Airflow task return value I am using the Snowflake database. Bear with me since I've just started using Airflow, and what I'm trying to do is to collect the return code from a BashOperator task and save it to a local variable, and then based on that return code branch out to another task. I have created a operator and it returns a token (just a string so hello world operator example works fine). And it's still the old syntax, and the Airflow docs promises. multiple_outputs. The first two are declared using TaskFlow, and automatically pass the return value of get_ip into compose_email, not only linking the XCom across, but automatically declaring that compose_email is downstream of get_ip. dates import days_ago from airflow. On your note: end_task = DummyOperator( task_id='end_task', trigger_rule="none_failed_min_one_success" ). Share. {'NewMeterManufacturer': manufacturer, 'NewMeterModel': model } When checking the task's XCom value it is showing the return_value as the the content of the return. json. execution_timeout controls the Learn how to use Airflow Taskflows to chain tasks with return values, enabling you to create more complex and dynamic ETL workflows. It seems small enough to not need the complexity of being turned into a Series at this point. Dict will unroll to XCom values with keys as XCom keys. Passing return value Here, there are three tasks - get_ip, compose_email, and send_email_notification. A task is an instance of a DAG that represents a unit of work. Fetching XCOM returns None value in Airflow. In contrast, with the TaskFlow API in Airflow 2. I have two tasks in an Airflow DAG like below. 3, sensor operators will be able to return XCOM values. You could chain this behavior by making the query you run output to a uniquely named table (maybe use When pulling one single task (task_id is None or a str) without specifying map_indexes, the return value is inferred from whether the specified task is mapped. But consider the following Knowing the size of the data you are passing between Airflow tasks is important when deciding which implementation method to use. The following is my code segment: I am build an airflow DAG with multiple PythonOperator nodes. Jinja-templated args for an operator can only be used for those fields that are listed as template_fields in the operator class. timestamp() * 1000 return str(int(timestamp)) class TemplatedArgsGlueOperator(AwsGlueJobOperator): template_fields = ("script _args Task that uses BranchPythonOperator to pull the value from xcom and check if previous task returned true or false and make the decision about the next task. 'new_config' generates the new config file, and 'next_task' tries to pull in the xcom value. Unfortunately, the only way you would know if they do/don’t return results is to dive into Operator’s source code (which I highly recommend as it will greatly improve your understanding how Airflow works). xcom_pull(dag_id='my_dag', task_ids=f"execute_my_steps. operators. task_id to reflect this relationship. 0. I think you are looking for include_prior_dates param of xcom_pull() method; Do note that it will return entire history of Xcoms (python list, each item being one xcom record) pushed by the given task (filtered by task_id(s)) and then you will have to manually filter-out the desired xcom using execution_date field; It maybe difficult to supply exact execution_date for I would like to create a conditional task in Airflow as described in the schema below. dummy import DummyOperator from airflow. Using Airflow 2. 2. py:174} INFO - Done. If i'm correct, airflow automatically pushes to xcom when a query returns a value. Beta Was this translation helpful? Give feedback. def create_dag(dag_id, schedule =True,dag=dag) t2 = PythonOperator(task_id='task2',python_callable=sendAlert,provide_context=True,dag=dag) return dag python-3 I would like to calculate dates before I created next task, Ideally one task per date. 1. get_records method (i am returning a small amount of kines - usually a single cell). Process(pid=00000, status='terminated') (00000) terminated with exit code -15. 11. How can I achieve this. sql) hook = DWPostgresHook(postgres_conn_id=self. Review resource requirements for this operation, and call list() explicitly to suppress this message. xcom_push(key='return_value', value=full_paths) Dynamically adding airflow tasks on the basis of DB return value. python_operator import PythonOperator from airflow. I have used Dynamic Task Mapping to pass a list to a single task or operator to have it process the list DAGs¶. If your goal is to use the output of the map_manufacturer_model function to another tasks, I would consider treating the object as a dict or string. Ask Question Asked 1 year, 3 months ago. example: var1 = [1,2,3,4] branch_operator takes the value from var1 The returned value, which in this case is a dictionary, Similarly, task dependencies are automatically generated within TaskFlows based on the functional invocation of tasks. json file in the airflow UI. How to Trigger a Task based on previous task status? 2. Context` object; Using the `Variable` object; We will discuss each of these methods in Task2 and Task3 should use the same run_id. But how can I store and access this returned value? For example: I have the following functions. I first thought INFO - Task exited with return code 0 constituted a success, but I see some failure logs also have this. Tasks call xcom_pull() to retrieve XComs, optionally applying filters based on criteria like key, source task_ids, and source dag_id. As a result of this behaviour, my entire dataframe (84mb) is being written to a log file at every task execution. otherwise the value of the xcom id "return_value" and its value its a dictionary. For example, when I do this in some function blah that is run in a ShortCircuitOperator:. Improve this question. I am trying to pass a list of strings from one task to another one via XCom but I do not seem to manage to get the pushed list interpreted back as a list. the file is created with a specific name e. database) return hook. This is because if a task returns a result, Airflow will automatically push it to XCom under the return_value key. For example in my case I had to return 2 values from the upstream task, so a Tuple made sense to me. 58. utils. This works as long as you triggered the subdag using the same execution date as your current DAG. Airflow tasks iterating over list should run sequentially. airflow xcom value into custom operator from dynamic task id. t1 = PythonOperator. What gets retiurned by a task is stored in XCom DB as serialized value so what you return must be serializable. 2. One of them returns a value that will later be used as a param of another operator. if you need to return each key of the return value you should set the task decorator of compare_release_files with multiple_outputs=True. Unable to push data to xcom in airflow. For the PythonOperator that is op_args, op_kwargs, and templates_dict. Tasks can be chained together to create a directed acyclic graph (DAG) that defines a workflow. However, when you look at the code of the postgresoperator you see that it has an execute method that calls the run method of the PostgresHook (extension of dbapi_hook). py:156} INFO - Task exited with return code 1 [2022-06-19, 18:27:00 +08] {taskinstance. Viewed 107 times To send data from one task to another you can use Airflow XCOM feature. But when I tried to used that in a for loop, it will fail due to NoneType, which makes sense since it hasn't be generated yet. Generally, tasks in Airflow don't share data between them, so XComs are a way to achieve them but are Airflow tasks in a loop based on dag_run conf value. 5. the output varies on each execution. py:1395} INFO - Marking task as UP_FOR_RETRY. Follow answered Apr 3, 2019 at 13:06. This is achieved by returning an instance of the PokeReturnValue object at the end of the poke() method: There are a few methods you can use to implement data sharing between your Airflow tasks. , task_2b finishes 1 hour Each XCom value is tied to a DAG ID, task ID, and key. 2 there was a breaking change, which fixed the issue you are having. Modified 1 year, The task_ids value in xcom_pull() Tasks can push XComs at any time by calling the xcom_push() method. Per exemple: def func_test(): return ['task_2', 'task_3'] The expected result that I'm trying to achieve is two new tasks based on the return value of task 1. The SnowflakeHook is now conforming to the same semantics as all the other DBApiHook implementations and returns the same kind of response in Make sure your class IS json serializable. import json from airflow import DAG from airflow. In Airflow, tasks are the most basic building blocks of a workflow. I tried TaskInstance. g. asked Dec 15, 2020 at 8:44. How to pass pandas dataframe to airflow tasks. expand(op_kwargs=generate_lambda_config()) How do you access the values and use it to trigger a following task for each value from the returned task? I have tried using it directly like I am trying to create an Airflow dag as described below: I have a quite large python code that eventually creates a file. Option 4: the "pythonic" way Chaining Tasks with Return Values. Defaults to False. But when trying to pull the return value inside the pythonOperator callable function, It is returning None. so now I have this task in the dag: check_last_run_date=SnowflakeGetDataOperator( task_id='check_last_run_date', To access the return value from the previous task, you can read it from xcom, but the read should be in an airflow operator in order to access the run context: Python Airflow - Return result from PythonOperator. Hot Network Questions When generating tasks dynamically, I need to have Task 2 be dependent of Task 1, Task1 >> Task 2 or task2. The issue I have is figuring out how to get the BashOperator to return something. trigger = TriggerDagRunOperator( return the entry saved under key='return_value' The {{ }} is syntax of Jinja engine that means "print" the value. When next_task passes the xcom return_value into the python_callable 'next_task', it fails with: TypeError: string indices must be integers. You just need to set dependency as: get_dog >> inspect_dog Log : [2021-10-31, 07:07:21 UTC] {python. Improve this answer. g sales20180802130200. Branch operator (like: BranchSQLOperator ) where the workflow branch based on the result of SQL query that checks if the table exist. A bit more involved @task. See Dynamic Task Mapping documentation This works, but now we are actually not defining the dependencies between tasks, but Airflow return values? Still feels like a hack. Is it possible to create new tasks based on a return of a function? python; airflow; Share. __bool__ [source] ¶ class airflow. get_records Below is the log AIRFLOW_CTX_TASK_ID=records AIRFLOW_CTX_EXECUTION_DATE=2020-03-05T11 step_id="{{ task_instance. Cross communication between tasks - Pass parameters from one task to another - Supports multiple parameters - Identified by key - Intended for use within a single DAG Usage: - “push” and “pull” Uses the Airflow metadatabase (Postgres / MySQL) xcom_push(key = ‘return_value’, value = ‘my value’) value = xcom_pull(task_ids I created a dag which contains a subdag for loop through a list which is return value of a task. :param is_done: Set to true to indicate the sensor can stop poking. Let's say the 'end_task' also requires any tasks that are not skipped to all finish before the 'end_task' operation can begin, and the series of tasks running in parallel may finish at different times (e. Airflow tasks in a loop based on dag_run conf value. This applies to all Airflow tasks, including sensors. subdag function def mySubDag(parent: Text, child: Text, args, **context): task = context['tasl_instance'] Launch a subdag with variable parallel tasks in airflow. The expected scenario is the following: Task 1 executes If Task 1 succeed, return "big_task" # run just this one task, skip all else elif Consider the following example, the first task will correspond to your SparkSubmitOperator task: _get_upstream_task Takes care of getting the state of the first task The problem I'm having with airflow is that the @task decorator appears to wrap all the outputs of my functions and makes their output value of type PlainXComArgs. I'm fairly In older Airflow versions using the old Graph view you can change the background and font color of the task group with the ui_color and ui_fgcolor parameters. There is a slight difference between the two ways you are pulling the XCom in your code snippets: one has task_ids=["task_1"] (a list arg) while the other has task_ids="task_1" (a str arg). xcom_push(key=db_con, value = db_log) return use xcom_pull to pull a key's value that same task pushed - Airflow. the following Airflow task is s3BucketUpload operator. The simplest answer is because xcom_push is not one of the params in BigQueryOperator nor BaseOperator nor LoggingMixin. timestamp = time_of_run. it needs to get the name of the file in order to make the upload to s3. Airflow create new tasks based on task return value. Airflow Taskflows: Chaining tasks with return values. BashOperator Hi thanks for the answer. 2, Airflow writes the tasks return values to the log files. Python command for executing functions In my actual DAG, I need to first get a list of IDs and then for each ID run a set of tasks. :param xcom_value: An optional XCOM value to be returned by the operator. Passing xcom value to JiraOperator in Airflow. xcom_pull(task_ids='Task1') In Airflow 2. I have a very simple DAG which includes a very simple task (PythonOperator) which gets some trivial json data from SWAPI API and returns an int. The Tasks might be executed at different machines so they need to be serialized/deserialized ot be I have a task in which the output is a dictionary with a list value in each key @task(task_id="gen_dict") def generate_dict(): AIP-42 added the ability to map list data into task kwargs in airflow 2. partial( task_id="invoke_lambda", retries=1, retry_delay=timedelta(seconds=30), python_callable=invoke_lambda_function, ). Follow edited Dec 15, 2020 at 11:53. py:92} ERROR - Failed to execute job 100 for task wait (too many values to unpack (expected 2); 107) [2022-06-19, 18:27:00 +08] {local_task_job. Since the task_ids are evaluated, or seem to be upfront, I cannot set the dependency in advance, any help would be appreciated. The How can I get xcom from an airflow task and create other tasks using theses values. python_command. In terms that create_job_flow task must run and save the value to the database before add_steps task can read the value. xcom_pull() to access to returned value of first task. x, tasks had to be explicitly created and dependencies specified as shown below. Any pointers are much appreciated. The BigQueryGetDataOperator does return (and thus push) some data but it works by table and column name. 3. Note, if a key is not specified to xcom_pull(), it uses the default of return_value. 3 with k8s executor. Includes examples of using XCom, It returns the data that was stored by the `xcom_push()` function. I am trying to pass a Python function in Airflow. But the printed value appears as 'None'. Ah, was totally unaware that you could directly use the return value of Python tasks as input to other tasks--I thought you had to pass from one task to Your problem is that you did not set dependency between the tasks so inspect_dog may run before or in parallel to get_dog when this happens get_dog will see no xcom value because inspect_dog didn't push it yet. pull xcom value inside custom operator airflow. The way to access fields from the Tuple I'm passing then is the following: "{{ task_instance. pass I'm currently experimenting with Airflow for monitoring tasks regarding Snowflake and I'd like to execute a simple DAG with one task that pushes a SQL query to in Snowflake and should check the returned value that should be a number to be greater than a defined threshold. 0. 10. expand? Using Airflow 2. the first python file can probably be ran insted of xcom_push=True , try do_xcom_push=True, It will bring all the stdout to the xcom with key return_value. Airflow 1. While Task1 return list of dictionary task2 and task3 try to use one dictionary element then I recommend storing it as a csv file. task_group import TaskGroup Things to keep in mind: Dynamically adding airflow tasks on the basis of DB return value. def check_condition(**kwargs): task 2 invoked only when the return value of task 1 is True? airflow; Share. dag_id=dag10-deferred What should be kept in mind is that if task returns results then these results will be available for “pull” in the next task. external_python decorator allows you to run an Airflow task in pre-defined, immutable virtualenv (or Python binary installed at system level without virtualenv). def values_from_db(): Dynamically adding airflow tasks on the basis of DB return value. Hello world. Coercing mapped lazy proxy return value from task forward_values to list, which may degrade performance. This is needed since the value that you are seeking exist only during run time. If you return a value from a function, this value is stored in xcom. paths = ['gs://{}/{}'. Using BigQueryCheckOperator to run a query that return boolean value (True if table exist, False otherwise) then you will be able to pull the boolean value from XCOM in your BashOperator. How can I set the function argument to a task that is the return from a previous task / function that was run. I have created an operator SnowflakeGetDataOperator that returns the snowflake hook. Any value that the execute method returns is saved as an Xcom message under The returned value, which in this case is a dictionary, will be made available for use in later tasks. If you are pushing with report_id key, then you need to pull with it as well. Airflow PythonOperator task fail Unable to store Airflow task objects to a dictionary. { task_id }", key='return_value') }}", The explanation why it happens: When task is assigned to TaskGroup the id of the task is no longer the task_id but it becomes group_id. You can pull XCOM values from another dag, by passing in the dag_id to xcom_pull() (see the task_instance. In this case the value of the int is 202. Whether to use dill or pickle for serialization. I have a workflow like below, Task2 generates a list and saves it to airflow variable "var1". Note that these tasks are defined programmatically, therefore I cannot simply use xcom_pull(task_id="some_task") because the tasks are defined in Hey so I am using Airflow 2. Provide context is required to use the referenced **kwargs, which I usually name that as **context. If not, value from the one single task instance is returned. 15 dynamic task creation. If the task to pull is mapped, an iterator (not a list) yielding XComs from mapped task instances is returned. When your task is within a task group, Since I'm building this for people who use airflow and build dags and I'm not an actual airflow user or dag developer I want to get advice on doing it properly. In your case, you could access it like so from other Python code: task_instance = kwargs['task_instance'] task_instance. XComs are designed to pass What is the appropriate way to reference an array parameter in . First, replace your params parameter to op_kwargs and remove the extra curly brackets for Jinja -- only 2 on either side of the expression. In this guide, you'll walk through the two most commonly used methods, learn when to use them, and use some example DAGs to If you want a task to have a maximum runtime, set its execution_timeout attribute to a datetime. xcom_push(key=<variable name>, value=<variable value>) To pull a XCOM object use This is so easy to implement , follow any three ways: Introduce a branch operator, in the function present the condition; Use the trigger rule for the task, to skip the task based on previous parameter I am using airflow, i want to pass the output of the function of task 1 to the task 2. use_dill. So any return value of PythonOperator is saved to XCom (something to be careful with!). Here is an example of how you can use XComs to pass data between tasks: python def task_1(): Passing a list of values from one task to another; This works because any task that returns a value is stored in xcom . task_id in task groups . I am using 'airflow test' to first run task 'set-tag' and then run 'get-tag' hoping to see the 'test_value' printed. timedelta value that is the maximum permissible runtime. xcom_pull() function documentation). 51 4 4 bronze use xcom_pull to pull a key's value that same task pushed - Airflow. base. Ask Question Asked 4 years, 1 month ago. In Airflow 1. For example, a simple DAG could consist of three tasks: A, B, and C. Airflow will infer that if you pass a list of task IDs, there should be multiple tasks to pull XComs from and will return a list In this task, when some event happened, I need to store the timestamp and retrieve this value in next task run (for the same task) and update it again if required. kubernetes decorator being "traditional" tasks -- however, what works (and is the way it's supposed to work in a taskflow dag, I think) was to The following parameters are supported in Docker Task decorator. [2022-06-19, 18:27:00 +08] {standard_task_runner. How do I pass the xcom return_value into the python callable 'next_task' as a dictionary? As that is what it Unlike in version 2. Second, and I am trying to implement basic ETL job, using Airflow, but stucked in one point: I have 3 functions. The first two are declared using TaskFlow, and automatically pass the return value of get_ip into There are three main ways to pass data between tasks in Airflow: Using XComs; Using the `dagster. Additional/less values can be returned by DB in each call. So it's better you use xcoms to pass data between tasks rather than as task callable parameters. 6. I was trying to use XCOM but its showing none as the value class %s', self. . Both methods do not return anything, as such it pushes nothing to xcom. 3 and Dynamic TaskGroup Mapping so I can iterate over rows in a table and use the values in those rows as parameters in this group of tasks. This import airflow from datetime import datetime, If an XCom value is supplied when the sensor is done, then the XCom value will be pushed through the operator return value. How do I reuse a value that is calculated on the DAG run Reuse parameter value across different tasks in Airflow. 3 if that makes a difference. Airflow 2 Push Xcom with Key Name. My second function is to receive that file and delete null values and return the DF again without null values. sensors. models import Variable from airflow. Task1 should be Operator as this will be used by many jobs as first tasks. ti. I'm expecting the file size under Value. In Airflow, a DAG – or a Directed Acyclic Graph – is a collection of all the tasks you want to run, organized in a way that reflects their relationships and dependencies. postgres_conn_id, schema=self. If set, function return value will be unrolled to multiple XCom values. either pushed within the task's execution or via its return value, as an input into downstream tasks. In apache-airflow-providers-snowflake==4. ' port = '5439' sslmode = 'require' ") task_instance = context['task_instance'] task_instance. Doing so I see the value in the xcom value for the dag execution. So on I I am new to Python and new to Airflow. Improve your data pipeline development Here, there are three tasks - get_ip, compose_email, and send_email_notification. def sum(a, b): return a + b def compare(c, d): return c > d And the following dag: Learn how to pass data between tasks in Airflow with this step-by-step guide. if you are using branch operator then the return value of the if/else block is the task_id itself. send_email_notification is a more traditional I'm doing something similar (dependencies A > B > C) and I've solved the approach using the XCOM pushed by default by the previous task. set_upstream(task1). In simple terms, PythonOperator is just an operator that will execute a python function. What I'm getting is key: return_value ; Value:ODAwMAo=. 3: Airflow create new tasks based on task return value. format(bucket, obj) for obj in my_list] kwargs['ti']. Ask Question Asked 3 years, 9 months ago. I want to fetch value from DB and run tasks in parallel for each value. I am running Airflow in a Docker container using the I have an Airflow TaskFlow task that returns output: @task def extract(**context): return { "json": "values" } How do I pass that to the Postgres Operator? The returned value, which in this case is a dictionary, Similarly, task dependencies are automatically generated within TaskFlows based on the functional invocation of tasks. Airflow The issue I was having (I think) was that I was trying to access task functionality in the dag, and either that's not possible or I haven't figured out how to do it , combined with the KubernetesPodOperator / @task. I am not seeing consistency. I am trying to access XCOM value while learning Airflow, but every time, I get None returned. Airflow 2 loosely coupling @task return values to receiving @task? 1. The argument type of task_ids matters when using xcom_pull(). I can use partial() and expand() to create tasks as well as here. Checking the xcom page, I'm not getting the expected result. To push to XCOM use. xcom_pull(task_ids='get_file_name')[0] }}" where [0] - used to access the first element of the Tuple - goes inside the Jinja template. Airflow - getting the execution_date in task when calling an Operator. Dynamically generate multiple tasks . I am new to Airflow and I am practicing a bit, for example I have a function that reads a file (excel) and returns the converted file to DataFrame. It could say that A has to run successfully before B can run, but C can run anytime. And I want to define global variables for each of them like: function a(): When you return something in your python_callable, you can access the returned value if you pass the task context to the next operator. Modified 4 years, 1 month ago. 0, the invocation itself automatically generates the dependencies. I'm trying to get the appropriate values in this list of Iterating through a python list of dictionaries using a xcom return value. Using PythonOperator, the returned value will be stored in XCOM by default, so all you need to do is add a xcom_pull in the BashOperator, something like this: also_run_this = bash_operator. DockerOperator has a parameter xcom_push which when set, pushes the output of the Docker container to Xcom: t1 = DockerOperator(task_id='run-hello-world-container', image='hello- @PhilippJohannis thanks for this, I changed xcom_push argument in my SSHOperator to do_xcom_push. Milan Milan. You should have a task that takes the parameter you It derives the PythonVirtualenvOperator and expects a Python function that returns a single task_id, a single task_group_id, or a list of task_ids and/or task_group_ids to follow. For example, INFO - Task exited with return code 1 or INFO - Task exited with return code 0 or INFO - Process psutil. For Apache Airflow, I have 3 tasks to run in same dags. That is all working fine, Similarly, task dependencies are automatically generated within TaskFlows based on the functional invocation of tasks. That's trivially achieved by templating the execution_date value:. If there are any errors and you want the task to failed state then you need to raise an Exception inside your python callable function. hkdlyd ktjqghql mlujh cdic fhna dba uaste qzne uwzlfm qpwonk