Multitenancy: Cómo servir a miles de clientes con una sola aplicación

1-- Ejemplo de tabla con tenant_id
2CREATE TABLE users (
3    id SERIAL PRIMARY KEY,
4    tenant_id UUID NOT NULL,
5    email VARCHAR(255) NOT NULL,
6    name VARCHAR(255) NOT NULL,
7    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
8);
9
10-- Índice para optimizar consultas por tenant
11CREATE INDEX idx_users_tenant_id ON users(tenant_id);
12
13-- Row Level Security (RLS) para garantizar aislamiento
14ALTER TABLE users ENABLE ROW LEVEL SECURITY;
15
16-- Política que solo permite ver datos del tenant actual
17CREATE POLICY tenant_isolation ON users
18    USING (tenant_id = current_setting('app.current_tenant_id')::UUID);

1-- Creación de esquemas por tenant
2CREATE SCHEMA tenant_company_a;
3CREATE SCHEMA tenant_company_b;
4
5-- Tablas en esquema dedicado
6CREATE TABLE tenant_company_a.users (
7    id SERIAL PRIMARY KEY,
8    email VARCHAR(255) NOT NULL,
9    name VARCHAR(255) NOT NULL,
10    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
11);
12
13CREATE TABLE tenant_company_b.users (
14    id SERIAL PRIMARY KEY,
15    email VARCHAR(255) NOT NULL,
16    name VARCHAR(255) NOT NULL,
17    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
18);

1// Entidad con tenant_id
2@Entity
3@Table(name = "users")
4data class User(
5    @Id
6    @GeneratedValue(strategy = GenerationType.IDENTITY)
7    val id: Long = 0,
8
9    @Column(name = "tenant_id", nullable = false)
10    val tenantId: UUID,
11
12    @Column(nullable = false)
13    val email: String,
14
15    @Column(nullable = false)
16    val name: String,
17
18    @CreationTimestamp
19    val createdAt: LocalDateTime = LocalDateTime.now()
20)

1// Interceptor para establecer el contexto del tenant
2@Component
3class TenantInterceptor : HandlerInterceptor {
4
5    override fun preHandle(
6        request: HttpServletRequest,
7        response: HttpServletResponse,
8        handler: Any
9    ): Boolean {
10        val token = extractJwtToken(request)
11        val tenantId = extractTenantFromToken(token)
12        
13        // Establecer tenant en el contexto de la aplicación
14        TenantContext.setCurrentTenant(tenantId)
15        
16        return true
17    }
18
19    override fun afterCompletion(
20        request: HttpServletRequest,
21        response: HttpServletResponse,
22        handler: Any,
23        ex: Exception?
24    ) {
25        // Limpiar contexto después de la request
26        TenantContext.clear()
27    }
28}

1// Repository con filtro automático por tenant
2@Repository
3interface UserRepository : JpaRepository<User, Long> {
4    
5    @Query("SELECT u FROM User u WHERE u.tenantId = :tenantId")
6    fun findByTenantId(@Param("tenantId") tenantId: UUID): List<User>
7    
8    @Query("SELECT u FROM User u WHERE u.tenantId = :tenantId AND u.email = :email")
9    fun findByTenantIdAndEmail(
10        @Param("tenantId") tenantId: UUID, 
11        @Param("email") email: String
12    ): User?
13}
14
15// Service que usa el contexto del tenant automáticamente
16@Service
17class UserService(private val userRepository: UserRepository) {
18    
19    fun getCurrentTenantUsers(): List<User> {
20        val currentTenantId = TenantContext.getCurrentTenant()
21        return userRepository.findByTenantId(currentTenantId)
22    }
23    
24    fun createUser(email: String, name: String): User {
25        val currentTenantId = TenantContext.getCurrentTenant()
26        val user = User(
27            tenantId = currentTenantId,
28            email = email,
29            name = name
30        )
31        return userRepository.save(user)
32    }
33}