garage/src/block/manager.rs

993 lines
29 KiB
Rust

use std::convert::TryInto;
use std::path::{Path, PathBuf};
use std::sync::Arc;
use std::time::Duration;
use async_trait::async_trait;
use serde::{Deserialize, Serialize};
use futures::future::*;
use futures::select;
use tokio::fs;
use tokio::io::{AsyncReadExt, AsyncWriteExt};
use tokio::sync::{watch, Mutex, Notify};
use opentelemetry::{
trace::{FutureExt as OtelFutureExt, TraceContextExt, Tracer},
Context, KeyValue,
};
use garage_util::data::*;
use garage_util::error::*;
use garage_util::metrics::RecordDuration;
use garage_util::sled_counter::SledCountedTree;
use garage_util::time::*;
use garage_util::tranquilizer::Tranquilizer;
use garage_rpc::system::System;
use garage_rpc::*;
use garage_table::replication::{TableReplication, TableShardedReplication};
use crate::block::*;
use crate::metrics::*;
use crate::rc::*;
/// Size under which data will be stored inlined in database instead of as files
pub const INLINE_THRESHOLD: usize = 3072;
// Timeout for RPCs that read and write blocks to remote nodes
const BLOCK_RW_TIMEOUT: Duration = Duration::from_secs(30);
// Timeout for RPCs that ask other nodes whether they need a copy
// of a given block before we delete it locally
const NEED_BLOCK_QUERY_TIMEOUT: Duration = Duration::from_secs(5);
// The delay between the time where a resync operation fails
// and the time when it is retried, with exponential backoff
// (multiplied by 2, 4, 8, 16, etc. for every consecutive failure).
const RESYNC_RETRY_DELAY: Duration = Duration::from_secs(60);
// The delay between the moment when the reference counter
// drops to zero, and the moment where we allow ourselves
// to delete the block locally.
pub(crate) const BLOCK_GC_DELAY: Duration = Duration::from_secs(600);
/// RPC messages used to share blocks of data between nodes
#[derive(Debug, Serialize, Deserialize)]
pub enum BlockRpc {
Ok,
/// Message to ask for a block of data, by hash
GetBlock(Hash),
/// Message to send a block of data, either because requested, of for first delivery of new
/// block
PutBlock {
hash: Hash,
data: DataBlock,
},
/// Ask other node if they should have this block, but don't actually have it
NeedBlockQuery(Hash),
/// Response : whether the node do require that block
NeedBlockReply(bool),
}
impl Rpc for BlockRpc {
type Response = Result<BlockRpc, Error>;
}
/// The block manager, handling block exchange between nodes, and block storage on local node
pub struct BlockManager {
/// Replication strategy, allowing to find on which node blocks should be located
pub replication: TableShardedReplication,
/// Directory in which block are stored
pub data_dir: PathBuf,
compression_level: Option<i32>,
background_tranquility: u32,
mutation_lock: Mutex<BlockManagerLocked>,
rc: BlockRc,
resync_queue: SledCountedTree,
resync_notify: Notify,
resync_errors: SledCountedTree,
system: Arc<System>,
endpoint: Arc<Endpoint<BlockRpc, Self>>,
metrics: BlockManagerMetrics,
}
// This custom struct contains functions that must only be ran
// when the lock is held. We ensure that it is the case by storing
// it INSIDE a Mutex.
struct BlockManagerLocked();
impl BlockManager {
pub fn new(
db: &sled::Db,
data_dir: PathBuf,
compression_level: Option<i32>,
background_tranquility: u32,
replication: TableShardedReplication,
system: Arc<System>,
) -> Arc<Self> {
let rc = db
.open_tree("block_local_rc")
.expect("Unable to open block_local_rc tree");
let rc = BlockRc::new(rc);
let resync_queue = db
.open_tree("block_local_resync_queue")
.expect("Unable to open block_local_resync_queue tree");
let resync_queue = SledCountedTree::new(resync_queue);
let resync_errors = db
.open_tree("block_local_resync_errors")
.expect("Unable to open block_local_resync_errors tree");
let resync_errors = SledCountedTree::new(resync_errors);
let endpoint = system
.netapp
.endpoint("garage_model/block.rs/Rpc".to_string());
let manager_locked = BlockManagerLocked();
let metrics = BlockManagerMetrics::new(resync_queue.clone(), resync_errors.clone());
let block_manager = Arc::new(Self {
replication,
data_dir,
compression_level,
background_tranquility,
mutation_lock: Mutex::new(manager_locked),
rc,
resync_queue,
resync_notify: Notify::new(),
resync_errors,
system,
endpoint,
metrics,
});
block_manager.endpoint.set_handler(block_manager.clone());
block_manager.clone().spawn_background_worker();
block_manager
}
/// Ask nodes that might have a (possibly compressed) block for it
async fn rpc_get_raw_block(&self, hash: &Hash) -> Result<DataBlock, Error> {
let who = self.replication.read_nodes(hash);
let resps = self
.system
.rpc
.try_call_many(
&self.endpoint,
&who[..],
BlockRpc::GetBlock(*hash),
RequestStrategy::with_priority(PRIO_NORMAL)
.with_quorum(1)
.with_timeout(BLOCK_RW_TIMEOUT)
.interrupt_after_quorum(true),
)
.await?;
for resp in resps {
if let BlockRpc::PutBlock { data, .. } = resp {
return Ok(data);
}
}
Err(Error::Message(format!(
"Unable to read block {:?}: no valid blocks returned",
hash
)))
}
// ---- Public interface ----
/// Ask nodes that might have a block for it
pub async fn rpc_get_block(&self, hash: &Hash) -> Result<Vec<u8>, Error> {
self.rpc_get_raw_block(hash).await?.verify_get(*hash)
}
/// Send block to nodes that should have it
pub async fn rpc_put_block(&self, hash: Hash, data: Vec<u8>) -> Result<(), Error> {
let who = self.replication.write_nodes(&hash);
let data = DataBlock::from_buffer(data, self.compression_level);
self.system
.rpc
.try_call_many(
&self.endpoint,
&who[..],
BlockRpc::PutBlock { hash, data },
RequestStrategy::with_priority(PRIO_NORMAL)
.with_quorum(self.replication.write_quorum())
.with_timeout(BLOCK_RW_TIMEOUT),
)
.await?;
Ok(())
}
/// Launch the repair procedure on the data store
///
/// This will list all blocks locally present, as well as those
/// that are required because of refcount > 0, and will try
/// to fix any mismatch between the two.
pub async fn repair_data_store(&self, must_exit: &watch::Receiver<bool>) -> Result<(), Error> {
// 1. Repair blocks from RC table.
for (i, entry) in self.rc.rc.iter().enumerate() {
let (hash, _) = entry?;
let hash = Hash::try_from(&hash[..]).unwrap();
self.put_to_resync(&hash, Duration::from_secs(0))?;
if i & 0xFF == 0 && *must_exit.borrow() {
return Ok(());
}
}
// 2. Repair blocks actually on disk
// Lists all blocks on disk and adds them to the resync queue.
// This allows us to find blocks we are storing but don't actually need,
// so that we can offload them if necessary and then delete them locally.
self.for_each_file(
(),
move |_, hash| async move {
self.put_to_resync(&hash, Duration::from_secs(0))
.map_err(Into::into)
},
must_exit,
)
.await
}
/// Verify integrity of each block on disk. Use `speed_limit` to limit the load generated by
/// this function.
pub async fn scrub_data_store(
&self,
must_exit: &watch::Receiver<bool>,
tranquility: u32,
) -> Result<(), Error> {
let tranquilizer = Tranquilizer::new(30);
self.for_each_file(
tranquilizer,
move |mut tranquilizer, hash| async move {
let _ = self.read_block(&hash).await;
tranquilizer.tranquilize(tranquility).await;
Ok(tranquilizer)
},
must_exit,
)
.await
}
/// Get lenght of resync queue
pub fn resync_queue_len(&self) -> usize {
self.resync_queue.len()
}
/// Get number of blocks that have an error
pub fn resync_errors_len(&self) -> usize {
self.resync_errors.len()
}
/// Get number of items in the refcount table
pub fn rc_len(&self) -> usize {
self.rc.rc.len()
}
//// ----- Managing the reference counter ----
/// Increment the number of time a block is used, putting it to resynchronization if it is
/// required, but not known
pub fn block_incref(&self, hash: &Hash) -> Result<(), Error> {
if self.rc.block_incref(hash)? {
// When the reference counter is incremented, there is
// normally a node that is responsible for sending us the
// data of the block. However that operation may fail,
// so in all cases we add the block here to the todo list
// to check later that it arrived correctly, and if not
// we will fecth it from someone.
self.put_to_resync(hash, 2 * BLOCK_RW_TIMEOUT)?;
}
Ok(())
}
/// Decrement the number of time a block is used
pub fn block_decref(&self, hash: &Hash) -> Result<(), Error> {
if self.rc.block_decref(hash)? {
// When the RC is decremented, it might drop to zero,
// indicating that we don't need the block.
// There is a delay before we garbage collect it;
// make sure that it is handled in the resync loop
// after that delay has passed.
self.put_to_resync(hash, BLOCK_GC_DELAY + Duration::from_secs(10))?;
}
Ok(())
}
// ---- Reading and writing blocks locally ----
/// Write a block to disk
async fn write_block(&self, hash: &Hash, data: &DataBlock) -> Result<BlockRpc, Error> {
let write_size = data.inner_buffer().len() as u64;
let res = self
.mutation_lock
.lock()
.await
.write_block(hash, data, self)
.bound_record_duration(&self.metrics.block_write_duration)
.await?;
self.metrics.bytes_written.add(write_size);
Ok(res)
}
/// Read block from disk, verifying it's integrity
async fn read_block(&self, hash: &Hash) -> Result<BlockRpc, Error> {
let data = self
.read_block_internal(hash)
.bound_record_duration(&self.metrics.block_read_duration)
.await?;
self.metrics
.bytes_read
.add(data.inner_buffer().len() as u64);
Ok(BlockRpc::PutBlock { hash: *hash, data })
}
async fn read_block_internal(&self, hash: &Hash) -> Result<DataBlock, Error> {
let mut path = self.block_path(hash);
let compressed = match self.is_block_compressed(hash).await {
Ok(c) => c,
Err(e) => {
// Not found but maybe we should have had it ??
self.put_to_resync(hash, 2 * BLOCK_RW_TIMEOUT)?;
return Err(Into::into(e));
}
};
if compressed {
path.set_extension("zst");
}
let mut f = fs::File::open(&path).await?;
let mut data = vec![];
f.read_to_end(&mut data).await?;
drop(f);
let data = if compressed {
DataBlock::Compressed(data)
} else {
DataBlock::Plain(data)
};
if data.verify(*hash).is_err() {
self.metrics.corruption_counter.add(1);
self.mutation_lock
.lock()
.await
.move_block_to_corrupted(hash, self)
.await?;
self.put_to_resync(hash, Duration::from_millis(0))?;
return Err(Error::CorruptData(*hash));
}
Ok(data)
}
/// Check if this node should have a block, but don't actually have it
async fn need_block(&self, hash: &Hash) -> Result<bool, Error> {
let BlockStatus { exists, needed } = self
.mutation_lock
.lock()
.await
.check_block_status(hash, self)
.await?;
Ok(needed.is_nonzero() && !exists)
}
/// Utility: gives the path of the directory in which a block should be found
fn block_dir(&self, hash: &Hash) -> PathBuf {
let mut path = self.data_dir.clone();
path.push(hex::encode(&hash.as_slice()[0..1]));
path.push(hex::encode(&hash.as_slice()[1..2]));
path
}
/// Utility: give the full path where a block should be found, minus extension if block is
/// compressed
fn block_path(&self, hash: &Hash) -> PathBuf {
let mut path = self.block_dir(hash);
path.push(hex::encode(hash.as_ref()));
path
}
/// Utility: check if block is stored compressed. Error if block is not stored
async fn is_block_compressed(&self, hash: &Hash) -> Result<bool, Error> {
let mut path = self.block_path(hash);
path.set_extension("zst");
if fs::metadata(&path).await.is_ok() {
return Ok(true);
}
path.set_extension("");
fs::metadata(&path).await.map(|_| false).map_err(Into::into)
}
// ---- Resync loop ----
// This part manages a queue of blocks that need to be
// "resynchronized", i.e. that need to have a check that
// they are at present if we need them, or that they are
// deleted once the garbage collection delay has passed.
//
// Here are some explanations on how the resync queue works.
// There are two Sled trees that are used to have information
// about the status of blocks that need to be resynchronized:
//
// - resync_queue: a tree that is ordered first by a timestamp
// (in milliseconds since Unix epoch) that is the time at which
// the resync must be done, and second by block hash.
// The key in this tree is just:
// concat(timestamp (8 bytes), hash (32 bytes))
// The value is the same 32-byte hash.
//
// - resync_errors: a tree that indicates for each block
// if the last resync resulted in an error, and if so,
// the following two informations (see the ErrorCounter struct):
// - how many consecutive resync errors for this block?
// - when was the last try?
// These two informations are used to implement an
// exponential backoff retry strategy.
// The key in this tree is the 32-byte hash of the block,
// and the value is the encoded ErrorCounter value.
//
// We need to have these two trees, because the resync queue
// is not just a queue of items to process, but a set of items
// that are waiting a specific delay until we can process them
// (the delay being necessary both internally for the exponential
// backoff strategy, and exposed as a parameter when adding items
// to the queue, e.g. to wait until the GC delay has passed).
// This is why we need one tree ordered by time, and one
// ordered by identifier of item to be processed (block hash).
//
// When the worker wants to process an item it takes from
// resync_queue, it checks in resync_errors that if there is an
// exponential back-off delay to await, it has passed before we
// process the item. If not, the item in the queue is skipped
// (but added back for later processing after the time of the
// delay).
//
// An alternative that would have seemed natural is to
// only add items to resync_queue with a processing time that is
// after the delay, but there are several issues with this:
// - This requires to synchronize updates to resync_queue and
// resync_errors (with the current model, there is only one thread,
// the worker thread, that accesses resync_errors,
// so no need to synchronize) by putting them both in a lock.
// This would mean that block_incref might need to take a lock
// before doing its thing, meaning it has much more chances of
// not completing successfully if something bad happens to Garage.
// Currently Garage is not able to recover from block_incref that
// doesn't complete successfully, because it is necessary to ensure
// the consistency between the state of the block manager and
// information in the BlockRef table.
// - If a resync fails, we put that block in the resync_errors table,
// and also add it back to resync_queue to be processed after
// the exponential back-off delay,
// but maybe the block is already scheduled to be resynced again
// at another time that is before the exponential back-off delay,
// and we have no way to check that easily. This means that
// in all cases, we need to check the resync_errors table
// in the resync loop at the time when a block is popped from
// the resync_queue.
// Overall, the current design is therefore simpler and more robust
// because it tolerates inconsistencies between the resync_queue
// and resync_errors table (items being scheduled in resync_queue
// for times that are earlier than the exponential back-off delay
// is a natural condition that is handled properly).
fn spawn_background_worker(self: Arc<Self>) {
// Launch a background workers for background resync loop processing
let background = self.system.background.clone();
tokio::spawn(async move {
tokio::time::sleep(Duration::from_secs(10)).await;
background.spawn_worker("block resync worker".into(), move |must_exit| {
self.resync_loop(must_exit)
});
});
}
fn put_to_resync(&self, hash: &Hash, delay: Duration) -> Result<(), sled::Error> {
let when = now_msec() + delay.as_millis() as u64;
self.put_to_resync_at(hash, when)
}
fn put_to_resync_at(&self, hash: &Hash, when: u64) -> Result<(), sled::Error> {
trace!("Put resync_queue: {} {:?}", when, hash);
let mut key = u64::to_be_bytes(when).to_vec();
key.extend(hash.as_ref());
self.resync_queue.insert(key, hash.as_ref())?;
self.resync_notify.notify_waiters();
Ok(())
}
async fn resync_loop(self: Arc<Self>, mut must_exit: watch::Receiver<bool>) {
let mut tranquilizer = Tranquilizer::new(30);
while !*must_exit.borrow() {
match self.resync_iter(&mut must_exit).await {
Ok(true) => {
tranquilizer.tranquilize(self.background_tranquility).await;
}
Ok(false) => {
tranquilizer.reset();
}
Err(e) => {
// The errors that we have here are only Sled errors
// We don't really know how to handle them so just ¯\_(ツ)_/¯
// (there is kind of an assumption that Sled won't error on us,
// if it does there is not much we can do -- TODO should we just panic?)
error!(
"Could not do a resync iteration: {} (this is a very bad error)",
e
);
tranquilizer.reset();
}
}
}
}
// The result of resync_iter is:
// - Ok(true) -> a block was processed (successfully or not)
// - Ok(false) -> no block was processed, but we are ready for the next iteration
// - Err(_) -> a Sled error occurred when reading/writing from resync_queue/resync_errors
async fn resync_iter(
&self,
must_exit: &mut watch::Receiver<bool>,
) -> Result<bool, sled::Error> {
if let Some(first_pair_res) = self.resync_queue.iter().next() {
let (time_bytes, hash_bytes) = first_pair_res?;
let time_msec = u64::from_be_bytes(time_bytes[0..8].try_into().unwrap());
let now = now_msec();
if now >= time_msec {
let hash = Hash::try_from(&hash_bytes[..]).unwrap();
if let Some(ec) = self.resync_errors.get(hash.as_slice())? {
let ec = ErrorCounter::decode(ec);
if now < ec.next_try() {
// if next retry after an error is not yet,
// don't do resync and return early, but still
// make sure the item is still in queue at expected time
self.put_to_resync_at(&hash, ec.next_try())?;
// ec.next_try() > now >= time_msec, so this remove
// is not removing the one we added just above
// (we want to do the remove after the insert to ensure
// that the item is not lost if we crash in-between)
self.resync_queue.remove(time_bytes)?;
return Ok(false);
}
}
let tracer = opentelemetry::global::tracer("garage");
let trace_id = gen_uuid();
let span = tracer
.span_builder("Resync block")
.with_trace_id(
opentelemetry::trace::TraceId::from_hex(&hex::encode(
&trace_id.as_slice()[..16],
))
.unwrap(),
)
.with_attributes(vec![KeyValue::new("block", format!("{:?}", hash))])
.start(&tracer);
let res = self
.resync_block(&hash)
.with_context(Context::current_with_span(span))
.bound_record_duration(&self.metrics.resync_duration)
.await;
self.metrics.resync_counter.add(1);
if let Err(e) = &res {
self.metrics.resync_error_counter.add(1);
warn!("Error when resyncing {:?}: {}", hash, e);
let err_counter = match self.resync_errors.get(hash.as_slice())? {
Some(ec) => ErrorCounter::decode(ec).add1(now + 1),
None => ErrorCounter::new(now + 1),
};
self.resync_errors
.insert(hash.as_slice(), err_counter.encode())?;
self.put_to_resync_at(&hash, err_counter.next_try())?;
// err_counter.next_try() >= now + 1 > now,
// the entry we remove from the queue is not
// the entry we inserted with put_to_resync_at
self.resync_queue.remove(time_bytes)?;
} else {
self.resync_errors.remove(hash.as_slice())?;
self.resync_queue.remove(time_bytes)?;
}
Ok(true)
} else {
let delay = tokio::time::sleep(Duration::from_millis(time_msec - now));
select! {
_ = delay.fuse() => {},
_ = self.resync_notify.notified().fuse() => {},
_ = must_exit.changed().fuse() => {},
}
Ok(false)
}
} else {
// Here we wait either for a notification that an item has been
// added to the queue, or for a constant delay of 10 secs to expire.
// The delay avoids a race condition where the notification happens
// between the time we checked the queue and the first poll
// to resync_notify.notified(): if that happens, we'll just loop
// back 10 seconds later, which is fine.
let delay = tokio::time::sleep(Duration::from_secs(10));
select! {
_ = delay.fuse() => {},
_ = self.resync_notify.notified().fuse() => {},
_ = must_exit.changed().fuse() => {},
}
Ok(false)
}
}
async fn resync_block(&self, hash: &Hash) -> Result<(), Error> {
let BlockStatus { exists, needed } = self
.mutation_lock
.lock()
.await
.check_block_status(hash, self)
.await?;
if exists != needed.is_needed() || exists != needed.is_nonzero() {
debug!(
"Resync block {:?}: exists {}, nonzero rc {}, deletable {}",
hash,
exists,
needed.is_nonzero(),
needed.is_deletable(),
);
}
if exists && needed.is_deletable() {
info!("Resync block {:?}: offloading and deleting", hash);
let mut who = self.replication.write_nodes(hash);
if who.len() < self.replication.write_quorum() {
return Err(Error::Message("Not trying to offload block because we don't have a quorum of nodes to write to".to_string()));
}
who.retain(|id| *id != self.system.id);
let msg = Arc::new(BlockRpc::NeedBlockQuery(*hash));
let who_needs_fut = who.iter().map(|to| {
self.system.rpc.call_arc(
&self.endpoint,
*to,
msg.clone(),
RequestStrategy::with_priority(PRIO_BACKGROUND)
.with_timeout(NEED_BLOCK_QUERY_TIMEOUT),
)
});
let who_needs_resps = join_all(who_needs_fut).await;
let mut need_nodes = vec![];
for (node, needed) in who.iter().zip(who_needs_resps.into_iter()) {
match needed.err_context("NeedBlockQuery RPC")? {
BlockRpc::NeedBlockReply(needed) => {
if needed {
need_nodes.push(*node);
}
}
m => {
return Err(Error::unexpected_rpc_message(m));
}
}
}
if !need_nodes.is_empty() {
trace!(
"Block {:?} needed by {} nodes, sending",
hash,
need_nodes.len()
);
for node in need_nodes.iter() {
self.metrics
.resync_send_counter
.add(1, &[KeyValue::new("to", format!("{:?}", node))]);
}
let put_block_message = self.read_block(hash).await?;
self.system
.rpc
.try_call_many(
&self.endpoint,
&need_nodes[..],
put_block_message,
RequestStrategy::with_priority(PRIO_BACKGROUND)
.with_quorum(need_nodes.len())
.with_timeout(BLOCK_RW_TIMEOUT),
)
.await
.err_context("PutBlock RPC")?;
}
info!(
"Deleting unneeded block {:?}, offload finished ({} / {})",
hash,
need_nodes.len(),
who.len()
);
self.mutation_lock
.lock()
.await
.delete_if_unneeded(hash, self)
.await?;
self.rc.clear_deleted_block_rc(hash)?;
}
if needed.is_nonzero() && !exists {
info!(
"Resync block {:?}: fetching absent but needed block (refcount > 0)",
hash
);
let block_data = self.rpc_get_raw_block(hash).await?;
self.metrics.resync_recv_counter.add(1);
self.write_block(hash, &block_data).await?;
}
Ok(())
}
// ---- Utility: iteration on files in the data directory ----
async fn for_each_file<F, Fut, State>(
&self,
state: State,
mut f: F,
must_exit: &watch::Receiver<bool>,
) -> Result<(), Error>
where
F: FnMut(State, Hash) -> Fut + Send,
Fut: Future<Output = Result<State, Error>> + Send,
State: Send,
{
self.for_each_file_rec(&self.data_dir, state, &mut f, must_exit)
.await
.map(|_| ())
}
fn for_each_file_rec<'a, F, Fut, State>(
&'a self,
path: &'a Path,
mut state: State,
f: &'a mut F,
must_exit: &'a watch::Receiver<bool>,
) -> BoxFuture<'a, Result<State, Error>>
where
F: FnMut(State, Hash) -> Fut + Send,
Fut: Future<Output = Result<State, Error>> + Send,
State: Send + 'a,
{
async move {
let mut ls_data_dir = fs::read_dir(path).await?;
while let Some(data_dir_ent) = ls_data_dir.next_entry().await? {
if *must_exit.borrow() {
break;
}
let name = data_dir_ent.file_name();
let name = if let Ok(n) = name.into_string() {
n
} else {
continue;
};
let ent_type = data_dir_ent.file_type().await?;
let name = name.strip_suffix(".zst").unwrap_or(&name);
if name.len() == 2 && hex::decode(&name).is_ok() && ent_type.is_dir() {
state = self
.for_each_file_rec(&data_dir_ent.path(), state, f, must_exit)
.await?;
} else if name.len() == 64 {
let hash_bytes = if let Ok(h) = hex::decode(&name) {
h
} else {
continue;
};
let mut hash = [0u8; 32];
hash.copy_from_slice(&hash_bytes[..]);
state = f(state, hash.into()).await?;
}
}
Ok(state)
}
.boxed()
}
}
#[async_trait]
impl EndpointHandler<BlockRpc> for BlockManager {
async fn handle(
self: &Arc<Self>,
message: &BlockRpc,
_from: NodeID,
) -> Result<BlockRpc, Error> {
match message {
BlockRpc::PutBlock { hash, data } => self.write_block(hash, data).await,
BlockRpc::GetBlock(h) => self.read_block(h).await,
BlockRpc::NeedBlockQuery(h) => self.need_block(h).await.map(BlockRpc::NeedBlockReply),
m => Err(Error::unexpected_rpc_message(m)),
}
}
}
struct BlockStatus {
exists: bool,
needed: RcEntry,
}
impl BlockManagerLocked {
async fn check_block_status(
&self,
hash: &Hash,
mgr: &BlockManager,
) -> Result<BlockStatus, Error> {
let exists = mgr.is_block_compressed(hash).await.is_ok();
let needed = mgr.rc.get_block_rc(hash)?;
Ok(BlockStatus { exists, needed })
}
async fn write_block(
&self,
hash: &Hash,
data: &DataBlock,
mgr: &BlockManager,
) -> Result<BlockRpc, Error> {
let compressed = data.is_compressed();
let data = data.inner_buffer();
let mut path = mgr.block_dir(hash);
let directory = path.clone();
path.push(hex::encode(hash));
fs::create_dir_all(&directory).await?;
let to_delete = match (mgr.is_block_compressed(hash).await, compressed) {
(Ok(true), _) => return Ok(BlockRpc::Ok),
(Ok(false), false) => return Ok(BlockRpc::Ok),
(Ok(false), true) => {
let path_to_delete = path.clone();
path.set_extension("zst");
Some(path_to_delete)
}
(Err(_), compressed) => {
if compressed {
path.set_extension("zst");
}
None
}
};
let mut path2 = path.clone();
path2.set_extension("tmp");
let mut f = fs::File::create(&path2).await?;
f.write_all(data).await?;
f.sync_all().await?;
drop(f);
fs::rename(path2, path).await?;
if let Some(to_delete) = to_delete {
fs::remove_file(to_delete).await?;
}
// We want to ensure that when this function returns, data is properly persisted
// to disk. The first step is the sync_all above that does an fsync on the data file.
// Now, we do an fsync on the containing directory, to ensure that the rename
// is persisted properly. See:
// http://thedjbway.b0llix.net/qmail/syncdir.html
let dir = fs::OpenOptions::new()
.read(true)
.mode(0)
.open(directory)
.await?;
dir.sync_all().await?;
drop(dir);
Ok(BlockRpc::Ok)
}
async fn move_block_to_corrupted(&self, hash: &Hash, mgr: &BlockManager) -> Result<(), Error> {
warn!(
"Block {:?} is corrupted. Renaming to .corrupted and resyncing.",
hash
);
let mut path = mgr.block_path(hash);
let mut path2 = path.clone();
if mgr.is_block_compressed(hash).await? {
path.set_extension("zst");
path2.set_extension("zst.corrupted");
} else {
path2.set_extension("corrupted");
}
fs::rename(path, path2).await?;
Ok(())
}
async fn delete_if_unneeded(&self, hash: &Hash, mgr: &BlockManager) -> Result<(), Error> {
let BlockStatus { exists, needed } = self.check_block_status(hash, mgr).await?;
if exists && needed.is_deletable() {
let mut path = mgr.block_path(hash);
if mgr.is_block_compressed(hash).await? {
path.set_extension("zst");
}
fs::remove_file(path).await?;
mgr.metrics.delete_counter.add(1);
}
Ok(())
}
}
/// Counts the number of errors when resyncing a block,
/// and the time of the last try.
/// Used to implement exponential backoff.
#[derive(Clone, Copy, Debug)]
struct ErrorCounter {
errors: u64,
last_try: u64,
}
impl ErrorCounter {
fn new(now: u64) -> Self {
Self {
errors: 1,
last_try: now,
}
}
fn decode(data: sled::IVec) -> Self {
Self {
errors: u64::from_be_bytes(data[0..8].try_into().unwrap()),
last_try: u64::from_be_bytes(data[8..16].try_into().unwrap()),
}
}
fn encode(&self) -> Vec<u8> {
[
u64::to_be_bytes(self.errors),
u64::to_be_bytes(self.last_try),
]
.concat()
}
fn add1(self, now: u64) -> Self {
Self {
errors: self.errors + 1,
last_try: now,
}
}
fn delay_msec(&self) -> u64 {
(RESYNC_RETRY_DELAY.as_millis() as u64) << std::cmp::min(self.errors - 1, 10)
}
fn next_try(&self) -> u64 {
self.last_try + self.delay_msec()
}
}