Marc Mintel
5397309103
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152 lines
4.5 KiB
Plaintext
152 lines
4.5 KiB
Plaintext
# Cache Store
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A Cache Store is responsible for storing and retrieving cached responses.
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It is also responsible for deciding which specific response to use based off of
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a response's `Vary` header (if present). It is expected to be compliant with
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[RFC-9111](https://www.rfc-editor.org/rfc/rfc9111.html).
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## Pre-built Cache Stores
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### `MemoryCacheStore`
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The `MemoryCacheStore` stores the responses in-memory.
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**Options**
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- `maxSize` - The maximum total size in bytes of all stored responses. Default `104857600` (100MB).
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- `maxCount` - The maximum amount of responses to store. Default `1024`.
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- `maxEntrySize` - The maximum size in bytes that a response's body can be. If a response's body is greater than or equal to this, the response will not be cached. Default `5242880` (5MB).
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### Getters
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#### `MemoryCacheStore.size`
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Returns the current total size in bytes of all stored responses.
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### Methods
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#### `MemoryCacheStore.isFull()`
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Returns a boolean indicating whether the cache has reached its maximum size or count.
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### Events
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#### `'maxSizeExceeded'`
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Emitted when the cache exceeds its maximum size or count limits. The event payload contains `size`, `maxSize`, `count`, and `maxCount` properties.
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### `SqliteCacheStore`
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The `SqliteCacheStore` stores the responses in a SQLite database.
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Under the hood, it uses Node.js' [`node:sqlite`](https://nodejs.org/api/sqlite.html) api.
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The `SqliteCacheStore` is only exposed if the `node:sqlite` api is present.
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**Options**
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- `location` - The location of the SQLite database to use. Default `:memory:`.
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- `maxCount` - The maximum number of entries to store in the database. Default `Infinity`.
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- `maxEntrySize` - The maximum size in bytes that a response's body can be. If a response's body is greater than or equal to this, the response will not be cached. Default `Infinity`.
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## Defining a Custom Cache Store
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The store must implement the following functions:
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### Getter: `isFull`
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Optional. This tells the cache interceptor if the store is full or not. If this is true,
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the cache interceptor will not attempt to cache the response.
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### Function: `get`
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Parameters:
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* **req** `Dispatcher.RequestOptions` - Incoming request
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Returns: `GetResult | Promise<GetResult | undefined> | undefined` - If the request is cached, the cached response is returned. If the request's method is anything other than HEAD, the response is also returned.
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If the request isn't cached, `undefined` is returned.
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Response properties:
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* **response** `CacheValue` - The cached response data.
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* **body** `Readable | undefined` - The response's body.
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### Function: `createWriteStream`
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Parameters:
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* **req** `Dispatcher.RequestOptions` - Incoming request
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* **value** `CacheValue` - Response to store
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Returns: `Writable | undefined` - If the store is full, return `undefined`. Otherwise, return a writable so that the cache interceptor can stream the body and trailers to the store.
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## `CacheValue`
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This is an interface containing the majority of a response's data (minus the body).
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### Property `statusCode`
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`number` - The response's HTTP status code.
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### Property `statusMessage`
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`string` - The response's HTTP status message.
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### Property `rawHeaders`
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`Buffer[]` - The response's headers.
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### Property `vary`
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`Record<string, string | string[]> | undefined` - The headers defined by the response's `Vary` header
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and their respective values for later comparison
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For example, for a response like
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```
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Vary: content-encoding, accepts
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content-encoding: utf8
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accepts: application/json
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```
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This would be
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```js
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{
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'content-encoding': 'utf8',
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accepts: 'application/json'
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}
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```
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### Property `cachedAt`
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`number` - Time in millis that this value was cached.
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### Property `staleAt`
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`number` - Time in millis that this value is considered stale.
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### Property `deleteAt`
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`number` - Time in millis that this value is to be deleted from the cache. This
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is either the same sa staleAt or the `max-stale` caching directive.
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The store must not return a response after the time defined in this property.
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## `CacheStoreReadable`
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This extends Node's [`Readable`](https://nodejs.org/api/stream.html#class-streamreadable)
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and defines extra properties relevant to the cache interceptor.
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### Getter: `value`
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The response's [`CacheStoreValue`](/docs/docs/api/CacheStore.md#cachestorevalue)
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## `CacheStoreWriteable`
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This extends Node's [`Writable`](https://nodejs.org/api/stream.html#class-streamwritable)
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and defines extra properties relevant to the cache interceptor.
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### Setter: `rawTrailers`
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If the response has trailers, the cache interceptor will pass them to the cache
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interceptor through this method.
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