Io-memcached NPM

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io-memcached

Memcached client for node.js.

Promise
build-in TCP Connection Pool
support memcached cluster, base on consistent hashing algorithm.

io-memcached is used in my production and works well.

Install

npm install io-memcached

Example

const Memcached = require('io-memcached');

const memcached = new Memcached(['127.0.0.1:11211'], {
    pool: {
        max: 10,
        min: 1
    },
    timeout: 3000
});

(async () => {
    try {
        const key = 'testkey';
        const data = 'test test\r test\n test\r\n \r\n';

        const s = await memcached.set(key, data);
        console.log(':::: set :::::', s);

        const g = await memcached.get(key);
        console.log(':::: get :::::', g);

        const d = await memcached.del(key);
        console.log(':::: del :::::', d);

        await memcached.set(key, 100);
        const cr = await memcached.incr(key, 123);
        console.log(':::: incr result :::::', cr);

        const dr = await memcached.decr(key, 12);
        console.log(':::: decr result :::::', dr);

        await memcached.del(key);
    } catch (error) {
        console.log('error:', error);
    }
})()

API

All public methods base on node native promise.

Setting up clent

The constructor of the memcached client take 2 different arguments server locations and options. Syntax:

var Memcached = require('io-memcached');
var memcached = new Memcached(Server locations, options);

server locations

For uniform style, server locations only support Array at now, even you have only one server. like this:

const memcached = new Memcached(['127.0.0.1:11211']);
const memcached = new Memcached(['192.168.0.1:11211', '192.168.0.2:11211'];

options

clusterAlg : cluster algorithm.
- c-hash : (default). consistent hashing algorithm.
- hash : hash mod algorithm.
clusterAlgFunc : custom cluster algorithm function. receive a key and return a server address, it will ignore the clusterAlg if clusterAlgFunc defined:

const servers = ['127.0.0.1:11211', '127.0.0.2:11211'];
const memcached3 = new Memcached(servers, {
    clusterAlgFunc: function(key) {
        // do something , and return a server address.
        // the result must be in server locations. if not , you will get 'cluster algorithm function error'.

        return '127.0.0.1:11211';
    }
});

pool :
- max : maximum number of tcp connection for everyone server. (default=1)
- min : minimum number of tcp connection to keep in pool at any given time. If this is set >= max, the pool will silently set the min to equal max. (default=0)
timeout : timeout for every request.(default=5000 ms)
maxWaitingClients : maximum number of queued requests allowed.(default=10000)

Get

get(key)

return different type:

undefined : if the key not exist in memcached.
value : the value will be JSON.parse() for object, Number() for number, Buffer.from() for binary, and default string.

Set

set(key, value, ttl=0)

this lib will auto generate flag and store it in memcached for different data type, it's build-in and the flag will be used in get method for parse result data. You do not need to care about it.

ttl is time-to-live for key-value, in seconds. '0' means never expire. Can be up to 30 days. After 30 days, is treated as a unix timestamp of an exact date.

return a string:

STORED : to indicate success.
NOT_STORED : to indicate the data was not stored, but not because of an error. This normally means that the condition for an "add" or a "replace" command wasn't met.
EXISTS : to indicate that the item you are trying to store with a "cas" command has been modified since you last fetched it.
NOT_FOUND : to indicate that the item you are trying to store with a "cas" command did not exist.

Delete

delete(key) alias del(key)

return a string:

DELETED : to indicate success.
NOT_FOUND : to indicate that the item with this key was not found.

Incr / Decr

incr(key, value)
decr(key, value)

return:

NOT_FOUND (string) : the key not exist.
value (number) : value is the new value of the item's data. if a client tries to decrease the value below 0, the new value will be 0.

Error

You should catch errors in you code.

common error

ERROR : means the client sent a nonexistent command name.
CLIENT_ERROR : means some sort of client error in the input line, i.e. the input doesn't conform to the protocol in some way.
SERVER_ERROR : means memcached server error.