|
| 1 | +use std::marker::PhantomData; |
| 2 | + |
| 3 | +use educe::Educe; |
| 4 | +use schemars::JsonSchema; |
| 5 | +use serde::{Deserialize, Serialize}; |
| 6 | + |
| 7 | +use crate::time::Duration; |
| 8 | + |
| 9 | +/// [`TtlCache`] with sensible defaults for a user information cache |
| 10 | +pub type UserInformationCache = TtlCache<UserInformationCacheDefaults>; |
| 11 | + |
| 12 | +/// Default tunings for [`UserInformationCache`]. |
| 13 | +#[derive(JsonSchema)] |
| 14 | +pub struct UserInformationCacheDefaults; |
| 15 | + |
| 16 | +impl TtlCacheDefaults for UserInformationCacheDefaults { |
| 17 | + fn entry_time_to_live() -> Duration { |
| 18 | + Duration::from_secs(30) |
| 19 | + } |
| 20 | + |
| 21 | + fn max_entries() -> u32 { |
| 22 | + 10_000 |
| 23 | + } |
| 24 | +} |
| 25 | + |
| 26 | +/// Structure to configure a TTL cache in a product. |
| 27 | +#[derive(Deserialize, Educe, JsonSchema, Serialize)] |
| 28 | +#[serde( |
| 29 | + rename_all = "camelCase", |
| 30 | + bound(deserialize = "D: TtlCacheDefaults", serialize = "D: TtlCacheDefaults") |
| 31 | +)] |
| 32 | +#[schemars( |
| 33 | + description = "Least Recently Used (LRU) cache with per-entry time-to-live (TTL) value.", |
| 34 | + // We don't care about the fields, but we also use JsonSchema to derive the name for the composite type |
| 35 | + bound(serialize = "D: TtlCacheDefaults + JsonSchema") |
| 36 | +)] |
| 37 | +#[educe( |
| 38 | + Clone(bound = false), |
| 39 | + Debug(bound = false), |
| 40 | + PartialEq(bound = false), |
| 41 | + Eq |
| 42 | +)] |
| 43 | +pub struct TtlCache<D> { |
| 44 | + /// Time to live per entry |
| 45 | + #[serde(default = "D::entry_time_to_live")] |
| 46 | + pub entry_time_to_live: Duration, |
| 47 | + |
| 48 | + /// Maximum number of entries in the cache; If this threshold is reached then the least |
| 49 | + /// recently used item is removed. |
| 50 | + #[serde(default = "D::max_entries")] |
| 51 | + pub max_entries: u32, |
| 52 | + |
| 53 | + #[serde(skip)] |
| 54 | + pub _defaults: PhantomData<D>, |
| 55 | +} |
| 56 | + |
| 57 | +impl<D: TtlCacheDefaults> Default for TtlCache<D> { |
| 58 | + fn default() -> Self { |
| 59 | + Self { |
| 60 | + entry_time_to_live: D::entry_time_to_live(), |
| 61 | + max_entries: D::max_entries(), |
| 62 | + _defaults: PhantomData, |
| 63 | + } |
| 64 | + } |
| 65 | +} |
| 66 | + |
| 67 | +/// A set of default values for [`TtlCache`]. |
| 68 | +/// |
| 69 | +/// This is extracted to a separate trait in order to be able to provide different |
| 70 | +/// default tunings for different use cases. |
| 71 | +pub trait TtlCacheDefaults { |
| 72 | + /// The default TTL the entries should have. |
| 73 | + fn entry_time_to_live() -> Duration; |
| 74 | + /// The default for the maximum number of entries |
| 75 | + fn max_entries() -> u32; |
| 76 | +} |
| 77 | + |
| 78 | +#[cfg(test)] |
| 79 | +mod tests { |
| 80 | + use super::*; |
| 81 | + |
| 82 | + type MyCache = TtlCache<UserInformationCacheDefaults>; |
| 83 | + |
| 84 | + #[test] |
| 85 | + fn test_defaults() { |
| 86 | + let my_cache: MyCache = Default::default(); |
| 87 | + assert_eq!(my_cache.entry_time_to_live, Duration::from_secs(30)); |
| 88 | + assert_eq!(my_cache.max_entries, 10_000); |
| 89 | + } |
| 90 | + |
| 91 | + #[test] |
| 92 | + fn test_deserialization_defaults() { |
| 93 | + let my_cache: MyCache = serde_json::from_str("{}").unwrap(); |
| 94 | + |
| 95 | + assert_eq!(my_cache.entry_time_to_live, Duration::from_secs(30)); |
| 96 | + assert_eq!(my_cache.max_entries, 10_000); |
| 97 | + } |
| 98 | + |
| 99 | + #[test] |
| 100 | + fn test_deserialization() { |
| 101 | + let my_cache: MyCache = serde_yaml::from_str("entryTimeToLive: 13h\n").unwrap(); |
| 102 | + |
| 103 | + assert_eq!( |
| 104 | + my_cache.entry_time_to_live, |
| 105 | + Duration::from_hours_unchecked(13) |
| 106 | + ); |
| 107 | + // As the field is not specified we default |
| 108 | + assert_eq!(my_cache.max_entries, 10_000); |
| 109 | + } |
| 110 | +} |
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