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// Package discover provides functions to get metadata for different
// cloud environments.
package discover
import (
"fmt"
"log"
"sort"
"strings"
"sync"
"github.com/hashicorp/go-discover/provider/aliyun"
"github.com/hashicorp/go-discover/provider/aws"
"github.com/hashicorp/go-discover/provider/gce"
"github.com/hashicorp/go-discover/provider/mdns"
"github.com/hashicorp/go-discover/provider/os"
"github.com/hashicorp/go-discover/provider/packet"
)
// Provider has lookup functions for meta data in a
// cloud environment.
type Provider interface {
// Addrs looks up addresses in the cloud environment according to the
// configuration provided in args.
Addrs(args map[string]string, l *log.Logger) ([]string, error)
// Help provides the configuration help for the command line client.
Help() string
}
// ProviderWithUserAgent is a provider that declares it's user agent. Not all
// providers support this.
type ProviderWithUserAgent interface {
// SetUserAgent sets the user agent on the provider to the provided string.
SetUserAgent(s string)
}
// Providers contains all available providers.
var Providers = map[string]Provider{
"aliyun": &aliyun.Provider{},
"aws": &aws.Provider{},
"gce": &gce.Provider{},
"mdns": &mdns.Provider{},
"os": &os.Provider{},
"packet": &packet.Provider{},
}
// Discover looks up metadata in different cloud environments.
type Discover struct {
// Providers is the list of address lookup providers.
// If nil, the default list of providers is used.
Providers map[string]Provider
// userAgent is the string to use for requests, when supported.
userAgent string
// once is used to initialize the actual list of providers.
once sync.Once
}
// Option is used as an initialization option/
type Option func(*Discover) error
// New creates a new discover client with the given options.
func New(opts ...Option) (*Discover, error) {
d := new(Discover)
for _, opt := range opts {
if err := opt(d); err != nil {
return nil, err
}
}
d.once.Do(d.initProviders)
return d, nil
}
// WithUserAgent allows specifying a custom user agent option to send with
// requests when the underlying client library supports it.
func WithUserAgent(agent string) Option {
return func(d *Discover) error {
d.userAgent = agent
return nil
}
}
// WithProviders allows specifying your own set of providers.
func WithProviders(m map[string]Provider) Option {
return func(d *Discover) error {
d.Providers = m
return nil
}
}
// initProviders sets the list of providers to the
// default list of providers if none are configured.
func (d *Discover) initProviders() {
if d.Providers == nil {
d.Providers = Providers
}
}
// Names returns the names of the configured providers.
func (d *Discover) Names() []string {
d.once.Do(d.initProviders)
var names []string
for n := range d.Providers {
names = append(names, n)
}
sort.Strings(names)
return names
}
var globalHelp = `The options for discovering ip addresses are provided as a
single string value in "key=value key=value ..." format where
the values are URL encoded.
provider=aws region=eu-west-1 ...
The options are provider specific and are listed below.
`
// Help describes the format of the configuration string for address discovery
// and the various provider specific options.
func (d *Discover) Help() string {
d.once.Do(d.initProviders)
h := []string{globalHelp}
for _, name := range d.Names() {
h = append(h, d.Providers[name].Help())
}
return strings.Join(h, "\n")
}
// Addrs discovers ip addresses of nodes that match the given filter criteria.
// The config string must have the format 'provider=xxx key=val key=val ...'
// where the keys and values are provider specific. The values are URL encoded.
func (d *Discover) Addrs(cfg string, l *log.Logger) ([]string, error) {
d.once.Do(d.initProviders)
args, err := Parse(cfg)
if err != nil {
return nil, fmt.Errorf("discover: %s", err)
}
name := args["provider"]
if name == "" {
return nil, fmt.Errorf("discover: no provider")
}
providers := d.Providers
if providers == nil {
providers = Providers
}
p := providers[name]
if p == nil {
return nil, fmt.Errorf("discover: unknown provider " + name)
}
l.Printf("[DEBUG] discover: Using provider %q", name)
if typ, ok := p.(ProviderWithUserAgent); ok {
typ.SetUserAgent(d.userAgent)
return p.Addrs(args, l)
}
return p.Addrs(args, l)
}
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