Bug in `moka::future::Cache::invalidate_all`? Elements not being invalidated immediatelly.

[moka-rs]

Bug in `moka::future::Cache::invalidate_all`? Elements not being invalidated immediatelly.

[tatsuya6502]

Thank you for reporting the bug. I was aware of it when I implemented invalidate_all function, but I have never had a chance to fix it and then forgot.

I fixed the bug with #156, and will release Moka v0.8.6 after I finish running a pre-release testing.

The root cause of the bug was that a cache entry's last_modified timestamp was not set to the current time when it was inserted to the cache. Instead, it was set to the time when the cache entry was properly admitted to the cache by a background thread called "housekeeper".

Because of this, invalidate_all function was unable to invalidate cache entries inserted just before calling invalidate_all.

You can confirm this behavior by modifying your reproducer code as the followings:

#[tokio::test]
async fn invalidate_all_without_sync() {
    let cache = Cache::new(1024);

    assert_eq!(cache.get(&0), None);
    cache.insert(0, 1).await;
    assert_eq!(cache.get(&0), Some(1));

    // In Moka v0.8.5 or earlier, you can workaround the issue
    // by doing one of the followings:
    // 
    // - Call `cache.sync()` before invalidating.
    //     - `cache.sync()` will run pending housekeeping task,
    //        so the entry's `last_modified` will be set to the
    //        current time.
    // - Or, wait some time for the housekeeping task to run.

    // Note that `cache.sync()` can be a heavy operation so it is
    // not recommended to call it very often.
    use moka::sync::ConcurrentCacheExt;
    cache.sync();

    // The housekeeping task will run ~0.5 seconds after the cache
    // creation. Then it will run with ~0.3 seconds interval if the
    // cache is not receiving heavy writes.
    // 
    // tokio::time::sleep(Duration::from_millis(520)).await;

    cache.invalidate_all();
    assert_eq!(cache.get(&0), None);
}

With the next release Moka v0.8.6 (that has the fix), you do not have to do the above workaround. I will let you know when I publish v0.8.6 to crates.io.

[tatsuya6502]

Hi @bsdinis. I have published Moka v0.8.6 to crates.io with the fix. Thanks!

[bsdinis]

Thanks so much!