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vendor: github.com/prometheus/client_golang v1.12.1

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Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This commit is contained in:
Sebastiaan van Stijn 2022-05-04 20:54:58 +02:00
parent 985711c1f4
commit ec47096efc
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574 changed files with 101741 additions and 22828 deletions
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374
vendor/google.golang.org/grpc/balancer/balancer.go generated vendored Normal file
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/*
*
* Copyright 2017 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 balancer defines APIs for load balancing in gRPC.
// All APIs in this package are experimental.
package balancer
import (
"context"
"encoding/json"
"errors"
"net"
"strings"
"google.golang.org/grpc/connectivity"
"google.golang.org/grpc/credentials"
"google.golang.org/grpc/internal"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/resolver"
"google.golang.org/grpc/serviceconfig"
)
var (
// m is a map from name to balancer builder.
m = make(map[string]Builder)
)
// Register registers the balancer builder to the balancer map. b.Name
// (lowercased) will be used as the name registered with this builder. If the
// Builder implements ConfigParser, ParseConfig will be called when new service
// configs are received by the resolver, and the result will be provided to the
// Balancer in UpdateClientConnState.
//
// NOTE: this function must only be called during initialization time (i.e. in
// an init() function), and is not thread-safe. If multiple Balancers are
// registered with the same name, the one registered last will take effect.
func Register(b Builder) {
m[strings.ToLower(b.Name())] = b
}
// unregisterForTesting deletes the balancer with the given name from the
// balancer map.
//
// This function is not thread-safe.
func unregisterForTesting(name string) {
delete(m, name)
}
func init() {
internal.BalancerUnregister = unregisterForTesting
}
// Get returns the resolver builder registered with the given name.
// Note that the compare is done in a case-insensitive fashion.
// If no builder is register with the name, nil will be returned.
func Get(name string) Builder {
if b, ok := m[strings.ToLower(name)]; ok {
return b
}
return nil
}
// SubConn represents a gRPC sub connection.
// Each sub connection contains a list of addresses. gRPC will
// try to connect to them (in sequence), and stop trying the
// remainder once one connection is successful.
//
// The reconnect backoff will be applied on the list, not a single address.
// For example, try_on_all_addresses -> backoff -> try_on_all_addresses.
//
// All SubConns start in IDLE, and will not try to connect. To trigger
// the connecting, Balancers must call Connect.
// When the connection encounters an error, it will reconnect immediately.
// When the connection becomes IDLE, it will not reconnect unless Connect is
// called.
//
// This interface is to be implemented by gRPC. Users should not need a
// brand new implementation of this interface. For the situations like
// testing, the new implementation should embed this interface. This allows
// gRPC to add new methods to this interface.
type SubConn interface {
// UpdateAddresses updates the addresses used in this SubConn.
// gRPC checks if currently-connected address is still in the new list.
// If it's in the list, the connection will be kept.
// If it's not in the list, the connection will gracefully closed, and
// a new connection will be created.
//
// This will trigger a state transition for the SubConn.
UpdateAddresses([]resolver.Address)
// Connect starts the connecting for this SubConn.
Connect()
}
// NewSubConnOptions contains options to create new SubConn.
type NewSubConnOptions struct {
// CredsBundle is the credentials bundle that will be used in the created
// SubConn. If it's nil, the original creds from grpc DialOptions will be
// used.
//
// Deprecated: Use the Attributes field in resolver.Address to pass
// arbitrary data to the credential handshaker.
CredsBundle credentials.Bundle
// HealthCheckEnabled indicates whether health check service should be
// enabled on this SubConn
HealthCheckEnabled bool
}
// State contains the balancer's state relevant to the gRPC ClientConn.
type State struct {
// State contains the connectivity state of the balancer, which is used to
// determine the state of the ClientConn.
ConnectivityState connectivity.State
// Picker is used to choose connections (SubConns) for RPCs.
Picker Picker
}
// ClientConn represents a gRPC ClientConn.
//
// This interface is to be implemented by gRPC. Users should not need a
// brand new implementation of this interface. For the situations like
// testing, the new implementation should embed this interface. This allows
// gRPC to add new methods to this interface.
type ClientConn interface {
// NewSubConn is called by balancer to create a new SubConn.
// It doesn't block and wait for the connections to be established.
// Behaviors of the SubConn can be controlled by options.
NewSubConn([]resolver.Address, NewSubConnOptions) (SubConn, error)
// RemoveSubConn removes the SubConn from ClientConn.
// The SubConn will be shutdown.
RemoveSubConn(SubConn)
// UpdateState notifies gRPC that the balancer's internal state has
// changed.
//
// gRPC will update the connectivity state of the ClientConn, and will call
// Pick on the new Picker to pick new SubConns.
UpdateState(State)
// ResolveNow is called by balancer to notify gRPC to do a name resolving.
ResolveNow(resolver.ResolveNowOptions)
// Target returns the dial target for this ClientConn.
//
// Deprecated: Use the Target field in the BuildOptions instead.
Target() string
}
// BuildOptions contains additional information for Build.
type BuildOptions struct {
// DialCreds is the transport credential the Balancer implementation can
// use to dial to a remote load balancer server. The Balancer implementations
// can ignore this if it does not need to talk to another party securely.
DialCreds credentials.TransportCredentials
// CredsBundle is the credentials bundle that the Balancer can use.
CredsBundle credentials.Bundle
// Dialer is the custom dialer the Balancer implementation can use to dial
// to a remote load balancer server. The Balancer implementations
// can ignore this if it doesn't need to talk to remote balancer.
Dialer func(context.Context, string) (net.Conn, error)
// ChannelzParentID is the entity parent's channelz unique identification number.
ChannelzParentID int64
// Target contains the parsed address info of the dial target. It is the same resolver.Target as
// passed to the resolver.
// See the documentation for the resolver.Target type for details about what it contains.
Target resolver.Target
}
// Builder creates a balancer.
type Builder interface {
// Build creates a new balancer with the ClientConn.
Build(cc ClientConn, opts BuildOptions) Balancer
// Name returns the name of balancers built by this builder.
// It will be used to pick balancers (for example in service config).
Name() string
}
// ConfigParser parses load balancer configs.
type ConfigParser interface {
// ParseConfig parses the JSON load balancer config provided into an
// internal form or returns an error if the config is invalid. For future
// compatibility reasons, unknown fields in the config should be ignored.
ParseConfig(LoadBalancingConfigJSON json.RawMessage) (serviceconfig.LoadBalancingConfig, error)
}
// PickInfo contains additional information for the Pick operation.
type PickInfo struct {
// FullMethodName is the method name that NewClientStream() is called
// with. The canonical format is /service/Method.
FullMethodName string
// Ctx is the RPC's context, and may contain relevant RPC-level information
// like the outgoing header metadata.
Ctx context.Context
}
// DoneInfo contains additional information for done.
type DoneInfo struct {
// Err is the rpc error the RPC finished with. It could be nil.
Err error
// Trailer contains the metadata from the RPC's trailer, if present.
Trailer metadata.MD
// BytesSent indicates if any bytes have been sent to the server.
BytesSent bool
// BytesReceived indicates if any byte has been received from the server.
BytesReceived bool
// ServerLoad is the load received from server. It's usually sent as part of
// trailing metadata.
//
// The only supported type now is *orca_v1.LoadReport.
ServerLoad interface{}
}
var (
// ErrNoSubConnAvailable indicates no SubConn is available for pick().
// gRPC will block the RPC until a new picker is available via UpdateState().
ErrNoSubConnAvailable = errors.New("no SubConn is available")
// ErrTransientFailure indicates all SubConns are in TransientFailure.
// WaitForReady RPCs will block, non-WaitForReady RPCs will fail.
//
// Deprecated: return an appropriate error based on the last resolution or
// connection attempt instead. The behavior is the same for any non-gRPC
// status error.
ErrTransientFailure = errors.New("all SubConns are in TransientFailure")
)
// PickResult contains information related to a connection chosen for an RPC.
type PickResult struct {
// SubConn is the connection to use for this pick, if its state is Ready.
// If the state is not Ready, gRPC will block the RPC until a new Picker is
// provided by the balancer (using ClientConn.UpdateState). The SubConn
// must be one returned by ClientConn.NewSubConn.
SubConn SubConn
// Done is called when the RPC is completed. If the SubConn is not ready,
// this will be called with a nil parameter. If the SubConn is not a valid
// type, Done may not be called. May be nil if the balancer does not wish
// to be notified when the RPC completes.
Done func(DoneInfo)
}
// TransientFailureError returns e. It exists for backward compatibility and
// will be deleted soon.
//
// Deprecated: no longer necessary, picker errors are treated this way by
// default.
func TransientFailureError(e error) error { return e }
// Picker is used by gRPC to pick a SubConn to send an RPC.
// Balancer is expected to generate a new picker from its snapshot every time its
// internal state has changed.
//
// The pickers used by gRPC can be updated by ClientConn.UpdateState().
type Picker interface {
// Pick returns the connection to use for this RPC and related information.
//
// Pick should not block. If the balancer needs to do I/O or any blocking
// or time-consuming work to service this call, it should return
// ErrNoSubConnAvailable, and the Pick call will be repeated by gRPC when
// the Picker is updated (using ClientConn.UpdateState).
//
// If an error is returned:
//
// - If the error is ErrNoSubConnAvailable, gRPC will block until a new
// Picker is provided by the balancer (using ClientConn.UpdateState).
//
// - If the error is a status error (implemented by the grpc/status
// package), gRPC will terminate the RPC with the code and message
// provided.
//
// - For all other errors, wait for ready RPCs will wait, but non-wait for
// ready RPCs will be terminated with this error's Error() string and
// status code Unavailable.
Pick(info PickInfo) (PickResult, error)
}
// Balancer takes input from gRPC, manages SubConns, and collects and aggregates
// the connectivity states.
//
// It also generates and updates the Picker used by gRPC to pick SubConns for RPCs.
//
// UpdateClientConnState, ResolverError, UpdateSubConnState, and Close are
// guaranteed to be called synchronously from the same goroutine. There's no
// guarantee on picker.Pick, it may be called anytime.
type Balancer interface {
// UpdateClientConnState is called by gRPC when the state of the ClientConn
// changes. If the error returned is ErrBadResolverState, the ClientConn
// will begin calling ResolveNow on the active name resolver with
// exponential backoff until a subsequent call to UpdateClientConnState
// returns a nil error. Any other errors are currently ignored.
UpdateClientConnState(ClientConnState) error
// ResolverError is called by gRPC when the name resolver reports an error.
ResolverError(error)
// UpdateSubConnState is called by gRPC when the state of a SubConn
// changes.
UpdateSubConnState(SubConn, SubConnState)
// Close closes the balancer. The balancer is not required to call
// ClientConn.RemoveSubConn for its existing SubConns.
Close()
}
// SubConnState describes the state of a SubConn.
type SubConnState struct {
// ConnectivityState is the connectivity state of the SubConn.
ConnectivityState connectivity.State
// ConnectionError is set if the ConnectivityState is TransientFailure,
// describing the reason the SubConn failed. Otherwise, it is nil.
ConnectionError error
}
// ClientConnState describes the state of a ClientConn relevant to the
// balancer.
type ClientConnState struct {
ResolverState resolver.State
// The parsed load balancing configuration returned by the builder's
// ParseConfig method, if implemented.
BalancerConfig serviceconfig.LoadBalancingConfig
}
// ErrBadResolverState may be returned by UpdateClientConnState to indicate a
// problem with the provided name resolver data.
var ErrBadResolverState = errors.New("bad resolver state")
// ConnectivityStateEvaluator takes the connectivity states of multiple SubConns
// and returns one aggregated connectivity state.
//
// It's not thread safe.
type ConnectivityStateEvaluator struct {
numReady uint64 // Number of addrConns in ready state.
numConnecting uint64 // Number of addrConns in connecting state.
}
// RecordTransition records state change happening in subConn and based on that
// it evaluates what aggregated state should be.
//
// - If at least one SubConn in Ready, the aggregated state is Ready;
// - Else if at least one SubConn in Connecting, the aggregated state is Connecting;
// - Else the aggregated state is TransientFailure.
//
// Idle and Shutdown are not considered.
func (cse *ConnectivityStateEvaluator) RecordTransition(oldState, newState connectivity.State) connectivity.State {
// Update counters.
for idx, state := range []connectivity.State{oldState, newState} {
updateVal := 2*uint64(idx) - 1 // -1 for oldState and +1 for new.
switch state {
case connectivity.Ready:
cse.numReady += updateVal
case connectivity.Connecting:
cse.numConnecting += updateVal
}
}
// Evaluate.
if cse.numReady > 0 {
return connectivity.Ready
}
if cse.numConnecting > 0 {
return connectivity.Connecting
}
return connectivity.TransientFailure
}

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vendor/google.golang.org/grpc/balancer/base/balancer.go generated vendored Normal file
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/*
*
* Copyright 2017 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 base
import (
"errors"
"fmt"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/connectivity"
"google.golang.org/grpc/grpclog"
"google.golang.org/grpc/resolver"
)
var logger = grpclog.Component("balancer")
type baseBuilder struct {
name string
pickerBuilder PickerBuilder
config Config
}
func (bb *baseBuilder) Build(cc balancer.ClientConn, opt balancer.BuildOptions) balancer.Balancer {
bal := &baseBalancer{
cc: cc,
pickerBuilder: bb.pickerBuilder,
subConns: make(map[resolver.Address]balancer.SubConn),
scStates: make(map[balancer.SubConn]connectivity.State),
csEvltr: &balancer.ConnectivityStateEvaluator{},
config: bb.config,
}
// Initialize picker to a picker that always returns
// ErrNoSubConnAvailable, because when state of a SubConn changes, we
// may call UpdateState with this picker.
bal.picker = NewErrPicker(balancer.ErrNoSubConnAvailable)
return bal
}
func (bb *baseBuilder) Name() string {
return bb.name
}
type baseBalancer struct {
cc balancer.ClientConn
pickerBuilder PickerBuilder
csEvltr *balancer.ConnectivityStateEvaluator
state connectivity.State
subConns map[resolver.Address]balancer.SubConn
scStates map[balancer.SubConn]connectivity.State
picker balancer.Picker
config Config
resolverErr error // the last error reported by the resolver; cleared on successful resolution
connErr error // the last connection error; cleared upon leaving TransientFailure
}
func (b *baseBalancer) ResolverError(err error) {
b.resolverErr = err
if len(b.subConns) == 0 {
b.state = connectivity.TransientFailure
}
if b.state != connectivity.TransientFailure {
// The picker will not change since the balancer does not currently
// report an error.
return
}
b.regeneratePicker()
b.cc.UpdateState(balancer.State{
ConnectivityState: b.state,
Picker: b.picker,
})
}
func (b *baseBalancer) UpdateClientConnState(s balancer.ClientConnState) error {
// TODO: handle s.ResolverState.ServiceConfig?
if logger.V(2) {
logger.Info("base.baseBalancer: got new ClientConn state: ", s)
}
// Successful resolution; clear resolver error and ensure we return nil.
b.resolverErr = nil
// addrsSet is the set converted from addrs, it's used for quick lookup of an address.
addrsSet := make(map[resolver.Address]struct{})
for _, a := range s.ResolverState.Addresses {
addrsSet[a] = struct{}{}
if _, ok := b.subConns[a]; !ok {
// a is a new address (not existing in b.subConns).
sc, err := b.cc.NewSubConn([]resolver.Address{a}, balancer.NewSubConnOptions{HealthCheckEnabled: b.config.HealthCheck})
if err != nil {
logger.Warningf("base.baseBalancer: failed to create new SubConn: %v", err)
continue
}
b.subConns[a] = sc
b.scStates[sc] = connectivity.Idle
sc.Connect()
}
}
for a, sc := range b.subConns {
// a was removed by resolver.
if _, ok := addrsSet[a]; !ok {
b.cc.RemoveSubConn(sc)
delete(b.subConns, a)
// Keep the state of this sc in b.scStates until sc's state becomes Shutdown.
// The entry will be deleted in UpdateSubConnState.
}
}
// If resolver state contains no addresses, return an error so ClientConn
// will trigger re-resolve. Also records this as an resolver error, so when
// the overall state turns transient failure, the error message will have
// the zero address information.
if len(s.ResolverState.Addresses) == 0 {
b.ResolverError(errors.New("produced zero addresses"))
return balancer.ErrBadResolverState
}
return nil
}
// mergeErrors builds an error from the last connection error and the last
// resolver error. Must only be called if b.state is TransientFailure.
func (b *baseBalancer) mergeErrors() error {
// connErr must always be non-nil unless there are no SubConns, in which
// case resolverErr must be non-nil.
if b.connErr == nil {
return fmt.Errorf("last resolver error: %v", b.resolverErr)
}
if b.resolverErr == nil {
return fmt.Errorf("last connection error: %v", b.connErr)
}
return fmt.Errorf("last connection error: %v; last resolver error: %v", b.connErr, b.resolverErr)
}
// regeneratePicker takes a snapshot of the balancer, and generates a picker
// from it. The picker is
// - errPicker if the balancer is in TransientFailure,
// - built by the pickerBuilder with all READY SubConns otherwise.
func (b *baseBalancer) regeneratePicker() {
if b.state == connectivity.TransientFailure {
b.picker = NewErrPicker(b.mergeErrors())
return
}
readySCs := make(map[balancer.SubConn]SubConnInfo)
// Filter out all ready SCs from full subConn map.
for addr, sc := range b.subConns {
if st, ok := b.scStates[sc]; ok && st == connectivity.Ready {
readySCs[sc] = SubConnInfo{Address: addr}
}
}
b.picker = b.pickerBuilder.Build(PickerBuildInfo{ReadySCs: readySCs})
}
func (b *baseBalancer) UpdateSubConnState(sc balancer.SubConn, state balancer.SubConnState) {
s := state.ConnectivityState
if logger.V(2) {
logger.Infof("base.baseBalancer: handle SubConn state change: %p, %v", sc, s)
}
oldS, ok := b.scStates[sc]
if !ok {
if logger.V(2) {
logger.Infof("base.baseBalancer: got state changes for an unknown SubConn: %p, %v", sc, s)
}
return
}
if oldS == connectivity.TransientFailure && s == connectivity.Connecting {
// Once a subconn enters TRANSIENT_FAILURE, ignore subsequent
// CONNECTING transitions to prevent the aggregated state from being
// always CONNECTING when many backends exist but are all down.
return
}
b.scStates[sc] = s
switch s {
case connectivity.Idle:
sc.Connect()
case connectivity.Shutdown:
// When an address was removed by resolver, b called RemoveSubConn but
// kept the sc's state in scStates. Remove state for this sc here.
delete(b.scStates, sc)
case connectivity.TransientFailure:
// Save error to be reported via picker.
b.connErr = state.ConnectionError
}
b.state = b.csEvltr.RecordTransition(oldS, s)
// Regenerate picker when one of the following happens:
// - this sc entered or left ready
// - the aggregated state of balancer is TransientFailure
// (may need to update error message)
if (s == connectivity.Ready) != (oldS == connectivity.Ready) ||
b.state == connectivity.TransientFailure {
b.regeneratePicker()
}
b.cc.UpdateState(balancer.State{ConnectivityState: b.state, Picker: b.picker})
}
// Close is a nop because base balancer doesn't have internal state to clean up,
// and it doesn't need to call RemoveSubConn for the SubConns.
func (b *baseBalancer) Close() {
}
// NewErrPicker returns a Picker that always returns err on Pick().
func NewErrPicker(err error) balancer.Picker {
return &errPicker{err: err}
}
// NewErrPickerV2 is temporarily defined for backward compatibility reasons.
//
// Deprecated: use NewErrPicker instead.
var NewErrPickerV2 = NewErrPicker
type errPicker struct {
err error // Pick() always returns this err.
}
func (p *errPicker) Pick(info balancer.PickInfo) (balancer.PickResult, error) {
return balancer.PickResult{}, p.err
}

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vendor/google.golang.org/grpc/balancer/base/base.go generated vendored Normal file
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/*
*
* Copyright 2017 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 base defines a balancer base that can be used to build balancers with
// different picking algorithms.
//
// The base balancer creates a new SubConn for each resolved address. The
// provided picker will only be notified about READY SubConns.
//
// This package is the base of round_robin balancer, its purpose is to be used
// to build round_robin like balancers with complex picking algorithms.
// Balancers with more complicated logic should try to implement a balancer
// builder from scratch.
//
// All APIs in this package are experimental.
package base
import (
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/resolver"
)
// PickerBuilder creates balancer.Picker.
type PickerBuilder interface {
// Build returns a picker that will be used by gRPC to pick a SubConn.
Build(info PickerBuildInfo) balancer.Picker
}
// PickerBuildInfo contains information needed by the picker builder to
// construct a picker.
type PickerBuildInfo struct {
// ReadySCs is a map from all ready SubConns to the Addresses used to
// create them.
ReadySCs map[balancer.SubConn]SubConnInfo
}
// SubConnInfo contains information about a SubConn created by the base
// balancer.
type SubConnInfo struct {
Address resolver.Address // the address used to create this SubConn
}
// Config contains the config info about the base balancer builder.
type Config struct {
// HealthCheck indicates whether health checking should be enabled for this specific balancer.
HealthCheck bool
}
// NewBalancerBuilder returns a base balancer builder configured by the provided config.
func NewBalancerBuilder(name string, pb PickerBuilder, config Config) balancer.Builder {
return &baseBuilder{
name: name,
pickerBuilder: pb,
config: config,
}
}

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vendor/google.golang.org/grpc/balancer/grpclb/state/state.go generated vendored Normal file
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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 state declares grpclb types to be set by resolvers wishing to pass
// information to grpclb via resolver.State Attributes.
package state
import (
"google.golang.org/grpc/resolver"
)
// keyType is the key to use for storing State in Attributes.
type keyType string
const key = keyType("grpc.grpclb.state")
// State contains gRPCLB-relevant data passed from the name resolver.
type State struct {
// BalancerAddresses contains the remote load balancer address(es). If
// set, overrides any resolver-provided addresses with Type of GRPCLB.
BalancerAddresses []resolver.Address
}
// Set returns a copy of the provided state with attributes containing s. s's
// data should not be mutated after calling Set.
func Set(state resolver.State, s *State) resolver.State {
state.Attributes = state.Attributes.WithValues(key, s)
return state
}
// Get returns the grpclb State in the resolver.State, or nil if not present.
// The returned data should not be mutated.
func Get(state resolver.State) *State {
s, _ := state.Attributes.Value(key).(*State)
return s
}

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vendor/google.golang.org/grpc/balancer/roundrobin/roundrobin.go generated vendored Normal file
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/*
*
* Copyright 2017 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 roundrobin defines a roundrobin balancer. Roundrobin balancer is
// installed as one of the default balancers in gRPC, users don't need to
// explicitly install this balancer.
package roundrobin
import (
"sync"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/balancer/base"
"google.golang.org/grpc/grpclog"
"google.golang.org/grpc/internal/grpcrand"
)
// Name is the name of round_robin balancer.
const Name = "round_robin"
var logger = grpclog.Component("roundrobin")
// newBuilder creates a new roundrobin balancer builder.
func newBuilder() balancer.Builder {
return base.NewBalancerBuilder(Name, &rrPickerBuilder{}, base.Config{HealthCheck: true})
}
func init() {
balancer.Register(newBuilder())
}
type rrPickerBuilder struct{}
func (*rrPickerBuilder) Build(info base.PickerBuildInfo) balancer.Picker {
logger.Infof("roundrobinPicker: newPicker called with info: %v", info)
if len(info.ReadySCs) == 0 {
return base.NewErrPicker(balancer.ErrNoSubConnAvailable)
}
var scs []balancer.SubConn
for sc := range info.ReadySCs {
scs = append(scs, sc)
}
return &rrPicker{
subConns: scs,
// Start at a random index, as the same RR balancer rebuilds a new
// picker when SubConn states change, and we don't want to apply excess
// load to the first server in the list.
next: grpcrand.Intn(len(scs)),
}
}
type rrPicker struct {
// subConns is the snapshot of the roundrobin balancer when this picker was
// created. The slice is immutable. Each Get() will do a round robin
// selection from it and return the selected SubConn.
subConns []balancer.SubConn
mu sync.Mutex
next int
}
func (p *rrPicker) Pick(balancer.PickInfo) (balancer.PickResult, error) {
p.mu.Lock()
sc := p.subConns[p.next]
p.next = (p.next + 1) % len(p.subConns)
p.mu.Unlock()
return balancer.PickResult{SubConn: sc}, nil
}