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package etcd
import (
"context"
"crypto/tls"
"crypto/x509"
"errors"
"io/ioutil"
"net"
"net/http"
"time"
etcd "go.etcd.io/etcd/client/v2"
)
var (
// ErrNoKey indicates a client method needs a key but receives none.
ErrNoKey = errors.New("no key provided")
// ErrNoValue indicates a client method needs a value but receives none.
ErrNoValue = errors.New("no value provided")
)
// Client is a wrapper around the etcd client.
type Client interface {
// GetEntries queries the given prefix in etcd and returns a slice
// containing the values of all keys found, recursively, underneath that
// prefix.
GetEntries(prefix string) ([]string, error)
// WatchPrefix watches the given prefix in etcd for changes. When a change
// is detected, it will signal on the passed channel. Clients are expected
// to call GetEntries to update themselves with the latest set of complete
// values. WatchPrefix will always send an initial sentinel value on the
// channel after establishing the watch, to ensure that clients always
// receive the latest set of values. WatchPrefix will block until the
// context passed to the NewClient constructor is terminated.
WatchPrefix(prefix string, ch chan struct{})
// Register a service with etcd.
Register(s Service) error
// Deregister a service with etcd.
Deregister(s Service) error
}
type client struct {
keysAPI etcd.KeysAPI
ctx context.Context
}
// ClientOptions defines options for the etcd client. All values are optional.
// If any duration is not specified, a default of 3 seconds will be used.
type ClientOptions struct {
Cert string
Key string
CACert string
DialTimeout time.Duration
DialKeepAlive time.Duration
HeaderTimeoutPerRequest time.Duration
}
// NewClient returns Client with a connection to the named machines. It will
// return an error if a connection to the cluster cannot be made. The parameter
// machines needs to be a full URL with schemas. e.g. "http://localhost:2379"
// will work, but "localhost:2379" will not.
func NewClient(ctx context.Context, machines []string, options ClientOptions) (Client, error) {
if options.DialTimeout == 0 {
options.DialTimeout = 3 * time.Second
}
if options.DialKeepAlive == 0 {
options.DialKeepAlive = 3 * time.Second
}
if options.HeaderTimeoutPerRequest == 0 {
options.HeaderTimeoutPerRequest = 3 * time.Second
}
transport := etcd.DefaultTransport
if options.Cert != "" && options.Key != "" {
tlsCert, err := tls.LoadX509KeyPair(options.Cert, options.Key)
if err != nil {
return nil, err
}
caCertCt, err := ioutil.ReadFile(options.CACert)
if err != nil {
return nil, err
}
caCertPool := x509.NewCertPool()
caCertPool.AppendCertsFromPEM(caCertCt)
transport = &http.Transport{
TLSClientConfig: &tls.Config{
Certificates: []tls.Certificate{tlsCert},
RootCAs: caCertPool,
},
Dial: func(network, address string) (net.Conn, error) {
return (&net.Dialer{
Timeout: options.DialTimeout,
KeepAlive: options.DialKeepAlive,
}).Dial(network, address)
},
}
}
ce, err := etcd.New(etcd.Config{
Endpoints: machines,
Transport: transport,
HeaderTimeoutPerRequest: options.HeaderTimeoutPerRequest,
})
if err != nil {
return nil, err
}
return &client{
keysAPI: etcd.NewKeysAPI(ce),
ctx: ctx,
}, nil
}
// GetEntries implements the etcd Client interface.
func (c *client) GetEntries(key string) ([]string, error) {
resp, err := c.keysAPI.Get(c.ctx, key, &etcd.GetOptions{Recursive: true})
if err != nil {
return nil, err
}
// Special case. Note that it's possible that len(resp.Node.Nodes) == 0 and
// resp.Node.Value is also empty, in which case the key is empty and we
// should not return any entries.
if len(resp.Node.Nodes) == 0 && resp.Node.Value != "" {
return []string{resp.Node.Value}, nil
}
entries := make([]string, len(resp.Node.Nodes))
for i, node := range resp.Node.Nodes {
entries[i] = node.Value
}
return entries, nil
}
// WatchPrefix implements the etcd Client interface.
func (c *client) WatchPrefix(prefix string, ch chan struct{}) {
watch := c.keysAPI.Watcher(prefix, &etcd.WatcherOptions{AfterIndex: 0, Recursive: true})
ch <- struct{}{} // make sure caller invokes GetEntries
for {
if _, err := watch.Next(c.ctx); err != nil {
return
}
ch <- struct{}{}
}
}
func (c *client) Register(s Service) error {
if s.Key == "" {
return ErrNoKey
}
if s.Value == "" {
return ErrNoValue
}
var err error
if s.TTL != nil {
_, err = c.keysAPI.Set(c.ctx, s.Key, s.Value, &etcd.SetOptions{
PrevExist: etcd.PrevIgnore,
TTL: s.TTL.ttl,
})
} else {
_, err = c.keysAPI.Create(c.ctx, s.Key, s.Value)
}
return err
}
func (c *client) Deregister(s Service) error {
if s.Key == "" {
return ErrNoKey
}
_, err := c.keysAPI.Delete(c.ctx, s.Key, s.DeleteOptions)
return err
}
|
