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package balancer |
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import ( |
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"encoding/json" |
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"fmt" |
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"sync" |
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"golang.org/x/exp/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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"google.golang.org/grpc/serviceconfig" |
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"github.com/Permify/permify/pkg/consistent" |
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) |
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// Package-level constants for the balancer name and consistent hash key. |
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const ( |
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Name = "consistenthashing" // Name of the balancer. |
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Key = "consistenthashkey" // Key for the consistent hash. |
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) |
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// Config represents the configuration for the consistent hashing balancer. |
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type Config struct { |
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serviceconfig.LoadBalancingConfig `json:"-"` // Embedding the base load balancing config. |
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PartitionCount int `json:"partitionCount,omitempty"` // Number of partitions in the consistent hash ring. |
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ReplicationFactor int `json:"replicationFactor,omitempty"` // Number of replicas for each member. |
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Load float64 `json:"load,omitempty"` // Load factor for balancing traffic. |
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PickerWidth int `json:"pickerWidth,omitempty"` // Number of closest members to consider in the picker. |
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} |
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// ServiceConfigJSON generates the JSON representation of the load balancer configuration. |
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func (c *Config) ServiceConfigJSON() (string, error) { |
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// Define the JSON wrapper structure for the load balancing config. |
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type Wrapper struct { |
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LoadBalancingConfig []map[string]*Config `json:"loadBalancingConfig"` |
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} |
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// Apply default values for zero fields. |
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if c.PartitionCount <= 0 { |
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c.PartitionCount = consistent.DefaultPartitionCount |
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} |
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if c.ReplicationFactor <= 0 { |
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c.ReplicationFactor = consistent.DefaultReplicationFactor |
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} |
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if c.Load <= 1.0 { |
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c.Load = consistent.DefaultLoad |
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} |
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if c.PickerWidth < 1 { |
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c.PickerWidth = consistent.DefaultPickerWidth |
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} |
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// Create the wrapper with the current configuration. |
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wrapper := Wrapper{ |
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LoadBalancingConfig: []map[string]*Config{ |
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{Name: c}, |
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}, |
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} |
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// Marshal the wrapped configuration to JSON. |
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jsonData, err := json.Marshal(wrapper) |
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if err != nil { |
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return "", fmt.Errorf("failed to marshal service config: %w", err) |
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} |
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return string(jsonData), nil |
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} |
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// NewBuilder initializes a new builder with the given hashing function. |
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func NewBuilder(fn consistent.Hasher) Builder { |
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return &builder{hasher: fn} |
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} |
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// ConsistentMember represents a member in the consistent hashing ring. |
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type ConsistentMember struct { |
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balancer.SubConn // Embedded SubConn for the gRPC connection. |
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name string // Unique identifier for the member. |
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} |
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// String returns the name of the ConsistentMember. |
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func (s ConsistentMember) String() string { return s.name } |
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// builder is responsible for creating and configuring the consistent hashing balancer. |
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type builder struct { |
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sync.Mutex // Mutex for thread-safe updates to the builder. |
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hasher consistent.Hasher // Hashing function for the consistent hash ring. |
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config Config // Current balancer configuration. |
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} |
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// Builder defines the interface for the consistent hashing balancer builder. |
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type Builder interface { |
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balancer.Builder // Interface for building balancers. |
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balancer.ConfigParser // Interface for parsing balancer configurations. |
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} |
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// Name returns the name of the balancer. |
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func (b *builder) Name() string { return Name } |
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// Build creates a new instance of the consistent hashing balancer. |
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func (b *builder) Build(cc balancer.ClientConn, _ balancer.BuildOptions) balancer.Balancer { |
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// Initialize a new balancer with default values. |
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bal := &Balancer{ |
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clientConn: cc, |
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addressSubConns: resolver.NewAddressMap(), |
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subConnStates: make(map[balancer.SubConn]connectivity.State), |
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connectivityEvaluator: &balancer.ConnectivityStateEvaluator{}, |
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state: connectivity.Connecting, // Initial state. |
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hasher: b.hasher, |
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picker: base.NewErrPicker(balancer.ErrNoSubConnAvailable), // Default picker with no SubConns available. |
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} |
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return bal |
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} |
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// ParseConfig parses the balancer configuration from the provided JSON. |
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func (b *builder) ParseConfig(rm json.RawMessage) (serviceconfig.LoadBalancingConfig, error) { |
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var cfg Config |
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// Unmarshal the JSON configuration into the Config struct. |
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if err := json.Unmarshal(rm, &cfg); err != nil { |
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return nil, fmt.Errorf("consistenthash: unable to unmarshal LB policy config: %s, error: %w", string(rm), err) |
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} |
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// Log the parsed configuration using structured logging. |
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slog.Info("Parsed balancer configuration", |
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slog.String("raw_json", string(rm)), // Log the raw JSON string. |
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slog.Any("config", cfg), // Log the unmarshaled Config struct. |
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) |
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// Set default values for configuration if not provided. |
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if cfg.PartitionCount <= 0 { |
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cfg.PartitionCount = consistent.DefaultPartitionCount |
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} |
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if cfg.ReplicationFactor <= 0 { |
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cfg.ReplicationFactor = consistent.DefaultReplicationFactor |
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} |
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if cfg.Load <= 1.0 { |
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cfg.Load = consistent.DefaultLoad |
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} |
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if cfg.PickerWidth < 1 { |
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cfg.PickerWidth = consistent.DefaultPickerWidth |
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} |
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// Update the builder's configuration with thread safety. |
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b.Lock() |
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b.config = cfg |
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b.Unlock() |
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return &cfg, nil |
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} |
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