clientv3

package
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 Go to latest Published: Mar 19, 2016 License: Apache-2.0 Imports: 14 Imported by: 0

README

etcd/clientv3

Godoc

etcd/clientv3 is the official Go etcd client for v3.

Install

go get github.com/coreos/etcd/clientv3

Get started

Create client using clientv3.New:

cli, err := clientv3.New(clientv3.Config{
	Endpoints:   []string{"localhost:12378", "localhost:22378", "localhost:32378"},
	DialTimeout: 5 * time.Second,
})
if err != nil {
	// handle error!
}
defer cli.Close()

etcd v3 uses gRPC for remote procedure calls. And clientv3 uses grpc-go to connect to etcd. Make sure to close the client after using it. If the client is not closed, the connection will have leaky goroutines. To specify client request timeout, pass context.WithTimeout to APIs:

ctx, cancel := context.WithTimeout(context.Background(), timeout)
resp, err := kvc.Put(ctx, "sample_key", "sample_value")
cancel()
if err != nil {
    // handle error!
}
// use the response

Error Handling

etcd client returns 2 types of errors:

  1. context error: canceled or deadline exceeded.
  2. gRPC error: see v3rpc/error.

Here is the example code to handle client errors:

resp, err := kvc.Put(ctx, "", "")
if err != nil {
	if err == context.Canceled {
		// ctx is canceled by another routine
	} else if err == context.DeadlineExceeded {
		// ctx is attached with a deadline and it exceeded
	} else if verr, ok := err.(*v3rpc.ErrEmptyKey); ok {
		// process (verr.Errors)
	} else {
		// bad cluster endpoints, which are not etcd servers
	}
}

Examples

More code examples can be found at GoDoc.

Documentation

Overview

Package clientv3 implements the official Go etcd client for v3.

Create client using `clientv3.New`: 

cli, err := clientv3.New(clientv3.Config{
	Endpoints:   []string{"localhost:12378", "localhost:22378", "localhost:32378"},
	DialTimeout: 5 * time.Second,
})
if err != nil {
	// handle error!
}
defer cli.Close()

Make sure to close the client after using it. If the client is not closed, the connection will have leaky goroutines.

To specify client request timeout, pass context.WithTimeout to APIs: 

ctx, cancel := context.WithTimeout(context.Background(), timeout)
resp, err := kvc.Put(ctx, "sample_key", "sample_value")
cancel()
if err != nil {
    // handle error!
}
// use the response

etcd client returns 2 types of errors:

  1. context error: canceled or deadline exceeded.
  2. gRPC error: see https://github.com/coreos/etcd/blob/master/etcdserver/api/v3rpc/error.go.

Here is the example code to handle client errors: 

resp, err := kvc.Put(ctx, "", "")
if err != nil {
	if err == context.Canceled {
		// ctx is canceled by another routine
	} else if err == context.DeadlineExceeded {
		// ctx is attached with a deadline and it exceeded
	} else if verr, ok := err.(*v3rpc.ErrEmptyKey); ok {
		// process (verr.Errors)
	} else {
		// bad cluster endpoints, which are not etcd servers
	}
}
Example 
package main

import (
	"log"
	"time"

	"github.com/coreos/etcd/Godeps/_workspace/src/golang.org/x/net/context"
	"github.com/coreos/etcd/clientv3"
)

var (
	dialTimeout    = 5 * time.Second
	requestTimeout = 1 * time.Second
	endpoints      = []string{"localhost:2378", "localhost:22378", "http://localhost:32380"}
)

func main() {
	cli, err := clientv3.New(clientv3.Config{
		Endpoints:   endpoints,
		DialTimeout: dialTimeout,
	})
	if err != nil {
		log.Fatal(err)
	}
	defer cli.Close() // make sure to close the client

	_, err = cli.Put(context.TODO(), "foo", "bar")
	if err != nil {
		log.Fatal(err)
	}
}

Output:

Index

Examples

Constants

This section is empty.

Variables

View Source 
var (
	ErrNoAvailableEndpoints = errors.New("etcdclient: no available endpoints")
)

Functions

This section is empty.

Types

type Auth 

type Auth interface {
	// AuthEnable enables auth of a etcd cluster.
	AuthEnable(ctx context.Context) (*AuthEnableResponse, error)
}

func NewAuth 

func NewAuth(c *Client) Auth

type AuthEnableResponse 

type AuthEnableResponse pb.AuthEnableResponse

type Client 

type Client struct {
	Cluster
	KV
	Lease
	Watcher
	Auth
	Maintenance
	// contains filtered or unexported fields
}

Client provides and manages an etcd v3 client session.

func New 

func New(cfg Config) (*Client, error)

New creates a new etcdv3 client from a given configuration.

func NewFromURL 

func NewFromURL(url string) (*Client, error)

NewFromURL creates a new etcdv3 client from a URL.

func (*Client) ActiveConnection 

func (c *Client) ActiveConnection() *grpc.ClientConn

ActiveConnection returns the current in-use connection

func (*Client) Close 

func (c *Client) Close() error

Close shuts down the client's etcd connections.

func (*Client) Ctx 

func (c *Client) Ctx() context.Context

Ctx is a context for "out of band" messages (e.g., for sending "clean up" message when another context is canceled). It is canceled on client Close().

func (*Client) Dial 

func (c *Client) Dial(endpoint string) (*grpc.ClientConn, error)

Dial establishes a connection for a given endpoint using the client's config

func (*Client) Endpoints 

func (c *Client) Endpoints() []string

Endpoints lists the registered endpoints for the client.

func (*Client) Errors 

func (c *Client) Errors() (errs []error)

Errors returns all errors that have been observed since called last.

type Cluster 

type Cluster interface {
	// MemberList lists the current cluster membership.
	MemberList(ctx context.Context) (*MemberListResponse, error)

	// MemberLeader returns the current leader member.
	MemberLeader(ctx context.Context) (*Member, error)

	// MemberAdd adds a new member into the cluster.
	MemberAdd(ctx context.Context, peerAddrs []string) (*MemberAddResponse, error)

	// MemberRemove removes an existing member from the cluster.
	MemberRemove(ctx context.Context, id uint64) (*MemberRemoveResponse, error)

	// MemberUpdate updates the peer addresses of the member.
	MemberUpdate(ctx context.Context, id uint64, peerAddrs []string) (*MemberUpdateResponse, error)
}
Example (MemberAdd) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints[:2],
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

peerURLs := endpoints[2:]
mresp, err := cli.MemberAdd(context.Background(), peerURLs)
if err != nil {
	log.Fatal(err)
}
fmt.Println("added member.PeerURLs:", mresp.Member.PeerURLs)
// added member.PeerURLs: [http://localhost:32380]

Output:
Example (MemberLeader) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

resp, err := cli.MemberLeader(context.Background())
if err != nil {
	log.Fatal(err)
}
fmt.Println("leader:", resp.Name)
// leader: infra1

Output:
Example (MemberList) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

resp, err := cli.MemberList(context.Background())
if err != nil {
	log.Fatal(err)
}
fmt.Println("members:", len(resp.Members))
// members: 3

Output:
Example (MemberRemove) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints[1:],
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

resp, err := cli.MemberList(context.Background())
if err != nil {
	log.Fatal(err)
}

_, err = cli.MemberRemove(context.Background(), resp.Members[0].ID)
if err != nil {
	log.Fatal(err)
}

Output:
Example (MemberUpdate) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

resp, err := cli.MemberList(context.Background())
if err != nil {
	log.Fatal(err)
}

peerURLs := []string{"http://localhost:12378"}
_, err = cli.MemberUpdate(context.Background(), resp.Members[0].ID, peerURLs)
if err != nil {
	log.Fatal(err)
}

Output:

func NewCluster 

func NewCluster(c *Client) Cluster

type Cmp 

type Cmp pb.Compare

func Compare 

func Compare(cmp Cmp, result string, v interface{}) Cmp

func CreatedRevision 

func CreatedRevision(key string) Cmp

func ModifiedRevision 

func ModifiedRevision(key string) Cmp

func Value 

func Value(key string) Cmp

func Version 

func Version(key string) Cmp

type CompareResult 

type CompareResult int

type CompareTarget 

type CompareTarget int
const (
	CompareVersion CompareTarget = iota
	CompareCreated
	CompareModified
	CompareValue
)

type Config 

type Config struct {
	// Endpoints is a list of URLs
	Endpoints []string

	// RetryDialer chooses the next endpoint to use
	RetryDialer EndpointDialer

	// DialTimeout is the timeout for failing to establish a connection.
	DialTimeout time.Duration

	// TLS holds the client secure credentials, if any.
	TLS *tls.Config
}

type DefragmentResponse 

type DefragmentResponse pb.DefragmentResponse

type DeleteResponse 

type DeleteResponse pb.DeleteRangeResponse

type EndpointDialer 

type EndpointDialer func(*Client) (*grpc.ClientConn, error)

EndpointDialer is a policy for choosing which endpoint to dial next

type GetResponse 

type GetResponse pb.RangeResponse

type KV 

type KV interface {
	// Put puts a key-value pair into etcd.
	// Note that key,value can be plain bytes array and string is
	// an immutable representation of that bytes array.
	// To get a string of bytes, do string([]byte(0x10, 0x20)).
	Put(ctx context.Context, key, val string, opts ...OpOption) (*PutResponse, error)

	// Get retrieves keys.
	// By default, Get will return the value for "key", if any.
	// When passed WithRange(end), Get will return the keys in the range [key, end).
	// When passed WithFromKey(), Get returns keys greater than or equal to key.
	// When passed WithRev(rev) with rev > 0, Get retrieves keys at the given revision;
	// if the required revision is compacted, the request will fail with ErrCompacted .
	// When passed WithLimit(limit), the number of returned keys is bounded by limit.
	// When passed WithSort(), the keys will be sorted.
	Get(ctx context.Context, key string, opts ...OpOption) (*GetResponse, error)

	// Delete deletes a key, or optionally using WithRange(end), [key, end).
	Delete(ctx context.Context, key string, opts ...OpOption) (*DeleteResponse, error)

	// Compact compacts etcd KV history before the given rev.
	Compact(ctx context.Context, rev int64) error

	// Do applies a single Op on KV without a transaction.
	// Do is useful when creating arbitrary operations to be issued at a
	// later time; the user can range over the operations, calling Do to
	// execute them. Get/Put/Delete, on the other hand, are best suited
	// for when the	operation should be issued at the time of declaration.
	Do(ctx context.Context, op Op) (OpResponse, error)

	// Txn creates a transaction.
	Txn(ctx context.Context) Txn
}
Example (Compact) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

ctx, cancel := context.WithTimeout(context.Background(), requestTimeout)
resp, err := cli.Get(ctx, "foo")
cancel()
if err != nil {
	log.Fatal(err)
}
compRev := resp.Header.Revision // specify compact revision of your choice

ctx, cancel = context.WithTimeout(context.Background(), requestTimeout)
err = cli.Compact(ctx, compRev)
cancel()
if err != nil {
	log.Fatal(err)
}

Output:
Example (Delete) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

ctx, cancel := context.WithTimeout(context.Background(), requestTimeout)
resp, err := cli.Delete(ctx, "key", clientv3.WithPrefix())
cancel()
if err != nil {
	log.Fatal(err)
}
fmt.Println("Deleted", resp.Deleted, "keys")
// Deleted n keys

Output:
Example (Do) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

ops := []clientv3.Op{
	clientv3.OpPut("put-key", "123"),
	clientv3.OpGet("put-key"),
	clientv3.OpPut("put-key", "456")}

for _, op := range ops {
	if _, err := cli.Do(context.TODO(), op); err != nil {
		log.Fatal(err)
	}
}

Output:
Example (Get) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

_, err = cli.Put(context.TODO(), "foo", "bar")
if err != nil {
	log.Fatal(err)
}

ctx, cancel := context.WithTimeout(context.Background(), requestTimeout)
resp, err := cli.Get(ctx, "foo")
cancel()
if err != nil {
	log.Fatal(err)
}
for _, ev := range resp.Kvs {
	fmt.Printf("%s : %s\n", ev.Key, ev.Value)
}
// foo : bar

Output:
Example (GetSortedPrefix) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

for i := range make([]int, 3) {
	ctx, cancel := context.WithTimeout(context.Background(), requestTimeout)
	_, err = cli.Put(ctx, fmt.Sprintf("key_%d", i), "value")
	cancel()
	if err != nil {
		log.Fatal(err)
	}
}

ctx, cancel := context.WithTimeout(context.Background(), requestTimeout)
resp, err := cli.Get(ctx, "key", clientv3.WithPrefix(), clientv3.WithSort(clientv3.SortByKey, clientv3.SortDescend))
cancel()
if err != nil {
	log.Fatal(err)
}
for _, ev := range resp.Kvs {
	fmt.Printf("%s : %s\n", ev.Key, ev.Value)
}
// key_2 : value
// key_1 : value
// key_0 : value

Output:
Example (Put) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

ctx, cancel := context.WithTimeout(context.Background(), requestTimeout)
resp, err := cli.Put(ctx, "sample_key", "sample_value")
cancel()
if err != nil {
	log.Fatal(err)
}
fmt.Println("current revision:", resp.Header.Revision) // revision start at 1
// current revision: 2

Output:
Example (Txn) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

kvc := clientv3.NewKV(cli)

_, err = kvc.Put(context.TODO(), "key", "xyz")
if err != nil {
	log.Fatal(err)
}

ctx, cancel := context.WithTimeout(context.Background(), requestTimeout)
_, err = kvc.Txn(ctx).
	If(clientv3.Compare(clientv3.Value("key"), ">", "abc")). // txn value comparisons are lexical
	Then(clientv3.OpPut("key", "XYZ")).                      // this runs, since 'xyz' > 'abc'
	Else(clientv3.OpPut("key", "ABC")).
	Commit()
cancel()
if err != nil {
	log.Fatal(err)
}

gresp, err := kvc.Get(context.TODO(), "key")
cancel()
if err != nil {
	log.Fatal(err)
}
for _, ev := range gresp.Kvs {
	fmt.Printf("%s : %s\n", ev.Key, ev.Value)
}
// key : XYZ

Output:

func NewKV 

func NewKV(c *Client) KV

type Lease 

type Lease interface {
	// Create creates a new lease.
	Create(ctx context.Context, ttl int64) (*LeaseCreateResponse, error)

	// Revoke revokes the given lease.
	Revoke(ctx context.Context, id LeaseID) (*LeaseRevokeResponse, error)

	// KeepAlive keeps the given lease alive forever.
	KeepAlive(ctx context.Context, id LeaseID) (<-chan *LeaseKeepAliveResponse, error)

	// KeepAliveOnce renews the lease once. In most of the cases, Keepalive
	// should be used instead of KeepAliveOnce.
	KeepAliveOnce(ctx context.Context, id LeaseID) (*LeaseKeepAliveResponse, error)

	// Close releases all resources Lease keeps for efficient communication
	// with the etcd server.
	Close() error
}
Example (Create) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

// minimum lease TTL is 5-second
resp, err := cli.Create(context.TODO(), 5)
if err != nil {
	log.Fatal(err)
}

// after 5 seconds, the key 'foo' will be removed
_, err = cli.Put(context.TODO(), "foo", "bar", clientv3.WithLease(clientv3.LeaseID(resp.ID)))
if err != nil {
	log.Fatal(err)
}

Output:
Example (KeepAlive) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

resp, err := cli.Create(context.TODO(), 5)
if err != nil {
	log.Fatal(err)
}

_, err = cli.Put(context.TODO(), "foo", "bar", clientv3.WithLease(clientv3.LeaseID(resp.ID)))
if err != nil {
	log.Fatal(err)
}

// the key 'foo' will be kept forever
_, err = cli.KeepAlive(context.TODO(), clientv3.LeaseID(resp.ID))
if err != nil {
	log.Fatal(err)
}

Output:
Example (KeepAliveOnce) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

resp, err := cli.Create(context.TODO(), 5)
if err != nil {
	log.Fatal(err)
}

_, err = cli.Put(context.TODO(), "foo", "bar", clientv3.WithLease(clientv3.LeaseID(resp.ID)))
if err != nil {
	log.Fatal(err)
}

// to renew the lease only once
_, err = cli.KeepAliveOnce(context.TODO(), clientv3.LeaseID(resp.ID))
if err != nil {
	log.Fatal(err)
}

Output:
Example (Revoke) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

resp, err := cli.Create(context.TODO(), 5)
if err != nil {
	log.Fatal(err)
}

_, err = cli.Put(context.TODO(), "foo", "bar", clientv3.WithLease(clientv3.LeaseID(resp.ID)))
if err != nil {
	log.Fatal(err)
}

// revoking lease expires the key attached to its lease ID
_, err = cli.Revoke(context.TODO(), clientv3.LeaseID(resp.ID))
if err != nil {
	log.Fatal(err)
}

gresp, err := cli.Get(context.TODO(), "foo")
if err != nil {
	log.Fatal(err)
}
fmt.Println("number of keys:", len(gresp.Kvs))
// number of keys: 0

Output:

func NewLease 

func NewLease(c *Client) Lease

type LeaseCreateResponse 

type LeaseCreateResponse pb.LeaseCreateResponse

type LeaseID 

type LeaseID int64
const (

	// NoLease is a lease ID for the absence of a lease.
	NoLease LeaseID = 0
)

type LeaseKeepAliveResponse 

type LeaseKeepAliveResponse pb.LeaseKeepAliveResponse

type LeaseRevokeResponse 

type LeaseRevokeResponse pb.LeaseRevokeResponse

type Maintenance 

type Maintenance interface {
	// Defragment defragments storage backend of the etcd member with given endpoint.
	// Defragment is only needed when deleting a large number of keys and want to reclaim
	// the resources.
	// Defragment is an expensive operation. User should avoid defragmenting multiple members
	// at the same time.
	// To defragment multiple members in the cluster, user need to call defragment multiple
	// times with different endpoints.
	Defragment(ctx context.Context, endpoint string) (*DefragmentResponse, error)
}

type Member 

type Member pb.Member

type MemberAddResponse 

type MemberAddResponse pb.MemberAddResponse

type MemberListResponse 

type MemberListResponse pb.MemberListResponse

type MemberRemoveResponse 

type MemberRemoveResponse pb.MemberRemoveResponse

type MemberUpdateResponse 

type MemberUpdateResponse pb.MemberUpdateResponse

type Op 

type Op struct {
	// contains filtered or unexported fields
}

Op represents an Operation that kv can execute.

func OpDelete 

func OpDelete(key string, opts ...OpOption) Op

func OpGet 

func OpGet(key string, opts ...OpOption) Op

func OpPut 

func OpPut(key, val string, opts ...OpOption) Op

type OpOption 

type OpOption func(*Op)

OpOption configures Operations like Get, Put, Delete.

func WithFirstCreate 

func WithFirstCreate() []OpOption

WithFirstCreate gets the key with the oldest creation revision in the request range.

func WithFirstKey 

func WithFirstKey() []OpOption

WithFirstKey gets the lexically first key in the request range.

func WithFirstRev 

func WithFirstRev() []OpOption

WithFirstRev gets the key with the oldest modification revision in the request range.

func WithFromKey 

func WithFromKey() OpOption

WithFromKey specifies the range of 'Get' or 'Delete' requests to be equal or greater than they key in the argument.

func WithLastCreate 

func WithLastCreate() []OpOption

WithLastCreate gets the key with the latest creation revision in the request range.

func WithLastKey 

func WithLastKey() []OpOption

WithLastKey gets the lexically last key in the request range.

func WithLastRev 

func WithLastRev() []OpOption

WithLastRev gets the key with the latest modification revision in the request range.

func WithLease 

func WithLease(leaseID LeaseID) OpOption

WithLease attaches a lease ID to a key in 'Put' request.

func WithLimit 

func WithLimit(n int64) OpOption

WithLimit limits the number of results to return from 'Get' request.

func WithPrefix 

func WithPrefix() OpOption

WithPrefix enables 'Get', 'Delete', or 'Watch' requests to operate on the keys with matching prefix. For example, 'Get(foo, WithPrefix())' can return 'foo1', 'foo2', and so on.

func WithProgressNotify 

func WithProgressNotify() OpOption

WithProgressNotify makes watch server send periodic progress updates. Progress updates have zero events in WatchResponse.

func WithRange 

func WithRange(endKey string) OpOption

WithRange specifies the range of 'Get' or 'Delete' requests. For example, 'Get' requests with 'WithRange(end)' returns the keys in the range [key, end).

func WithRev 

func WithRev(rev int64) OpOption

WithRev specifies the store revision for 'Get' request. Or the start revision of 'Watch' request.

func WithSerializable 

func WithSerializable() OpOption

WithSerializable makes 'Get' request serializable. By default, it's linearizable. Serializable requests are better for lower latency requirement.

func WithSort 

func WithSort(target SortTarget, order SortOrder) OpOption

WithSort specifies the ordering in 'Get' request. It requires 'WithRange' and/or 'WithPrefix' to be specified too. 'target' specifies the target to sort by: key, version, revisions, value. 'order' can be either 'SortNone', 'SortAscend', 'SortDescend'.

type OpResponse 

type OpResponse struct {
	// contains filtered or unexported fields
}

type PutResponse 

type PutResponse pb.PutResponse

type SortOption 

type SortOption struct {
	Target SortTarget
	Order  SortOrder
}

type SortOrder 

type SortOrder int
const (
	SortNone SortOrder = iota
	SortAscend
	SortDescend
)

type SortTarget 

type SortTarget int
const (
	SortByKey SortTarget = iota
	SortByVersion
	SortByCreatedRev
	SortByModifiedRev
	SortByValue
)

type Txn 

type Txn interface {
	// If takes a list of comparison. If all comparisons passed in succeed,
	// the operations passed into Then() will be executed. Or the operations
	// passed into Else() will be executed.
	If(cs ...Cmp) Txn

	// Then takes a list of operations. The Ops list will be executed, if the
	// comparisons passed in If() succeed.
	Then(ops ...Op) Txn

	// Else takes a list of operations. The Ops list will be executed, if the
	// comparisons passed in If() fail.
	Else(ops ...Op) Txn

	// Commit tries to commit the transaction.
	Commit() (*TxnResponse, error)
}

Tx.If( 

Compare(Value(k1), ">", v1),
Compare(Version(k1), "=", 2)

).Then( 

OpPut(k2,v2), OpPut(k3,v3)

).Else( 

OpPut(k4,v4), OpPut(k5,v5)

).Commit()

type TxnResponse 

type TxnResponse pb.TxnResponse

type WatchChan 

type WatchChan <-chan WatchResponse

type WatchResponse 

type WatchResponse struct {
	Header pb.ResponseHeader
	Events []*storagepb.Event

	// CompactRevision is the minimum revision the watcher may receive.
	CompactRevision int64

	// Canceled is used to indicate watch failure.
	// If the watch failed and the stream was about to close, before the channel is closed,
	// the channel sends a final response that has Canceled set to true with a non-nil Err().
	Canceled bool
}

func (*WatchResponse) Err 

func (wr *WatchResponse) Err() error

Err is the error value if this WatchResponse holds an error.

func (*WatchResponse) IsProgressNotify 

func (wr *WatchResponse) IsProgressNotify() bool

IsProgressNotify returns true if the WatchResponse is progress notification.

type Watcher 

type Watcher interface {
	// Watch watches on a key or prefix. The watched events will be returned
	// through the returned channel.
	// If the watch is slow or the required rev is compacted, the watch request
	// might be canceled from the server-side and the chan will be closed.
	// 'opts' can be: 'WithRev' and/or 'WitchPrefix'.
	Watch(ctx context.Context, key string, opts ...OpOption) WatchChan

	// Close closes the watcher and cancels all watch requests.
	Close() error
}
Example (Watch) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

rch := cli.Watch(context.Background(), "foo")
for wresp := range rch {
	for _, ev := range wresp.Events {
		fmt.Printf("%s %q : %q\n", ev.Type, ev.Kv.Key, ev.Kv.Value)
	}
}
// PUT "foo" : "bar"

Output:
Example (WatchPrefix) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}
defer cli.Close()

rch := cli.Watch(context.Background(), "foo", clientv3.WithPrefix())
for wresp := range rch {
	for _, ev := range wresp.Events {
		fmt.Printf("%s %q : %q\n", ev.Type, ev.Kv.Key, ev.Kv.Value)
	}
}
// PUT "foo1" : "bar"

Output:
Example (WatchProgressNotify) 
cli, err := clientv3.New(clientv3.Config{
	Endpoints:   endpoints,
	DialTimeout: dialTimeout,
})
if err != nil {
	log.Fatal(err)
}

rch := cli.Watch(context.Background(), "foo", clientv3.WithProgressNotify())
wresp := <-rch
fmt.Printf("wresp.Header.Revision: %d\n", wresp.Header.Revision)
fmt.Println("wresp.IsProgressNotify:", wresp.IsProgressNotify())
// wresp.Header.Revision: 0
// wresp.IsProgressNotify: true

Output:

func NewWatcher 

func NewWatcher(c *Client) Watcher

Source Files

View all Source files

Directories

Path Synopsis
Package concurrency implements concurrency operations on top of etcd such as distributed locks, barriers, and elections.
 Package concurrency implements concurrency operations on top of etcd such as distributed locks, barriers, and elections.
Package integration implements tests built upon embedded etcd, and focuses on correctness of etcd client.
 Package integration implements tests built upon embedded etcd, and focuses on correctness of etcd client.
Package mirror implements etcd mirroring operations.
 Package mirror implements etcd mirroring operations.

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