Package Exports

mu-dns

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Readme

mu-transport

The official dns service discovery adapter for mu

Sponsor: nearForm
Status: Experimental

Part of the Official [mu][Mu Suite].

mu-dns is the dns service discovery adapter for [mu][mu].

Install
API
License

Install

$ npm install mu-dns

Purpose

The mu-dns adapter performs DNS lookups either directly against a nominated DNS server or using the system resolver mechanism. It is intended for use in container based deployments for example with Kubernetes or with the fuge development tool.

Operation

Lookup sequence

Mu-dns resolves services as follows:

Perform an SRV query to determine service port number and canonical name
Then perform an A query against the canonical name to determine one or more ip addresses

mode

Mu-dns operates in one of two modes, direct or system depending on the environment configuration.

if DNS_HOST variable is present in the environment then a direct lookup is performed in this case
- Use DNS_HOST and DNS_PORT to connect directly to a DNS server. If DNS_PORT is not set default to 53053 as the port number
if DNS_HOST is not present then use the system based resolver for queries

Query formation

Mu-dns forms SRV queries as follows:

_<port name>._<protocol name>.<service name>.<namespace>.<suffix>

The query is constructed as follows:

<port name> must be supplied
<protocol name> may be supplied, defaults to '_tcp'
<service name> must be supplied
<namespace> may be supplied, otherwise the DNS_NAMESPACE variable is used if supplied, otherwise defaults to 'default'
<suffix> may be supplied, otherwise the DNS_SUFFIX variable is used if supplied, otherwise defaults to 'svc.cluster.local'

Examples

var mu = require('mu')()
var tcp = require('mu-tcp')
var dns = require('mu-dns')

mu.outbound({role: 'basic'}, dns(tcp, {name: 'my_service', portName: '_main'}))

In the above example service name and portName are supplied, this will result in SRV query: '_main._tcp.my_service.default.svc.cluster.local'

mu-dns