lib.rs:

简单的模块化预写日志实现。

示例

use growthring::{WALStoreAIO, wal::WALLoader};
use futures::executor::block_on;
let mut loader = WALLoader::new();
loader.file_nbit(9).block_nbit(8);


// Start with empty WAL (truncate = true).
let store = WALStoreAIO::new("./walfiles", true, None, None).unwrap();
let mut wal = block_on(loader.load(store, |_, _| {Ok(())}, 0)).unwrap();
// Write a vector of records to WAL.
for f in wal.grow(vec!["record1(foo)", "record2(bar)", "record3(foobar)"]).into_iter() {
    let ring_id = block_on(f).unwrap().1;
    println!("WAL recorded record to {:?}", ring_id);
}


// Load from WAL (truncate = false).
let store = WALStoreAIO::new("./walfiles", false, None, None).unwrap();
let mut wal = block_on(loader.load(store, |payload, ringid| {
    // redo the operations in your application
    println!("recover(payload={}, ringid={:?})",
             std::str::from_utf8(&payload).unwrap(),
             ringid);
    Ok(())
}, 0)).unwrap();
// We saw some log playback, even there is no failure.
// Let's try to grow the WAL to create many files.
let ring_ids = wal.grow((1..100).into_iter().map(|i| "a".repeat(i)).collect::<Vec<_>>())
                  .into_iter().map(|f| block_on(f).unwrap().1).collect::<Vec<_>>();
// Then assume all these records are not longer needed. We can tell WALWriter by the `peel`
// method.
block_on(wal.peel(ring_ids, 0)).unwrap();
// There will only be one remaining file in ./walfiles.

let store = WALStoreAIO::new("./walfiles", false, None, None).unwrap();
let wal = block_on(loader.load(store, |payload, _| {
    println!("payload.len() = {}", payload.len());
    Ok(())
}, 0)).unwrap();
// After each recovery, the ./walfiles is empty.