garage/src/table/table_sync.rs

891 lines
22 KiB
Rust

use rand::Rng;
use std::collections::{BTreeMap, VecDeque};
use std::sync::{Arc, Mutex};
use std::time::{Duration, Instant};
use futures::future::join_all;
use futures::{pin_mut, select};
use futures_util::future::*;
use futures_util::stream::*;
use serde::{Deserialize, Serialize};
use serde_bytes::ByteBuf;
use tokio::sync::{mpsc, watch};
use garage_rpc::ring::Ring;
use garage_util::data::*;
use garage_util::error::Error;
use crate::*;
const MAX_DEPTH: usize = 16;
const SCAN_INTERVAL: Duration = Duration::from_secs(3600);
const CHECKSUM_CACHE_TIMEOUT: Duration = Duration::from_secs(1800);
const TABLE_SYNC_RPC_TIMEOUT: Duration = Duration::from_secs(30);
pub struct TableSyncer<F: TableSchema, R: TableReplication> {
table: Arc<Table<F, R>>,
todo: Mutex<SyncTodo>,
cache: Vec<Mutex<BTreeMap<SyncRange, RangeChecksumCache>>>,
}
#[derive(Serialize, Deserialize)]
pub(crate) enum SyncRPC {
GetRootChecksumRange(Hash, Hash),
RootChecksumRange(SyncRange),
Checksums(Vec<RangeChecksum>),
Difference(Vec<SyncRange>, Vec<Arc<ByteBuf>>),
}
struct SyncTodo {
todo: Vec<TodoPartition>,
}
#[derive(Debug, Clone)]
struct TodoPartition {
// Partition consists in hashes between begin included and end excluded
begin: Hash,
end: Hash,
// Are we a node that stores this partition or not?
retain: bool,
}
// A SyncRange defines a query on the dataset stored by a node, in the following way:
// - all items whose key are >= `begin`
// - stopping at the first item whose key hash has at least `level` leading zero bytes (excluded)
// - except if the first item of the range has such many leading zero bytes
// - and stopping at `end` (excluded) if such an item is not found
// The checksum itself does not store all of the items in the database, only the hashes of the "sub-ranges"
// i.e. of ranges of level `level-1` that cover the same range
// (ranges of level 0 do not exist and their hash is simply the hash of the first item >= begin)
// See RangeChecksum for the struct that stores this information.
#[derive(Hash, PartialEq, Eq, Debug, Clone, Serialize, Deserialize)]
pub(crate) struct SyncRange {
begin: Vec<u8>,
end: Vec<u8>,
level: usize,
}
impl std::cmp::PartialOrd for SyncRange {
fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
Some(self.cmp(other))
}
}
impl std::cmp::Ord for SyncRange {
fn cmp(&self, other: &Self) -> std::cmp::Ordering {
self.begin
.cmp(&other.begin)
.then(self.level.cmp(&other.level))
.then(self.end.cmp(&other.end))
}
}
#[derive(Debug, Clone, Serialize, Deserialize)]
pub(crate) struct RangeChecksum {
bounds: SyncRange,
children: Vec<(SyncRange, Hash)>,
found_limit: Option<Vec<u8>>,
#[serde(skip, default = "std::time::Instant::now")]
time: Instant,
}
#[derive(Debug, Clone)]
struct RangeChecksumCache {
hash: Option<Hash>, // None if no children
found_limit: Option<Vec<u8>>,
time: Instant,
}
impl<F, R> TableSyncer<F, R>
where
F: TableSchema + 'static,
R: TableReplication + 'static,
{
pub(crate) async fn launch(table: Arc<Table<F, R>>) -> Arc<Self> {
let todo = SyncTodo { todo: Vec::new() };
let syncer = Arc::new(TableSyncer {
table: table.clone(),
todo: Mutex::new(todo),
cache: (0..MAX_DEPTH)
.map(|_| Mutex::new(BTreeMap::new()))
.collect::<Vec<_>>(),
});
let (busy_tx, busy_rx) = mpsc::unbounded_channel();
let s1 = syncer.clone();
table
.system
.background
.spawn_worker(
format!("table sync watcher for {}", table.name),
move |must_exit: watch::Receiver<bool>| s1.watcher_task(must_exit, busy_rx),
)
.await;
let s2 = syncer.clone();
table
.system
.background
.spawn_worker(
format!("table syncer for {}", table.name),
move |must_exit: watch::Receiver<bool>| s2.syncer_task(must_exit, busy_tx),
)
.await;
let s3 = syncer.clone();
tokio::spawn(async move {
tokio::time::delay_for(Duration::from_secs(20)).await;
s3.add_full_scan().await;
});
syncer
}
async fn watcher_task(
self: Arc<Self>,
mut must_exit: watch::Receiver<bool>,
mut busy_rx: mpsc::UnboundedReceiver<bool>,
) -> Result<(), Error> {
let mut prev_ring: Arc<Ring> = self.table.system.ring.borrow().clone();
let mut ring_recv: watch::Receiver<Arc<Ring>> = self.table.system.ring.clone();
let mut nothing_to_do_since = Some(Instant::now());
while !*must_exit.borrow() {
let s_ring_recv = ring_recv.recv().fuse();
let s_busy = busy_rx.recv().fuse();
let s_must_exit = must_exit.recv().fuse();
let s_timeout = tokio::time::delay_for(Duration::from_secs(1)).fuse();
pin_mut!(s_ring_recv, s_busy, s_must_exit, s_timeout);
select! {
new_ring_r = s_ring_recv => {
if let Some(new_ring) = new_ring_r {
debug!("({}) Adding ring difference to syncer todo list", self.table.name);
self.todo.lock().unwrap().add_ring_difference(&self.table, &prev_ring, &new_ring);
prev_ring = new_ring;
}
}
busy_opt = s_busy => {
if let Some(busy) = busy_opt {
if busy {
nothing_to_do_since = None;
} else {
if nothing_to_do_since.is_none() {
nothing_to_do_since = Some(Instant::now());
}
}
}
}
must_exit_v = s_must_exit => {
if must_exit_v.unwrap_or(false) {
break;
}
}
_ = s_timeout => {
if nothing_to_do_since.map(|t| Instant::now() - t >= SCAN_INTERVAL).unwrap_or(false) {
nothing_to_do_since = None;
debug!("({}) Adding full scan to syncer todo list", self.table.name);
self.add_full_scan().await;
}
}
}
}
Ok(())
}
pub async fn add_full_scan(&self) {
self.todo.lock().unwrap().add_full_scan(&self.table);
}
async fn syncer_task(
self: Arc<Self>,
mut must_exit: watch::Receiver<bool>,
busy_tx: mpsc::UnboundedSender<bool>,
) -> Result<(), Error> {
while !*must_exit.borrow() {
let task = self.todo.lock().unwrap().pop_task();
if let Some(partition) = task {
busy_tx.send(true)?;
let res = self
.clone()
.sync_partition(&partition, &mut must_exit)
.await;
if let Err(e) = res {
warn!(
"({}) Error while syncing {:?}: {}",
self.table.name, partition, e
);
}
} else {
busy_tx.send(false)?;
tokio::time::delay_for(Duration::from_secs(1)).await;
}
}
Ok(())
}
async fn sync_partition(
self: Arc<Self>,
partition: &TodoPartition,
must_exit: &mut watch::Receiver<bool>,
) -> Result<(), Error> {
if partition.retain {
let my_id = self.table.system.id;
let nodes = self
.table
.replication
.write_nodes(&partition.begin, &self.table.system)
.into_iter()
.filter(|node| *node != my_id)
.collect::<Vec<_>>();
debug!(
"({}) Preparing to sync {:?} with {:?}...",
self.table.name, partition, nodes
);
let root_cks = self.root_checksum(&partition.begin, &partition.end, must_exit)?;
let mut sync_futures = nodes
.iter()
.map(|node| {
self.clone().do_sync_with(
partition.clone(),
root_cks.clone(),
*node,
must_exit.clone(),
)
})
.collect::<FuturesUnordered<_>>();
let mut n_errors = 0;
while let Some(r) = sync_futures.next().await {
if let Err(e) = r {
n_errors += 1;
warn!("({}) Sync error: {}", self.table.name, e);
}
}
if n_errors > self.table.replication.max_write_errors() {
return Err(Error::Message(format!(
"Sync failed with too many nodes (should have been: {:?}).",
nodes
)));
}
} else {
self.offload_partition(&partition.begin, &partition.end, must_exit)
.await?;
}
Ok(())
}
// Offload partition: this partition is not something we are storing,
// so send it out to all other nodes that store it and delete items locally.
// We don't bother checking if the remote nodes already have the items,
// we just batch-send everything. Offloading isn't supposed to happen very often.
// If any of the nodes that are supposed to store the items is unable to
// save them, we interrupt the process.
async fn offload_partition(
self: &Arc<Self>,
begin: &Hash,
end: &Hash,
must_exit: &mut watch::Receiver<bool>,
) -> Result<(), Error> {
let mut counter: usize = 0;
while !*must_exit.borrow() {
let mut items = Vec::new();
for item in self.table.store.range(begin.to_vec()..end.to_vec()) {
let (key, value) = item?;
items.push((key.to_vec(), Arc::new(ByteBuf::from(value.as_ref()))));
if items.len() >= 1024 {
break;
}
}
if items.len() > 0 {
let nodes = self
.table
.replication
.write_nodes(&begin, &self.table.system)
.into_iter()
.collect::<Vec<_>>();
if nodes.contains(&self.table.system.id) {
warn!("Interrupting offload as partitions seem to have changed");
break;
}
counter += 1;
debug!(
"Offloading {} items from {:?}..{:?} ({})",
items.len(),
begin,
end,
counter
);
self.offload_items(&items, &nodes[..]).await?;
} else {
break;
}
}
Ok(())
}
async fn offload_items(
self: &Arc<Self>,
items: &Vec<(Vec<u8>, Arc<ByteBuf>)>,
nodes: &[UUID],
) -> Result<(), Error> {
let values = items.iter().map(|(_k, v)| v.clone()).collect::<Vec<_>>();
let update_msg = Arc::new(TableRPC::<F>::Update(values));
for res in join_all(nodes.iter().map(|to| {
self.table
.rpc_client
.call_arc(*to, update_msg.clone(), TABLE_SYNC_RPC_TIMEOUT)
}))
.await
{
res?;
}
// All remote nodes have written those items, now we can delete them locally
let mut not_removed = 0;
for (k, v) in items.iter() {
if !self.table.delete_if_equal(&k[..], &v[..])? {
not_removed += 1;
}
}
if not_removed > 0 {
debug!("{} items not removed during offload because they changed in between (trying again...)", not_removed);
}
Ok(())
}
fn root_checksum(
self: &Arc<Self>,
begin: &Hash,
end: &Hash,
must_exit: &mut watch::Receiver<bool>,
) -> Result<RangeChecksum, Error> {
for i in 1..MAX_DEPTH {
let rc = self.range_checksum(
&SyncRange {
begin: begin.to_vec(),
end: end.to_vec(),
level: i,
},
must_exit,
)?;
if rc.found_limit.is_none() {
return Ok(rc);
}
}
Err(Error::Message(format!(
"Unable to compute root checksum (this should never happen)"
)))
}
fn range_checksum(
self: &Arc<Self>,
range: &SyncRange,
must_exit: &mut watch::Receiver<bool>,
) -> Result<RangeChecksum, Error> {
assert!(range.level != 0);
trace!("Call range_checksum {:?}", range);
if range.level == 1 {
let mut children = vec![];
for item in self
.table
.store
.range(range.begin.clone()..range.end.clone())
{
let (key, value) = item?;
let key_hash = blake2sum(&key[..]);
if children.len() > 0
&& key_hash.as_slice()[0..range.level]
.iter()
.all(|x| *x == 0u8)
{
trace!(
"range_checksum {:?} returning {} items",
range,
children.len()
);
return Ok(RangeChecksum {
bounds: range.clone(),
children,
found_limit: Some(key.to_vec()),
time: Instant::now(),
});
}
let item_range = SyncRange {
begin: key.to_vec(),
end: vec![],
level: 0,
};
children.push((item_range, blake2sum(&value[..])));
}
trace!(
"range_checksum {:?} returning {} items",
range,
children.len()
);
Ok(RangeChecksum {
bounds: range.clone(),
children,
found_limit: None,
time: Instant::now(),
})
} else {
let mut children = vec![];
let mut sub_range = SyncRange {
begin: range.begin.clone(),
end: range.end.clone(),
level: range.level - 1,
};
let mut time = Instant::now();
while !*must_exit.borrow() {
let sub_ck = self.range_checksum_cached_hash(&sub_range, must_exit)?;
if let Some(hash) = sub_ck.hash {
children.push((sub_range.clone(), hash));
if sub_ck.time < time {
time = sub_ck.time;
}
}
if sub_ck.found_limit.is_none() || sub_ck.hash.is_none() {
trace!(
"range_checksum {:?} returning {} items",
range,
children.len()
);
return Ok(RangeChecksum {
bounds: range.clone(),
children,
found_limit: None,
time,
});
}
let found_limit = sub_ck.found_limit.unwrap();
let actual_limit_hash = blake2sum(&found_limit[..]);
if actual_limit_hash.as_slice()[0..range.level]
.iter()
.all(|x| *x == 0u8)
{
trace!(
"range_checksum {:?} returning {} items",
range,
children.len()
);
return Ok(RangeChecksum {
bounds: range.clone(),
children,
found_limit: Some(found_limit.clone()),
time,
});
}
sub_range.begin = found_limit;
}
trace!("range_checksum {:?} exiting due to must_exit", range);
Err(Error::Message(format!("Exiting.")))
}
}
fn range_checksum_cached_hash(
self: &Arc<Self>,
range: &SyncRange,
must_exit: &mut watch::Receiver<bool>,
) -> Result<RangeChecksumCache, Error> {
{
let mut cache = self.cache[range.level].lock().unwrap();
if let Some(v) = cache.get(&range) {
if Instant::now() - v.time < CHECKSUM_CACHE_TIMEOUT {
return Ok(v.clone());
}
}
cache.remove(&range);
}
let v = self.range_checksum(&range, must_exit)?;
trace!(
"({}) New checksum calculated for {}-{}/{}, {} children",
self.table.name,
hex::encode(&range.begin)
.chars()
.take(16)
.collect::<String>(),
hex::encode(&range.end).chars().take(16).collect::<String>(),
range.level,
v.children.len()
);
let hash = if v.children.len() > 0 {
Some(blake2sum(&rmp_to_vec_all_named(&v)?[..]))
} else {
None
};
let cache_entry = RangeChecksumCache {
hash,
found_limit: v.found_limit,
time: v.time,
};
let mut cache = self.cache[range.level].lock().unwrap();
cache.insert(range.clone(), cache_entry.clone());
Ok(cache_entry)
}
async fn do_sync_with(
self: Arc<Self>,
partition: TodoPartition,
root_ck: RangeChecksum,
who: UUID,
mut must_exit: watch::Receiver<bool>,
) -> Result<(), Error> {
let mut todo = VecDeque::new();
// If their root checksum has level > than us, use that as a reference
let root_cks_resp = self
.table
.rpc_client
.call(
who,
TableRPC::<F>::SyncRPC(SyncRPC::GetRootChecksumRange(
partition.begin.clone(),
partition.end.clone(),
)),
TABLE_SYNC_RPC_TIMEOUT,
)
.await?;
if let TableRPC::<F>::SyncRPC(SyncRPC::RootChecksumRange(range)) = root_cks_resp {
if range.level > root_ck.bounds.level {
let their_root_range_ck = self.range_checksum(&range, &mut must_exit)?;
todo.push_back(their_root_range_ck);
} else {
todo.push_back(root_ck);
}
} else {
return Err(Error::Message(format!(
"Invalid respone to GetRootChecksumRange RPC: {}",
debug_serialize(root_cks_resp)
)));
}
while !todo.is_empty() && !*must_exit.borrow() {
let total_children = todo.iter().map(|x| x.children.len()).fold(0, |x, y| x + y);
trace!(
"({}) Sync with {:?}: {} ({}) remaining",
self.table.name,
who,
todo.len(),
total_children
);
let step_size = std::cmp::min(16, todo.len());
let step = todo.drain(..step_size).collect::<Vec<_>>();
let rpc_resp = self
.table
.rpc_client
.call(
who,
TableRPC::<F>::SyncRPC(SyncRPC::Checksums(step)),
TABLE_SYNC_RPC_TIMEOUT,
)
.await?;
if let TableRPC::<F>::SyncRPC(SyncRPC::Difference(mut diff_ranges, diff_items)) =
rpc_resp
{
if diff_ranges.len() > 0 || diff_items.len() > 0 {
info!(
"({}) Sync with {:?}: difference {} ranges, {} items",
self.table.name,
who,
diff_ranges.len(),
diff_items.len()
);
}
let mut items_to_send = vec![];
for differing in diff_ranges.drain(..) {
if differing.level == 0 {
items_to_send.push(differing.begin);
} else {
let checksum = self.range_checksum(&differing, &mut must_exit)?;
todo.push_back(checksum);
}
}
if diff_items.len() > 0 {
self.table.handle_update(&diff_items[..]).await?;
}
if items_to_send.len() > 0 {
self.send_items(who, items_to_send).await?;
}
} else {
return Err(Error::Message(format!(
"Unexpected response to sync RPC checksums: {}",
debug_serialize(&rpc_resp)
)));
}
}
Ok(())
}
async fn send_items(&self, who: UUID, item_list: Vec<Vec<u8>>) -> Result<(), Error> {
info!(
"({}) Sending {} items to {:?}",
self.table.name,
item_list.len(),
who
);
let mut values = vec![];
for item in item_list.iter() {
if let Some(v) = self.table.store.get(&item[..])? {
values.push(Arc::new(ByteBuf::from(v.as_ref())));
}
}
let rpc_resp = self
.table
.rpc_client
.call(who, TableRPC::<F>::Update(values), TABLE_SYNC_RPC_TIMEOUT)
.await?;
if let TableRPC::<F>::Ok = rpc_resp {
Ok(())
} else {
Err(Error::Message(format!(
"Unexpected response to RPC Update: {}",
debug_serialize(&rpc_resp)
)))
}
}
pub(crate) async fn handle_rpc(
self: &Arc<Self>,
message: &SyncRPC,
mut must_exit: watch::Receiver<bool>,
) -> Result<SyncRPC, Error> {
match message {
SyncRPC::GetRootChecksumRange(begin, end) => {
let root_cks = self.root_checksum(&begin, &end, &mut must_exit)?;
Ok(SyncRPC::RootChecksumRange(root_cks.bounds))
}
SyncRPC::Checksums(checksums) => {
self.handle_checksums_rpc(&checksums[..], &mut must_exit)
.await
}
_ => Err(Error::Message(format!("Unexpected sync RPC"))),
}
}
async fn handle_checksums_rpc(
self: &Arc<Self>,
checksums: &[RangeChecksum],
must_exit: &mut watch::Receiver<bool>,
) -> Result<SyncRPC, Error> {
let mut ret_ranges = vec![];
let mut ret_items = vec![];
for their_ckr in checksums.iter() {
let our_ckr = self.range_checksum(&their_ckr.bounds, must_exit)?;
for (their_range, their_hash) in their_ckr.children.iter() {
let differs = match our_ckr
.children
.binary_search_by(|(our_range, _)| our_range.cmp(&their_range))
{
Err(_) => {
if their_range.level >= 1 {
let cached_hash =
self.range_checksum_cached_hash(&their_range, must_exit)?;
cached_hash.hash.map(|h| h != *their_hash).unwrap_or(true)
} else {
true
}
}
Ok(i) => our_ckr.children[i].1 != *their_hash,
};
if differs {
ret_ranges.push(their_range.clone());
if their_range.level == 0 {
if let Some(item_bytes) =
self.table.store.get(their_range.begin.as_slice())?
{
ret_items.push(Arc::new(ByteBuf::from(item_bytes.to_vec())));
}
}
}
}
for (our_range, _hash) in our_ckr.children.iter() {
if let Some(their_found_limit) = &their_ckr.found_limit {
if our_range.begin.as_slice() > their_found_limit.as_slice() {
break;
}
}
let not_present = our_ckr
.children
.binary_search_by(|(their_range, _)| their_range.cmp(&our_range))
.is_err();
if not_present {
if our_range.level > 0 {
ret_ranges.push(our_range.clone());
}
if our_range.level == 0 {
if let Some(item_bytes) =
self.table.store.get(our_range.begin.as_slice())?
{
ret_items.push(Arc::new(ByteBuf::from(item_bytes.to_vec())));
}
}
}
}
}
let n_checksums = checksums
.iter()
.map(|x| x.children.len())
.fold(0, |x, y| x + y);
if ret_ranges.len() > 0 || ret_items.len() > 0 {
trace!(
"({}) Checksum comparison RPC: {} different + {} items for {} received",
self.table.name,
ret_ranges.len(),
ret_items.len(),
n_checksums
);
}
Ok(SyncRPC::Difference(ret_ranges, ret_items))
}
pub(crate) fn invalidate(self: &Arc<Self>, item_key: &[u8]) {
for i in 1..MAX_DEPTH {
let needle = SyncRange {
begin: item_key.to_vec(),
end: vec![],
level: i,
};
let mut cache = self.cache[i].lock().unwrap();
if let Some(cache_entry) = cache.range(..=needle).rev().next() {
if cache_entry.0.begin[..] <= *item_key && cache_entry.0.end[..] > *item_key {
let index = cache_entry.0.clone();
drop(cache_entry);
cache.remove(&index);
}
}
}
}
}
impl SyncTodo {
fn add_full_scan<F: TableSchema, R: TableReplication>(&mut self, table: &Table<F, R>) {
let my_id = table.system.id;
self.todo.clear();
let ring = table.system.ring.borrow().clone();
let split_points = table.replication.split_points(&ring);
for i in 0..split_points.len() - 1 {
let begin = split_points[i];
let end = split_points[i + 1];
let nodes = table.replication.replication_nodes(&begin, &ring);
let retain = nodes.contains(&my_id);
if !retain {
// Check if we have some data to send, otherwise skip
if table.store.range(begin..end).next().is_none() {
continue;
}
}
self.todo.push(TodoPartition { begin, end, retain });
}
}
fn add_ring_difference<F: TableSchema, R: TableReplication>(
&mut self,
table: &Table<F, R>,
old_ring: &Ring,
new_ring: &Ring,
) {
let my_id = table.system.id;
// If it is us who are entering or leaving the system,
// initiate a full sync instead of incremental sync
if old_ring.config.members.contains_key(&my_id)
!= new_ring.config.members.contains_key(&my_id)
{
self.add_full_scan(table);
return;
}
let mut all_points = None
.into_iter()
.chain(table.replication.split_points(old_ring).drain(..))
.chain(table.replication.split_points(new_ring).drain(..))
.chain(self.todo.iter().map(|x| x.begin))
.chain(self.todo.iter().map(|x| x.end))
.collect::<Vec<_>>();
all_points.sort();
all_points.dedup();
let mut old_todo = std::mem::replace(&mut self.todo, vec![]);
old_todo.sort_by(|x, y| x.begin.cmp(&y.begin));
let mut new_todo = vec![];
for i in 0..all_points.len() - 1 {
let begin = all_points[i];
let end = all_points[i + 1];
let was_ours = table
.replication
.replication_nodes(&begin, &old_ring)
.contains(&my_id);
let is_ours = table
.replication
.replication_nodes(&begin, &new_ring)
.contains(&my_id);
let was_todo = match old_todo.binary_search_by(|x| x.begin.cmp(&begin)) {
Ok(_) => true,
Err(j) => {
(j > 0 && old_todo[j - 1].begin < end && begin < old_todo[j - 1].end)
|| (j < old_todo.len()
&& old_todo[j].begin < end && begin < old_todo[j].end)
}
};
if was_todo || (is_ours && !was_ours) || (was_ours && !is_ours) {
new_todo.push(TodoPartition {
begin,
end,
retain: is_ours,
});
}
}
self.todo = new_todo;
}
fn pop_task(&mut self) -> Option<TodoPartition> {
if self.todo.is_empty() {
return None;
}
let i = rand::thread_rng().gen_range::<usize, _, _>(0, self.todo.len());
if i == self.todo.len() - 1 {
self.todo.pop()
} else {
let replacement = self.todo.pop().unwrap();
let ret = std::mem::replace(&mut self.todo[i], replacement);
Some(ret)
}
}
}