sql read write support (#4976)

Co-authored-by: light.zhou <light.zhou@bkyo.io>

core/stores/sqlx/rwstrategy.go

@@ -0,0 +1,65 @@
+package sqlx
+
+import "context"
+
+const (
+	// policyRoundRobin round-robin policy for selecting replicas.
+	policyRoundRobin = "round-robin"
+	// policyRandom random policy for selecting replicas.
+	policyRandom = "random"
+
+	// readPrimaryMode indicates that the operation is a read,
+	// but should be performed on the primary database instance.
+	//
+	// This mode is used in scenarios where data freshness and consistency are critical,
+	// such as immediately after writes or where replication lag may cause stale reads.
+	readPrimaryMode readWriteMode = "read-primary"
+
+	// readReplicaMode indicates that the operation is a read from replicas.
+	// This is suitable for scenarios where eventual consistency is acceptable,
+	// and the goal is to offload traffic from the primary and improve read scalability.
+	readReplicaMode readWriteMode = "read-replica"
+
+	// writeMode indicates that the operation is a write operation (to primary).
+	writeMode readWriteMode = "write"
+
+	// notSpecifiedMode indicates that the read/write mode is not specified.
+	notSpecifiedMode readWriteMode = ""
+)
+
+type readWriteMode string
+
+var readWriteModeKey struct{}
+
+func (m readWriteMode) isValid() bool {
+	return m == readPrimaryMode || m == readReplicaMode || m == writeMode
+}
+
+func getReadWriteMode(ctx context.Context) readWriteMode {
+	if mode := ctx.Value(readWriteModeKey); mode != nil {
+		if v, ok := mode.(readWriteMode); ok && v.isValid() {
+			return v
+		}
+	}
+
+	return notSpecifiedMode
+}
+
+func useReplica(ctx context.Context) bool {
+	return getReadWriteMode(ctx) == readReplicaMode
+}
+
+// WithReadPrimaryMode sets the context to read-primary mode.
+func WithReadPrimaryMode(ctx context.Context) context.Context {
+	return context.WithValue(ctx, readWriteModeKey, readPrimaryMode)
+}
+
+// WithReadReplicaMode sets the context to read-replica mode.
+func WithReadReplicaMode(ctx context.Context) context.Context {
+	return context.WithValue(ctx, readWriteModeKey, readReplicaMode)
+}
+
+// WithWriteMode sets the context to write mode, indicating that the operation is a write operation.
+func WithWriteMode(ctx context.Context) context.Context {
+	return context.WithValue(ctx, readWriteModeKey, writeMode)
+}