(Vec<u8>),
+}
+
+impl From<Vec<u8>> for K2vValue {
+	fn from(v: Vec<u8>) -> Self {
+		K2vValue::Value(v)
+	}
+}
+
+impl From<Option<Vec<u8>>> for K2vValue {
+	fn from(v: Option<Vec<u8>>) -> Self {
+		match v {
+			Some(v) => K2vValue::Value(v),
+			None => K2vValue::Tombstone,
+		}
+	}
+}
+
+impl<'de> Deserialize<'de> for K2vValue {
+	fn deserialize<D>(d: D) -> Result<Self, D::Error>
+	where
+		D: Deserializer<'de>,
+	{
+		let val: Option<&str> = Option::deserialize(d)?;
+		Ok(match val {
+			Some(s) => {
+				K2vValue::Value(base64::decode(s).map_err(|_| DeError::custom("invalid base64"))?)
+			}
+			None => K2vValue::Tombstone,
+		})
+	}
+}
+
+impl Serialize for K2vValue {
+	fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+	where
+		S: Serializer,
+	{
+		match self {
+			K2vValue::Tombstone => serializer.serialize_none(),
+			K2vValue::Value(v) => {
+				let b64 = base64::encode(v);
+				serializer.serialize_str(&b64)
+			}
+		}
+	}
+}
+
+/// A set of K2vValue and associated causality information.
+#[derive(Debug, Clone, Serialize)]
+pub struct CausalValue {
+	pub causality: CausalityToken,
+	pub value: Vec<K2vValue>,
+}
+
+/// Result of paginated requests.
+#[derive(Debug, Clone)]
+pub struct PaginatedRange<V> {
+	pub items: BTreeMap<String, V>,
+	pub next_start: Option<String>,
+}
+
+/// Filter for batch operations.
+#[derive(Debug, Default, Clone, Deserialize, Serialize)]
+pub struct Filter<'a> {
+	pub start: Option<&'a str>,
+	pub end: Option<&'a str>,
+	pub prefix: Option<&'a str>,
+	pub limit: Option<u64>,
+	#[serde(default)]
+	pub reverse: bool,
+}
+
+impl<'a> Filter<'a> {
+	fn insert_params(&self, req: &mut SignedRequest) {
+		if let Some(start) = &self.start {
+			req.add_param("start", start);
+		}
+		if let Some(end) = &self.end {
+			req.add_param("end", end);
+		}
+		if let Some(prefix) = &self.prefix {
+			req.add_param("prefix", prefix);
+		}
+		if let Some(limit) = &self.limit {
+			req.add_param("limit", &limit.to_string());
+		}
+		if self.reverse {
+			req.add_param("reverse", "true");
+		}
+	}
+}
+
+#[derive(Debug, Clone, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct ReadIndexResponse<'a> {
+	#[serde(flatten, borrow)]
+	#[allow(dead_code)]
+	filter: Filter<'a>,
+	partition_keys: Vec<ReadIndexItem>,
+	#[allow(dead_code)]
+	more: bool,
+	next_start: Option<String>,
+}
+
+#[derive(Debug, Clone, Deserialize)]
+struct ReadIndexItem {
+	pk: String,
+	#[serde(flatten)]
+	info: PartitionInfo,
+}
+
+/// Information about data stored with a given partition key.
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct PartitionInfo {
+	pub entries: u64,
+	pub conflicts: u64,
+	pub values: u64,
+	pub bytes: u64,
+}
+
+/// Single sub-operation of an InsertBatch.
+#[derive(Debug, Clone, Serialize)]
+pub struct BatchInsertOp<'a> {
+	#[serde(rename = "pk")]
+	pub partition_key: &'a str,
+	#[serde(rename = "sk")]
+	pub sort_key: &'a str,
+	#[serde(rename = "ct")]
+	pub causality: Option<CausalityToken>,
+	#[serde(rename = "v")]
+	pub value: K2vValue,
+}
+
+/// Single sub-operation of a ReadBatch.
+#[derive(Debug, Default, Clone, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct BatchReadOp<'a> {
+	pub partition_key: &'a str,
+	#[serde(flatten, borrow)]
+	pub filter: Filter<'a>,
+	#[serde(default)]
+	pub single_item: bool,
+	#[serde(default)]
+	pub conflicts_only: bool,
+	#[serde(default)]
+	pub tombstones: bool,
+}
+
+#[derive(Debug, Clone, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct BatchReadResponse<'a> {
+	#[serde(flatten, borrow)]
+	#[allow(dead_code)]
+	op: BatchReadOp<'a>,
+	items: Vec<BatchReadItem>,
+	#[allow(dead_code)]
+	more: bool,
+	next_start: Option<String>,
+}
+
+#[derive(Debug, Clone, Deserialize)]
+struct BatchReadItem {
+	sk: String,
+	ct: CausalityToken,
+	v: Vec<K2vValue>,
+}
+
+/// Single sub-operation of a DeleteBatch
+#[derive(Debug, Clone, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct BatchDeleteOp<'a> {
+	pub partition_key: &'a str,
+	pub prefix: Option<&'a str>,
+	pub start: Option<&'a str>,
+	pub end: Option<&'a str>,
+	#[serde(default)]
+	pub single_item: bool,
+}
+
+impl<'a> BatchDeleteOp<'a> {
+	pub fn new(partition_key: &'a str) -> Self {
+		BatchDeleteOp {
+			partition_key,
+			prefix: None,
+			start: None,
+			end: None,
+			single_item: false,
+		}
+	}
+}
+
+#[derive(Debug, Clone, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct BatchDeleteResponse<'a> {
+	#[serde(flatten, borrow)]
+	#[allow(dead_code)]
+	filter: BatchDeleteOp<'a>,
+	deleted_items: u64,
+}
+
+struct Response {
+	body: Vec<u8>,
+	status: StatusCode,
+	causality_token: Option<CausalityToken>,
+	content_type: Option<String>,
+}