msg

Documentation

Overview

Package msg defines the Service structure which is used for service discovery.

Index

• func Domain(s string) string
• func Path(s, prefix string) string
• func PathWithWildcard(s, prefix string) (string, bool)
• type Service
  • func Group(sx []Service) []Service
  • func (s *Service) HostType() (what uint16, normalized net.IP)
  • func (s *Service) NewA(name string, ip net.IP) *dns.A
  • func (s *Service) NewAAAA(name string, ip net.IP) *dns.AAAA
  • func (s *Service) NewCNAME(name string, target string) *dns.CNAME
  • func (s *Service) NewMX(name string) *dns.MX
  • func (s *Service) NewNS(name string) *dns.NS
  • func (s *Service) NewPTR(name string, target string) *dns.PTR
  • func (s *Service) NewSRV(name string, weight uint16) *dns.SRV
  • func (s *Service) NewTXT(name string) *dns.TXT
  • func (s *Service) RR() *dns.TXT

Functions

func Domain

func Domain(s string) string

Domain is the opposite of Path.

func Path

func Path(s, prefix string) string

Path converts a domainname to an etcd path. If s looks like service.staging.skydns.local., the resulting key will be /skydns/local/skydns/staging/service .

func PathWithWildcard

func PathWithWildcard(s, prefix string) (string, bool)

PathWithWildcard ascts as Path, but if a name contains wildcards (* or any), the name will be chopped of before the (first) wildcard, and we do a highler evel search and later find the matching names. So service.*.skydns.local, will look for all services under skydns.local and will later check for names that match service.*.skydns.local. If a wildcard is found the returned bool is true.

Types

type Service

type Service struct {
	Host     string `json:"host,omitempty"`
	Port     int    `json:"port,omitempty"`
	Priority int    `json:"priority,omitempty"`
	Weight   int    `json:"weight,omitempty"`
	Text     string `json:"text,omitempty"`
	Mail     bool   `json:"mail,omitempty"` // Be an MX record. Priority becomes Preference.
	TTL      uint32 `json:"ttl,omitempty"`

	// When a SRV record with a "Host: IP-address" is added, we synthesize
	// a srv.Target domain name.  Normally we convert the full Key where
	// the record lives to a DNS name and use this as the srv.Target.  When
	// TargetStrip > 0 we strip the left most TargetStrip labels from the
	// DNS name.
	TargetStrip int `json:"targetstrip,omitempty"`

	// Group is used to group (or *not* to group) different services
	// together. Services with an identical Group are returned in the same
	// answer.
	Group string `json:"group,omitempty"`

	// Etcd key where we found this service and ignored from json un-/marshalling
	Key string `json:"-"`
}

Service defines a discoverable service in etcd. It is the rdata from a SRV record, but with a twist. Host (Target in SRV) must be a domain name, but if it looks like an IP address (4/6), we will treat it like an IP address.

func Group

func Group(sx []Service) []Service

Group checks the services in sx, it looks for a Group attribute on the shortest keys. If there are multiple shortest keys *and* the group attribute disagrees (and is not empty), we don't consider it a group. If a group is found, only services with *that* group (or no group) will be returned.

func (*Service) HostType

func (s *Service) HostType() (what uint16, normalized net.IP)

HostType returns the DNS type of what is encoded in the Service Host field. We're reusing dns.TypeXXX to not reinvent a new set of identifiers.

dns.TypeA: the service's Host field contains an A record. dns.TypeAAAA: the service's Host field contains an AAAA record. dns.TypeCNAME: the service's Host field contains a name.

Note that a service can double/triple as a TXT record or MX record.

func (*Service) NewA

func (s *Service) NewA(name string, ip net.IP) *dns.A

NewA returns a new A record based on the Service.

func (*Service) NewAAAA

func (s *Service) NewAAAA(name string, ip net.IP) *dns.AAAA

NewAAAA returns a new AAAA record based on the Service.

func (*Service) NewCNAME

func (s *Service) NewCNAME(name string, target string) *dns.CNAME

NewCNAME returns a new CNAME record based on the Service.

func (*Service) NewMX

func (s *Service) NewMX(name string) *dns.MX

NewMX returns a new MX record based on the Service.

func (*Service) NewNS

func (s *Service) NewNS(name string) *dns.NS

NewNS returns a new NS record based on the Service.

func (*Service) NewPTR

func (s *Service) NewPTR(name string, target string) *dns.PTR

NewPTR returns a new PTR record based on the Service.

func (*Service) NewSRV

func (s *Service) NewSRV(name string, weight uint16) *dns.SRV

NewSRV returns a new SRV record based on the Service.

func (*Service) NewTXT

func (s *Service) NewTXT(name string) *dns.TXT

NewTXT returns a new TXT record based on the Service.

func (*Service) RR

func (s *Service) RR() *dns.TXT

RR returns an RR representation of s. It is in a condensed form to minimize space when this is returned in a DNS message. The RR will look like:

	1.rails.production.east.skydns.local. 300 CH TXT "service1.example.com:8080(10,0,,false)[0,]"
                     etcd Key              Ttl               Host:Port          <   see below   >

between parens: (Priority, Weight, Text (only first 200 bytes!), Mail) between blockquotes: [TargetStrip,Group] If the record is synthesised by CoreDNS (i.e. no lookup in etcd happened):

TODO(miek): what to put here?