DonHaul opened a new issue, #57604:
URL: https://github.com/apache/airflow/issues/57604
### Apache Airflow version
Other Airflow 2/3 version (please specify below)
### If "Other Airflow 2/3 version" selected, which one?
3.0.1
### What happened?
I have recentrly increase the number of `max_active_runs` to 64, but the
scheduler keeps showing the following error:
`dag cannot be started due to dag max_active_runs constraint; active_runs=16
max_active_runs=64` which
doenst make much sense.
Here are some examples:
```
2025-10-31T08:44:00.092+0000] {scheduler_job_runner.py:1802} INFO - dag
cannot be started due to dag max_active_runs constraint; active_runs=16
max_active_runs=64 dag_id=hep_create_dag
run_id=1f537f7a-5022-47e1-bfa3-ec2f150f4571
[2025-10-31T08:44:00.094+0000] {scheduler_job_runner.py:1802} INFO - dag
cannot be started due to dag max_active_runs constraint; active_runs=16
max_active_runs=64 dag_id=hep_create_dag
run_id=12401d58-e44c-40e2-87f8-009725832346
[2025-10-31T08:44:00.095+0000] {scheduler_job_runner.py:1802} INFO - dag
cannot be started due to dag max_active_runs constraint; active_runs=16
max_active_runs=64 dag_id=hep_create_dag
run_id=e3ed3ee4-b1c6-4577-9fcb-63a8c10ba0e6
[2025-10-31T08:44:00.096+0000] {scheduler_job_runner.py:1802} INFO - dag
cannot be started due to dag max_active_runs constraint; active_runs=16
max_active_runs=64 dag_id=hep_create_dag
run_id=0ee100f7-08e1-4c8a-bcb4-e1aa2c5eabde
[2025-10-31T08:44:00.097+0000] {scheduler_job_runner.py:1802} INFO - dag
cannot be started due to dag max_active_runs constraint; active_runs=16
max_active_runs=64 dag_id=hep_create_dag
run_id=ee99ce33-b5f6-4ab6-80d2-9300a95e6180
[2025-10-31T08:44:00.098+0000] {scheduler_job_runner.py:1802} INFO - dag
cannot be started due to dag max_active_runs constraint; active_runs=16
max_active_runs=64 dag_id=hep_create_dag
run_id=68b10c34-3371-4aa4-997f-9d22da87271a
```
My guess is that `dag.max_active_runs` and `dag_run.max_active_runs` can at
times be different things:
https://github.com/apache/airflow/blob/26c93bc52b8eb37818f4fd88b26caf8ccca5c159/airflow-core/src/airflow/jobs/scheduler_job_runner.py#L1878-L1884
### What you think should happen instead?
The number of dag runs should ramp up to 64
### How to reproduce
Have initially the `max_active_runs` at 16, redeploy with `max_active_runs`
at 64
### Operating System
Debian GNU/Linux 12 (bookworm)
### Versions of Apache Airflow Providers
_No response_
### Deployment
Official Apache Airflow Helm Chart
### Deployment details
`airflow.cfg` core section:
```
[core]
dags_folder = /opt/airflow/dags
hostname_callable = airflow.utils.net.getfqdn
might_contain_dag_callable =
airflow.utils.file.might_contain_dag_via_default_heuristic
default_timezone = utc
executor = CeleryExecutor
auth_manager =
airflow.providers.fab.auth_manager.fab_auth_manager.FabAuthManager
simple_auth_manager_users = admin:admin
simple_auth_manager_all_admins = False
# simple_auth_manager_passwords_file =
parallelism = 64
max_active_tasks_per_dag = 66
dags_are_paused_at_creation = false
max_active_runs_per_dag = 64
max_consecutive_failed_dag_runs_per_dag = 0
# mp_start_method =
load_examples = false
plugins_folder = /opt/airflow/plugins
execute_tasks_new_python_interpreter = False
fernet_key = N0REWDNyQ1ExZm9WRXRtZDhWQzR0aEphOFh1bXhQOEI=
donot_pickle = True
dagbag_import_timeout = 30.0
dagbag_import_error_tracebacks = True
dagbag_import_error_traceback_depth = 2
default_impersonation =
security =
unit_test_mode = False
allowed_deserialization_classes = airflow.*
allowed_deserialization_classes_regexp =
killed_task_cleanup_time = 60
dag_run_conf_overrides_params = True
dag_discovery_safe_mode = True
dag_ignore_file_syntax = glob
default_task_retries = 0
default_task_retry_delay = 300
max_task_retry_delay = 86400
default_task_weight_rule = downstream
task_success_overtime = 20
default_task_execution_timeout =
min_serialized_dag_update_interval = 30
compress_serialized_dags = False
min_serialized_dag_fetch_interval = 10
max_num_rendered_ti_fields_per_task = 30
xcom_backend = airflow.sdk.execution_time.xcom.BaseXCom
lazy_load_plugins = True
lazy_discover_providers = True
hide_sensitive_var_conn_fields = True
sensitive_var_conn_names =
default_pool_task_slot_count = 128
max_map_length = 4096
daemon_umask = 0o077
```
i can provide more details if required
### Anything else?
_No response_
### Are you willing to submit PR?
- [ ] Yes I am willing to submit a PR!
### Code of Conduct
- [x] I agree to follow this project's [Code of
Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)
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