feat(stackable-operator): Add cache structure

crates/stackable-operator/CHANGELOG.md

@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased]
 
+### Added
+
+- Add `TtlCache` structure ([#943]).
+
+[#943]: https://github.com/stackabletech/operator-rs/pull/943
+
 ## [0.84.0] - 2025-01-16
 
 ### Added

crates/stackable-operator/src/commons/cache.rs

@@ -0,0 +1,38 @@
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+
+use crate::time::Duration;
+
+/// Least Recently Used (LRU) cache with per-entry time-to-live (TTL) value.
+#[derive(Clone, Debug, Deserialize, Eq, JsonSchema, PartialEq, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct TtlCache {
+    /// Time to live per entry; Entries which were not queried within the given duration, are
+    /// removed.
+    #[serde(default = "TtlCache::default_entry_time_to_live")]
+    pub entry_time_to_live: Duration,
+
+    /// Maximum number of entries in the cache; If this threshold is reached then the least
+    /// recently used item is removed.
+    #[serde(default = "TtlCache::default_max_entries")]
+    pub max_entries: u32,
+}
+
+impl TtlCache {
+    const fn default_entry_time_to_live() -> Duration {
+        Duration::from_secs(30)
+    }
+
+    const fn default_max_entries() -> u32 {
+        1000
+    }
+}
+
+impl Default for TtlCache {
+    fn default() -> Self {
+        Self {
+            entry_time_to_live: Self::default_entry_time_to_live(),
+            max_entries: Self::default_max_entries(),
+        }
+    }
+}

crates/stackable-operator/src/commons/mod.rs

@@ -2,6 +2,7 @@
 
 pub mod affinity;
 pub mod authentication;
+pub mod cache;
 pub mod cluster_operation;
 pub mod listener;
 pub mod networking;