kaxil opened a new pull request, #57208:
URL: https://github.com/apache/airflow/pull/57208
Currently, custom labels defined via `map_index_template` for mapped tasks
are only rendered and displayed in the UI after task completion. This means
users see only numeric indices (0, 1, 2...) while tasks are running, making it
difficult to identify which specific mapped task instance is executing.
For example, if a mapped task processes different customers, users want to
see "customer_alice" or "customer_bob" in the UI while the task is running, not
just "0" or "1".
The `map_index_template` may reference context
variables set during task execution (e.g., XCom values, return values from
`execute()`, etc.). These variables are only available after the task's execute
method completes, which is why rendering was originally delayed until task
completion.
Example problematic template:
```
"Processing {{ ti.xcom_pull(key='customer_name') }}"
```
or one that access Task Attributes:
```
"Processing {{ task.value }}"
```
This PR implements a two-phase rendering approach:
Phase 1:
- Renders `map_index_template` immediately after template rendering, before
task execution
- Uses available context variables (task, dag, run_id, logical_date, etc.)
- Sends the rendered label to the API server for immediate UI display
- If rendering fails (e.g., due to missing variables), error is suppressed
and logged at debug level
- Provides immediate feedback for templates using pre-execution context
Phase 2:
- Re-renders `map_index_template` with full context after task execution
- Includes all execution-time variables (XCom, Task attributes, return
values, etc.)
- Only sends update if the value changed from Phase 1
- Handles both success and failure cases
- For failures, suppresses rendering errors to avoid masking task errors
For templates with execution-time variables, the label updates after
execution completes with the final rendered value.
Fixes https://github.com/apache/airflow/issues/39118
Fixes https://github.com/apache/airflow/issues/56722
<img width="1716" height="857" alt="image"
src="https://github.com/user-attachments/assets/e32b46a2-b18d-4dc4-a4e9-cf6978370574";
/>
<!--
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.
-->
<!--
Thank you for contributing! Please make sure that your code changes
are covered with tests. And in case of new features or big changes
remember to adjust the documentation.
Feel free to ping committers for the review!
In case of an existing issue, reference it using one of the following:
closes: #ISSUE
related: #ISSUE
How to write a good git commit message:
http://chris.beams.io/posts/git-commit/
-->
<!-- Please keep an empty line above the dashes. -->
---
**^ Add meaningful description above**
Read the **[Pull Request
Guidelines](https://github.com/apache/airflow/blob/main/contributing-docs/05_pull_requests.rst#pull-request-guidelines)**
for more information.
In case of fundamental code changes, an Airflow Improvement Proposal
([AIP](https://cwiki.apache.org/confluence/display/AIRFLOW/Airflow+Improvement+Proposals))
is needed.
In case of a new dependency, check compliance with the [ASF 3rd Party
License Policy](https://www.apache.org/legal/resolved.html#category-x).
In case of backwards incompatible changes please leave a note in a
newsfragment file, named `{pr_number}.significant.rst` or
`{issue_number}.significant.rst`, in
[airflow-core/newsfragments](https://github.com/apache/airflow/tree/main/airflow-core/newsfragments).
--
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.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
