---
title: Functions
description: Public API reference for the Consensus extension
---

## Extension Entry Points

| Function | Description |
|---|---|
| `NewExtension(opts ...ConfigOption) forge.Extension` | Create the consensus extension with functional options |
| `NewExtensionWithConfig(config Config) forge.Extension` | Create with a complete config |
| `DefaultConfig() Config` | Returns the default configuration |

## Extension Accessors

| Method | Description |
|---|---|
| `Service() ConsensusService` | Access the consensus service |
| `IsLeader() bool` | Check if this node is the current leader |
| `GetLeader() (string, error)` | Get the current leader's node ID |
| `GetRole() string` | Get the current role (leader, follower, candidate) |
| `GetStats() map[string]any` | Get consensus statistics |
| `GetClusterInfo() map[string]any` | Get cluster membership info |

## ConsensusService Interface

### Operations

| Method | Description |
|---|---|
| `Apply(ctx, cmd) (any, error)` | Apply a command through the Raft log (write operation) |
| `Read(ctx, query) (any, error)` | Read from the state machine (consistent read) |

### Lifecycle

| Method | Description |
|---|---|
| `Start(ctx) error` | Start the Raft node |
| `Stop(ctx) error` | Stop the Raft node |
| `HealthCheck(ctx) error` | Check node and cluster health |

### Leadership

| Method | Description |
|---|---|
| `IsLeader() bool` | Check if this node is the leader |
| `GetLeader() (string, error)` | Get the leader node ID |
| `GetRole() string` | Get the current role |

### Cluster

| Method | Description |
|---|---|
| `GetStats() map[string]any` | Runtime statistics |
| `GetClusterInfo() map[string]any` | Cluster membership information |
| `UpdateConfig(config) error` | Update configuration at runtime |

## LeadershipChecker

| Method | Description |
|---|---|
| `NewLeadershipChecker(service ConsensusService)` | Create a leadership checker |
| `RequireLeader() bool` | Returns true if current node is leader |
| `RequireQuorum() bool` | Returns true if cluster has quorum |

## Error Helpers

| Function | Description |
|---|---|
| `NewNotLeaderError(leaderID) error` | Create a not-leader error with leader hint |
| `NewNoLeaderError() error` | Create a no-leader error |
| `NewTimeoutError(operation) error` | Create a timeout error |
| `NewNoQuorumError(available, required) error` | Create a quorum error |
| `IsNotLeaderError(err) bool` | Check if error is not-leader |
| `IsNoLeaderError(err) bool` | Check if no leader elected |
| `IsNoQuorumError(err) bool` | Check if quorum lost |
| `IsRetryable(err) bool` | Check if error is transient |
| `IsFatal(err) bool` | Check if error is unrecoverable |