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

/* -------------------------------------------------------------------------- *\
 *          Apache 2.0 License Copyright © 2022-2023 The Aurae Authors        *
 *                                                                            *
 *                +--------------------------------------------+              *
 *                |   █████╗ ██╗   ██╗██████╗  █████╗ ███████╗ |              *
 *                |  ██╔══██╗██║   ██║██╔══██╗██╔══██╗██╔════╝ |              *
 *                |  ███████║██║   ██║██████╔╝███████║█████╗   |              *
 *                |  ██╔══██║██║   ██║██╔══██╗██╔══██║██╔══╝   |              *
 *                |  ██║  ██║╚██████╔╝██║  ██║██║  ██║███████╗ |              *
 *                |  ╚═╝  ╚═╝ ╚═════╝ ╚═╝  ╚═╝╚═╝  ╚═╝╚══════╝ |              *
 *                +--------------------------------------------+              *
 *                                                                            *
 *                         Distributed Systems Runtime                        *
 *                                                                            *
 * -------------------------------------------------------------------------- *
 *                                                                            *
 *   Licensed under the Apache License, Version 2.0 (the "License");          *
 *   you may not use this file except in compliance with the License.         *
 *   You may obtain a copy of the License at                                  *
 *                                                                            *
 *       http://www.apache.org/licenses/LICENSE-2.0                           *
 *                                                                            *
 *   Unless required by applicable law or agreed to in writing, software      *
 *   distributed under the License is distributed on an "AS IS" BASIS,        *
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. *
 *   See the License for the specific language governing permissions and      *
 *   limitations under the License.                                           *
 *                                                                            *
\* -------------------------------------------------------------------------- */
use std::collections::HashMap;
use std::ffi::OsString;
use tracing::warn;
use walkdir::DirEntryExt;
use walkdir::WalkDir;

/// Cache that is used for looking up cgroup paths by inode number.
///
/// TODO (jeroensoeters) maybe change this to an LRU cache in the future? Also
/// we should think if inode wraparound is a potential issue. We could look at
/// how the Linux inode cache is implemented:
/// https://elixir.bootlin.com/linux/latest/source/fs/inode.c
#[derive(Debug)]
pub(crate) struct CgroupCache {
    root: OsString,
    cache: HashMap<u64, OsString>,
}

impl CgroupCache {
    pub fn new(root: OsString) -> Self {
        Self { root, cache: HashMap::new() }
    }

    pub fn get(&mut self, ino: u64) -> Option<OsString> {
        if let Some(path) = self.cache.get(&ino) {
            Some(path.clone())
        } else {
            self.refresh_cache();
            self.cache.get(&ino).cloned()
        }
    }

    fn refresh_cache(&mut self) {
        WalkDir::new(&self.root).into_iter().for_each(|res| match res {
            Ok(dir_entry) => {
                _ = self.cache.insert(dir_entry.ino(), dir_entry.path().into());
            }
            Err(e) => {
                warn!("could not read from {:?}: {}", self.root, e);
            }
        });
    }
}

#[cfg(test)]
mod test {
    use std::fs;
    use std::fs::File;
    use std::os::unix::fs::DirEntryExt;

    use super::*;

    #[test]
    fn get_must_return_none_when_file_doesnt_exist() {
        let mut cache = CgroupCache::new(OsString::from("/tmp"));

        assert_eq!(cache.get(123), None);
    }

    #[test]
    fn get_must_return_file_for_ino() {
        let mut cache = CgroupCache::new(OsString::from("/tmp"));

        let file_name1 = uuid::Uuid::new_v4().to_string();
        let ino1 = create_file(&OsString::from(&file_name1));

        let file_name2 = uuid::Uuid::new_v4().to_string();
        let ino2 = create_file(&OsString::from(&file_name2));

        assert!(cache.get(ino1).is_some());
        assert!(cache
            .get(ino1)
            .expect("should not happen")
            .eq_ignore_ascii_case(format!("/tmp/{file_name1}")));

        assert!(cache.get(ino2).is_some());
        assert!(cache
            .get(ino2)
            .expect("should not happen")
            .eq_ignore_ascii_case(format!("/tmp/{file_name2}")));
    }

    fn create_file(file_name: &OsString) -> u64 {
        let _file = File::create(format!(
            "/tmp/{}",
            file_name
                .to_ascii_lowercase()
                .to_str()
                .expect("couldn't convert filename")
        ))
        .expect("couldn't create file");
        let dir_entry = fs::read_dir("/tmp")
            .expect("tmp dir entries")
            .find(|e| {
                println!("{:?}", e.as_ref().expect("").file_name());
                e.as_ref()
                    .expect("file")
                    .file_name()
                    .eq_ignore_ascii_case(file_name)
            })
            .expect("couldn't find file")
            .expect("dir entry");
        dir_entry.ino()
    }
}