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Class: Cacher ​

The cache component: a key-value cache with expiration, backed by one or more stores (memory, file, Redis, Memcache, MongoDB, SQLite, PostgreSQL, MySQL). Register it in the components of an application with buildCacherOptions (or {class: Cacher, ...options}) and get it with getObject() or @Inject; it is a singleton. Without stores, it caches in memory.

The stores connect when the component is created: when one fails to connect, the others are disconnected and the creation fails with its error (the application does not start). A store whose driver package is not installed fails with CacheDriverNotFoundException. The stores disconnect when the component is destroyed, after the background refreshes in progress and the file store's pending writes.

With several stores, they are tiers, the first one the fastest: a read returns the entry of the first store holding it, a write or a deletion goes to all of them. Only Cacher.wrap copies an entry found in a lower store to the stores above it.

The TTLs are in milliseconds: an entry whose TTL is 0 or unset (without the ttl option) never expires; an expired entry is a miss. The memory store keeps the values by reference (a cached object changed afterwards is changed in the cache); the other stores keep them as JSON: the Buffers are kept, but a Date comes back as its ISO string, a class instance as a plain object, a Map or a Set as {}, and a bigint fails the write.

A store failing to read is a miss (its error is emitted as an 'error' event); a store failing to write or delete rejects the call, unless the nonBlocking option is set.

Example ​

typescript
import {Application, Component} from 'lakutata'
import {Inject} from 'lakutata/decorator/di'
import {buildCacherOptions, type Cacher} from 'lakutata/com/cacher'

type Product = {id: number, name: string}

class Catalog extends Component {
    @Inject('cache')
    protected readonly cache: Cacher

    public async product(id: number): Promise<Product> {
        //Computed once, then read from the cache for 5 minutes (recomputed in the background in its last minute)
        return this.cache.wrap(`product:${id}`, async (): Promise<Product> => ({id: id, name: `Product ${id}`}), {
            ttl: 300000,
            refreshThreshold: 60000
        })
    }

    public async rename(id: number, name: string): Promise<void> {
        await this.cache.set(`product:${id}`, {id: id, name: name}, 300000)
    }

    public async remove(id: number): Promise<void> {
        await this.cache.del(`product:${id}`)
    }
}

Application
    .run(() => ({
        id: 'catalog.app',
        name: 'Catalog',
        components: {
            //A local file tier in front of Redis (the "redis" package installed)
            cache: buildCacherOptions({
                stores: [
                    {type: 'file', filename: './cache/catalog.json'},
                    {type: 'redis', host: '127.0.0.1', namespace: 'catalog'}
                ],
                ttl: 600000
            }),
            catalog: {class: Catalog}
        }
    }))
    .onLaunched(async (app: Application): Promise<void> => {
        const cache: Cacher = await app.getObject('cache')
        cache.on('error', (error: Error): void => console.error('Cache store error', error))
        const catalog: Catalog = await app.getObject('catalog')
        console.log(await catalog.product(1))
    })

Extends ​

Constructors ​

Constructor ​

new Cacher(cradleProxy): Cacher

Called by the container only: an object is created through a container (see the class description), never with new.

Parameters ​

cradleProxy ​

Record<string | symbol, any>

The container's resolution proxy.

Returns ​

Cacher

Inherited from ​

Component.constructor

Properties ​

constructor ​

constructor: Function

The initial value of Object.prototype.constructor is the standard built-in Object constructor.

Inherited from ​

Component.constructor

Accessors ​

$id ​

Get Signature ​

get $id(): string | symbol

The name the object was registered under (its key in the module options), or a symbol of its class for an object registered by its class or built without registration.

Returns ​

string | symbol

Inherited from ​

Component.$id

$symbol ​

Get Signature ​

get $symbol(): symbol

A symbol unique to the instance (made from its $uuid), created on first read.

Returns ​

symbol

Inherited from ​

Component.$symbol

$uuid ​

Get Signature ​

get $uuid(): string

A random UUID identifying the instance.

Returns ​

string

Inherited from ​

Component.$uuid

className ​

Get Signature ​

get static className(): string

The name of the class.

Returns ​

string

Inherited from ​

Component.className

className ​

Get Signature ​

get className(): string

The name of the object's class.

Returns ​

string

Inherited from ​

Component.className

Methods ​

[asyncDispose]() ​

[asyncDispose](): Promise<void>

Dispose the object at the end of an await using block, as BaseObject.dispose.

Returns ​

Promise<void>

Resolves once the object is destroyed.

Inherited from ​

Component.[asyncDispose]

acceptsOption() ​

static acceptsOption(name, value): boolean

Whether the class accepts an option which is not one of its @Configurable properties (an option it reads with getConfigurableRecords()): the modules check the options of the objects they declare and warn of the options the classes do not accept. Override it in the classes reading options without configurable properties.

Parameters ​

name ​

string

The option name.

value ​

unknown

The option value.

Returns ​

boolean

true when the option is accepted; false by default.

Inherited from ​

Component.acceptsOption

addListener() ​

addListener(event, listener): this

Add a listener called synchronously, at the emitting, after the event's other listeners. Unlike on(), its listener runs before emit() returns.

Parameters ​

event ​

string | symbol | event[]

The event: a name ('order.paid', the parts separated by dots, with the wildcards * for one part and ** for any parts) or the parts as an array (['order', 'paid']). A symbol is an event of its own (matched by the wildcard * as a name of one part).

listener ​

ListenerFn

The function called with the event's values.

Returns ​

this

The component, for chaining.

Inherited from ​

Component.addListener

assign() ​

Call Signature ​

static assign<T, U>(target, source): T & U

Copy the values of all of the enumerable own properties from one or more source objects to a target object. Returns the target object.

Type Parameters ​
T ​

T extends object

U ​

U

Parameters ​
target ​

T

The target object to copy to.

source ​

U

The source object from which to copy properties.

Returns ​

T & U

Inherited from ​

Component.assign

Call Signature ​

static assign<T, U, V>(target, source1, source2): T & U & V

Copy the values of all of the enumerable own properties from one or more source objects to a target object. Returns the target object.

Type Parameters ​
T ​

T extends object

U ​

U

V ​

V

Parameters ​
target ​

T

The target object to copy to.

source1 ​

U

The first source object from which to copy properties.

source2 ​

V

The second source object from which to copy properties.

Returns ​

T & U & V

Inherited from ​

Component.assign

Call Signature ​

static assign<T, U, V, W>(target, source1, source2, source3): T & U & V & W

Copy the values of all of the enumerable own properties from one or more source objects to a target object. Returns the target object.

Type Parameters ​
T ​

T extends object

U ​

U

V ​

V

W ​

W

Parameters ​
target ​

T

The target object to copy to.

source1 ​

U

The first source object from which to copy properties.

source2 ​

V

The second source object from which to copy properties.

source3 ​

W

The third source object from which to copy properties.

Returns ​

T & U & V & W

Inherited from ​

Component.assign

Call Signature ​

static assign(target, ...sources): any

Copy the values of all of the enumerable own properties from one or more source objects to a target object. Returns the target object.

Parameters ​
target ​

object

The target object to copy to.

sources ​

...any[]

One or more source objects from which to copy properties

Returns ​

any

Inherited from ​

Component.assign

clear() ​

clear(): Promise<boolean>

Delete all the entries of each store: the entries of its namespace when it has one, otherwise all its entries (except, in Redis, the keys containing the keyPrefixSeparator, which belong to the namespaces). A Memcache store flushes the whole server, its namespace ignored. A 'clear' event is emitted once done; when a store fails, a 'clear' event carrying the error is emitted and the call rejects (unless nonBlocking, which resolves and emits the event at once).

Returns ​

Promise<boolean>

Always true.

Throws ​

The failure of a store, without nonBlocking.

create() ​

Call Signature ​

static create(o): any

Creates an object that has the specified prototype or that has null prototype.

Parameters ​
o ​

object | null

Object to use as a prototype. May be null.

Returns ​

any

Inherited from ​

Component.create

Call Signature ​

static create(o, properties): any

Creates an object that has the specified prototype, and that optionally contains specified properties.

Parameters ​
o ​

object | null

Object to use as a prototype. May be null

properties ​

PropertyDescriptorMap & ThisType<any>

JavaScript object that contains one or more property descriptors.

Returns ​

any

Inherited from ​

Component.create

defineProperties() ​

static defineProperties<T>(o, properties): T

Adds one or more properties to an object, and/or modifies attributes of existing properties.

Type Parameters ​

T ​

T

Parameters ​

o ​

T

Object on which to add or modify the properties. This can be a native JavaScript object or a DOM object.

properties ​

PropertyDescriptorMap & ThisType<any>

JavaScript object that contains one or more descriptor objects. Each descriptor object describes a data property or an accessor property.

Returns ​

T

Inherited from ​

Component.defineProperties

defineProperty() ​

static defineProperty<T>(o, p, attributes): T

Adds a property to an object, or modifies attributes of an existing property.

Type Parameters ​

T ​

T

Parameters ​

o ​

T

Object on which to add or modify the property. This can be a native JavaScript object (that is, a user-defined object or a built in object) or a DOM object.

p ​

PropertyKey

The property name.

attributes ​

PropertyDescriptor & ThisType<any>

Descriptor for the property. It can be for a data property or an accessor property.

Returns ​

T

Inherited from ​

Component.defineProperty

del() ​

del(key): Promise<boolean>

Delete a key from all the stores. A 'del' event is emitted once deleted; when a store fails, a 'del' event carrying the error is emitted and the call rejects. With nonBlocking, it resolves and emits the 'del' event before the stores are done, a failure emitting a second 'del' event carrying the error.

Parameters ​

key ​

string

The key; a missing key is not an error.

Returns ​

Promise<boolean>

Always true, whether the key existed or not.

Throws ​

The failure of a store, without nonBlocking.

dispose() ​

dispose(): Promise<void>

Destroy the object: its beforeDestroy(), the objects it created, then its destroy(). Calling it more than once destroys once. A disposed singleton or scoped object is dropped from its container, which creates a new one on the next request. Using a destroyed object (getObject(), buildObject()) throws an ObjectDestroyedException.

Returns ​

Promise<void>

Resolves once the object is destroyed.

Throws ​

The error of the object's own beforeDestroy() or destroy() (an AggregateError when several fail); the errors of the objects it created are reported through the application's logger instead.

Inherited from ​

Component.dispose

emit() ​

emit(event, ...values): boolean

Emit an event: the listeners added by addListener() and onAny() are called now, in order; the ones added by on(), once(), many() and their prepended forms are scheduled (an error they throw is an unhandled rejection). Use emitRequest() to wait for the listeners and their results.

Parameters ​

event ​

string | symbol | event[]

The event: a name ('order.paid', the parts separated by dots, with the wildcards * for one part and ** for any parts) or the parts as an array (['order', 'paid']). A symbol is an event of its own (matched by the wildcard * as a name of one part).

values ​

...any[]

The values passed to the listeners.

Returns ​

boolean

true when the event has listeners.

Throws ​

The error emitted as an 'error' event which has no listener.

Inherited from ​

Component.emit

emitRequest() ​

emitRequest(event, ...values): Promise<any[]>

Emit an event and wait for its listeners (the asynchronous ones included).

Parameters ​

event ​

string | symbol | event[]

The event: a name ('order.paid', the parts separated by dots, with the wildcards * for one part and ** for any parts) or the parts as an array (['order', 'paid']). A symbol is an event of its own (matched by the wildcard * as a name of one part).

values ​

...any[]

The values passed to the listeners.

Returns ​

Promise<any[]>

The results of the listeners, in their order (an empty array without listener).

Throws ​

The first error thrown by a listener, or the error emitted as an 'error' event which has no listener.

Inherited from ​

Component.emitRequest

entries() ​

Call Signature ​

static entries<T>(o): [string, T][]

Returns an array of key/values of the enumerable own properties of an object

Type Parameters ​
T ​

T

Parameters ​
o ​

{[s: string]: T; } | ArrayLike<T>

Object that contains the properties and methods. This can be an object that you created or an existing Document Object Model (DOM) object.

Returns ​

[string, T][]

Inherited from ​

Component.entries

Call Signature ​

static entries(o): [string, any][]

Returns an array of key/values of the enumerable own properties of an object

Parameters ​
o ​

{ }

Object that contains the properties and methods. This can be an object that you created or an existing Document Object Model (DOM) object.

Returns ​

[string, any][]

Inherited from ​

Component.entries

eventNames() ​

eventNames(nsAsArray?): (string | symbol | event[])[]

The events having listeners, in no guaranteed order.

Parameters ​

nsAsArray? ​

boolean

Return each namespaced event as the array of its parts (['order', 'paid']) instead of its name ('order.paid'); false by default.

Returns ​

(string | symbol | event[])[]

The events.

Inherited from ​

Component.eventNames

freeze() ​

Call Signature ​

static freeze<T>(f): T

Prevents the modification of existing property attributes and values, and prevents the addition of new properties.

Type Parameters ​
T ​

T extends Function

Parameters ​
f ​

T

Object on which to lock the attributes.

Returns ​

T

Inherited from ​

Component.freeze

Call Signature ​

static freeze<T, U>(o): Readonly<T>

Prevents the modification of existing property attributes and values, and prevents the addition of new properties.

Type Parameters ​
T ​

T extends object

U ​

U extends string | number | bigint | boolean | symbol

Parameters ​
o ​

T

Object on which to lock the attributes.

Returns ​

Readonly<T>

Inherited from ​

Component.freeze

Call Signature ​

static freeze<T>(o): Readonly<T>

Prevents the modification of existing property attributes and values, and prevents the addition of new properties.

Type Parameters ​
T ​

T

Parameters ​
o ​

T

Object on which to lock the attributes.

Returns ​

Readonly<T>

Inherited from ​

Component.freeze

fromEntries() ​

Call Signature ​

static fromEntries<T>(entries): object

Returns an object created by key-value entries for properties and methods

Type Parameters ​
T ​

T = any

Parameters ​
entries ​

Iterable<readonly [PropertyKey, T]>

An iterable object that contains key-value entries for properties and methods.

Returns ​

object

Inherited from ​

Component.fromEntries

Call Signature ​

static fromEntries(entries): any

Returns an object created by key-value entries for properties and methods

Parameters ​
entries ​

Iterable<readonly any[]>

An iterable object that contains key-value entries for properties and methods.

Returns ​

any

Inherited from ​

Component.fromEntries

get() ​

get<T>(key): Promise<T>

Read the value of a key, from the first store holding it. It does not copy the value to the stores above (see Cacher.wrap). A failing store is a miss (its error emitted as an 'error' event): it never rejects.

Type Parameters ​

T ​

T = any

Parameters ​

key ​

string

The key.

Returns ​

Promise<T>

The value; undefined when the key is missing or expired (or when undefined was cached).

getMaxListeners() ​

getMaxListeners(): number

The number of listeners of one event above which a possible memory leak is warned of.

Returns ​

number

The number, 0 for no warning.

Inherited from ​

Component.getMaxListeners

getMethod() ​

getMethod(name, throwExceptionIfNotFound?): (...args) => any

Get a method bound to the object, to call it by name.

Parameters ​

name ​

string | symbol

The method name or symbol.

throwExceptionIfNotFound? ​

boolean

Throw when the method does not exist, instead of returning a function doing nothing; false by default.

Returns ​

The bound method, or a function doing nothing (returning undefined) when it does not exist.

(...args) => any

Throws ​

When the method does not exist and throwExceptionIfNotFound is true.

Inherited from ​

Component.getMethod

getOwnPropertyDescriptor() ​

static getOwnPropertyDescriptor(o, p): PropertyDescriptor | undefined

Gets the own property descriptor of the specified object. An own property descriptor is one that is defined directly on the object and is not inherited from the object's prototype.

Parameters ​

o ​

any

Object that contains the property.

p ​

PropertyKey

Name of the property.

Returns ​

PropertyDescriptor | undefined

Inherited from ​

Component.getOwnPropertyDescriptor

getOwnPropertyDescriptors() ​

static getOwnPropertyDescriptors<T>(o): { [P in string | number | symbol]: TypedPropertyDescriptor<T[P]> } & object

Returns an object containing all own property descriptors of an object

Type Parameters ​

T ​

T

Parameters ​

o ​

T

Object that contains the properties and methods. This can be an object that you created or an existing Document Object Model (DOM) object.

Returns ​

{ [P in string | number | symbol]: TypedPropertyDescriptor<T[P]> } & object

Inherited from ​

Component.getOwnPropertyDescriptors

getOwnPropertyNames() ​

static getOwnPropertyNames(o): string[]

Returns the names of the own properties of an object. The own properties of an object are those that are defined directly on that object, and are not inherited from the object's prototype. The properties of an object include both fields (objects) and functions.

Parameters ​

o ​

any

Object that contains the own properties.

Returns ​

string[]

Inherited from ​

Component.getOwnPropertyNames

getOwnPropertySymbols() ​

static getOwnPropertySymbols(o): symbol[]

Returns an array of all symbol properties found directly on object o.

Parameters ​

o ​

any

Object to retrieve the symbols from.

Returns ​

symbol[]

Inherited from ​

Component.getOwnPropertySymbols

getProperty() ​

getProperty<T>(propertyKey, defaultValue?): T

Read an own property of the object.

Type Parameters ​

T ​

T = any

Parameters ​

propertyKey ​

string

The property name.

defaultValue? ​

T

The value returned when the object has no own property of this name.

Returns ​

T

The property value, or the default value.

Inherited from ​

Component.getProperty

getPrototypeOf() ​

static getPrototypeOf(o): any

Returns the prototype of an object.

Parameters ​

o ​

any

The object that references the prototype.

Returns ​

any

Inherited from ​

Component.getPrototypeOf

getTTL() ​

getTTL(key): Promise<number>

Read when a key expires. Despite its name, it returns a point in time, not a remaining duration: compute the time left with expires - Date.now().

Parameters ​

key ​

string

The key.

Returns ​

Promise<number>

The expiration time, in milliseconds since the epoch; -1 when the key is missing, expired or never expires.

hasListeners() ​

hasListeners(event?): boolean

Whether an event has listeners (the wildcard listeners matching it included; the listeners of onAny() excluded).

Parameters ​

event? ​

string | symbol | event[]

The event name, its parts as an array, or a symbol; any event when omitted.

Returns ​

boolean

true when there are listeners.

Inherited from ​

Component.hasListeners

hasMethod() ​

hasMethod(name): boolean

Whether the object has a method of this name or symbol (a function of its class, not an own property).

Parameters ​

name ​

string | symbol

The method name or symbol.

Returns ​

boolean

true when the method exists.

Inherited from ​

Component.hasMethod

hasOwn() ​

static hasOwn(o, v): boolean

Determines whether an object has a property with the specified name.

Parameters ​

o ​

object

An object.

v ​

PropertyKey

A property name.

Returns ​

boolean

Inherited from ​

Component.hasOwn

hasOwnProperty() ​

hasOwnProperty(v): boolean

Determines whether an object has a property with the specified name.

Parameters ​

v ​

PropertyKey

A property name.

Returns ​

boolean

Inherited from ​

Component.hasOwnProperty

hasProperty() ​

hasProperty(propertyKey): boolean

Whether the object has an own property (not a method or accessor of its class) of this name or symbol.

Parameters ​

propertyKey ​

string | symbol

The property name or symbol.

Returns ​

boolean

true when the property exists.

Inherited from ​

Component.hasProperty

is() ​

static is(value1, value2): boolean

Returns true if the values are the same value, false otherwise.

Parameters ​

value1 ​

any

The first value.

value2 ​

any

The second value.

Returns ​

boolean

Inherited from ​

Component.is

isExtensible() ​

static isExtensible(o): boolean

Returns a value that indicates whether new properties can be added to an object.

Parameters ​

o ​

any

Object to test.

Returns ​

boolean

Inherited from ​

Component.isExtensible

isFrozen() ​

static isFrozen(o): boolean

Returns true if existing property attributes and values cannot be modified in an object, and new properties cannot be added to the object.

Parameters ​

o ​

any

Object to test.

Returns ​

boolean

Inherited from ​

Component.isFrozen

isPrototypeOf() ​

isPrototypeOf(v): boolean

Determines whether an object exists in another object's prototype chain.

Parameters ​

v ​

Object

Another object whose prototype chain is to be checked.

Returns ​

boolean

Inherited from ​

Component.isPrototypeOf

isSealed() ​

static isSealed(o): boolean

Returns true if existing property attributes cannot be modified in an object and new properties cannot be added to the object.

Parameters ​

o ​

any

Object to test.

Returns ​

boolean

Inherited from ​

Component.isSealed

keys() ​

Call Signature ​

static keys(o): string[]

Returns the names of the enumerable string properties and methods of an object.

Parameters ​
o ​

object

Object that contains the properties and methods. This can be an object that you created or an existing Document Object Model (DOM) object.

Returns ​

string[]

Inherited from ​

Component.keys

Call Signature ​

static keys(o): string[]

Returns the names of the enumerable string properties and methods of an object.

Parameters ​
o ​

{ }

Object that contains the properties and methods. This can be an object that you created or an existing Document Object Model (DOM) object.

Returns ​

string[]

Inherited from ​

Component.keys

listenerCount() ​

listenerCount(event?): number

The number of listeners of an event (the wildcard listeners matching it included), or of every event (the listeners of onAny() excluded).

Parameters ​

event? ​

string | symbol | event[]

The event name or its parts as an array; every event when omitted.

Returns ​

number

The number of listeners.

Inherited from ​

Component.listenerCount

listeners() ​

listeners(event?): ListenerFn[]

The listeners of an event, or of every event.

Parameters ​

event? ​

string | symbol | event[]

The event name (the wildcard listeners matching it included), its parts as an array, or a symbol; every event when omitted (the listeners of onAny() excluded).

Returns ​

ListenerFn[]

A copy of the listeners; changing it does not change the listeners.

Inherited from ​

Component.listeners

listenersAny() ​

listenersAny(): ListenerFn[]

The listeners of every event, added by onAny() and prependAny().

Returns ​

ListenerFn[]

A copy of these listeners; changing it does not change the listeners.

Inherited from ​

Component.listenersAny

many() ​

many(event, timesToListen, listener): this

Add a listener called for the event's next emittings, then removed.

Parameters ​

event ​

string | symbol | event[]

The event: a name ('order.paid', the parts separated by dots, with the wildcards * for one part and ** for any parts) or the parts as an array (['order', 'paid']). A symbol is an event of its own (matched by the wildcard * as a name of one part).

timesToListen ​

number

The number of emittings the listener is called for.

listener ​

ListenerFn

The function called with the event's values, asynchronously after the emitting (in a later turn of the event loop); its result (or the promise it returns) is collected by emitRequest().

Returns ​

this

The component, for chaining.

Inherited from ​

Component.many

multipleDel() ​

multipleDel(keys): Promise<boolean>

Delete several keys from all the stores. No 'del' event is emitted; a failure is emitted as an 'error' event and rejects the call (unless nonBlocking).

Parameters ​

keys ​

string[]

The keys; the missing ones are not an error.

Returns ​

Promise<boolean>

Always true, whether the keys existed or not.

Throws ​

The failure of a store, without nonBlocking.

multipleGet() ​

multipleGet(keys): Promise<any[]>

Read the values of several keys; each key from the first store holding it (the missing keys only are asked to the next store). A failing store misses all its keys (its error emitted as an 'error' event): it never rejects.

Parameters ​

keys ​

string[]

The keys.

Returns ​

Promise<any[]>

The values, in the order of the keys: undefined for the missing and expired ones.

multipleSet() ​

multipleSet(options): Promise<MultipleSetInput[]>

Cache several values, in all the stores (in one batch per store where the store allows it). No 'set' event is emitted; a failure is emitted as an 'error' event and rejects the call (unless nonBlocking).

Parameters ​

options ​

MultipleSetInput[]

The entries; an entry without ttl gets the cache's ttl option.

Returns ​

Promise<MultipleSetInput[]>

The entries written, their TTL resolved.

Throws ​

The failure of a store, without nonBlocking.

off() ​

off(event, listener): this

Remove a listener of an event; nothing happens when it was not added.

Parameters ​

event ​

string | symbol | event[]

The event the listener was added for.

listener ​

ListenerFn

The listener to remove.

Returns ​

this

The component, for chaining.

Inherited from ​

Component.off

offAny() ​

offAny(listener): this

Remove a listener of every event added by onAny() or prependAny().

Parameters ​

listener ​

ListenerFn

The listener to remove.

Returns ​

this

The component, for chaining.

Inherited from ​

Component.offAny

on() ​

Call Signature ​

on(event, listener): this

Listen to the writes of Cacher.set and Cacher.wrap, successful or failed (data.error). The listener is called asynchronously, after the emitting.

Parameters ​
event ​

"set"

'set'.

listener ​

(data) => void

Called with the key, the value and the error of a failed write.

Returns ​

this

The component, for chaining.

Overrides ​

Component.on

Call Signature ​

on(event, listener): this

Listen to the deletions of Cacher.del, successful or failed (data.error). The listener is called asynchronously, after the emitting.

Parameters ​
event ​

"del"

'del'.

listener ​

(data) => void

Called with the key and the error of a failed deletion.

Returns ​

this

The component, for chaining.

Overrides ​

Component.on

Call Signature ​

on(event, listener): this

Listen to the clearings of Cacher.clear, successful or failed. The listener is called asynchronously, after the emitting.

Parameters ​
event ​

"clear"

'clear'.

listener ​

(error?) => void

Called without argument on a success, with the error on a failure.

Returns ​

this

The component, for chaining.

Overrides ​

Component.on

Call Signature ​

on(event, listener): this

Listen to the background refreshes of Cacher.wrap, successful or failed (data.error). The listener is called asynchronously, after the emitting.

Parameters ​
event ​

"refresh"

'refresh'.

listener ​

(data) => void

Called with the key, the new value (the cached one on a failure) and the error of a failure.

Returns ​

this

The component, for chaining.

Overrides ​

Component.on

Call Signature ​

on(event, listener): this

Listen to the store errors which reject no call: the failed reads (counted as misses), the failures of Cacher.multipleSet and Cacher.multipleDel, of the copies to the upper stores, and the errors of the connections (a lost Redis connection, a failed file write…). Without listener, these errors are dropped. The listener is called asynchronously, after the emitting.

Parameters ​
event ​

"error"

'error'.

listener ​

(error) => void

Called with the error.

Returns ​

this

The component, for chaining.

Overrides ​

Component.on

onAny() ​

onAny(listener): this

Add a listener of every event, called synchronously at the emitting, before the event's own listeners.

Parameters ​

listener ​

EventAndListener

The function called with the event name, then the event's values.

Returns ​

this

The component, for chaining.

Inherited from ​

Component.onAny

once() ​

once(event, listener): this

Add a listener called for the event's next emitting only, then removed.

Parameters ​

event ​

string | symbol | event[]

The event: a name ('order.paid', the parts separated by dots, with the wildcards * for one part and ** for any parts) or the parts as an array (['order', 'paid']). A symbol is an event of its own (matched by the wildcard * as a name of one part).

listener ​

ListenerFn

The function called with the event's values, asynchronously after the emitting (in a later turn of the event loop); its result (or the promise it returns) is collected by emitRequest().

Returns ​

this

The component, for chaining.

Inherited from ​

Component.once

prependAny() ​

prependAny(listener): this

Add a listener of every event, before the other listeners of every event, called synchronously at the emitting.

Parameters ​

listener ​

EventAndListener

The function called with the event name, then the event's values.

Returns ​

this

The component, for chaining.

Inherited from ​

Component.prependAny

prependListener() ​

prependListener(event, listener): this

Add a listener before the event's other listeners.

Parameters ​

event ​

string | symbol | event[]

The event: a name ('order.paid', the parts separated by dots, with the wildcards * for one part and ** for any parts) or the parts as an array (['order', 'paid']). A symbol is an event of its own (matched by the wildcard * as a name of one part).

listener ​

ListenerFn

The function called with the event's values, asynchronously after the emitting (in a later turn of the event loop); its result (or the promise it returns) is collected by emitRequest().

Returns ​

this

The component, for chaining.

Inherited from ​

Component.prependListener

prependMany() ​

prependMany(event, timesToListen, listener): this

Add a listener called for the event's next emittings, then removed; it is placed before the event's other listeners.

Parameters ​

event ​

string | symbol | event[]

The event: a name ('order.paid', the parts separated by dots, with the wildcards * for one part and ** for any parts) or the parts as an array (['order', 'paid']). A symbol is an event of its own (matched by the wildcard * as a name of one part).

timesToListen ​

number

The number of emittings the listener is called for.

listener ​

ListenerFn

The function called with the event's values, asynchronously after the emitting (in a later turn of the event loop); its result (or the promise it returns) is collected by emitRequest().

Returns ​

this

The component, for chaining.

Inherited from ​

Component.prependMany

prependOnceListener() ​

prependOnceListener(event, listener): this

Add a listener called for the event's next emitting only, then removed; it is placed before the event's other listeners.

Parameters ​

event ​

string | symbol | event[]

The event: a name ('order.paid', the parts separated by dots, with the wildcards * for one part and ** for any parts) or the parts as an array (['order', 'paid']). A symbol is an event of its own (matched by the wildcard * as a name of one part).

listener ​

ListenerFn

The function called with the event's values, asynchronously after the emitting (in a later turn of the event loop); its result (or the promise it returns) is collected by emitRequest().

Returns ​

this

The component, for chaining.

Inherited from ​

Component.prependOnceListener

preventExtensions() ​

static preventExtensions<T>(o): T

Prevents the addition of new properties to an object.

Type Parameters ​

T ​

T

Parameters ​

o ​

T

Object to make non-extensible.

Returns ​

T

Inherited from ​

Component.preventExtensions

propertyIsEnumerable() ​

propertyIsEnumerable(v): boolean

Determines whether a specified property is enumerable.

Parameters ​

v ​

PropertyKey

A property name.

Returns ​

boolean

Inherited from ​

Component.propertyIsEnumerable

propertyNames() ​

propertyNames(): string[]

The names of the object's own properties (not its class's methods and accessors).

Returns ​

string[]

The names.

Inherited from ​

Component.propertyNames

propertySymbols() ​

propertySymbols(): symbol[]

The symbols of the object's own properties.

Returns ​

symbol[]

The symbols.

Inherited from ​

Component.propertySymbols

reload() ​

reload(): Promise<void>

Destroy the component and initialize it again (same instance): its dependencies are injected again and its init() runs again; its listeners are removed by the teardown. Its configured values are kept.

Returns ​

Promise<void>

Resolves once the component is ready again.

Throws ​

When its parent has been destroyed.

Throws ​

The error of its teardown or of its initialization.

Inherited from ​

Component.reload

removeAllListeners() ​

removeAllListeners(event?): this

Remove the listeners of an event, or all the listeners.

Parameters ​

event? ​

string | symbol | event[]

The event whose listeners are removed; all the listeners when omitted.

Returns ​

this

The component, for chaining.

Inherited from ​

Component.removeAllListeners

removeListener() ​

removeListener(event, listener): this

Remove a listener of an event, as off().

Parameters ​

event ​

string | symbol | event[]

The event the listener was added for.

listener ​

ListenerFn

The listener to remove.

Returns ​

this

The component, for chaining.

Inherited from ​

Component.removeListener

seal() ​

static seal<T>(o): T

Prevents the modification of attributes of existing properties, and prevents the addition of new properties.

Type Parameters ​

T ​

T

Parameters ​

o ​

T

Object on which to lock the attributes.

Returns ​

T

Inherited from ​

Component.seal

set() ​

set<T>(key, value, ttl?): Promise<T>

Cache a value under a key, in all the stores, replacing the previous one. A 'set' event is emitted once written; when a store fails, a 'set' event carrying the error is emitted and the call rejects.

With nonBlocking, the call resolves and the 'set' event is emitted before the stores are written; a failure then emits a second 'set' event carrying the error.

Type Parameters ​

T ​

T

Parameters ​

key ​

string

The key.

value ​

T

The value. The stores other than the memory one keep it as JSON.

ttl? ​

number

The time to live, in milliseconds; 0 never expires. Defaults to the cache's ttl option (never expires without it).

Returns ​

Promise<T>

The value given.

Throws ​

The failure of a store (its driver's error, or a TypeError for a value JSON cannot write), without nonBlocking.

setMaxListeners() ​

setMaxListeners(n): void

Set the number of listeners of one event above which a possible memory leak is warned of (the maxListeners option, 11 by default); the listeners are never limited.

Parameters ​

n ​

number

The number, 0 for no warning.

Returns ​

void

Inherited from ​

Component.setMaxListeners

setProperty() ​

setProperty(propertyKey, value): void

Set a property of the object; the value is not validated, even for a @Configurable property.

Parameters ​

propertyKey ​

string

The property name.

value ​

any

The value.

Returns ​

void

Inherited from ​

Component.setProperty

setPrototypeOf() ​

static setPrototypeOf(o, proto): any

Sets the prototype of a specified object o to object proto or null. Returns the object o.

Parameters ​

o ​

any

The object to change its prototype.

proto ​

object | null

The value of the new prototype or null.

Returns ​

any

Inherited from ​

Component.setPrototypeOf

toLocaleString() ​

toLocaleString(): string

Returns a date converted to a string using the current locale.

Returns ​

string

Inherited from ​

Component.toLocaleString

toString() ​

toString(): string

Returns a string representation of an object.

Returns ​

string

Inherited from ​

Component.toString

valueOf() ​

valueOf(): Object

Returns the primitive value of the specified object.

Returns ​

Object

Inherited from ​

Component.valueOf

values() ​

Call Signature ​

static values<T>(o): T[]

Returns an array of values of the enumerable own properties of an object

Type Parameters ​
T ​

T

Parameters ​
o ​

{[s: string]: T; } | ArrayLike<T>

Object that contains the properties and methods. This can be an object that you created or an existing Document Object Model (DOM) object.

Returns ​

T[]

Inherited from ​

Component.values

Call Signature ​

static values(o): any[]

Returns an array of values of the enumerable own properties of an object

Parameters ​
o ​

{ }

Object that contains the properties and methods. This can be an object that you created or an existing Document Object Model (DOM) object.

Returns ​

any[]

Inherited from ​

Component.values

wrap() ​

wrap<T>(key, fn, options?): Promise<T>

Read the value of a key, or compute it and cache it when it is missing or expired (the cache-aside pattern).

  • The concurrent calls on the same key share one call and its result, whatever their fn and options.
  • A value found in a lower store is copied to the stores above it, with the time it has left (or the ttl of the call when it never expires).
  • With a refresh threshold, a cached value with less time to live than the threshold is returned at once and recomputed in the background (one refresh per key at a time), then written to its store and the stores above (to all the stores with refreshAllStores); a 'refresh' event reports the new value or the failure, the cached value kept then. A threshold higher than the TTL refreshes the value on each call.
  • A computed value is written with Cacher.set (a 'set' event); undefined is cached too.

Type Parameters ​

T ​

T

Parameters ​

key ​

string

The key.

fn ​

() => T | Promise<T>

Computes the value when it is missing; its failure rejects the call and nothing is cached.

options? ​

number | WrapOptions<T>

The time to live in milliseconds (0 never expires), or the TTL and the refresh threshold. Default to the cache's ttl and refreshThreshold options.

Returns ​

Promise<T>

The cached or computed value.

Throws ​

The error thrown by fn, or the failure of a store writing the computed value (without nonBlocking).

Example ​

typescript
import type {Cacher} from 'lakutata/com/cacher'

declare const cache: Cacher
declare function loadRates(): Promise<Record<string, number>>

//Loaded at most once per hour; in its last 5 minutes, served while reloaded in the background
const rates: Record<string, number> = await cache.wrap('rates', loadRates, {ttl: 3600000, refreshThreshold: 300000})
//A TTL depending on the value
const user: {id: number, guest: boolean} = await cache.wrap('user:1', async () => ({id: 1, guest: true}), {
    ttl: (value: {id: number, guest: boolean}): number => value.guest ? 60000 : 3600000
})

Released under the MIT License.

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