Allow DBDagBag TTL cache eviction without a size cap

[aeroyorch]

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Allow DBDagBag TTL cache eviction without a size cap (i.e. cache_size=0, cache_ttl>0).

Related to #69001 and #69007

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---

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[SameerMesiah97]

Just one nit. Looks good otherwise.

[aeroyorch]

Just one nit. Looks good otherwise.

Thanks for the review! Changes already implemented

[lohyenshen]

hi, may I know what airflow version would this be released to?

[vatsrahul1001]

The DBDagBag fix itself looks right, but I don't think it's reachable from the actual config path yet. create_dag_bag() in api_fastapi/common/dagbag.py still does:

if cache_size <= 0:
    return DBDagBag(cache_size=0)

That early-return fires whenever dag_cache_size <= 0 and never even reads cache_ttl_config, so setting dag_cache_size = 0 + dag_cache_ttl = 3600 in airflow.cfg still ends up as a plain unbounded dict with no eviction. test_create_dag_bag_cache_modes still asserts exactly that (the "size_zero_unbounded" case expects dict/_use_cache=False for cache_size=0, cache_ttl=3600), and config.yml's dag_cache_size description still says 0 means "unbounded dict, no eviction" with no mention of TTL-only mode.

Could you also update create_dag_bag() to pass cache_ttl through when cache_size<=0, add a case to test_create_dag_bag_cache_modes covering that combo, and touch up the config.yml wording? Otherwise this fix isn't actually reachable by anyone configuring it through airflow.cfg.

[aeroyorch]

The DBDagBag fix itself looks right, but I don't think it's reachable from the actual config path yet. create_dag_bag() in api_fastapi/common/dagbag.py still does:

if cache_size <= 0:
    return DBDagBag(cache_size=0)

That early-return fires whenever dag_cache_size <= 0 and never even reads cache_ttl_config, so setting dag_cache_size = 0 + dag_cache_ttl = 3600 in airflow.cfg still ends up as a plain unbounded dict with no eviction. test_create_dag_bag_cache_modes still asserts exactly that (the "size_zero_unbounded" case expects dict/_use_cache=False for cache_size=0, cache_ttl=3600), and config.yml's dag_cache_size description still says 0 means "unbounded dict, no eviction" with no mention of TTL-only mode.

Could you also update create_dag_bag() to pass cache_ttl through when cache_size<=0, add a case to test_create_dag_bag_cache_modes covering that combo, and touch up the config.yml wording? Otherwise this fix isn't actually reachable by anyone configuring it through airflow.cfg.

Thanks for the review. Changes already implemented :)

[vatsrahul1001]

LGTM!, can be merged after code owners review

[vatsrahul1001]

Moving to 3.3.2 as this is still pending code owner review and do not want to rush on merging this as it not critical

[aeroyorch]

Moving to 3.3.2 as this is still pending code owner review and do not want to rush on merging this as it not critical

No problem. In the meantime, I can work on some of the other items to fix #69001