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simple.rs
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simple.rs
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use crate::snapshot::{BytesSnapshot, FileSnapshot};
use crate::{Index, MakeSnapshot, RaftApp, SnapshotStream};
use ::bytes::Bytes;
use anyhow::Result;
use async_trait::async_trait;
/// Restricted RaftApp where snapshot is an explicit byte sequence.
#[async_trait]
pub trait RaftAppSimple: Sync + Send + 'static {
async fn process_read(&self, request: &[u8]) -> Result<Vec<u8>>;
async fn process_write(&self, request: &[u8]) -> Result<(Vec<u8>, Option<Vec<u8>>)>;
async fn install_snapshot(&self, snapshot: Option<&[u8]>) -> Result<()>;
async fn fold_snapshot(
&self,
old_snapshot: Option<&[u8]>,
requests: Vec<&[u8]>,
) -> Result<Vec<u8>>;
}
/// The repository of the snapshot resources.
#[async_trait]
pub trait SnapshotRepository: Sync + Send + 'static {
async fn save_snapshot_stream(&self, st: SnapshotStream, snapshot_index: Index) -> Result<()>;
async fn open_snapshot_stream(&self, index: Index) -> Result<SnapshotStream>;
async fn delete_snapshot(&self, index: Index) -> Result<()>;
}
use std::collections::HashMap;
use std::sync::Arc;
use std::sync::RwLock;
/// In-memory implementation of `SnapshotRepository`.
pub struct BytesRepository {
resources: Arc<RwLock<HashMap<Index, BytesSnapshot>>>,
}
impl BytesRepository {
pub fn new() -> Self {
Self {
resources: Arc::new(RwLock::new(HashMap::new())),
}
}
}
#[async_trait]
impl SnapshotRepository for BytesRepository {
async fn save_snapshot_stream(&self, st: SnapshotStream, snapshot_index: Index) -> Result<()> {
let bin = BytesSnapshot::save_snapshot_stream(st).await.unwrap();
self.resources.write().unwrap().insert(snapshot_index, bin);
Ok(())
}
async fn open_snapshot_stream(&self, index: Index) -> Result<SnapshotStream> {
let bin = self.resources.read().unwrap().get(&index).unwrap().clone();
let st = bin.open_snapshot_stream().await;
Ok(st)
}
async fn delete_snapshot(&self, index: Index) -> Result<()> {
self.resources.write().unwrap().remove(&index);
Ok(())
}
}
use std::path::{Path, PathBuf};
/// Persistent implementation of `SnapshotRepository`.
pub struct FileRepository {
root_dir: PathBuf,
}
impl FileRepository {
pub fn destroy(root_dir: &Path) -> Result<()> {
std::fs::remove_dir_all(root_dir).ok();
Ok(())
}
/// Create the initial state.
/// You should call `destory` before calling this function.
pub fn create(root_dir: &Path) -> Result<()> {
std::fs::create_dir(root_dir)?;
Ok(())
}
pub fn open(root_dir: &Path) -> Result<Self> {
Ok(Self {
root_dir: root_dir.to_owned(),
})
}
fn snapshot_path(&self, i: Index) -> PathBuf {
self.root_dir.join(format!("{}", i))
}
}
#[async_trait]
impl SnapshotRepository for FileRepository {
async fn save_snapshot_stream(&self, st: SnapshotStream, snapshot_index: Index) -> Result<()> {
let path = self.snapshot_path(snapshot_index);
FileSnapshot::save_snapshot_stream(st, &path).await?;
Ok(())
}
async fn open_snapshot_stream(&self, index: Index) -> Result<SnapshotStream> {
let path = self.snapshot_path(index);
let snap = FileSnapshot { path };
snap.open_snapshot_stream().await
}
async fn delete_snapshot(&self, index: Index) -> Result<()> {
let path = self.snapshot_path(index);
tokio::fs::remove_file(&path).await.ok();
Ok(())
}
}
#[cfg(test)]
mod tests {
use super::*;
use serial_test::serial;
#[test]
#[serial]
fn test_file_repository() {
let path = Path::new("/tmp/lol-test-file-repo");
FileRepository::destroy(&path).unwrap();
FileRepository::create(&path).unwrap();
}
}
/// ToRaftApp turns an instance of RaftAppSimple into
/// a RaftApp instance.
pub struct ToRaftApp {
app: Box<dyn RaftAppSimple>,
repo: Box<dyn SnapshotRepository>,
}
impl ToRaftApp {
pub fn new(app: impl RaftAppSimple, store: impl SnapshotRepository) -> Self {
Self {
app: Box::new(app),
repo: Box::new(store),
}
}
async fn save_snapshot(&self, bin: Bytes, idx: Index) -> Result<()> {
let bin = BytesSnapshot { contents: bin };
let inp = bin.open_snapshot_stream().await;
self.repo.save_snapshot_stream(inp, idx).await
}
async fn get_snapshot(&self, idx: Index) -> Result<Bytes> {
let st = self.repo.open_snapshot_stream(idx).await?;
let bin = BytesSnapshot::save_snapshot_stream(st).await?;
Ok(bin.contents)
}
}
#[async_trait]
impl RaftApp for ToRaftApp {
async fn process_read(&self, request: &[u8]) -> Result<Vec<u8>> {
self.app.process_read(request).await
}
async fn process_write(
&self,
request: &[u8],
entry_index: Index,
) -> Result<(Vec<u8>, MakeSnapshot)> {
let (res, new_snapshot) = self.app.process_write(request).await?;
let make_snapshot = match new_snapshot {
Some(x) => {
let ok = self.save_snapshot(x.into(), entry_index).await.is_ok();
if ok {
MakeSnapshot::CopySnapshot
} else {
MakeSnapshot::None
}
}
None => MakeSnapshot::None,
};
Ok((res, make_snapshot))
}
async fn install_snapshot(&self, snapshot: Option<Index>) -> Result<()> {
let snapshot = match snapshot {
Some(idx) => Some(self.get_snapshot(idx).await?),
None => None,
};
self.app.install_snapshot(snapshot.as_deref()).await
}
async fn fold_snapshot(
&self,
old_snapshot: Option<Index>,
requests: Vec<&[u8]>,
snapshot_index: Index,
) -> Result<()> {
let old_snapshot = match old_snapshot {
Some(idx) => Some(self.get_snapshot(idx).await?),
None => None,
};
let new_snapshot = self
.app
.fold_snapshot(old_snapshot.as_deref(), requests)
.await?;
self.save_snapshot(new_snapshot.into(), snapshot_index)
.await
}
async fn save_snapshot(&self, st: SnapshotStream, idx: Index) -> Result<()> {
let b = BytesSnapshot::save_snapshot_stream(st).await?;
self.save_snapshot(b.contents, idx).await
}
async fn open_snapshot(&self, x: Index) -> Result<SnapshotStream> {
self.repo.open_snapshot_stream(x).await
}
async fn delete_snapshot(&self, idx: Index) -> Result<()> {
self.repo.delete_snapshot(idx).await
}
}