use core::ops::Bound; 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_db as db; use garage_util::data::*; use garage_util::error::*; use garage_util::metrics::RecordDuration; 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 minimum retry delay is 60 seconds = 1 minute // The maximum retry delay is 60 seconds * 2^6 = 60 seconds << 6 = 64 minutes (~1 hour) const RESYNC_RETRY_DELAY_MAX_BACKOFF_POWER: u64 = 6; // 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; } /// 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, background_tranquility: u32, mutation_lock: Mutex, rc: BlockRc, resync_queue: db::Tree, resync_notify: Notify, resync_errors: db::Tree, system: Arc, endpoint: Arc>, 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: &db::Db, data_dir: PathBuf, compression_level: Option, background_tranquility: u32, replication: TableShardedReplication, system: Arc, ) -> Arc { 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_errors = db .open_tree("block_local_resync_errors") .expect("Unable to open block_local_resync_errors tree"); let endpoint = system .netapp .endpoint("garage_block/manager.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 { 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, 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) -> 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) -> Result<(), Error> { // 1. Repair blocks from RC table. let mut next_start: Option = None; loop { // We have to do this complicated two-step process where we first read a bunch // of hashes from the RC table, and then insert them in the to-resync queue, // because of SQLite. Basically, as long as we have an iterator on a DB table, // we can't do anything else on the DB. The naive approach (which we had previously) // of just iterating on the RC table and inserting items one to one in the resync // queue can't work here, it would just provoke a deadlock in the SQLite adapter code. // This is mostly because the Rust bindings for SQLite assume a worst-case scenario // where SQLite is not compiled in thread-safe mode, so we have to wrap everything // in a mutex (see db/sqlite_adapter.rs). let mut batch_of_hashes = vec![]; let start_bound = match next_start.as_ref() { None => Bound::Unbounded, Some(x) => Bound::Excluded(x.as_slice()), }; for entry in self .rc .rc .range::<&[u8], _>((start_bound, Bound::Unbounded))? { let (hash, _) = entry?; let hash = Hash::try_from(&hash[..]).unwrap(); batch_of_hashes.push(hash); if batch_of_hashes.len() >= 1000 { break; } } if batch_of_hashes.is_empty() { break; } for hash in batch_of_hashes.into_iter() { self.put_to_resync(&hash, Duration::from_secs(0))?; next_start = Some(hash) } if *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, 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) -> Result { Ok(self.resync_queue.len()?) } /// Get number of blocks that have an error pub fn resync_errors_len(&self) -> Result { Ok(self.resync_errors.len()?) } /// Get number of items in the refcount table pub fn rc_len(&self) -> Result { Ok(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: &Arc, tx: &mut db::Transaction, hash: Hash) -> db::Result<()> { if self.rc.block_incref(tx, &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. let this = self.clone(); tokio::spawn(async move { tokio::time::sleep(Duration::from_secs(1)).await; if let Err(e) = this.put_to_resync(&hash, 2 * BLOCK_RW_TIMEOUT) { error!("Block {:?} could not be put in resync queue: {}.", hash, e); } }); } Ok(()) } /// Decrement the number of time a block is used pub fn block_decref(self: &Arc, tx: &mut db::Transaction, hash: Hash) -> db::Result<()> { if self.rc.block_decref(tx, &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. let this = self.clone(); tokio::spawn(async move { tokio::time::sleep(Duration::from_secs(1)).await; if let Err(e) = this.put_to_resync(&hash, BLOCK_GC_DELAY + Duration::from_secs(10)) { error!("Block {:?} could not be put in resync queue: {}.", hash, e); } }); } Ok(()) } // ---- Reading and writing blocks locally ---- /// Write a block to disk async fn write_block(&self, hash: &Hash, data: &DataBlock) -> Result { 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 { 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 { 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 { 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 { 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) { // 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) -> db::Result<()> { 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) -> db::Result<()> { 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, mut must_exit: watch::Receiver) { 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) -> Result { if let Some((time_bytes, hash_bytes)) = self.resync_queue.first()? { 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( &self, state: State, mut f: F, must_exit: &watch::Receiver, ) -> Result<(), Error> where F: FnMut(State, Hash) -> Fut + Send, Fut: Future> + 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, ) -> BoxFuture<'a, Result> where F: FnMut(State, Hash) -> Fut + Send, Fut: Future> + 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 for BlockManager { async fn handle( self: &Arc, message: &BlockRpc, _from: NodeID, ) -> Result { 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 { 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 { 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: &db::Value) -> 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 { [ 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, RESYNC_RETRY_DELAY_MAX_BACKOFF_POWER) } fn next_try(&self) -> u64 { self.last_try + self.delay_msec() } }