forked from Deuxfleurs/garage
Safety: never voluntarily delete block in 10min interval after RC reaches zero
This commit is contained in:
parent
cc255d46cd
commit
74a7a550eb
3 changed files with 182 additions and 51 deletions
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@ -446,7 +446,7 @@ impl AdminRpcHandler {
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if opt.detailed {
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writeln!(
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&mut ret,
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" number of blocks: {}",
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" number of RC entries (~= number of blocks): {}",
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self.garage.block_manager.rc_len()
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)
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.unwrap();
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@ -8,8 +8,7 @@ pub enum Command {
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#[structopt(name = "server")]
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Server,
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/// Print identifier (public key) of this garage node.
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/// Generates a new keypair if necessary.
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/// Print identifier (public key) of this Garage node
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#[structopt(name = "node-id")]
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NodeId(NodeIdOpt),
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@ -31,10 +31,20 @@ pub const INLINE_THRESHOLD: usize = 3072;
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pub const BACKGROUND_WORKERS: u64 = 1;
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pub const BACKGROUND_TRANQUILITY: u32 = 3;
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const BLOCK_RW_TIMEOUT: Duration = Duration::from_secs(42);
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const BLOCK_GC_TIMEOUT: Duration = Duration::from_secs(60);
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// Timeout for RPCs that read and write blocks to remote nodes
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const BLOCK_RW_TIMEOUT: Duration = Duration::from_secs(30);
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// Timeout for RPCs that ask other nodes whether they need a copy
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// of a given block before we delete it locally
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const NEED_BLOCK_QUERY_TIMEOUT: Duration = Duration::from_secs(5);
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const RESYNC_RETRY_TIMEOUT: Duration = Duration::from_secs(10);
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// The delay between the time where a resync operation fails
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// and the time when it is retried.
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const RESYNC_RETRY_DELAY: Duration = Duration::from_secs(60);
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// The delay between the moment when the reference counter
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// drops to zero, and the moment where we allow ourselves
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// to delete the block locally.
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const BLOCK_GC_DELAY: Duration = Duration::from_secs(600);
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/// RPC messages used to share blocks of data between nodes
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#[derive(Debug, Serialize, Deserialize)]
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@ -180,7 +190,7 @@ impl BlockManager {
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/// that are required because of refcount > 0, and will try
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/// to fix any mismatch between the two.
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pub async fn repair_data_store(&self, must_exit: &watch::Receiver<bool>) -> Result<(), Error> {
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// 1. Repair blocks from RC table
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// 1. Repair blocks from RC table.
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let garage = self.garage.load_full().unwrap();
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let mut last_hash = None;
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for (i, entry) in garage.block_ref_table.data.store.iter().enumerate() {
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@ -245,40 +255,51 @@ impl BlockManager {
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/// Increment the number of time a block is used, putting it to resynchronization if it is
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/// required, but not known
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pub fn block_incref(&self, hash: &Hash) -> Result<(), Error> {
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let old_rc = self.rc.fetch_and_update(&hash, |old| {
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let old_v = old.map(u64_from_be_bytes).unwrap_or(0);
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Some(u64::to_be_bytes(old_v + 1).to_vec())
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})?;
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let old_rc = old_rc.map(u64_from_be_bytes).unwrap_or(0);
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if old_rc == 0 {
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self.put_to_resync(hash, BLOCK_RW_TIMEOUT)?;
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let old_rc = self
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.rc
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.fetch_and_update(&hash, |old| RcEntry::parse_opt(old).increment().serialize())?;
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let old_rc = RcEntry::parse_opt(old_rc);
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if old_rc.is_zero() {
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// When the reference counter is incremented, there is
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// normally a node that is responsible for sending us the
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// data of the block. However that operation may fail,
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// so in all cases we add the block here to the todo list
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// to check later that it arrived correctly, and if not
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// we will fecth it from someone.
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self.put_to_resync(hash, 2 * BLOCK_RW_TIMEOUT)?;
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}
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Ok(())
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}
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/// Decrement the number of time a block is used
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pub fn block_decref(&self, hash: &Hash) -> Result<(), Error> {
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let new_rc = self.rc.update_and_fetch(&hash, |old| {
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let old_v = old.map(u64_from_be_bytes).unwrap_or(0);
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if old_v > 1 {
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Some(u64::to_be_bytes(old_v - 1).to_vec())
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} else {
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None
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}
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})?;
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if new_rc.is_none() {
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self.put_to_resync(hash, BLOCK_GC_TIMEOUT)?;
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let new_rc = self
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.rc
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.update_and_fetch(&hash, |old| RcEntry::parse_opt(old).decrement().serialize())?;
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let new_rc = RcEntry::parse_opt(new_rc);
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if let RcEntry::Deletable { .. } = new_rc {
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self.put_to_resync(hash, BLOCK_GC_DELAY + Duration::from_secs(10))?;
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}
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Ok(())
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}
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/// Read a block's reference count
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pub fn get_block_rc(&self, hash: &Hash) -> Result<u64, Error> {
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Ok(self
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.rc
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.get(hash.as_ref())?
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.map(u64_from_be_bytes)
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.unwrap_or(0))
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fn get_block_rc(&self, hash: &Hash) -> Result<RcEntry, Error> {
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Ok(RcEntry::parse_opt(self.rc.get(hash.as_ref())?))
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}
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/// Delete an entry in the RC table if it is deletable and the
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/// deletion time has passed
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fn clear_deleted_block_rc(&self, hash: &Hash) -> Result<(), Error> {
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let now = now_msec();
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self.rc.update_and_fetch(&hash, |rcval| {
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let updated = match RcEntry::parse_opt(rcval) {
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RcEntry::Deletable { at_time } if now > at_time => RcEntry::Absent,
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v => v,
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};
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updated.serialize()
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})?;
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Ok(())
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}
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// ---- Reading and writing blocks locally ----
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@ -300,7 +321,7 @@ impl BlockManager {
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Ok(f) => f,
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Err(e) => {
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// Not found but maybe we should have had it ??
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self.put_to_resync(hash, Duration::from_millis(0))?;
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self.put_to_resync(hash, 2 * BLOCK_RW_TIMEOUT)?;
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return Err(Into::into(e));
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}
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};
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@ -314,6 +335,7 @@ impl BlockManager {
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.await
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.move_block_to_corrupted(hash, self)
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.await?;
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self.put_to_resync(hash, Duration::from_millis(0))?;
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return Err(Error::CorruptData(*hash));
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}
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@ -328,7 +350,7 @@ impl BlockManager {
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.await
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.check_block_status(hash, self)
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.await?;
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Ok(needed && !exists)
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Ok(needed.is_nonzero() && !exists)
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}
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/// Utility: gives the path of the directory in which a block should be found
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@ -349,7 +371,7 @@ impl BlockManager {
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// ---- Resync loop ----
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pub fn spawn_background_worker(self: Arc<Self>) {
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// Launch 2 simultaneous workers for background resync loop preprocessing
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// Launch n simultaneous workers for background resync loop preprocessing
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for i in 0..BACKGROUND_WORKERS {
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let bm2 = self.clone();
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let background = self.system.background.clone();
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@ -407,7 +429,7 @@ impl BlockManager {
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let res = self.resync_block(&hash).await;
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if let Err(e) = &res {
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warn!("Error when resyncing {:?}: {}", hash, e);
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self.put_to_resync(&hash, RESYNC_RETRY_TIMEOUT)?;
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self.put_to_resync(&hash, RESYNC_RETRY_DELAY)?;
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}
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Ok(true)
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} else {
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@ -437,15 +459,18 @@ impl BlockManager {
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.check_block_status(hash, self)
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.await?;
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if exists != needed {
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info!(
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"Resync block {:?}: exists {}, needed {}",
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hash, exists, needed
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if exists != needed.is_needed() || exists != needed.is_nonzero() {
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debug!(
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"Resync block {:?}: exists {}, nonzero rc {}, deletable {}",
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hash,
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exists,
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needed.is_nonzero(),
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needed.is_deletable(),
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);
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}
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if exists && !needed {
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trace!("Offloading block {:?}", hash);
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if exists && needed.is_deletable() {
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info!("Resync block {:?}: offloading and deleting", hash);
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let mut who = self.replication.write_nodes(hash);
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if who.len() < self.replication.write_quorum() {
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@ -488,7 +513,7 @@ impl BlockManager {
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need_nodes.len()
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);
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let put_block_message = self.read_block(hash).await.err_context("PutBlock RPC")?;
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let put_block_message = self.read_block(hash).await?;
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self.system
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.rpc
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.try_call_many(
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@ -499,10 +524,11 @@ impl BlockManager {
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.with_quorum(need_nodes.len())
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.with_timeout(BLOCK_RW_TIMEOUT),
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)
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.await?;
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.await
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.err_context("PutBlock RPC")?;
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}
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info!(
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"Deleting block {:?}, offload finished ({} / {})",
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"Deleting unneeded block {:?}, offload finished ({} / {})",
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hash,
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need_nodes.len(),
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who.len()
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@ -513,12 +539,16 @@ impl BlockManager {
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.await
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.delete_if_unneeded(hash, self)
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.await?;
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self.clear_deleted_block_rc(hash)?;
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}
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if needed && !exists {
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// TODO find a way to not do this if they are sending it to us
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// Let's suppose this isn't an issue for now with the BLOCK_RW_TIMEOUT delay
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// between the RC being incremented and this part being called.
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if needed.is_nonzero() && !exists {
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info!(
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"Resync block {:?}: fetching absent but needed block (refcount > 0)",
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hash
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);
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let block_data = self.rpc_get_block(hash).await?;
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self.write_block(hash, &block_data[..]).await?;
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}
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@ -526,6 +556,8 @@ impl BlockManager {
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Ok(())
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}
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// ---- Utility: iteration on files in the data directory ----
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async fn for_each_file<F, Fut, State>(
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&self,
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state: State,
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@ -608,7 +640,7 @@ impl EndpointHandler<BlockRpc> for BlockManager {
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struct BlockStatus {
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exists: bool,
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needed: bool,
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needed: RcEntry,
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}
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impl BlockManagerLocked {
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@ -620,7 +652,7 @@ impl BlockManagerLocked {
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let path = mgr.block_path(hash);
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let exists = fs::metadata(&path).await.is_ok();
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let needed = mgr.get_block_rc(hash)? > 0;
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let needed = mgr.get_block_rc(hash)?;
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Ok(BlockStatus { exists, needed })
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}
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@ -659,14 +691,13 @@ impl BlockManagerLocked {
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let mut path2 = path.clone();
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path2.set_extension("corrupted");
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fs::rename(path, path2).await?;
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mgr.put_to_resync(hash, Duration::from_millis(0))?;
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Ok(())
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}
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async fn delete_if_unneeded(&self, hash: &Hash, mgr: &BlockManager) -> Result<(), Error> {
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let BlockStatus { exists, needed } = self.check_block_status(hash, mgr).await?;
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if exists && !needed {
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if exists && needed.is_deletable() {
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let path = mgr.block_path(hash);
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fs::remove_file(path).await?;
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}
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@ -680,3 +711,104 @@ fn u64_from_be_bytes<T: AsRef<[u8]>>(bytes: T) -> u64 {
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x8.copy_from_slice(bytes.as_ref());
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u64::from_be_bytes(x8)
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}
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/// Describes the state of the reference counter for a block
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#[derive(Clone, Copy, Debug)]
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enum RcEntry {
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/// Present: the block has `count` references, with `count` > 0.
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///
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/// This is stored as u64::to_be_bytes(count)
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Present { count: u64 },
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/// Deletable: the block has zero references, and can be deleted
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/// once time (returned by now_msec) is larger than at_time
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/// (in millis since Unix epoch)
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///
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/// This is stored as [0u8; 8] followed by u64::to_be_bytes(at_time),
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/// (this allows for the data format to be backwards compatible with
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/// previous Garage versions that didn't have this intermediate state)
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Deletable { at_time: u64 },
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/// Absent: the block has zero references, and can be deleted
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/// immediately
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Absent,
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}
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impl RcEntry {
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fn parse(bytes: &[u8]) -> Self {
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if bytes.len() == 8 {
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RcEntry::Present {
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count: u64::from_be_bytes(bytes.try_into().unwrap()),
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}
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} else if bytes.len() == 16 {
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RcEntry::Deletable {
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at_time: u64::from_be_bytes(bytes[8..16].try_into().unwrap()),
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}
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} else {
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panic!("Invalid RC entry: {:?}, database is corrupted. This is an error Garage is currently unable to recover from. Sorry, and also please report a bug.",
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bytes
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)
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}
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}
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fn parse_opt<V: AsRef<[u8]>>(bytes: Option<V>) -> Self {
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bytes
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.map(|b| Self::parse(b.as_ref()))
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.unwrap_or(Self::Absent)
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}
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fn serialize(self) -> Option<Vec<u8>> {
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match self {
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RcEntry::Present { count } => Some(u64::to_be_bytes(count).to_vec()),
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RcEntry::Deletable { at_time } => {
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Some([u64::to_be_bytes(0), u64::to_be_bytes(at_time)].concat())
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}
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RcEntry::Absent => None,
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}
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}
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fn increment(self) -> Self {
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let old_count = match self {
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RcEntry::Present { count } => count,
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_ => 0,
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};
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RcEntry::Present {
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count: old_count + 1,
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}
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}
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fn decrement(self) -> Self {
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match self {
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RcEntry::Present { count } => {
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if count > 1 {
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RcEntry::Present { count: count - 1 }
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} else {
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RcEntry::Deletable {
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at_time: now_msec() + BLOCK_GC_DELAY.as_millis() as u64,
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}
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}
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}
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del => del,
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}
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}
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fn is_zero(&self) -> bool {
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matches!(self, RcEntry::Deletable { .. } | RcEntry::Absent)
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}
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fn is_nonzero(&self) -> bool {
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!self.is_zero()
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}
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fn is_deletable(&self) -> bool {
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match self {
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RcEntry::Present { .. } => false,
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RcEntry::Deletable { at_time } => now_msec() > *at_time,
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RcEntry::Absent => true,
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}
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}
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fn is_needed(&self) -> bool {
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!self.is_deletable()
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}
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}
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