Multi-Database Query Routing with Custom Error Handling Hooks

class TenantDatabaseRouter:
    """Routes read/write operations and manages fallback errors."""
    def db_for_read(self, model, **hints):
        tenant = hints.get("tenant_id")
        if not tenant:
            raise KeyError("Missing tenant_id hint in query routing context")
        return f"tenant_{tenant}"
 
    def db_for_write(self, model, **hints):
        return self.db_for_read(model, **hints)
 
    def allow_relation(self, obj1, obj2, **hints):
        return obj1._state.db == obj2._state.db
 
    def allow_migrate(self, db, app_label, model_name=None, **hints):
        return db.startswith("tenant_")