risingwave_storage/hummock/
time_travel_version_cache.rs

1// Copyright 2025 RisingWave Labs
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15use std::future::Future;
16use std::pin::Pin;
17
18use futures::FutureExt;
19use futures::future::Shared;
20use moka::sync::Cache;
21use risingwave_hummock_sdk::HummockEpoch;
22
23use crate::hummock::HummockResult;
24use crate::hummock::local_version::pinned_version::PinnedVersion;
25
26type InflightResult = Shared<Pin<Box<dyn Future<Output = HummockResult<PinnedVersion>> + Send>>>;
27
28/// A naive cache to reduce number of RPC sent to meta node.
29pub struct SimpleTimeTravelVersionCache {
30    cache: Cache<(u32, HummockEpoch), InflightResult>,
31}
32
33impl SimpleTimeTravelVersionCache {
34    pub fn new(capacity: u64) -> Self {
35        let cache = Cache::builder().max_capacity(capacity).build();
36        Self { cache }
37    }
38
39    pub async fn get_or_insert(
40        &self,
41        table_id: u32,
42        epoch: HummockEpoch,
43        fetch: impl Future<Output = HummockResult<PinnedVersion>> + Send + 'static,
44    ) -> HummockResult<PinnedVersion> {
45        self.cache
46            .entry((table_id, epoch))
47            .or_insert_with_if(
48                || fetch.boxed().shared(),
49                |inflight| {
50                    if let Some(result) = inflight.peek() {
51                        return result.is_err();
52                    }
53                    false
54                },
55            )
56            .value()
57            .clone()
58            .await
59    }
60}
risingwave_storage/hummock/time_travel_version_cache.rs

risingwave_storage/hummock/
time_travel_version_cache.rs
