Show custom instance names for a mapped task in UI

airflow/api_connexion/openapi/v1.yaml

@@ -3582,6 +3582,13 @@ components:
           type: string
         sla_miss:
           $ref: "#/components/schemas/SLAMiss"
+        rendered_map_index:
+          description: |
+            Rendered name of an expanded task instance, if the task is mapped.
+
+            *New in version 2.9.0*
+          type: string
+          nullable: true
         rendered_fields:
           description: |
             JSON object describing rendered fields.

airflow/api_connexion/schemas/task_instance_schema.py

@@ -67,6 +67,7 @@ class Meta:
     executor_config = auto_field()
     note = auto_field()
     sla_miss = fields.Nested(SlaMissSchema, dump_default=None)
+    rendered_map_index = auto_field()
     rendered_fields = JsonObjectField(dump_default={})
     trigger = fields.Nested(TriggerSchema)
     triggerer_job = fields.Nested(JobSchema)

airflow/decorators/base.py

@@ -459,6 +459,7 @@ def _expand(self, expand_input: ExpandInput, *, strict: bool) -> XComArg:
             expand_input=EXPAND_INPUT_EMPTY,  # Don't use this; mapped values go to op_kwargs_expand_input.
             partial_kwargs=partial_kwargs,
             task_id=task_id,
+            map_index_template=partial_kwargs.pop("map_index_template", None),
             params=partial_params,
             deps=MappedOperator.deps_for(self.operator_class),
             operator_extra_links=self.operator_class.operator_extra_links,

airflow/models/baseoperator.py

@@ -245,6 +245,7 @@ def partial(
     priority_weight: int | ArgNotSet = NOTSET,
     weight_rule: str | ArgNotSet = NOTSET,
     sla: timedelta | None | ArgNotSet = NOTSET,
+    map_index_template: str | None | ArgNotSet = NOTSET,
     max_active_tis_per_dag: int | None | ArgNotSet = NOTSET,
     max_active_tis_per_dagrun: int | None | ArgNotSet = NOTSET,
     on_execute_callback: None | TaskStateChangeCallback | list[TaskStateChangeCallback] | ArgNotSet = NOTSET,
@@ -289,6 +290,7 @@ def partial(
         "dag": dag,
         "task_group": task_group,
         "task_id": task_id,
+        "map_index_template": map_index_template,
         "start_date": start_date,
         "end_date": end_date,
         "owner": owner,
@@ -781,6 +783,7 @@ def __init__(
         resources: dict[str, Any] | None = None,
         run_as_user: str | None = None,
         task_concurrency: int | None = None,
+        map_index_template: str | None = None,
         max_active_tis_per_dag: int | None = None,
         max_active_tis_per_dagrun: int | None = None,
         executor_config: dict | None = None,
@@ -933,6 +936,7 @@ def __init__(
         self.max_active_tis_per_dag: int | None = max_active_tis_per_dag
         self.max_active_tis_per_dagrun: int | None = max_active_tis_per_dagrun
         self.do_xcom_push: bool = do_xcom_push
+        self.map_index_template: str | None = map_index_template
         self.multiple_outputs: bool = multiple_outputs
 
         self.doc_md = doc_md
@@ -1572,6 +1576,7 @@ def get_serialized_fields(cls):
                     "is_setup",
                     "is_teardown",
                     "on_failure_fail_dagrun",
+                    "map_index_template",
                 }
             )
             DagContext.pop_context_managed_dag()

airflow/models/mappedoperator.py

@@ -211,6 +211,7 @@ def _expand(self, expand_input: ExpandInput, *, strict: bool) -> MappedOperator:
             expand_input=expand_input,
             partial_kwargs=partial_kwargs,
             task_id=task_id,
+            map_index_template=partial_kwargs.pop("map_index_template", None),
             params=self.params,
             deps=MappedOperator.deps_for(self.operator_class),
             operator_extra_links=self.operator_class.operator_extra_links,
@@ -280,6 +281,7 @@ class MappedOperator(AbstractOperator):
     end_date: pendulum.DateTime | None
     upstream_task_ids: set[str] = attr.ib(factory=set, init=False)
     downstream_task_ids: set[str] = attr.ib(factory=set, init=False)
+    map_index_template: str | None
 
     _disallow_kwargs_override: bool
     """Whether execution fails if ``expand_input`` has duplicates to ``partial_kwargs``.

airflow/models/taskinstance.py

@@ -749,6 +749,7 @@ def get_triggering_events() -> dict[str, list[DatasetEvent | DatasetEventPydanti
         "inlets": task.inlets,
         "logical_date": logical_date,
         "macros": macros,
+        "map_index_template": task.map_index_template,
         "next_ds": get_next_ds(),
         "next_ds_nodash": get_next_ds_nodash(),
         "next_execution_date": get_next_execution_date(),
@@ -1251,6 +1252,7 @@ class TaskInstance(Base, LoggingMixin):
     pid = Column(Integer)
     executor_config = Column(ExecutorConfigType(pickler=dill))
     updated_at = Column(UtcDateTime, default=timezone.utcnow, onupdate=timezone.utcnow)
+    rendered_map_index = Column(String(64))
 
     external_executor_id = Column(StringID())
 
@@ -2511,7 +2513,12 @@ def signal_handler(signum, frame):
             self.task.params = context["params"]
 
             with set_current_context(context):
-                task_orig = self.render_templates(context=context)
+                dag = self.task.get_dag()
+                if dag is not None:
+                    jinja_env = dag.get_template_env()
+                else:
+                    jinja_env = None
+                task_orig = self.render_templates(context=context, jinja_env=jinja_env)
 
             if not test_mode:
                 rtif = RenderedTaskInstanceFields(ti=self, render_templates=False)
@@ -2546,10 +2553,16 @@ def signal_handler(signum, frame):
             # Execute the task
             with set_current_context(context):
                 result = self._execute_task(context, task_orig)
+
             # Run post_execute callback
             # Is never MappedOperator at this point
             self.task.post_execute(context=context, result=result)  # type: ignore[union-attr]
 
+            # DAG authors define map_index_template at the task level
+            if jinja_env is not None and (template := context.get("map_index_template")) is not None:
+                rendered_map_index = self.rendered_map_index = jinja_env.from_string(template).render(context)
+                self.log.info("Map index rendered as %s", rendered_map_index)
+
         Stats.incr(f"operator_successes_{self.task.task_type}", tags=self.stats_tags)
         # Same metric with tagging
         Stats.incr("operator_successes", tags={**self.stats_tags, "task_type": self.task.task_type})
@@ -2921,7 +2934,9 @@ def overwrite_params_with_dag_run_conf(self, params: dict, dag_run: DagRun):
             self.log.debug("Updating task params (%s) with DagRun.conf (%s)", params, dag_run.conf)
             params.update(dag_run.conf)
 
-    def render_templates(self, context: Context | None = None) -> Operator:
+    def render_templates(
+        self, context: Context | None = None, jinja_env: jinja2.Environment | None = None
+    ) -> Operator:
         """Render templates in the operator fields.
 
         If the task was originally mapped, this may replace ``self.task`` with
@@ -2936,7 +2951,7 @@ def render_templates(self, context: Context | None = None) -> Operator:
         # unmapped BaseOperator created by this function! This is because the
         # MappedOperator is useless for template rendering, and we need to be
         # able to access the unmapped task instead.
-        original_task.render_template_fields(context)
+        original_task.render_template_fields(context, jinja_env)
 
         return original_task
 

airflow/operators/python.py

@@ -312,6 +312,7 @@ class _BasePythonVirtualenvOperator(PythonOperator, metaclass=ABCMeta):
         "ds_nodash",
         "expanded_ti_count",
         "inlets",
+        "map_index_template",
         "next_ds",
         "next_ds_nodash",
         "outlets",

airflow/serialization/pydantic/taskinstance.py

@@ -100,6 +100,7 @@ class TaskInstancePydantic(BaseModelPydantic, LoggingMixin):
     pid: Optional[int]
     executor_config: Any
     updated_at: Optional[datetime]
+    rendered_map_index: Optional[str]
     external_executor_id: Optional[str]
     trigger_id: Optional[int]
     trigger_timeout: Optional[datetime]

airflow/serialization/schema.json

@@ -287,7 +287,8 @@
         "_log_config_logger_name": { "type": "string" },
         "_is_mapped": { "const": true, "$comment": "only present when True" },
         "expand_input": { "type": "object" },
-        "partial_kwargs": { "type": "object" }
+        "partial_kwargs": { "type": "object" },
+        "map_index_template": { "type": "string" }
       },
       "dependencies": {
         "expand_input": ["partial_kwargs", "_is_mapped"],

airflow/serialization/serialized_objects.py

@@ -1125,6 +1125,7 @@ def deserialize_operator(cls, encoded_op: dict[str, Any]) -> Operator:
                 task_group=None,
                 start_date=None,
                 end_date=None,
+                map_index_template=None,
                 disallow_kwargs_override=encoded_op["_disallow_kwargs_override"],
                 expand_input_attr=encoded_op["_expand_input_attr"],
             )

airflow/utils/context.py

@@ -59,6 +59,7 @@
     "inlets",
     "logical_date",
     "macros",
+    "map_index_template",
     "next_ds",
     "next_ds_nodash",
     "next_execution_date",

airflow/utils/context.pyi

@@ -71,6 +71,7 @@ class Context(TypedDict, total=False):
     inlets: list
     logical_date: DateTime
     macros: Any
+    map_index_template: str
     next_ds: str | None
     next_ds_nodash: str | None
     next_execution_date: DateTime | None

airflow/www/static/js/dag/details/Header.tsx

@@ -30,6 +30,7 @@ import useSelection from "src/dag/useSelection";
 import Time from "src/components/Time";
 import { useGridData } from "src/api";
 import RunTypeIcon from "src/components/RunTypeIcon";
+import { useTaskInstance } from "src/api";
 
 import BreadcrumbText from "./BreadcrumbText";
 
@@ -45,6 +46,15 @@ const Header = () => {
     onSelect,
     clearSelection,
   } = useSelection();
+
+  const { data: taskInstance } = useTaskInstance({
+    dagId,
+    dagRunId: runId || "",
+    taskId: taskId || "",
+    mapIndex,
+    enabled: mapIndex !== undefined
+  });
+
   const dagRun = dagRuns.find((r) => r.runId === runId);
 
   const group = getTask({ taskId, task: groups });
@@ -65,9 +75,9 @@ const Header = () => {
     // If a runId includes the runtype then parse the time, otherwise use the custom run id
     const runName =
       runId.includes("manual__") ||
-      runId.includes("scheduled__") ||
-      runId.includes("backfill__") ||
-      runId.includes("dataset_triggered__") ? (
+        runId.includes("scheduled__") ||
+        runId.includes("backfill__") ||
+        runId.includes("dataset_triggered__") ? (
         <Time dateTime={getDagRunLabel({ dagRun, ordering })} />
       ) : (
         runId
@@ -131,7 +141,7 @@ const Header = () => {
           <BreadcrumbLink
             _hover={isMappedTaskDetails ? { cursor: "default" } : undefined}
           >
-            <BreadcrumbText label="Map Index" value={mapIndex} />
+            <BreadcrumbText label="Map Index" value={taskInstance?.renderedMapIndex || mapIndex} />
           </BreadcrumbLink>
         </BreadcrumbItem>
       )}

airflow/www/static/js/dag/details/taskInstance/Details.tsx

@@ -177,6 +177,12 @@ const Details = ({ gridInstance, taskInstance, group }: Props) => {
               <Td>{taskInstance.mapIndex}</Td>
             </Tr>
           )}
+          {taskInstance?.renderedMapIndex !== undefined && (
+            <Tr>
+              <Td>Rendered Map Index</Td>
+              <Td>{taskInstance.renderedMapIndex}</Td>
+            </Tr>
+          )}
           {!!taskInstance?.tryNumber && (
             <Tr>
               <Td>Try Number</Td>

airflow/www/static/js/dag/details/taskInstance/MappedInstances.tsx

@@ -18,7 +18,7 @@
  */
 
 import React, { useState, useMemo, useRef } from "react";
-import { Flex, Box } from "@chakra-ui/react";
+import { Flex, Box, VisuallyHidden } from "@chakra-ui/react";
 import { snakeCase } from "lodash";
 import type { Row, SortingRule } from "react-table";
 
@@ -69,6 +69,7 @@ const MappedInstances = ({ dagId, runId, taskId, onRowClicked }: Props) => {
     () =>
       taskInstances.map((mi) => ({
         ...mi,
+        renderedMapIndex: mi.renderedMapIndex,
         state: (
           <Flex alignItems="center">
             <StatusWithNotes
@@ -94,6 +95,9 @@ const MappedInstances = ({ dagId, runId, taskId, onRowClicked }: Props) => {
       {
         Header: "Map Index",
         accessor: "mapIndex",
+        Cell: ({ cell: { row } }: any) => (
+          row.original.renderedMapIndex || row.original.mapIndex
+        )
       },
       {
         Header: "State",

airflow/www/static/js/types/api-generated.ts

@@ -1443,6 +1443,12 @@ export interface components {
       pid?: number | null;
       executor_config?: string;
       sla_miss?: components["schemas"]["SLAMiss"];
+      /**
+       * @description Rendered name of an expanded task instance, if the task is mapped.
+       *
+       * *New in version 2.9.0*
+       */
+      rendered_map_index?: string | null;
       /**
        * @description JSON object describing rendered fields.
        *

docs/apache-airflow/authoring-and-scheduling/dynamic-task-mapping.rst

@@ -171,6 +171,44 @@ As well as a single parameter it is possible to pass multiple parameters to expa
 
 This would result in the add task being called 6 times. Please note, however, that the order of expansion is not guaranteed.
 
+Named mapping
+-------------
+
+By default, mapped tasks are assigned an integer index. It is possible to override the integer index for each mapped task in the Airflow UI with a name based on the task's input. This is done by providing a Jinja template for the task with ``map_index_template``. This template is rendered after each expanded task is executed using the task context. This means you can reference attributes on the task like this:
+
+.. code-block:: python
+
+    from airflow.providers.common.sql.operators.sql import SQLExecuteQueryOperator
+
+
+    # The two expanded task instances will be named "2024-01-01" and "2024-01-02".
+    SQLExecuteQueryOperator.partial(
+        ...,
+        sql="SELECT * FROM data WHERE date = %(date)s",
+        map_index_template="""{{ task.parameters['date'] }}""",
+    ).expand(
+        parameters=[{"date": "2024-01-01"}, {"date": "2024-01-02"}],
+    )
+
+In the above example, the expanded task instances will be named "2024-01-01" and "2024-01-02". The names show up in the Airflow UI instead of "0" and "1", respectively.
+
+Since the template is rendered after the main execution block, it is possible to also dynamically inject into the rendering context. This is useful when the logic to render a desirable name is difficult to express in the Jinja template syntax, particularly in a taskflow function. For example:
+
+.. code-block:: python
+
+    from airflow.operators.python import get_current_context
+
+
+    @task(map_index_template="{{ my_variable }}")
+    def my_task(my_value: str):
+        context = get_current_context()
+        context["my_variable"] = my_value * 3
+        ...  # Normal execution...
+
+
+    # The task instances will be named "aaa" and "bbb".
+    my_task.expand(my_value=["a", "b"])
+
 Mapping with non-TaskFlow operators
 ===================================
 

docs/apache-airflow/templates-ref.rst

@@ -74,6 +74,7 @@ Variable                                    Type                  Description
 ``{{ run_id }}``                            str                   The currently running :class:`~airflow.models.dagrun.DagRun` run ID.
 ``{{ dag_run }}``                           DagRun                The currently running :class:`~airflow.models.dagrun.DagRun`.
 ``{{ test_mode }}``                         bool                  Whether the task instance was run by the ``airflow test`` CLI.
+``{{ map_index_template }}``                None | str            Template used to render the expanded task instance of a mapped task. Setting this value will be reflected in the rendered result.
 ``{{ expanded_ti_count }}``                 int | ``None``        | Number of task instances that a mapped task was expanded into. If
                                                                   | the current task is not mapped, this should be ``None``.
                                                                   | Added in version 2.5.

tests/api_connexion/endpoints/test_mapped_task_instance_endpoint.py

@@ -234,6 +234,7 @@ def test_mapped_task_instances(self, one_task_with_mapped_tis, session):
             "queue": "default",
             "queued_when": None,
             "rendered_fields": {},
+            "rendered_map_index": None,
             "sla_miss": None,
             "start_date": "2020-01-01T00:00:00+00:00",
             "state": "success",