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package balancer |
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import ( |
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"errors" |
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"fmt" |
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"log/slog" |
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"google.golang.org/grpc/balancer" |
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"google.golang.org/grpc/balancer/base" |
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"google.golang.org/grpc/connectivity" |
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"google.golang.org/grpc/resolver" |
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"github.com/Permify/permify/pkg/consistent" |
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) |
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type Balancer struct { |
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// Current overall connectivity state of the balancer. |
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state connectivity.State |
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// The ClientConn to communicate with the gRPC client. |
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clientConn balancer.ClientConn |
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// Current picker used to select SubConns for requests. |
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picker balancer.Picker |
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// Evaluates connectivity state transitions for SubConns. |
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connectivityEvaluator *balancer.ConnectivityStateEvaluator |
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// Map of resolver addresses to SubConns. |
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addressSubConns *resolver.AddressMap |
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// Tracks the connectivity state of each SubConn. |
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subConnStates map[balancer.SubConn]connectivity.State |
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// Configuration for consistent hashing and replication. |
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config *Config |
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// Consistent hashing mechanism to distribute requests. |
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consistent *consistent.Consistent |
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// Hasher used by the consistent hashing mechanism. |
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hasher consistent.Hasher |
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// Stores the last resolver error encountered. |
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lastResolverError error |
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// Stores the last connection error encountered. |
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lastConnectionError error |
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} |
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func (b *Balancer) ResolverError(err error) { |
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b.lastResolverError = err |
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if b.addressSubConns.Len() == 0 { |
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b.state = connectivity.TransientFailure |
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b.picker = base.NewErrPicker(errors.Join(b.lastConnectionError, b.lastResolverError)) |
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} |
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if b.state != connectivity.TransientFailure { |
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return |
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} |
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// Update the balancer state and picker. |
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b.clientConn.UpdateState(balancer.State{ |
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ConnectivityState: b.state, |
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Picker: b.picker, |
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}) |
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} |
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func (b *Balancer) UpdateClientConnState(s balancer.ClientConnState) error { |
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// Log the new ClientConn state. |
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slog.Info("Received new ClientConn state", |
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slog.Any("state", s), |
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) |
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// Reset any existing resolver error. |
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b.lastResolverError = nil |
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// Handle changes to the balancer configuration. |
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if s.BalancerConfig != nil { |
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svcConfig := s.BalancerConfig.(*Config) |
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if b.config == nil || svcConfig.ReplicationFactor != b.config.ReplicationFactor { |
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slog.Info("Updating consistent hashing configuration", |
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slog.Int("partition_count", svcConfig.PartitionCount), |
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slog.Int("replication_factor", svcConfig.ReplicationFactor), |
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slog.Float64("load", svcConfig.Load), |
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slog.Int("picker_width", svcConfig.PickerWidth), |
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) |
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b.consistent = consistent.New(consistent.Config{ |
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PartitionCount: svcConfig.PartitionCount, |
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ReplicationFactor: svcConfig.ReplicationFactor, |
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Load: svcConfig.Load, |
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PickerWidth: svcConfig.PickerWidth, |
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Hasher: b.hasher, |
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}) |
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b.config = svcConfig |
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} |
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} |
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// Check if the consistent hashing configuration exists. |
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if b.consistent == nil { |
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slog.Error("No consistent hashing configuration found") |
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b.picker = base.NewErrPicker(errors.Join(b.lastConnectionError, b.lastResolverError)) |
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b.clientConn.UpdateState(balancer.State{ConnectivityState: b.state, Picker: b.picker}) |
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return fmt.Errorf("no consistent hashing configuration found") |
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} |
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// Maintain a set of addresses provided by the resolver. |
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addrsSet := resolver.NewAddressMap() |
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for _, addr := range s.ResolverState.Addresses { |
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addrsSet.Set(addr, nil) |
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// Add new SubConns for addresses that are not already tracked. |
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if _, ok := b.addressSubConns.Get(addr); !ok { |
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sc, err := b.clientConn.NewSubConn([]resolver.Address{addr}, balancer.NewSubConnOptions{HealthCheckEnabled: false}) |
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if err != nil { |
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slog.Warn("Failed to create new SubConn", |
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slog.String("address", addr.Addr), |
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slog.String("server_name", addr.ServerName), |
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slog.String("error", err.Error()), |
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) |
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continue |
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} |
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b.addressSubConns.Set(addr, sc) |
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b.subConnStates[sc] = connectivity.Idle |
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b.connectivityEvaluator.RecordTransition(connectivity.Shutdown, connectivity.Idle) |
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sc.Connect() |
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b.consistent.Add(ConsistentMember{ |
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SubConn: sc, |
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name: fmt.Sprintf("%s|%s", addr.ServerName, addr.Addr), |
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}) |
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} |
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} |
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// Remove SubConns that are no longer part of the resolved addresses. |
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for _, addr := range b.addressSubConns.Keys() { |
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sci, _ := b.addressSubConns.Get(addr) |
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sc := sci.(balancer.SubConn) |
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if _, ok := addrsSet.Get(addr); !ok { |
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slog.Info("Removing SubConn", |
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slog.String("address", addr.Addr), |
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slog.String("server_name", addr.ServerName), |
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) |
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b.clientConn.RemoveSubConn(sc) |
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b.addressSubConns.Delete(addr) |
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b.consistent.Remove(ConsistentMember{ |
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SubConn: sc, |
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name: fmt.Sprintf("%s|%s", addr.ServerName, addr.Addr), |
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}.String()) |
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} |
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} |
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// Log the current members in the consistent hashing ring. |
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slog.Info("Current consistent members", |
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slog.Int("member_count", len(b.consistent.Members())), |
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) |
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for _, m := range b.consistent.Members() { |
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slog.Info("Consistent member", slog.String("member", m.String())) |
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} |
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// Handle the case where the resolver produces zero addresses. |
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if len(s.ResolverState.Addresses) == 0 { |
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err := errors.New("resolver produced zero addresses") |
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b.ResolverError(err) |
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slog.Error("Resolver produced zero addresses") |
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return balancer.ErrBadResolverState |
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} |
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// Update the picker based on the current balancer state. |
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if b.state == connectivity.TransientFailure { |
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slog.Warn("Transient failure detected, using error picker") |
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b.picker = base.NewErrPicker(errors.Join(b.lastConnectionError, b.lastResolverError)) |
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} else { |
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width := b.config.PickerWidth |
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if width < 1 { |
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width = 1 |
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} |
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slog.Info("Creating new picker", |
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slog.Int("width", width), |
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) |
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b.picker = &picker{ |
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consistent: b.consistent, |
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width: width, |
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} |
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} |
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// Update the ClientConn state with the new picker. |
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slog.Info("Updating ClientConn state", |
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slog.String("connectivity_state", b.state.String()), |
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) |
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b.clientConn.UpdateState(balancer.State{ConnectivityState: b.state, Picker: b.picker}) |
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return nil |
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} |
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func (b *Balancer) UpdateSubConnState(sc balancer.SubConn, state balancer.SubConnState) { |
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s := state.ConnectivityState |
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slog.Info("Received SubConn state change", |
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slog.String("connectivity_state", s.String()), |
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slog.String("sub_conn", fmt.Sprintf("%p", sc)), |
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) |
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oldS, ok := b.subConnStates[sc] |
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if !ok { |
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slog.Warn("State change for unknown SubConn", |
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slog.String("connectivity_state", s.String()), |
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slog.String("sub_conn", fmt.Sprintf("%p", sc)), |
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) |
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return |
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} |
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if oldS == connectivity.TransientFailure && (s == connectivity.Connecting || s == connectivity.Idle) { |
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if s == connectivity.Idle { |
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slog.Info("Transitioning SubConn to connecting state", |
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slog.String("sub_conn", fmt.Sprintf("%p", sc)), |
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) |
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sc.Connect() |
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} |
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return |
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} |
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b.subConnStates[sc] = s |
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switch s { |
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case connectivity.Idle: |
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slog.Info("SubConn is idle, initiating connection", |
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slog.String("sub_conn", fmt.Sprintf("%p", sc)), |
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) |
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sc.Connect() |
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case connectivity.Shutdown: |
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slog.Info("Removing shutdown SubConn", |
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slog.String("sub_conn", fmt.Sprintf("%p", sc)), |
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) |
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delete(b.subConnStates, sc) |
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case connectivity.TransientFailure: |
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slog.Warn("SubConn in transient failure", |
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slog.String("sub_conn", fmt.Sprintf("%p", sc)), |
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slog.String("error", state.ConnectionError.Error()), |
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) |
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b.lastConnectionError = state.ConnectionError |
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} |
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b.state = b.connectivityEvaluator.RecordTransition(oldS, s) |
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slog.Info("Updating ClientConn state", |
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slog.String("connectivity_state", b.state.String()), |
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) |
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b.clientConn.UpdateState(balancer.State{ConnectivityState: b.state, Picker: b.picker}) |
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} |
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func (b *Balancer) Close() {} |
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Permify /
permify
