cached-provider

Optimize data creation by synchronizing and caching

• Check cached object
  • If valid cache exist, return cached value (hitA)
• Synchronize execution
  • Check cached object
    • If valid cache exist, return cached value (hitS)
  • Call provider to update cached value
  • return cached value (miss)

How to install

npm install cached-provider

How to use

Lazy Cache

Call provider once, and keep the result until TTL.

const value = cached({
    ttl: 1000 * 60,// Cache TTL for get
    provider: async () => "slow data provider"
})
await value() // Access Value

Eager Cache

In addition to lazy caching, run cache update automatically to minimize get latency

const value = cached({
    ttl: 1000 * 60,// Cache TTL for get
    provider: async () => "slow data provider",
    autoUpdater: {
        interval: 1000 * 5, // Validate cache every 5 sec
        ttl: 1000 * 50, // Cache TTL for update , which should be smaller than TTL for get
    }
})
await value() // Access Value

Smart Eager Cache

Adjust cache update interval based on user access.

const value = cached({
    ttl: 1000 * 60 * 60,
    provider: async () => "slow data provider",
    autoUpdater: {
        interval: 1000 * 5, // Validate cache every 5 sec
        ttl: ({sinceAccessedAt}) => {
            // Cache TTL for update , which should be smaller than TTL for get
            // Use longer update cycle when the value is not accessed
            return (sinceAccessedAt !== undefined) && (sinceAccessedAt < 1000 * 60 * 10)
                ? 1000 * 50
                : 1000 * 60 * 59
        }
    }
})
await value() // Access Value

validator callback

In addition to the time based cache expire, you can add validator callback to validate cache object just before using it

How to shut down auto updater

If you specify onShouldContinue callback, cached provider ask you if it can continue running auto updater.

See example/example.ts for detail

export type CachedProviderOptions<T> = {
    autoUpdater?: {
        onShouldContinue?: () => boolean
    }
}

Monitoring Cache Behavior

onEvent callback allow you to monitor cache access in detail

See example/example.ts for detail

export type CachedProviderOptions<T> = {
    onEvent?: CacheEventCallback
}

export type MethodType = "get" | "update"
export type EventType = "hitA" | "hitS" | "miss"

export type CacheEvent = {
    methodType: MethodType
    eventType: EventType
    requestAt: Date
    responseAt: Date
    cachedAt: Date
}

export type CacheEventCallback = (event: CacheEvent) => void

MethodType

| type | description | |--------|--------------------------------| | get | Get method call (on demand) | | update | Update method call (scheduled) |

EventType

| type | description | |------|----------------------------------------------| | hitA | Cache hit before synchronization. Super fast | | hitS | Cache hit after synchronization. Fast | | miss | Cache miss, updated value. Slow |

Examples

% npx ts-node example/example.ts 
Sample: Lazy Cache
┌─────────┬────────────┬───────────┬───────┬─────┬─────┬─────┐
│ (index) │ methodType │ eventType │ count │ min │ avg │ max │
├─────────┼────────────┼───────────┼───────┼─────┼─────┼─────┤
│ 0       │ 'get'      │ 'hitA'    │ 38    │ 0   │ 0   │ 1   │
│ 1       │ 'get'      │ 'hitS'    │ 8     │ 98  │ 150 │ 201 │
│ 2       │ 'get'      │ 'miss'    │ 4     │ 300 │ 301 │ 302 │
└─────────┴────────────┴───────────┴───────┴─────┴─────┴─────┘
Sample: Lazy Cache with warmup
┌─────────┬────────────┬───────────┬───────┬─────┬─────┬─────┐
│ (index) │ methodType │ eventType │ count │ min │ avg │ max │
├─────────┼────────────┼───────────┼───────┼─────┼─────┼─────┤
│ 0       │ 'get'      │ 'hitA'    │ 40    │ 0   │ 0   │ 1   │
│ 1       │ 'get'      │ 'hitS'    │ 6     │ 99  │ 150 │ 203 │
│ 2       │ 'get'      │ 'miss'    │ 3     │ 301 │ 302 │ 303 │
└─────────┴────────────┴───────────┴───────┴─────┴─────┴─────┘
Sample: Eager Cache
┌─────────┬────────────┬───────────┬───────┬─────┬─────┬─────┐
│ (index) │ methodType │ eventType │ count │ min │ avg │ max │
├─────────┼────────────┼───────────┼───────┼─────┼─────┼─────┤
│ 0       │ 'get'      │ 'hitA'    │ 47    │ 0   │ 0   │ 1   │
│ 1       │ 'get'      │ 'hitS'    │ 2     │ 99  │ 149 │ 198 │
│ 2       │ 'get'      │ 'miss'    │ 1     │ 301 │ 301 │ 301 │
│ 3       │ 'update'   │ 'hitA'    │ 30    │ 0   │ 0   │ 1   │
│ 4       │ 'update'   │ 'hitS'    │ 12    │ 99  │ 150 │ 201 │
│ 5       │ 'update'   │ 'miss'    │ 5     │ 301 │ 302 │ 302 │
└─────────┴────────────┴───────────┴───────┴─────┴─────┴─────┘
Sample: Eager Cache with warmup
┌─────────┬────────────┬───────────┬───────┬─────┬─────┬─────┐
│ (index) │ methodType │ eventType │ count │ min │ avg │ max │
├─────────┼────────────┼───────────┼───────┼─────┼─────┼─────┤
│ 0       │ 'get'      │ 'hitA'    │ 50    │ 0   │ 0   │ 1   │
│ 1       │ 'update'   │ 'hitA'    │ 32    │ 0   │ 0   │ 1   │
│ 2       │ 'update'   │ 'hitS'    │ 15    │ 1   │ 140 │ 201 │
│ 3       │ 'update'   │ 'miss'    │ 6     │ 300 │ 301 │ 302 │
└─────────┴────────────┴───────────┴───────┴─────┴─────┴─────┘

Version History

• 1.1.0
  • Add validator callback
• 1.0.5
  • Enhance publish step
• 1.0.4
  • Use seq based id instead of UUID for object id
• 1.0.3
  • Add unit tests
• 1.0.2
  • Update README(typo)
• 1.0.1
  • Update README
• 1.0.0
  • Initial Release

License

This project is under the MIT license. Copyright (c) 2024 Tomohisa Ota