Struct CacheSystemBuilder 

pub struct CacheSystemBuilder { /* private fields */ }

Builder for constructing CacheSystem with custom backends

This builder allows you to configure custom L1 (in-memory) and L2 (distributed) cache backends, enabling you to swap Moka and Redis with alternative implementations.

Multi-Tier Support (v0.5.0+)

The builder now supports dynamic multi-tier architectures (L1+L2+L3+L4+…). Use .with_tier() to add custom tiers, or .with_l3() / .with_l4() for convenience.

Default Behavior

If no custom backends are provided, the builder uses:

• L1: Moka in-memory cache
• L2: Redis distributed cache

Type Safety

The builder accepts any type that implements the required traits:

• L1 backends must implement CacheBackend
• L2 backends must implement L2CacheBackend (extends CacheBackend)
• All tier backends must implement L2CacheBackend (for TTL support)
• Streaming backends must implement StreamingBackend

Example - Default 2-Tier

use multi_tier_cache::CacheSystemBuilder;

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    // Use default backends (Moka + Redis)
    let cache = CacheSystemBuilder::new()
        .build()
        .await?;

    Ok(())
}

Example - Custom 3-Tier (v0.5.0+)

use multi_tier_cache::{CacheSystemBuilder, TierConfig};
use std::sync::Arc;

let l1 = Arc::new(L1Cache::new().await?);
let l2 = Arc::new(L2Cache::new().await?);
let l3 = Arc::new(RocksDBCache::new("/tmp/cache").await?);

let cache = CacheSystemBuilder::new()
    .with_tier(l1, TierConfig::as_l1())
    .with_tier(l2, TierConfig::as_l2())
    .with_l3(l3)  // Convenience method
    .build()
    .await?;

Implementations

impl CacheSystemBuilder

pub fn new() -> Self

Create a new builder with no custom backends configured

By default, calling .build() will use Moka (L1) and Redis (L2). Use .with_tier() to configure multi-tier architecture (v0.5.0+).

pub fn with_l1(self, backend: Arc<dyn CacheBackend>) -> Self

Configure a custom L1 (in-memory) cache backend

Arguments

• backend - Any type implementing CacheBackend trait

Example

use std::sync::Arc;
use multi_tier_cache::CacheSystemBuilder;

let custom_l1 = Arc::new(MyCustomL1::new());

let cache = CacheSystemBuilder::new()
    .with_l1(custom_l1)
    .build()
    .await?;

pub fn with_l2(self, backend: Arc<dyn L2CacheBackend>) -> Self

Configure a custom L2 (distributed) cache backend

Arguments

• backend - Any type implementing L2CacheBackend trait

Example

use std::sync::Arc;
use multi_tier_cache::CacheSystemBuilder;

let custom_l2 = Arc::new(MyMemcachedBackend::new());

let cache = CacheSystemBuilder::new()
    .with_l2(custom_l2)
    .build()
    .await?;

pub fn with_streams(self, backend: Arc<dyn StreamingBackend>) -> Self

Configure a custom streaming backend

This is optional. If not provided, streaming functionality will use the L2 backend if it implements StreamingBackend.

Arguments

• backend - Any type implementing StreamingBackend trait

Example

use std::sync::Arc;
use multi_tier_cache::CacheSystemBuilder;

let kafka_backend = Arc::new(MyKafkaBackend::new());

let cache = CacheSystemBuilder::new()
    .with_streams(kafka_backend)
    .build()
    .await?;

pub fn with_tier( self, backend: Arc<dyn L2CacheBackend>, config: TierConfig, ) -> Self

Configure a cache tier with custom settings (v0.5.0+)

Add a cache tier to the multi-tier architecture. Tiers will be sorted by tier_level during build.

Arguments

• backend - Any type implementing L2CacheBackend trait
• config - Tier configuration (level, promotion, TTL scale)

Example

use multi_tier_cache::{CacheSystemBuilder, TierConfig, L1Cache, L2Cache};
use std::sync::Arc;

let l1 = Arc::new(L1Cache::new().await?);
let l2 = Arc::new(L2Cache::new().await?);
let l3 = Arc::new(RocksDBCache::new("/tmp").await?);

let cache = CacheSystemBuilder::new()
    .with_tier(l1, TierConfig::as_l1())
    .with_tier(l2, TierConfig::as_l2())
    .with_tier(l3, TierConfig::as_l3())
    .build()
    .await?;

pub fn with_l3(self, backend: Arc<dyn L2CacheBackend>) -> Self

Convenience method to add L3 cache tier (v0.5.0+)

Adds a cold storage tier with 2x TTL multiplier.

Arguments

• backend - L3 backend (e.g., RocksDB, LevelDB)

Example

use std::sync::Arc;

let rocksdb = Arc::new(RocksDBCache::new("/tmp/l3cache").await?);

let cache = CacheSystemBuilder::new()
    .with_l3(rocksdb)
    .build()
    .await?;

pub fn with_l4(self, backend: Arc<dyn L2CacheBackend>) -> Self

Convenience method to add L4 cache tier (v0.5.0+)

Adds an archive storage tier with 8x TTL multiplier.

Arguments

• backend - L4 backend (e.g., S3, file system)

Example

use std::sync::Arc;

let s3_cache = Arc::new(S3Cache::new("my-bucket").await?);

let cache = CacheSystemBuilder::new()
    .with_l4(s3_cache)
    .build()
    .await?;

pub async fn build(self) -> Result<CacheSystem>

Build the CacheSystem with configured or default backends

If no custom backends were provided via .with_l1() or .with_l2(), this method creates default backends (Moka for L1, Redis for L2).

Multi-Tier Mode (v0.5.0+)

If tiers were configured via .with_tier(), .with_l3(), or .with_l4(), the builder creates a multi-tier CacheManager using new_with_tiers().

Returns

• Ok(CacheSystem) - Successfully constructed cache system
• Err(e) - Failed to initialize backends (e.g., Redis connection error)

Example - Default 2-Tier

use multi_tier_cache::CacheSystemBuilder;

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    let cache = CacheSystemBuilder::new()
        .build()
        .await?;

    // Use cache_manager for operations
    let manager = cache.cache_manager();

    Ok(())
}

Errors

Returns an error if the default backends cannot be initialized.

Trait Implementations

impl Default for CacheSystemBuilder

fn default() -> Self

Returns the “default value” for a type.