finish compaction

Signed-off-by: Alex Chi <iskyzh@gmail.com>

.gitignore

@@ -1,3 +1,4 @@
 /target
 .vscode/
 sync-tmp/
+mini-lsm.db/

Cargo.lock

@@ -203,11 +203,10 @@ dependencies = [
 
 [[package]]
 name = "crossbeam-channel"
-version = "0.5.6"
+version = "0.5.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c2dd04ddaf88237dc3b8d8f9a3c1004b506b54b3313403944054d23c0870c521"
+checksum = "176dc175b78f56c0f321911d9c8eb2b77a78a4860b9c19db83835fea1a46649b"
 dependencies = [
- "cfg-if",
  "crossbeam-utils",
 ]
 
@@ -238,12 +237,9 @@ dependencies = [
 
 [[package]]
 name = "crossbeam-utils"
-version = "0.8.14"
+version = "0.8.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4fb766fa798726286dbbb842f174001dab8abc7b627a1dd86e0b7222a95d929f"
-dependencies = [
- "cfg-if",
-]
+checksum = "248e3bacc7dc6baa3b21e405ee045c3047101a49145e7e9eca583ab4c2ca5345"
 
 [[package]]
 name = "duct"
@@ -400,6 +396,7 @@ dependencies = [
  "arc-swap",
  "bytes",
  "clap",
+ "crossbeam-channel",
  "crossbeam-epoch",
  "crossbeam-skiplist",
  "moka",

README.md

@@ -43,12 +43,13 @@ We are working on a new version of the mini-lsm tutorial that is split into 3 we
 | 1.4            | Merge Iterators                                 | ✅        | ✅            | ✅       |
 | 1.5            | Storage Engine - Read Path                      | ✅        | ✅            | ✅       |
 | 1.6            | Storage Engine - Write Path                     | ✅        | ✅            | ✅       |
-| 2.1            | Compaction - Get Started                        | ✅        | 🚧            | 🚧       |
-| 2.2            | Compaction Strategy - Tiered                    | ✅        |              |         |
-| 2.3            | Compaction Strategy - Leveled                   | ✅        |              |         |
-| 2.4            | Manifest                                        |          |              |         |
-| 2.5            | Write-Ahead Log                                 |          |              |         |
-| 2.6            | Bloom Filter and Key Compression                |          |              |         |
+| 1.7            | Bloom Filter and Key Compression                |          |              |         |
+| 2.1            | Compaction Introduction                         | ✅        | 🚧            | 🚧       |
+| 2.2            | Compaction Strategy - Simple                    | ✅        | 🚧            | 🚧       |
+| 2.3            | Compaction Strategy - Tiered                    | ✅        |              |         |
+| 2.4            | Compaction Strategy - Leveled                   | ✅        |              |         |
+| 2.5            | Manifest                                        |          |              |         |
+| 2.6            | Write-Ahead Log                                 |          |              |         |
 | 3.1            | Timestamp Encoding + Prefix Bloom Filter        |          |              |         |
 | 3.2            | Snapshot Read                                   |          |              |         |
 | 3.3            | Watermark and Garbage Collection                |          |              |         |

mini-lsm/Cargo.toml

@@ -19,6 +19,7 @@ ouroboros = "0.15"
 moka = "0.9"
 clap = { version = "4.4.17", features = ["derive"] }
 rand = "0.8.5"
+crossbeam-channel = "0.5.11"
 
 [dev-dependencies]
 tempfile = "3"

mini-lsm/src/bin/compaction_simulator.rs

@@ -323,7 +323,7 @@ fn main() {
             iterations,
         } => {
             let controller = TieredCompactionController::new(TieredCompactionOptions {
-                level0_file_num_compaction_trigger,
+                num_tiers: level0_file_num_compaction_trigger,
                 max_size_amplification_percent,
                 size_ratio,
                 min_merge_width,

mini-lsm/src/bin/minilsm_cli.rs

@@ -0,0 +1,62 @@
+use std::time::Duration;
+
+use anyhow::Result;
+use mini_lsm::compact::{CompactionOptions, SimpleLeveledCompactionOptions};
+use mini_lsm::lsm_storage::{LsmStorageOptions, MiniLsm};
+
+fn main() -> Result<()> {
+    let lsm = MiniLsm::open(
+        "mini-lsm.db",
+        LsmStorageOptions {
+            block_size: 4096,
+            target_sst_size: 2 << 20,
+            compaction_options: CompactionOptions::Simple(SimpleLeveledCompactionOptions {
+                size_ratio_percent: 200,
+                level0_file_num_compaction_trigger: 2,
+                max_levels: 4,
+            }),
+        },
+    )?;
+    let mut epoch = 0;
+    loop {
+        let mut line = String::new();
+        std::io::stdin().read_line(&mut line)?;
+        let line = line.trim().to_string();
+        if line.starts_with("fill ") {
+            let Some((_, options)) = line.split_once(' ') else {
+                println!("invalid command");
+                continue;
+            };
+            let Some((begin, end)) = options.split_once(' ') else {
+                println!("invalid command");
+                continue;
+            };
+            let begin = begin.parse::<u64>()?;
+            let end = end.parse::<u64>()?;
+
+            for i in begin..=end {
+                lsm.put(
+                    format!("{}", i).as_bytes(),
+                    format!("value{}@{}", i, epoch).as_bytes(),
+                )?;
+            }
+
+            println!("{} values filled with epoch {}", end - begin + 1, epoch);
+        } else if line.starts_with("get ") {
+            let Some((_, key)) = line.split_once(' ') else {
+                println!("invalid command");
+                continue;
+            };
+            if let Some(value) = lsm.get(key.as_bytes())? {
+                println!("{}={:?}", key, value);
+            } else {
+                println!("{} not exist", key);
+            }
+        } else if line == "flush" {
+            lsm.force_flush_imm_memtables()?;
+        } else {
+            println!("invalid command: {}", line);
+        }
+        epoch += 1;
+    }
+}

mini-lsm/src/compact.rs

@@ -3,6 +3,7 @@ mod simple_leveled;
 mod tiered;
 
 use std::sync::Arc;
+use std::time::Duration;
 
 use anyhow::Result;
 pub use leveled::{LeveledCompactionController, LeveledCompactionOptions, LeveledCompactionTask};
@@ -13,18 +14,25 @@ pub use tiered::{TieredCompactionController, TieredCompactionOptions, TieredComp
 
 use crate::iterators::merge_iterator::MergeIterator;
 use crate::iterators::StorageIterator;
-use crate::lsm_storage::LsmStorageInner;
+use crate::lsm_storage::{LsmStorageInner, LsmStorageState};
 use crate::table::{SsTable, SsTableBuilder, SsTableIterator};
 
 pub(crate) enum CompactionTask {
     Leveled(LeveledCompactionTask),
     Tiered(TieredCompactionTask),
     Simple(SimpleLeveledCompactionTask),
+    ForceFullCompaction(Vec<usize>),
 }
 
-struct CompactOptions {
-    block_size: usize,
-    target_sst_size: usize,
+impl CompactionTask {
+    fn compact_to_bottom_level(&self) -> bool {
+        match self {
+            CompactionTask::ForceFullCompaction(_) => true,
+            CompactionTask::Leveled(task) => task.is_lower_level_bottom_level,
+            CompactionTask::Simple(task) => task.is_lower_level_bottom_level,
+            CompactionTask::Tiered(task) => task.bottom_tier_included,
+        }
+    }
 }
 
 pub(crate) enum CompactionController {
@@ -34,6 +42,43 @@ pub(crate) enum CompactionController {
     NoCompaction,
 }
 
+impl CompactionController {
+    fn generate_compaction_task(&self, snapshot: &LsmStorageState) -> Option<CompactionTask> {
+        match self {
+            CompactionController::Leveled(ctrl) => ctrl
+                .generate_compaction_task(&snapshot)
+                .map(CompactionTask::Leveled),
+            CompactionController::Simple(ctrl) => ctrl
+                .generate_compaction_task(&snapshot)
+                .map(CompactionTask::Simple),
+            CompactionController::Tiered(ctrl) => ctrl
+                .generate_compaction_task(&snapshot)
+                .map(CompactionTask::Tiered),
+            CompactionController::NoCompaction => unreachable!(),
+        }
+    }
+
+    fn apply_compaction_result(
+        &self,
+        snapshot: &LsmStorageState,
+        task: &CompactionTask,
+        output: &[usize],
+    ) -> (LsmStorageState, Vec<usize>) {
+        match (self, task) {
+            (CompactionController::Leveled(ctrl), CompactionTask::Leveled(task)) => {
+                ctrl.apply_compaction_result(&snapshot, task, output)
+            }
+            (CompactionController::Simple(ctrl), CompactionTask::Simple(task)) => {
+                ctrl.apply_compaction_result(&snapshot, task, output)
+            }
+            (CompactionController::Tiered(ctrl), CompactionTask::Tiered(task)) => {
+                ctrl.apply_compaction_result(&snapshot, task, output)
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+
 impl CompactionController {
     pub fn flush_to_l0(&self) -> bool {
         if let Self::Leveled(_) | Self::Simple(_) | Self::NoCompaction = self {
@@ -57,12 +102,37 @@ pub enum CompactionOptions {
 }
 
 impl LsmStorageInner {
-    #[allow(dead_code)]
-    fn compact(
-        &self,
-        tables: Vec<Arc<SsTable>>,
-        options: CompactOptions,
-    ) -> Result<Vec<Arc<SsTable>>> {
+    fn compact(&self, task: &CompactionTask) -> Result<Vec<Arc<SsTable>>> {
+        let table_ids = match task {
+            CompactionTask::Leveled(task) => task
+                .lower_level_sst_ids
+                .iter()
+                .copied()
+                .chain(task.upper_level_sst_ids.iter().copied())
+                .collect::<Vec<_>>(),
+            CompactionTask::Simple(task) => task
+                .lower_level_sst_ids
+                .iter()
+                .copied()
+                .chain(task.upper_level_sst_ids.iter().copied())
+                .collect::<Vec<_>>(),
+            CompactionTask::Tiered(task) => task
+                .tiers
+                .iter()
+                .map(|(_, files)| files)
+                .flatten()
+                .copied()
+                .collect::<Vec<_>>(),
+            CompactionTask::ForceFullCompaction(l0_ssts) => l0_ssts.clone(),
+        };
+        let tables: Vec<Arc<SsTable>> = {
+            let state = self.state.read();
+            table_ids
+                .iter()
+                .map(|id| state.sstables.get(id).unwrap().clone())
+                .collect::<Vec<_>>()
+        };
+
         let mut iters = Vec::new();
         iters.reserve(tables.len());
         for table in tables.iter() {
@@ -75,11 +145,11 @@ impl LsmStorageInner {
         let mut builder = None;
         let mut new_sst = vec![];
 
-        let compact_to_bottom_level = false;
+        let compact_to_bottom_level = task.compact_to_bottom_level();
 
         while iter.is_valid() {
             if builder.is_none() {
-                builder = Some(SsTableBuilder::new(options.block_size));
+                builder = Some(SsTableBuilder::new(self.options.block_size));
             }
             let builder_inner = builder.as_mut().unwrap();
             if compact_to_bottom_level {
@@ -91,7 +161,7 @@ impl LsmStorageInner {
             }
             iter.next()?;
 
-            if builder_inner.estimated_size() >= options.target_sst_size {
+            if builder_inner.estimated_size() >= self.options.target_sst_size {
                 let sst_id = self.next_sst_id(); // lock dropped here
                 let builder = builder.take().unwrap();
                 let sst = Arc::new(builder.build(
@@ -114,10 +184,67 @@ impl LsmStorageInner {
         Ok(new_sst)
     }
 
+    fn trigger_compaction(&self) -> Result<()> {
+        let snapshot = {
+            let state = self.state.read();
+            state.clone()
+        };
+        let task = self
+            .compaction_controller
+            .generate_compaction_task(&snapshot);
+        let Some(task) = task else {
+            return Ok(());
+        };
+        println!("running compaction task");
+        let sstables = self.compact(&task)?;
+        let output = sstables.iter().map(|x| x.sst_id()).collect::<Vec<_>>();
+        let ssts_to_remove = {
+            let _state_lock = self.state_lock.lock();
+            let (mut snapshot, files_to_remove) = self
+                .compaction_controller
+                .apply_compaction_result(&self.state.read(), &task, &output);
+            let mut ssts_to_remove = Vec::with_capacity(files_to_remove.len());
+            for file_to_remove in &files_to_remove {
+                let result = snapshot.sstables.remove(file_to_remove);
+                assert!(result.is_some());
+                ssts_to_remove.push(result.unwrap());
+            }
+            for file_to_add in sstables {
+                let result = snapshot.sstables.insert(file_to_add.sst_id(), file_to_add);
+                assert!(result.is_none());
+            }
+            let mut state = self.state.write();
+            *state = Arc::new(snapshot);
+            ssts_to_remove
+        };
+        for sst in ssts_to_remove {
+            std::fs::remove_file(self.path_of_sst(sst.sst_id()))?;
+        }
+        Ok(())
+    }
+
     pub(crate) fn spawn_compaction_thread(
         self: &Arc<Self>,
-        rx: std::sync::mpsc::Receiver<()>,
+        rx: crossbeam_channel::Receiver<()>,
     ) -> Result<Option<std::thread::JoinHandle<()>>> {
+        if let CompactionOptions::Leveled(_)
+        | CompactionOptions::Simple(_)
+        | CompactionOptions::Tiered(_) = self.options.compaction_options
+        {
+            let this = self.clone();
+            let handle = std::thread::spawn(move || {
+                let ticker = crossbeam_channel::tick(Duration::from_millis(50));
+                loop {
+                    crossbeam_channel::select! {
+                        recv(ticker) -> _ => if let Err(e) = this.trigger_compaction() {
+                            eprintln!("compaction failed: {}", e);
+                        },
+                        recv(rx) -> _ => return
+                    }
+                }
+            });
+            return Ok(Some(handle));
+        }
         Ok(None)
     }
 }

mini-lsm/src/compact/leveled.rs

@@ -8,6 +8,7 @@ pub struct LeveledCompactionTask {
     pub upper_level_sst_ids: Vec<usize>,
     pub lower_level: usize,
     pub lower_level_sst_ids: Vec<usize>,
+    pub is_lower_level_bottom_level: bool,
 }
 
 #[derive(Debug, Clone)]
@@ -115,6 +116,7 @@ impl LeveledCompactionController {
                     &snapshot.l0_sstables,
                     base_level,
                 ),
+                is_lower_level_bottom_level: base_level == self.options.max_levels,
             });
         }
 
@@ -143,6 +145,7 @@ impl LeveledCompactionController {
                     &[selected_sst],
                     level + 1,
                 ),
+                is_lower_level_bottom_level: level + 1 == self.options.max_levels,
             });
         }
         None

mini-lsm/src/compact/simple_leveled.rs

@@ -13,6 +13,7 @@ pub struct SimpleLeveledCompactionTask {
     pub upper_level_sst_ids: Vec<usize>,
     pub lower_level: usize,
     pub lower_level_sst_ids: Vec<usize>,
+    pub is_lower_level_bottom_level: bool,
 }
 
 pub struct SimpleLeveledCompactionController {
@@ -57,6 +58,7 @@ impl SimpleLeveledCompactionController {
                     },
                     lower_level,
                     lower_level_sst_ids: snapshot.levels[lower_level - 1].1.clone(),
+                    is_lower_level_bottom_level: lower_level == self.options.max_levels,
                 });
             }
         }

mini-lsm/src/compact/tiered.rs

@@ -4,11 +4,12 @@ use crate::lsm_storage::LsmStorageState;
 
 pub struct TieredCompactionTask {
     pub tiers: Vec<(usize, Vec<usize>)>,
+    pub bottom_tier_included: bool,
 }
 
 #[derive(Debug, Clone)]
 pub struct TieredCompactionOptions {
-    pub level0_file_num_compaction_trigger: usize,
+    pub num_tiers: usize,
     pub max_size_amplification_percent: usize,
     pub size_ratio: usize,
     pub min_merge_width: usize,
@@ -31,7 +32,7 @@ impl TieredCompactionController {
             snapshot.l0_sstables.is_empty(),
             "should not add l0 ssts in tiered compaction"
         );
-        if snapshot.levels.len() < self.options.level0_file_num_compaction_trigger {
+        if snapshot.levels.len() < self.options.num_tiers {
             return None;
         }
         // compaction triggered by space amplification ratio
@@ -48,6 +49,7 @@ impl TieredCompactionController {
             );
             return Some(TieredCompactionTask {
                 tiers: snapshot.levels.clone(),
+                bottom_tier_included: true,
             });
         }
         let size_ratio_trigger = (100.0 + self.options.size_ratio as f64) / 100.0;
@@ -69,12 +71,12 @@ impl TieredCompactionController {
                         .take(id + 2)
                         .cloned()
                         .collect::<Vec<_>>(),
+                    bottom_tier_included: id + 2 >= snapshot.levels.len(),
                 });
             }
         }
         // trying to reduce sorted runs without respecting size ratio
-        let num_tiers_to_take =
-            snapshot.levels.len() - self.options.level0_file_num_compaction_trigger + 2;
+        let num_tiers_to_take = snapshot.levels.len() - self.options.num_tiers + 2;
         println!("compaction triggered by reducing sorted runs");
         return Some(TieredCompactionTask {
             tiers: snapshot
@@ -83,6 +85,7 @@ impl TieredCompactionController {
                 .take(num_tiers_to_take)
                 .cloned()
                 .collect::<Vec<_>>(),
+            bottom_tier_included: snapshot.levels.len() >= num_tiers_to_take,
         });
     }
 

mini-lsm/src/lsm_storage.rs

@@ -64,9 +64,9 @@ impl LsmStorageState {
 }
 
 pub struct LsmStorageOptions {
-    block_size: usize,
-    target_sst_size: usize,
-    compaction_options: CompactionOptions,
+    pub block_size: usize,
+    pub target_sst_size: usize,
+    pub compaction_options: CompactionOptions,
 }
 
 impl LsmStorageOptions {
@@ -82,17 +82,17 @@ impl LsmStorageOptions {
 /// The storage interface of the LSM tree.
 pub(crate) struct LsmStorageInner {
     pub(crate) state: Arc<RwLock<Arc<LsmStorageState>>>,
-    state_lock: Mutex<()>,
+    pub(crate) state_lock: Mutex<()>,
     path: PathBuf,
     pub(crate) block_cache: Arc<BlockCache>,
     next_sst_id: AtomicUsize,
-    options: Arc<LsmStorageOptions>,
-    compaction_controller: CompactionController,
+    pub(crate) options: Arc<LsmStorageOptions>,
+    pub(crate) compaction_controller: CompactionController,
 }
 
 pub struct MiniLsm {
     inner: Arc<LsmStorageInner>,
-    compaction_notifier: std::sync::mpsc::Sender<()>,
+    compaction_notifier: crossbeam_channel::Sender<()>,
     compaction_thread: Mutex<Option<std::thread::JoinHandle<()>>>,
 }
 
@@ -116,7 +116,7 @@ impl MiniLsm {
 
     pub fn open(path: impl AsRef<Path>, options: LsmStorageOptions) -> Result<Arc<Self>> {
         let inner = Arc::new(LsmStorageInner::open(path, options)?);
-        let (tx, rx) = std::sync::mpsc::channel();
+        let (tx, rx) = crossbeam_channel::unbounded();
         let compaction_thread = inner.spawn_compaction_thread(rx)?;
         Ok(Arc::new(Self {
             inner,
@@ -144,6 +144,10 @@ impl MiniLsm {
     ) -> Result<FusedIterator<LsmIterator>> {
         self.inner.scan(lower, upper)
     }
+
+    pub fn force_flush_imm_memtables(&self) -> Result<()> {
+        self.inner.force_flush_imm_memtables()
+    }
 }
 
 impl LsmStorageInner {
@@ -153,10 +157,14 @@ impl LsmStorageInner {
     }
 
     pub(crate) fn open(path: impl AsRef<Path>, options: LsmStorageOptions) -> Result<Self> {
+        let path = path.as_ref();
+        if !path.exists() {
+            std::fs::create_dir_all(path)?;
+        }
         Ok(Self {
             state: Arc::new(RwLock::new(Arc::new(LsmStorageState::create(&options)))),
             state_lock: Mutex::new(()),
-            path: path.as_ref().to_path_buf(),
+            path: path.to_path_buf(),
             block_cache: Arc::new(BlockCache::new(1 << 20)), // 4GB block cache,
             next_sst_id: AtomicUsize::new(1),
             compaction_controller: match &options.compaction_options {
@@ -291,6 +299,7 @@ impl LsmStorageInner {
                 // In tiered compaction, create a new tier
                 snapshot.levels.insert(0, (sst_id, vec![sst_id]));
             }
+            println!("flushed {}.sst with size={}", sst_id, sst.table_size());
             snapshot.sstables.insert(sst_id, sst);
             // Update the snapshot.
             *guard = Arc::new(snapshot);

mini-lsm/src/table.rs

@@ -37,7 +37,7 @@ impl BlockMeta {
             // The size of key length
             estimated_size += std::mem::size_of::<u16>();
             // The size of actual key
-            estimated_size += meta.first_key.len();
+            estimated_size += meta.last_key.len();
         }
         // Reserve the space to improve performance, especially when the size of incoming data is
         // large