iomem

iomem

WARNING! THIS SOFTWARE IS UNFINISHED! ANYTHING CAN CHANGE AT ANY MOMENT!

Memcached client implementing binary protocol with native multiple keys support.

Features

• Binary Memcached protocol implementation
• Multiple keys support aka multi-get, multi-set, multi-del, etc..
• Async interface
• Streams interface
• Hashring aka consistent hashing

Installation

yarn add iomem

or

npm install iomem

Usage

Default

const Mem = require('iomem')
const iomem = new Mem()

await iomem.set('test:key', 'hello')
const value = await iomem.get('test:key')

console.log(value)

iomem.end() // call end() when your script or web server exits

Multi-get, multi-set, multi-del, etc..

const Mem = require('iomem')
const iomem = new Mem()

// set the same value for multiple keys
await iomem.set(['test:key1', 'test:key2'], 'test')

// set different values with `key => value` object
await iomem.setk({ 'test:key1': 'hello', 'test:key2': 'world' })

// get values as an array
await iomem.get(['test:key1', 'test:key2'])

// get values as a `key => value` object
await iomem.getk(['test:key1', 'test:key2'])

// delete keys 
await iomem.del(['test:key1', 'test:key2'])

...

iomem.end() // call end() when your script or web server exits

For more details please see Commands section.

Custom servers

const Mem = require('iomem')
const iomem = new Mem(['127.0.0.1:11211', '127.0.0.2:11211'])
...
iomem.end() // call end() when your script or web server exits

Supported address formats:

// host
or
// host:port
or
// username:password@host:port
or
// username:password@host
or
// /path/to/memcached.sock

Commands

Please note that the library automatically performs value serialization and deserialization. Here is a list of the possible value types:

value: string|String|Number|BigInt|Boolean|Date|Array|Buffer|Object|null

Be aware that any value in the below commands list refers to a value of any type specified above.

The following data types for key and expiry are must by ensured by the library user:

key: string - storage key, 250 bytes max as defined in Memcached

expiry: unsigned integer - time interval in seconds, defaults to expiry from the client config.

For more details please Memcached commands.

GET

get(key): value|null - get a value for a single key.

get([key1, ...]): [value, ...] - get an array of values for multiple keys.

getk(key): {key: value}|null - get a key => value object for a single key.

getk([key1, ...]): {key: value, ...} - get a key => value object for multiple keys.

gets(key): {key: cas}|null - get a key => cas object for a single key.

gets([key1, ...]): {key: cas, ...} - get a key => cas object for multiple keys.

getsv(key): {key: {value, cas}}|null - get a key => { value, cas } object for a single key.

getsv([key1, ...]): {key: {value, cas}}, ...} - get a key => { value, cas } object for multiple keys.

SET

Set methods return true when all values were successfully set. Otherwise, when client receives 0x0001 or 0x0002 statuses from Memcached (this is abnormal behavior for set commands), the returned value will be false.

set(key, value, expiry): true|false - set a value for a single key.

set([key1, ...], value, expiry): true|false - set the same value for multiple keys.

setk({key: value, ...}, expiry): true|false - set multiple values with key => value object.

ADD

Add commands set a key only when it is not set yet (a key does not exist in the Memcached). The methods will return false when at least one key was not successfully set (meaning a key was already set with some value, so it was not set with the value you provided with a command).

add(key, value, expiry): true|false - add a value for a single key.

add([key1, ...], value, expiry): true|false - add the same value for multiple keys.

addk({key: value, ...}, expiry): true|false - add multiple values with key => value object.

REPLACE

Replace commands set a new value for a key only when it is already set with some value (a key does exist in the Memcached). The methods will return false when at least one key was not successfully set (meaning a key did not exist in the Memcached when you ran a command).

replace(key, value, expiry): true|false - replace a value for a single key.

replace([key1, ...], value, expiry): true|false - replace the same value for multiple keys.

replacek({key: value, ...}, expiry): true|false - replace multiple values with key => value object.

CAS

The cas command sets a key with a new value only when cas parameter matches cas value stored in the key. To retrieve the current cas value for a key please see GET commands.

cas(key, value, cas, expiry): true|false - set a value if the cas matches.

DEL

Delete commands delete a key only when it exists. The methods will return false when at least one key does not exist.

del(key): true|false - delete a key.

del([key1, ...]): true|false - delete multiple keys.

INCERMENT AND DECREMENT

Increment and decrement commands add or substract the specified delta value from the current counter value initialized with initial value. You can use SET, ADD, REPLACE commands to set a counter value.

incr(key, initial, delta, expiry): value - increments counter and returns its value.

decr(key, initial, delta, expiry): value - decrements coutner and returns its value.

Paramters:

initial: BigInt - initial counter value

delta: BigInt - amount to add or substruct from a counter

expiry - see Commands

If you want to get the current value from a counter without changing its value, use GET commands and manually deserialize the response buffer.

...
const FLAGS = require('iomem/src/flags')
const { deserialize } = require('iomem/src/serializer')

deserialize(await iomem.get('test:foo'), FLAGS.bigint)
...

FLUSH

flush() - flush cached items.

flush(expiry) - flush cached items in expiry seconds.

Streams

Case #1:

Force iomem methods to return a stream instead of a promise by passing stream: true flag.

const Mem = require('iomem')
const iomem = new Mem(['127.0.0.1:11211'], { stream: true })

const { pipeline, Writable } = require('node:stream')

class Echo extends Writable {
  constructor (opts) {
    super({ objectMode: true, ...opts })
  }

  _write (data, _, cb) {
    console.log(data)
    cb()
  }
}

pipeline(iomem.get('test:a'), new Echo(), err => {
  if (err) {
    console.error(err)
  }
})

...

iomem.end() // call end() when your script or web server exits

Case #2:

Create a stream with special method called stream and supply data with readable stream. Do not care about stream flag.

This is the recommended approach

const Mem = require('iomem')
const iomem = new Mem(['127.0.0.1:11211'])

const { pipeline, Readable, Writable } = require('node:stream')

class Echo extends Writable {
  constructor (opts) {
    super({ objectMode: true, ...opts })
  }

  _write (data, _, cb) {
    console.log(data)
    cb()
  }
}

pipeline(Readable.from([Mem.get('test:a')][Symbol.iterator]()), iomem.stream(), new Echo(), err => {
  if (err) {
    console.error(err)
  }
})

...

iomem.end() // call end() when your script or web server exits

Case #3:

Combine case #1 with readable stream to supply extra data into the stream.

const Mem = require('iomem')
const iomem = new Mem(['127.0.0.1:11211'], { stream: true })

const { pipeline, Readable, Writable } = require('node:stream')

class Echo extends Writable {
  constructor (opts) {
    super({ objectMode: true, ...opts })
  }

  _write (data, _, cb) {
    console.log(data)
    cb()
  }
}

pipeline(Readable.from([Mem.get('test:a')][Symbol.iterator]()), iomem.get('test:b'), new Echo(), err => {
  if (err) {
    console.error(err)
  }
})

...

iomem.end() // call end() when your script or web server exits

Options

{
  stream: false, // set true to force client methods return streams instead of promises
  expiry: 60 * 60 * 24 * 1, // 1 day, time interval in seconds
  maxConnections: 10, // max connections per server
  connectionTimeout: 1000, // connection timeout in milliseconds
  timeout: 500, // request timeout in milliseconds
  retries: 2, // request retries - max retries
  retriesDelay: 100, // request retries - initial delay
  retriesFactor: 2 // request retries - exponential factor
}

Please take a look at Case #2 for a better approach before enabling stream flag.