garage/src/model/index_counter.rs
Alex 5768bf3622 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: Deuxfleurs/garage#293
Co-authored-by: Alex <alex@adnab.me>
Co-committed-by: Alex <alex@adnab.me>
2022-05-10 13:16:57 +02:00

305 lines
7.7 KiB
Rust

use std::collections::{hash_map, BTreeMap, HashMap};
use std::marker::PhantomData;
use std::sync::Arc;
use std::time::Duration;
use serde::{Deserialize, Serialize};
use tokio::sync::{mpsc, watch};
use garage_rpc::ring::Ring;
use garage_rpc::system::System;
use garage_util::data::*;
use garage_util::error::*;
use garage_table::crdt::*;
use garage_table::replication::TableShardedReplication;
use garage_table::*;
pub trait CounterSchema: Clone + PartialEq + Send + Sync + 'static {
const NAME: &'static str;
type P: PartitionKey + Clone + PartialEq + Serialize + for<'de> Deserialize<'de> + Send + Sync;
type S: SortKey + Clone + PartialEq + Serialize + for<'de> Deserialize<'de> + Send + Sync;
}
/// A counter entry in the global table
#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
pub struct CounterEntry<T: CounterSchema> {
pub pk: T::P,
pub sk: T::S,
pub values: BTreeMap<String, CounterValue>,
}
impl<T: CounterSchema> Entry<T::P, T::S> for CounterEntry<T> {
fn partition_key(&self) -> &T::P {
&self.pk
}
fn sort_key(&self) -> &T::S {
&self.sk
}
fn is_tombstone(&self) -> bool {
self.values
.iter()
.all(|(_, v)| v.node_values.iter().all(|(_, (_, v))| *v == 0))
}
}
impl<T: CounterSchema> CounterEntry<T> {
pub fn filtered_values(&self, ring: &Ring) -> HashMap<String, i64> {
let nodes = &ring.layout.node_id_vec[..];
self.filtered_values_with_nodes(nodes)
}
pub fn filtered_values_with_nodes(&self, nodes: &[Uuid]) -> HashMap<String, i64> {
let mut ret = HashMap::new();
for (name, vals) in self.values.iter() {
let new_vals = vals
.node_values
.iter()
.filter(|(n, _)| nodes.contains(n))
.map(|(_, (_, v))| *v)
.collect::<Vec<_>>();
if !new_vals.is_empty() {
ret.insert(
name.clone(),
new_vals.iter().fold(i64::MIN, |a, b| std::cmp::max(a, *b)),
);
}
}
ret
}
}
/// A counter entry in the global table
#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
pub struct CounterValue {
pub node_values: BTreeMap<Uuid, (u64, i64)>,
}
impl<T: CounterSchema> Crdt for CounterEntry<T> {
fn merge(&mut self, other: &Self) {
for (name, e2) in other.values.iter() {
if let Some(e) = self.values.get_mut(name) {
e.merge(e2);
} else {
self.values.insert(name.clone(), e2.clone());
}
}
}
}
impl Crdt for CounterValue {
fn merge(&mut self, other: &Self) {
for (node, (t2, e2)) in other.node_values.iter() {
if let Some((t, e)) = self.node_values.get_mut(node) {
if t2 > t {
*e = *e2;
}
} else {
self.node_values.insert(*node, (*t2, *e2));
}
}
}
}
pub struct CounterTable<T: CounterSchema> {
_phantom_t: PhantomData<T>,
}
impl<T: CounterSchema> TableSchema for CounterTable<T> {
const TABLE_NAME: &'static str = T::NAME;
type P = T::P;
type S = T::S;
type E = CounterEntry<T>;
type Filter = (DeletedFilter, Vec<Uuid>);
fn updated(&self, _old: Option<&Self::E>, _new: Option<&Self::E>) {
// nothing for now
}
fn matches_filter(entry: &Self::E, filter: &Self::Filter) -> bool {
if filter.0 == DeletedFilter::Any {
return true;
}
let is_tombstone = entry
.filtered_values_with_nodes(&filter.1[..])
.iter()
.all(|(_, v)| *v == 0);
filter.0.apply(is_tombstone)
}
}
// ----
pub struct IndexCounter<T: CounterSchema> {
this_node: Uuid,
local_counter: sled::Tree,
propagate_tx: mpsc::UnboundedSender<(T::P, T::S, LocalCounterEntry)>,
pub table: Arc<Table<CounterTable<T>, TableShardedReplication>>,
}
impl<T: CounterSchema> IndexCounter<T> {
pub fn new(
system: Arc<System>,
replication: TableShardedReplication,
db: &sled::Db,
) -> Arc<Self> {
let background = system.background.clone();
let (propagate_tx, propagate_rx) = mpsc::unbounded_channel();
let this = Arc::new(Self {
this_node: system.id,
local_counter: db
.open_tree(format!("local_counter:{}", T::NAME))
.expect("Unable to open local counter tree"),
propagate_tx,
table: Table::new(
CounterTable {
_phantom_t: Default::default(),
},
replication,
system,
db,
),
});
let this2 = this.clone();
background.spawn_worker(
format!("{} index counter propagator", T::NAME),
move |must_exit| this2.clone().propagate_loop(propagate_rx, must_exit),
);
this
}
pub fn count(&self, pk: &T::P, sk: &T::S, counts: &[(&str, i64)]) -> Result<(), Error> {
let tree_key = self.table.data.tree_key(pk, sk);
let new_entry = self.local_counter.transaction(|tx| {
let mut entry = match tx.get(&tree_key[..])? {
Some(old_bytes) => {
rmp_serde::decode::from_read_ref::<_, LocalCounterEntry>(&old_bytes)
.map_err(Error::RmpDecode)
.map_err(sled::transaction::ConflictableTransactionError::Abort)?
}
None => LocalCounterEntry {
values: BTreeMap::new(),
},
};
for (s, inc) in counts.iter() {
let mut ent = entry.values.entry(s.to_string()).or_insert((0, 0));
ent.0 += 1;
ent.1 += *inc;
}
let new_entry_bytes = rmp_to_vec_all_named(&entry)
.map_err(Error::RmpEncode)
.map_err(sled::transaction::ConflictableTransactionError::Abort)?;
tx.insert(&tree_key[..], new_entry_bytes)?;
Ok(entry)
})?;
if let Err(e) = self.propagate_tx.send((pk.clone(), sk.clone(), new_entry)) {
error!(
"Could not propagate updated counter values, failed to send to channel: {}",
e
);
}
Ok(())
}
async fn propagate_loop(
self: Arc<Self>,
mut propagate_rx: mpsc::UnboundedReceiver<(T::P, T::S, LocalCounterEntry)>,
must_exit: watch::Receiver<bool>,
) {
// This loop batches updates to counters to be sent all at once.
// They are sent once the propagate_rx channel has been emptied (or is closed).
let mut buf = HashMap::new();
let mut errors = 0;
loop {
let (ent, closed) = match propagate_rx.try_recv() {
Ok(ent) => (Some(ent), false),
Err(mpsc::error::TryRecvError::Empty) if buf.is_empty() => {
match propagate_rx.recv().await {
Some(ent) => (Some(ent), false),
None => (None, true),
}
}
Err(mpsc::error::TryRecvError::Empty) => (None, false),
Err(mpsc::error::TryRecvError::Disconnected) => (None, true),
};
if let Some((pk, sk, counters)) = ent {
let tree_key = self.table.data.tree_key(&pk, &sk);
let dist_entry = counters.into_counter_entry::<T>(self.this_node, pk, sk);
match buf.entry(tree_key) {
hash_map::Entry::Vacant(e) => {
e.insert(dist_entry);
}
hash_map::Entry::Occupied(mut e) => {
e.get_mut().merge(&dist_entry);
}
}
// As long as we can add entries, loop back and add them to batch
// before sending batch to other nodes
continue;
}
if !buf.is_empty() {
let entries = buf.iter().map(|(_k, v)| v);
if let Err(e) = self.table.insert_many(entries).await {
errors += 1;
if errors >= 2 && *must_exit.borrow() {
error!("({}) Could not propagate {} counter values: {}, these counters will not be updated correctly.", T::NAME, buf.len(), e);
break;
}
warn!("({}) Could not propagate {} counter values: {}, retrying in 5 seconds (retry #{})", T::NAME, buf.len(), e, errors);
tokio::time::sleep(Duration::from_secs(5)).await;
continue;
}
buf.clear();
errors = 0;
}
if closed || *must_exit.borrow() {
break;
}
}
}
}
#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
struct LocalCounterEntry {
values: BTreeMap<String, (u64, i64)>,
}
impl LocalCounterEntry {
fn into_counter_entry<T: CounterSchema>(
self,
this_node: Uuid,
pk: T::P,
sk: T::S,
) -> CounterEntry<T> {
CounterEntry {
pk,
sk,
values: self
.values
.into_iter()
.map(|(name, (ts, v))| {
let mut node_values = BTreeMap::new();
node_values.insert(this_node, (ts, v));
(name, CounterValue { node_values })
})
.collect(),
}
}
}