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
148
149
150
151

use std::path::Path;
use std::sync::{Arc, RwLock};
use std::time::Duration;

use once_cell::sync::Lazy;
use polars_core::config;
use polars_error::PolarsResult;
use polars_utils::aliases::PlHashMap;

use super::entry::{FileCacheEntry, DATA_PREFIX, METADATA_PREFIX};
use super::eviction::EvictionManager;
use super::file_fetcher::FileFetcher;
use super::utils::FILE_CACHE_PREFIX;
use crate::prelude::is_cloud_url;

pub static FILE_CACHE: Lazy<FileCache> = Lazy::new(|| {
    let prefix = FILE_CACHE_PREFIX.as_ref();
    let prefix = Arc::<Path>::from(prefix);

    if config::verbose() {
        eprintln!("file cache prefix: {}", prefix.to_str().unwrap());
    }

    EvictionManager {
        prefix: prefix.clone(),
        files_to_remove: None,
        limit_since_last_access: Duration::from_secs(
            std::env::var("POLARS_FILE_CACHE_TTL")
                .map(|x| x.parse::<u64>().expect("integer"))
                .unwrap_or(60 * 60),
        ),
    }
    .run_in_background();

    FileCache::new(prefix)
});

pub struct FileCache {
    prefix: Arc<Path>,
    entries: Arc<RwLock<PlHashMap<Arc<str>, Arc<FileCacheEntry>>>>,
}

impl FileCache {
    fn new(prefix: Arc<Path>) -> Self {
        let path = &prefix
            .as_ref()
            .join(std::str::from_utf8(&[METADATA_PREFIX]).unwrap());
        let _ = std::fs::create_dir_all(path);
        assert!(
            path.is_dir(),
            "failed to create file cache metadata directory: {}",
            path.to_str().unwrap(),
        );

        let path = &prefix
            .as_ref()
            .join(std::str::from_utf8(&[DATA_PREFIX]).unwrap());
        let _ = std::fs::create_dir_all(path);
        assert!(
            path.is_dir(),
            "failed to create file cache data directory: {}",
            path.to_str().unwrap(),
        );

        Self {
            prefix,
            entries: Default::default(),
        }
    }

    /// If `uri` is a local path, it must be an absolute path.
    pub fn init_entry<F: Fn() -> PolarsResult<Arc<dyn FileFetcher>>>(
        &self,
        uri: Arc<str>,
        get_file_fetcher: F,
    ) -> PolarsResult<Arc<FileCacheEntry>> {
        let verbose = config::verbose();

        #[cfg(debug_assertions)]
        {
            // Local paths must be absolute or else the cache would be wrong.
            if !crate::utils::is_cloud_url(uri.as_ref()) {
                let path = Path::new(uri.as_ref());
                assert_eq!(path, std::fs::canonicalize(path).unwrap().as_path());
            }
        }

        {
            let entries = self.entries.read().unwrap();

            if let Some(entry) = entries.get(uri.as_ref()) {
                if verbose {
                    eprintln!(
                        "[file_cache] init_entry: return existing entry for uri = {}",
                        uri.clone()
                    );
                }
                return Ok(entry.clone());
            }
        }

        let uri_hash = blake3::hash(uri.as_bytes())
            .to_hex()
            .get(..32)
            .unwrap()
            .to_string();

        {
            let mut entries = self.entries.write().unwrap();

            // May have been raced
            if let Some(entry) = entries.get(uri.as_ref()) {
                if verbose {
                    eprintln!("[file_cache] init_entry: return existing entry for uri = {} (lost init race)", uri.clone());
                }
                return Ok(entry.clone());
            }

            if verbose {
                eprintln!(
                    "[file_cache] init_entry: creating new entry for uri = {}, hash = {}",
                    uri.clone(),
                    uri_hash.clone()
                );
            }

            let entry = Arc::new(FileCacheEntry::new(
                uri.clone(),
                uri_hash,
                self.prefix.clone(),
                get_file_fetcher()?,
            ));
            entries.insert_unique_unchecked(uri, entry.clone());
            Ok(entry.clone())
        }
    }

    /// This function can accept relative local paths.
    pub fn get_entry(&self, uri: &str) -> Option<Arc<FileCacheEntry>> {
        if is_cloud_url(uri) {
            self.entries.read().unwrap().get(uri).map(Arc::clone)
        } else {
            let uri = std::fs::canonicalize(uri).unwrap();
            self.entries
                .read()
                .unwrap()
                .get(uri.to_str().unwrap())
                .map(Arc::clone)
        }
    }
}