Add dbx library: PostgreSQL cluster with master/replica routing, retry, health checking

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

node.go

@@ -0,0 +1,110 @@
+package dbx
+
+import (
+	"context"
+	"sync/atomic"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// Node wraps a pgxpool.Pool with health state and a human-readable name.
+type Node struct {
+	name    string
+	pool    *pgxpool.Pool
+	healthy atomic.Bool
+}
+
+// newNode creates a Node from an existing pool.
+func newNode(name string, pool *pgxpool.Pool) *Node {
+	n := &Node{
+		name: name,
+		pool: pool,
+	}
+	n.healthy.Store(true)
+	return n
+}
+
+// connectNode parses the NodeConfig, creates a pgxpool.Pool, and returns a Node.
+func connectNode(ctx context.Context, cfg NodeConfig) (*Node, error) {
+	poolCfg, err := pgxpool.ParseConfig(cfg.DSN)
+	if err != nil {
+		return nil, err
+	}
+	applyPoolConfig(poolCfg, cfg.Pool)
+
+	pool, err := pgxpool.NewWithConfig(ctx, poolCfg)
+	if err != nil {
+		return nil, err
+	}
+	return newNode(cfg.Name, pool), nil
+}
+
+func applyPoolConfig(dst *pgxpool.Config, src PoolConfig) {
+	if src.MaxConns > 0 {
+		dst.MaxConns = src.MaxConns
+	}
+	if src.MinConns > 0 {
+		dst.MinConns = src.MinConns
+	}
+	if src.MaxConnLifetime > 0 {
+		dst.MaxConnLifetime = src.MaxConnLifetime
+	}
+	if src.MaxConnIdleTime > 0 {
+		dst.MaxConnIdleTime = src.MaxConnIdleTime
+	}
+	if src.HealthCheckPeriod > 0 {
+		dst.HealthCheckPeriod = src.HealthCheckPeriod
+	}
+}
+
+// Name returns the node's human-readable name.
+func (n *Node) Name() string { return n.name }
+
+// IsHealthy reports whether the node is considered healthy.
+func (n *Node) IsHealthy() bool { return n.healthy.Load() }
+
+// Pool returns the underlying pgxpool.Pool.
+func (n *Node) Pool() *pgxpool.Pool { return n.pool }
+
+// --- DB interface implementation ---
+
+func (n *Node) Exec(ctx context.Context, sql string, args ...any) (pgconn.CommandTag, error) {
+	return n.pool.Exec(ctx, sql, args...)
+}
+
+func (n *Node) Query(ctx context.Context, sql string, args ...any) (pgx.Rows, error) {
+	return n.pool.Query(ctx, sql, args...)
+}
+
+func (n *Node) QueryRow(ctx context.Context, sql string, args ...any) pgx.Row {
+	return n.pool.QueryRow(ctx, sql, args...)
+}
+
+func (n *Node) SendBatch(ctx context.Context, b *pgx.Batch) pgx.BatchResults {
+	return n.pool.SendBatch(ctx, b)
+}
+
+func (n *Node) CopyFrom(ctx context.Context, tableName pgx.Identifier, columnNames []string, rowSrc pgx.CopyFromSource) (int64, error) {
+	return n.pool.CopyFrom(ctx, tableName, columnNames, rowSrc)
+}
+
+func (n *Node) Begin(ctx context.Context) (pgx.Tx, error) {
+	return n.pool.Begin(ctx)
+}
+
+func (n *Node) BeginTx(ctx context.Context, txOptions pgx.TxOptions) (pgx.Tx, error) {
+	return n.pool.BeginTx(ctx, txOptions)
+}
+
+func (n *Node) Ping(ctx context.Context) error {
+	return n.pool.Ping(ctx)
+}
+
+func (n *Node) Close() {
+	n.pool.Close()
+}
+
+// Compile-time check that *Node implements DB.
+var _ DB = (*Node)(nil)