1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147

use async_stream::try_stream;
use futures::stream::BoxStream;
use lru::LruCache;
use nix_compat::nixbase32;
use std::num::NonZeroUsize;
use std::sync::Arc;
use tokio::sync::RwLock;
use tonic::async_trait;
use tracing::instrument;

use tvix_castore::composition::{CompositionContext, ServiceBuilder};
use tvix_castore::Error;

use super::{PathInfo, PathInfoService};

pub struct LruPathInfoService {
    instance_name: String,
    lru: Arc<RwLock<LruCache<[u8; 20], PathInfo>>>,
}

impl LruPathInfoService {
    pub fn with_capacity(instance_name: String, capacity: NonZeroUsize) -> Self {
        Self {
            instance_name,
            lru: Arc::new(RwLock::new(LruCache::new(capacity))),
        }
    }
}

#[async_trait]
impl PathInfoService for LruPathInfoService {
    #[instrument(level = "trace", skip_all, fields(path_info.digest = nixbase32::encode(&digest), instance_name = %self.instance_name))]
    async fn get(&self, digest: [u8; 20]) -> Result<Option<PathInfo>, Error> {
        Ok(self.lru.write().await.get(&digest).cloned())
    }

    #[instrument(level = "trace", skip_all, fields(path_info.root_node = ?path_info.node, instance_name = %self.instance_name))]
    async fn put(&self, path_info: PathInfo) -> Result<PathInfo, Error> {
        self.lru
            .write()
            .await
            .put(*path_info.store_path.digest(), path_info.clone());

        Ok(path_info)
    }

    fn list(&self) -> BoxStream<'static, Result<PathInfo, Error>> {
        let lru = self.lru.clone();
        Box::pin(try_stream! {
            let lru = lru.read().await;
            let it = lru.iter();

            for (_k,v) in it {
                yield v.clone()
            }
        })
    }
}

#[derive(serde::Deserialize, Debug)]
#[serde(deny_unknown_fields)]
pub struct LruPathInfoServiceConfig {
    capacity: NonZeroUsize,
}

impl TryFrom<url::Url> for LruPathInfoServiceConfig {
    type Error = Box<dyn std::error::Error + Send + Sync>;
    fn try_from(_url: url::Url) -> Result<Self, Self::Error> {
        Err(Error::StorageError(
            "Instantiating a LruPathInfoService from a url is not supported".into(),
        )
        .into())
    }
}

#[async_trait]
impl ServiceBuilder for LruPathInfoServiceConfig {
    type Output = dyn PathInfoService;
    async fn build<'a>(
        &'a self,
        instance_name: &str,
        _context: &CompositionContext,
    ) -> Result<Arc<dyn PathInfoService>, Box<dyn std::error::Error + Send + Sync + 'static>> {
        Ok(Arc::new(LruPathInfoService::with_capacity(
            instance_name.to_string(),
            self.capacity,
        )))
    }
}

#[cfg(test)]
mod test {
    use nix_compat::store_path::StorePath;
    use std::{num::NonZeroUsize, sync::LazyLock};

    use crate::{
        pathinfoservice::{LruPathInfoService, PathInfo, PathInfoService},
        tests::fixtures::PATH_INFO,
    };
    static PATHINFO_2: LazyLock<PathInfo> = LazyLock::new(|| {
        let mut p = PATH_INFO.clone();
        p.store_path = StorePath::from_name_and_digest_fixed("dummy", [1; 20]).unwrap();
        p
    });

    static PATHINFO_2_DIGEST: LazyLock<[u8; 20]> =
        LazyLock::new(|| *PATHINFO_2.store_path.digest());

    #[tokio::test]
    async fn evict() {
        let svc = LruPathInfoService::with_capacity("test".into(), NonZeroUsize::new(1).unwrap());

        // pathinfo_1 should not be there
        assert!(svc
            .get(*PATH_INFO.store_path.digest())
            .await
            .expect("no error")
            .is_none());

        // insert it
        svc.put(PATH_INFO.clone()).await.expect("no error");

        // now it should be there.
        assert_eq!(
            Some(PATH_INFO.clone()),
            svc.get(*PATH_INFO.store_path.digest())
                .await
                .expect("no error")
        );

        // insert pathinfo_2. This will evict pathinfo 1
        svc.put(PATHINFO_2.clone()).await.expect("no error");

        // now pathinfo 2 should be there.
        assert_eq!(
            Some(PATHINFO_2.clone()),
            svc.get(*PATHINFO_2_DIGEST).await.expect("no error")
        );

        // … but pathinfo 1 not anymore.
        assert!(svc
            .get(*PATH_INFO.store_path.digest())
            .await
            .expect("no error")
            .is_none());
    }
}