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singleton.go
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singleton.go
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/*
*
* Copyright 2020 gRPC authors.
*
* 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 xdsclient
import (
"bytes"
"encoding/json"
"fmt"
"sync"
"time"
"google.golang.org/grpc/xds/internal/xdsclient/bootstrap"
)
const defaultWatchExpiryTimeout = 15 * time.Second
// This is the Client returned by New(). It contains one client implementation,
// and maintains the refcount.
var singletonClient = &clientRefCounted{}
// To override in tests.
var bootstrapNewConfig = bootstrap.NewConfig
// clientRefCounted is ref-counted, and to be shared by the xds resolver and
// balancer implementations, across multiple ClientConns and Servers.
type clientRefCounted struct {
*clientImpl
// This mu protects all the fields, including the embedded clientImpl above.
mu sync.Mutex
refCount int
}
// New returns a new xdsClient configured by the bootstrap file specified in env
// variable GRPC_XDS_BOOTSTRAP or GRPC_XDS_BOOTSTRAP_CONFIG.
//
// The returned xdsClient is a singleton. This function creates the xds client
// if it doesn't already exist.
//
// Note that the first invocation of New() or NewWithConfig() sets the client
// singleton. The following calls will return the singleton xds client without
// checking or using the config.
func New() (XDSClient, error) {
// This cannot just return newRefCounted(), because in error cases, the
// returned nil is a typed nil (*clientRefCounted), which may cause nil
// checks fail.
c, err := newRefCounted()
if err != nil {
return nil, err
}
return c, nil
}
func newRefCounted() (*clientRefCounted, error) {
singletonClient.mu.Lock()
defer singletonClient.mu.Unlock()
// If the client implementation was created, increment ref count and return
// the client.
if singletonClient.clientImpl != nil {
singletonClient.refCount++
return singletonClient, nil
}
// Create the new client implementation.
config, err := bootstrapNewConfig()
if err != nil {
return nil, fmt.Errorf("xds: failed to read bootstrap file: %v", err)
}
c, err := newWithConfig(config, defaultWatchExpiryTimeout)
if err != nil {
return nil, err
}
singletonClient.clientImpl = c
singletonClient.refCount++
return singletonClient, nil
}
// NewWithConfig returns a new xdsClient configured by the given config.
//
// The returned xdsClient is a singleton. This function creates the xds client
// if it doesn't already exist.
//
// Note that the first invocation of New() or NewWithConfig() sets the client
// singleton. The following calls will return the singleton xds client without
// checking or using the config.
//
// This function is internal only, for c2p resolver and testing to use. DO NOT
// use this elsewhere. Use New() instead.
func NewWithConfig(config *bootstrap.Config) (XDSClient, error) {
singletonClient.mu.Lock()
defer singletonClient.mu.Unlock()
// If the client implementation was created, increment ref count and return
// the client.
if singletonClient.clientImpl != nil {
singletonClient.refCount++
return singletonClient, nil
}
// Create the new client implementation.
c, err := newWithConfig(config, defaultWatchExpiryTimeout)
if err != nil {
return nil, err
}
singletonClient.clientImpl = c
singletonClient.refCount++
return singletonClient, nil
}
// Close closes the client. It does ref count of the xds client implementation,
// and closes the gRPC connection to the management server when ref count
// reaches 0.
func (c *clientRefCounted) Close() {
c.mu.Lock()
defer c.mu.Unlock()
c.refCount--
if c.refCount == 0 {
c.clientImpl.Close()
// Set clientImpl back to nil. So if New() is called after this, a new
// implementation will be created.
c.clientImpl = nil
}
}
// NewWithConfigForTesting is exported for testing only.
//
// Note that this function doesn't set the singleton, so that the testing states
// don't leak.
func NewWithConfigForTesting(config *bootstrap.Config, watchExpiryTimeout time.Duration) (XDSClient, error) {
cl, err := newWithConfig(config, watchExpiryTimeout)
if err != nil {
return nil, err
}
return &clientRefCounted{clientImpl: cl, refCount: 1}, nil
}
// NewClientWithBootstrapContents returns an xds client for this config,
// separate from the global singleton. This should be used for testing
// purposes only.
func NewClientWithBootstrapContents(contents []byte) (XDSClient, error) {
// Normalize the contents
buf := bytes.Buffer{}
err := json.Indent(&buf, contents, "", "")
if err != nil {
return nil, fmt.Errorf("xds: error normalizing JSON: %v", err)
}
contents = bytes.TrimSpace(buf.Bytes())
clientsMu.Lock()
defer clientsMu.Unlock()
if c := clients[string(contents)]; c != nil {
c.mu.Lock()
// Since we don't remove the *Client from the map when it is closed, we
// need to recreate the impl if the ref count dropped to zero.
if c.refCount > 0 {
c.refCount++
c.mu.Unlock()
return c, nil
}
c.mu.Unlock()
}
bcfg, err := bootstrap.NewConfigFromContents(contents)
if err != nil {
return nil, fmt.Errorf("xds: error with bootstrap config: %v", err)
}
cImpl, err := newWithConfig(bcfg, defaultWatchExpiryTimeout)
if err != nil {
return nil, err
}
c := &clientRefCounted{clientImpl: cImpl, refCount: 1}
clients[string(contents)] = c
return c, nil
}
var (
clients = map[string]*clientRefCounted{}
clientsMu sync.Mutex
)