Example: Use raft engine as wal

examples/single_group_wal.rs

@@ -0,0 +1,58 @@
+// Copyright (c) 2017-present, PingCAP, Inc. Licensed under Apache-2.0.
+
+use raft::eraftpb::Entry;
+use raft_engine::{Config, Engine, LogBatch, MessageExt};
+
+#[derive(Clone)]
+pub struct EntryType;
+
+impl MessageExt for EntryType {
+    type Entry = Entry;
+    fn index(e: &Self::Entry) -> u64 {
+        e.index
+    }
+}
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let dir = "/tmp/raft-wal";
+    let _ = std::fs::remove_dir_all(dir);
+
+    let region_id = 1u64;
+
+    // Open engine
+    let cfg = Config { dir: dir.to_owned(), ..Default::default() };
+    let engine = Engine::open(cfg)?;
+
+    // Write 5 entries
+    let mut entries = Vec::new();
+    for i in 1..=5 {
+        let mut entry = Entry::new();
+        entry.index = i;
+        entry.set_data(format!("data {}", i).into_bytes().into());
+        entries.push(entry);
+    }
+
+    let mut batch = LogBatch::default();
+    batch.add_entries::<EntryType>(region_id, &entries)?;
+    engine.write(&mut batch, true)?;
+
+    println!("Wrote 5 entries");
+
+    // Read them back
+    let mut fetched = Vec::new();
+    engine.fetch_entries_to::<EntryType>(region_id, 1, 6, None, &mut fetched)?;
+
+    for e in &fetched {
+        println!("Read index {}: {}", e.index, String::from_utf8_lossy(e.get_data()));
+    }
+
+    // Write metadata
+    let mut batch = LogBatch::default();
+    batch.put(region_id, b"committed".to_vec(), b"5".to_vec())?;
+    batch.put(region_id, b"applied".to_vec(), b"5".to_vec())?;
+    engine.write(&mut batch, false)?;
+
+    println!("\nWrote metadata");
+
+    Ok(())
+}