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

``shell
npm install cached-provider
`

How to use

Lazy Cache

Call provider once, and keep the result until TTL.

`typescript
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

`typescript
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.

`typescript
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

`typescript
export type CachedProviderOptions = {
autoUpdater?: {
onShouldContinue?: () => boolean
}
}
`

Monitoring Cache Behavior

onEvent callback allow you to monitor cache access in detail

See example/example.ts for detail

`typescript
export type CachedProviderOptions = {
onEvent?: CacheEventCallback
}
`

`typescript
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