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client.go
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client.go
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// Copyright 2016 CoreOS, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package clientv3
import (
"sync"
"github.com/coreos/etcd/Godeps/_workspace/src/google.golang.org/grpc"
"github.com/coreos/etcd/Godeps/_workspace/src/google.golang.org/grpc/codes"
pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
)
// Client provides and manages an etcd v3 client session.
type Client struct {
// KV is the keyvalue API for the client's connection.
KV pb.KVClient
// Lease is the lease API for the client's connection.
Lease pb.LeaseClient
// Watch is the watch API for the client's connection.
Watch pb.WatchClient
// Cluster is the cluster API for the client's connection.
Cluster pb.ClusterClient
conn *grpc.ClientConn
cfg Config
mu sync.RWMutex // protects connection selection and error list
errors []error // errors passed to retryConnection
}
// EndpointDialer is a policy for choosing which endpoint to dial next
type EndpointDialer func(*Client) (*grpc.ClientConn, error)
type Config struct {
// Endpoints is a list of URLs
Endpoints []string
// RetryDialer chooses the next endpoint to use
RetryDialer EndpointDialer
// TODO TLS options
}
// New creates a new etcdv3 client from a given configuration.
func New(cfg Config) (*Client, error) {
if cfg.RetryDialer == nil {
cfg.RetryDialer = dialEndpointList
}
// use a temporary skeleton client to bootstrap first connection
conn, err := cfg.RetryDialer(&Client{cfg: cfg})
if err != nil {
return nil, err
}
return newClient(conn, &cfg), nil
}
// NewFromURL creates a new etcdv3 client from a URL.
func NewFromURL(url string) (*Client, error) {
return New(Config{Endpoints: []string{url}})
}
// NewFromConn creates a new etcdv3 client from an established grpc Connection.
func NewFromConn(conn *grpc.ClientConn) *Client { return newClient(conn, nil) }
// Clone creates a copy of client with the old connection and new API clients.
func (c *Client) Clone() *Client { return newClient(c.conn, &c.cfg) }
// Close shuts down the client's etcd connections.
func (c *Client) Close() error {
return c.conn.Close()
}
// Endpoints lists the registered endpoints for the client.
func (c *Client) Endpoints() []string { return c.cfg.Endpoints }
// Errors returns all errors that have been observed since called last.
func (c *Client) Errors() (errs []error) {
c.mu.Lock()
defer c.mu.Unlock()
errs = c.errors
c.errors = nil
return errs
}
// Dial establishes a connection for a given endpoint using the client's config
func (c *Client) Dial(endpoint string) (*grpc.ClientConn, error) {
// TODO: enable grpc.WithTransportCredentials(creds)
return grpc.Dial(endpoint, grpc.WithInsecure())
}
func newClient(conn *grpc.ClientConn, cfg *Config) *Client {
if cfg == nil {
cfg = &Config{RetryDialer: dialEndpointList}
}
return &Client{
KV: pb.NewKVClient(conn),
Lease: pb.NewLeaseClient(conn),
Watch: pb.NewWatchClient(conn),
Cluster: pb.NewClusterClient(conn),
conn: conn,
cfg: *cfg,
}
}
// activeConnection returns the current in-use connection
func (c *Client) activeConnection() *grpc.ClientConn {
c.mu.RLock()
defer c.mu.RUnlock()
return c.conn
}
// refreshConnection establishes a new connection
func (c *Client) retryConnection(oldConn *grpc.ClientConn, err error) (*grpc.ClientConn, error) {
c.mu.Lock()
defer c.mu.Unlock()
if err != nil {
c.errors = append(c.errors, err)
}
if oldConn != c.conn {
// conn has already been updated
return c.conn, nil
}
conn, dialErr := c.cfg.RetryDialer(c)
if dialErr != nil {
c.errors = append(c.errors, dialErr)
return nil, dialErr
}
c.conn = conn
return c.conn, nil
}
// dialEndpoints attempts to connect to each endpoint in order until a
// connection is established.
func dialEndpointList(c *Client) (*grpc.ClientConn, error) {
var err error
for _, ep := range c.Endpoints() {
conn, curErr := c.Dial(ep)
if err != nil {
err = curErr
} else {
return conn, nil
}
}
return nil, err
}
func isRPCError(err error) bool {
return grpc.Code(err) != codes.Unknown
}