forked from Deuxfleurs/garage
Implement GC delay for table data
This commit is contained in:
parent
74a7a550eb
commit
ad7ab31411
3 changed files with 76 additions and 44 deletions
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@ -1,3 +1,4 @@
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use std::convert::TryInto;
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use std::path::{Path, PathBuf};
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use std::sync::Arc;
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use std::time::Duration;
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@ -422,7 +423,7 @@ impl BlockManager {
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async fn resync_iter(&self, must_exit: &mut watch::Receiver<bool>) -> Result<bool, Error> {
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if let Some((time_bytes, hash_bytes)) = self.resync_queue.pop_min()? {
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let time_msec = u64_from_be_bytes(&time_bytes[0..8]);
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let time_msec = u64::from_be_bytes(time_bytes[0..8].try_into().unwrap());
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let now = now_msec();
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if now >= time_msec {
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let hash = Hash::try_from(&hash_bytes[..]).unwrap();
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@ -705,13 +706,6 @@ impl BlockManagerLocked {
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}
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}
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fn u64_from_be_bytes<T: AsRef<[u8]>>(bytes: T) -> u64 {
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assert!(bytes.as_ref().len() == 8);
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let mut x8 = [0u8; 8];
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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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@ -55,7 +55,7 @@ where
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.expect("Unable to open DB Merkle TODO tree");
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let gc_todo = db
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.open_tree(&format!("{}:gc_todo", name))
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.open_tree(&format!("{}:gc_todo_v2", name))
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.expect("Unable to open DB tree");
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Arc::new(Self {
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108
src/table/gc.rs
108
src/table/gc.rs
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@ -1,4 +1,5 @@
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use std::collections::HashMap;
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use std::convert::TryInto;
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use std::sync::Arc;
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use std::time::Duration;
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@ -13,6 +14,7 @@ use tokio::sync::watch;
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use garage_util::data::*;
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use garage_util::error::*;
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use garage_util::time::*;
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use garage_rpc::system::System;
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use garage_rpc::*;
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@ -24,6 +26,11 @@ use crate::schema::*;
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const TABLE_GC_BATCH_SIZE: usize = 1024;
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const TABLE_GC_RPC_TIMEOUT: Duration = Duration::from_secs(30);
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// GC delay for table entries: 1 day (24 hours)
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// (the delay before the entry is added in the GC todo list
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// and the moment the garbage collection actually happens)
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const TABLE_GC_DELAY: Duration = Duration::from_secs(24 * 3600);
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pub(crate) struct TableGc<F: TableSchema + 'static, R: TableReplication + 'static> {
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system: Arc<System>,
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data: Arc<TableData<F, R>>,
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@ -72,35 +79,49 @@ where
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async fn gc_loop(self: Arc<Self>, mut must_exit: watch::Receiver<bool>) {
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while !*must_exit.borrow() {
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match self.gc_loop_iter().await {
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Ok(true) => {
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Ok(None) => {
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// Stuff was done, loop immediately
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continue;
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}
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Ok(false) => {
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// Nothing was done, sleep for some time (below)
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Ok(Some(wait_delay)) => {
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// Nothing was done, wait specified delay.
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select! {
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_ = tokio::time::sleep(wait_delay).fuse() => {},
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_ = must_exit.changed().fuse() => {},
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}
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}
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Err(e) => {
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warn!("({}) Error doing GC: {}", self.data.name, e);
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}
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}
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select! {
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_ = tokio::time::sleep(Duration::from_secs(10)).fuse() => {},
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_ = must_exit.changed().fuse() => {},
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}
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}
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}
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async fn gc_loop_iter(&self) -> Result<bool, Error> {
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async fn gc_loop_iter(&self) -> Result<Option<Duration>, Error> {
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let now = now_msec();
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let mut entries = vec![];
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let mut excluded = vec![];
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// List entries in the GC todo list
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// These entries are put there when a tombstone is inserted in the table
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// This is detected and done in data.rs in update_entry
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// (see update_entry in data.rs)
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for entry_kv in self.data.gc_todo.iter() {
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let (k, vhash) = entry_kv?;
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let mut todo_entry = GcTodoEntry::parse(&k, &vhash);
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if todo_entry.deletion_time() > now {
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if entries.is_empty() && excluded.is_empty() {
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// If the earliest entry in the todo list shouldn't yet be processed,
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// return a duration to wait in the loop
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return Ok(Some(Duration::from_millis(
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todo_entry.deletion_time() - now,
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)));
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} else {
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// Otherwise we have some entries to process, do a normal iteration.
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break;
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}
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}
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let vhash = Hash::try_from(&vhash[..]).unwrap();
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// Check if the tombstone is still the current value of the entry.
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@ -134,8 +155,9 @@ where
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// and for which they are still currently tombstones in the table.
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if entries.is_empty() {
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// Nothing to do in this iteration
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return Ok(false);
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// Nothing to do in this iteration (no entries present)
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// Wait for a default delay of 60 seconds
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return Ok(Some(Duration::from_secs(60)));
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}
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debug!("({}) GC: doing {} items", self.data.name, entries.len());
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@ -181,7 +203,7 @@ where
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}
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if errs.is_empty() {
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Ok(true)
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Ok(None)
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} else {
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Err(Error::Message(
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errs.into_iter()
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@ -189,19 +211,20 @@ where
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.collect::<Vec<_>>()
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.join(", "),
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))
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.err_context("in try_send_and_delete:")
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.err_context("in try_send_and_delete in table GC:")
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}
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}
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async fn try_send_and_delete(
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&self,
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nodes: Vec<Uuid>,
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items: Vec<GcTodoEntry>,
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mut items: Vec<GcTodoEntry>,
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) -> Result<(), Error> {
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let n_items = items.len();
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// Strategy: we first send all of the values to the remote nodes,
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// to ensure that they are aware of the tombstone state.
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// to ensure that they are aware of the tombstone state,
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// and that the previous state was correctly overwritten
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// (if they have a newer state that overrides the tombstone, that's fine).
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// Second, once everyone is at least at the tombstone state,
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// we instruct everyone to delete the tombstone IF that is still their current state.
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@ -209,13 +232,14 @@ where
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// tombstone in the CRDT lattice, and it will be propagated back to us at some point
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// (either just a regular update that hasn't reached us yet, or later when the
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// table is synced).
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// Here, we store in updates all of the tombstones to send for step 1,
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// and in deletes the list of keys and hashes of value for step 2.
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let mut updates = vec![];
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let mut deletes = vec![];
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for item in items {
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updates.push(ByteBuf::from(item.value.unwrap()));
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deletes.push((ByteBuf::from(item.key), item.value_hash));
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for item in items.iter_mut() {
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updates.push(ByteBuf::from(item.value.take().unwrap()));
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deletes.push((ByteBuf::from(item.key.clone()), item.value_hash));
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}
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// Step 1: ensure everyone is at least at tombstone in CRDT lattice
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@ -250,7 +274,7 @@ where
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.try_call_many(
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&self.endpoint,
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&nodes[..],
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GcRpc::DeleteIfEqualHash(deletes.clone()),
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GcRpc::DeleteIfEqualHash(deletes),
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RequestStrategy::with_priority(PRIO_BACKGROUND)
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.with_quorum(nodes.len())
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.with_timeout(TABLE_GC_RPC_TIMEOUT),
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@ -260,24 +284,16 @@ where
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// GC has been successfull for all of these entries.
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// We now remove them all from our local table and from the GC todo list.
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for (k, vhash) in deletes {
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for item in items {
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self.data
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.delete_if_equal_hash(&k[..], vhash)
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.delete_if_equal_hash(&item.key[..], item.value_hash)
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.err_context("GC: local delete tombstones")?;
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self.todo_remove_if_equal(&k[..], vhash)
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item.remove_if_equal(&self.data.gc_todo)
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.err_context("GC: remove from todo list after successfull GC")?;
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}
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Ok(())
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}
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fn todo_remove_if_equal(&self, key: &[u8], vhash: Hash) -> Result<(), Error> {
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let _ = self
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.data
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.gc_todo
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.compare_and_swap::<_, _, Vec<u8>>(key, Some(vhash), None)?;
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Ok(())
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}
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}
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#[async_trait]
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GcRpc::DeleteIfEqualHash(items) => {
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for (key, vhash) in items.iter() {
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self.data.delete_if_equal_hash(&key[..], *vhash)?;
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self.todo_remove_if_equal(&key[..], *vhash)?;
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}
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Ok(GcRpc::Ok)
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}
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/// An entry stored in the gc_todo Sled tree associated with the table
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/// Contains helper function for parsing, saving, and removing
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/// such entry in Sled
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///
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/// Format of an entry:
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/// - key = 8 bytes: timestamp of tombstone
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/// (used to implement GC delay)
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/// n bytes: key in the main data table
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/// - value = hash of the table entry to delete (the tombstone)
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/// for verification purpose, because we don't want to delete
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/// things that aren't tombstones
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pub(crate) struct GcTodoEntry {
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tombstone_timestamp: u64,
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key: Vec<u8>,
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value_hash: Hash,
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value: Option<Vec<u8>>,
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@ -319,6 +343,7 @@ impl GcTodoEntry {
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/// serialized value
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pub(crate) fn new(key: Vec<u8>, value_hash: Hash) -> Self {
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Self {
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tombstone_timestamp: now_msec(),
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key,
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value_hash,
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value: None,
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@ -328,7 +353,8 @@ impl GcTodoEntry {
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/// Parses a GcTodoEntry from a (k, v) pair stored in the gc_todo tree
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pub(crate) fn parse(sled_k: &[u8], sled_v: &[u8]) -> Self {
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Self {
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key: sled_k.to_vec(),
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tombstone_timestamp: u64::from_be_bytes(sled_k[0..8].try_into().unwrap()),
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key: sled_k[8..].to_vec(),
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value_hash: Hash::try_from(sled_v).unwrap(),
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value: None,
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}
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@ -336,7 +362,7 @@ impl GcTodoEntry {
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/// Saves the GcTodoEntry in the gc_todo tree
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pub(crate) fn save(&self, gc_todo_tree: &sled::Tree) -> Result<(), Error> {
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gc_todo_tree.insert(&self.key[..], self.value_hash.as_slice())?;
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gc_todo_tree.insert(self.todo_table_key(), self.value_hash.as_slice())?;
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Ok(())
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}
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@ -347,10 +373,22 @@ impl GcTodoEntry {
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/// what we have to do is still the same
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pub(crate) fn remove_if_equal(&self, gc_todo_tree: &sled::Tree) -> Result<(), Error> {
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let _ = gc_todo_tree.compare_and_swap::<_, _, Vec<u8>>(
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&self.key[..],
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&self.todo_table_key()[..],
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Some(self.value_hash),
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None,
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)?;
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Ok(())
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}
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fn todo_table_key(&self) -> Vec<u8> {
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[
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&u64::to_be_bytes(self.tombstone_timestamp)[..],
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&self.key[..],
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]
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.concat()
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}
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fn deletion_time(&self) -> u64 {
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self.tombstone_timestamp + TABLE_GC_DELAY.as_millis() as u64
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}
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}
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