coufon commented on a change in pull request #5701: [AIRFLOW-5088] Add DAG serialization using JSON URL: https://github.com/apache/airflow/pull/5701#discussion_r310732823
########## File path: airflow/dag/serialization.py ########## @@ -0,0 +1,316 @@ +# -*- coding: utf-8 -*- +# +# Licensed to the Apache Software Foundation (ASF) under one +# or more contributor license agreements. See the NOTICE file +# distributed with this work for additional information +# regarding copyright ownership. The ASF licenses this file +# to you under the Apache License, Version 2.0 (the +# "License"); you may not use this file except in compliance +# with the License. You may obtain a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, +# software distributed under the License is distributed on an +# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +# KIND, either express or implied. See the License for the +# specific language governing permissions and limitations +# under the License. + +"""DAG serialization with JSON.""" + +from enum import Enum +from enum import unique +import json +import logging +import datetime +import dateutil.parser +import pendulum + +from airflow.models import BaseOperator +from airflow.models import DAG +from airflow.models.connection import Connection +from airflow.www.utils import get_python_source + + +# Serialization failure returns 'failed'. +FAILED = 'serialization_failed' + + +# Fields of an encoded object in serialization. +@unique +class Encoding(str, Enum): + """Enum of encoding constants.""" + TYPE = '__type' + VAR = '__var' + + +# Supported types for encoding. primitives and list are not encoded. +@unique +class DagTypes(str, Enum): + """Enum of supported attribute types of DAG.""" + DAG = 'dag' + OP = 'operator' + DATETIME = 'datetime' + TIMEDELTA = 'timedelta' + TIMEZONE = 'timezone' + DICT = 'dict' + SET = 'set' + TUPLE = 'tuple' + + +class Serialization(): + """Serialization provides utils for serialization.""" + + # JSON primitive types. + _primitive_types = (int, bool, float, str) + # Time types. + _datetime_types = (datetime.datetime, datetime.date, datetime.time) + # Object types that are always excluded. + # TODO(coufon): not needed if _dag_included_fields and _op_included_fields are customized. + _excluded_types = (logging.Logger, Connection, type) + + @classmethod + def to_json(cls, x): + """Stringifies DAGs and operators contained by x and returns a JSON string of x.""" + return json.dumps(cls._serialize(x, {}), ensure_ascii=True) + + @classmethod + def from_json(cls, encoded_x): + """Deserializes encoded_x and reconstructs all DAGs and operators it contains.""" + return cls._deserialize(json.loads(encoded_x), {}) + + @classmethod + def encode(cls, x, type_): + """Encode data by a JSON dict.""" + return {Encoding.VAR: x, Encoding.TYPE: type_} + + @classmethod + def serialize_object(cls, x, visited_dags, included_fields): + """Helper function to serialize an object as a JSON dict.""" + new_x = {} + for k in included_fields: + # None is ignored in serialized form and is added back in deserialization. + v = getattr(x, k, None) + if not cls._is_excluded(v): + new_x[k] = cls._serialize(v, visited_dags) + return new_x + + @classmethod + def deserialize_object(cls, x, new_x, included_fields, visited_dags): + """Deserialize and copy the attributes of dict x to a new object new_x. + + It does not create new_x because if x is a DAG, new_x should be added into visited_dag + ahead of calling this function. + """ + for k in included_fields: + if k in x: + setattr(new_x, k, cls._deserialize(x[k], visited_dags)) + else: + setattr(new_x, k, None) + + @classmethod + def _is_primitive(cls, x): + """Primitive types.""" + return x is None or isinstance(x, cls._primitive_types) + + @classmethod + def _is_excluded(cls, x): + """Types excluded from serialization. + + TODO(coufon): not needed if _dag_included_fields and _op_included_fields are customized. + """ + return x is None or isinstance(x, cls._excluded_types) + + @classmethod + def _serialize(cls, x, visited_dags): # pylint: disable=too-many-return-statements + """Helper function of depth first search for serialization. + + visited_dags stores DAGs that are being stringifying for have been stringified, + for: + (1) preventing deadlock loop caused by task.dag, task._dag, and dag.parent_dag; + (2) replacing the fields in (1) with serialized counterparts. + + The serialization protocol is: + (1) keeping JSON supported types: primitives, dict, list; + (2) encoding other types as {TYPE, 'foo', VAR, 'bar'}, the deserialization + step decode VAR according to TYPE; + (3) Operator has a special field CLASS to record the original class + name for displaying in UI. + """ + try: + if cls._is_primitive(x): + return x + elif isinstance(x, dict): + return cls.encode( + {str(k): cls._serialize(v, visited_dags) + for k, v in x.items()}, + type_=DagTypes.DICT) + elif isinstance(x, list): + return [cls._serialize(v, visited_dags) for v in x] + elif isinstance(x, DAG): + return SerializedDAG.serialize_dag(x, visited_dags) + elif isinstance(x, BaseOperator): + return SerializedOperator.serialize_operator(x, visited_dags) + elif isinstance(x, cls._datetime_types): + return cls.encode(x.isoformat(), type_=DagTypes.DATETIME) + elif isinstance(x, datetime.timedelta): + return cls.encode(x.total_seconds(), type_=DagTypes.TIMEDELTA) + elif isinstance(x, pendulum.tz.Timezone): + return cls.encode(str(x.name), type_=DagTypes.TIMEZONE) + elif callable(x): + return str(get_python_source(x)) + elif isinstance(x, set): + return cls.encode( + [cls._serialize(v, visited_dags) for v in x], type_=DagTypes.SET) + elif isinstance(x, tuple): + return cls.encode( + [cls._serialize(v, visited_dags) for v in x], type_=DagTypes.TUPLE) + else: + logging.debug('Cast type %s to str in serialization.', type(x)) + return str(x) + except Exception: # pylint: disable=broad-except + logging.warning('Failed to stringify.', exc_info=True) + return FAILED + + @classmethod + def _deserialize(cls, encoded_x, visited_dags): # pylint: disable=too-many-return-statements + """Helper function of depth first search for deserialization.""" + try: + # JSON primitives (except for dict) are not encoded. + if cls._is_primitive(encoded_x): + return encoded_x + elif isinstance(encoded_x, list): + return [cls._deserialize(v, visited_dags) for v in encoded_x] + + assert isinstance(encoded_x, dict) + var = encoded_x[Encoding.VAR] + type_ = encoded_x[Encoding.TYPE] + + if type_ == DagTypes.DICT: + return {k: cls._deserialize(v, visited_dags) for k, v in var.items()} + elif type_ == DagTypes.DAG: + if isinstance(var, dict): + return SerializedDAG.deserialize_dag(var, visited_dags) + elif isinstance(var, str) and var in visited_dags: + # dag_id is stored in the serailized form for a visited DAGs. + return visited_dags[var] + logging.warning('Invalid DAG %s in deserialization.', var) + return None + elif type_ == DagTypes.OP: + return SerializedOperator.deserialize_operator(var, visited_dags) + elif type_ == DagTypes.DATETIME: + return dateutil.parser.parse(var) + elif type_ == DagTypes.TIMEDELTA: + return datetime.timedelta(seconds=var) + elif type_ == DagTypes.TIMEZONE: + return pendulum.tz.timezone(name=var) + elif type_ == DagTypes.SET: + return {cls._deserialize(v, visited_dags) for v in var} + elif type_ == DagTypes.TUPLE: + return tuple([cls._deserialize(v, visited_dags) for v in var]) + else: + logging.warning('Invalid type %s in deserialization.', type_) + return None + except Exception: # pylint: disable=broad-except + logging.warning('Failed to deserialize %s.', + encoded_x, exc_info=True) + return None + + +class SerializedDAG(DAG, Serialization): + """A JSON serializable representation of DAG. + + A stringified DAG can only be used in the scope of scheduler and webserver, because fields + that are not serializable, such as functions and customer defined classes, are casted to + strings. + Compared with SimpleDAG: SerializedDAG contains all information for webserver. + Compared with DagPickle: DagPickle contains all information for worker, but some DAGs are + not pickable. SerializedDAG works for all DAGs. + """ + # Stringified DAGs and operators contain exactly these fields. + # TODO(coufon): to customize included fields and keep only necessary fields. + _dag_included_fields = list(vars(DAG(dag_id='test')).keys()) + + @classmethod + def serialize_dag(cls, dag, visited_dags): + """Returns a serialized DAG. + + :param dag: a DAG. + :type dag: airflow.models.DAG + """ + if dag.dag_id in visited_dags: + return {Encoding.TYPE: DagTypes.DAG, Encoding.VAR: str(dag.dag_id)} + + new_dag = {Encoding.TYPE: DagTypes.DAG} + visited_dags[dag.dag_id] = new_dag + new_dag[Encoding.VAR] = cls.serialize_object( + dag, visited_dags, included_fields=cls._dag_included_fields) + return new_dag + + @classmethod + def deserialize_dag(cls, encoded_dag, visited_dags): + """Returns a deserialized DAG. + + :param encoded_dag: a JSON dict of serialized DAG. + :type encoded_dag: dict + """ + dag = SerializedDAG(dag_id=encoded_dag['_dag_id']) + visited_dags[dag.dag_id] = dag + cls.deserialize_object(encoded_dag, dag, cls._dag_included_fields, visited_dags) + return dag + + +class SerializedOperator(BaseOperator, Serialization): + """A JSON serializable representation of operator. + + All operators are casted to SerializedOperator after deserialization. + Class specific attributes used by UI are move to object attributes. + """ + _op_included_fields = list(vars(BaseOperator(task_id='test')).keys()) + [ + '_dag', '_task_type', 'ui_color', 'ui_fgcolor', 'template_fields'] Review comment: Not. vars(object) does not return class properties. Here is the full list returned: >>> list(vars(BaseOperator(task_id='test')).keys()) ['task_id', 'owner', 'email', 'email_on_retry', 'email_on_failure', 'start_date', 'end_date', 'trigger_rule', 'depends_on_past', 'wait_for_downstream', '_schedule_interval', 'retries', 'queue', 'pool', 'sla', 'execution_timeout', 'on_failure_callback', 'on_success_callback', 'on_retry_callback', 'retry_delay', 'retry_exponential_backoff', 'max_retry_delay', 'params', 'priority_weight', 'weight_rule', 'resources', 'run_as_user', 'task_concurrency', 'executor_config', 'do_xcom_push', '_upstream_task_ids', '_downstream_task_ids', '_log', 'inlets', 'outlets', 'lineage_data', '_inlets', '_outlets'] ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. 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