thesix 0.2.0

Policy-driven six-tier cache orchestration for Rust
Documentation 
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use std::time::Duration;

use crate::error::CacheError;
use crate::key::KeyRef;
use crate::tier::TierId;

pub trait CacheTier<V>: Send + Sync {
    fn name(&self) -> String;

    fn get(&self, key: &KeyRef<'_>) -> Result<Option<V>, CacheError>;

    fn set(&self, key: &KeyRef<'_>, value: V, ttl: Option<Duration>) -> Result<(), CacheError>;

    fn remove(&self, key: &KeyRef<'_>) -> Result<(), CacheError>;

    fn contains(&self, key: &KeyRef<'_>) -> Result<bool, CacheError>;

    fn health(&self) -> TierHealth;

    fn tier_id(&self) -> TierId;
}

#[derive(Debug, Clone)]
pub struct TierHealth {
    pub consecutive_failures: u64,
    pub last_failure_timestamp: Option<std::time::SystemTime>,
    pub health_score: f64,
    /// Remaining capacity signal in the range `0.0..=1.0` (1.0 = fully free).
    /// Tiers that do not track capacity leave this at the default.
    pub availability: f64,
}

impl Default for TierHealth {
    fn default() -> Self {
        TierHealth {
            consecutive_failures: 0,
            last_failure_timestamp: None,
            health_score: 1.0,
            availability: 1.0,
        }
    }
}

impl TierHealth {
    pub fn healthy(&self) -> bool {
        self.consecutive_failures == 0
    }

    pub fn is_circuit_open(&self) -> bool {
        self.consecutive_failures >= 5
    }
}