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Re: About the DAG discovering not synced between scheduler and webserver


Hi,


It seems that Airflow handles bellow situation currently:


-  DAGs discovered in scheduler, but not discovered by webserver yet

-  DAGs discovered in webserver, but not discovered by scheduler yet


I still don't quite understand why there is the discovering logic separately in scheduler and webserver, based on my understanding webserver only needs to display the orm_dags from metadb, is there any requirement or design consideration besides this ?


Many thanks for any information.


Thanks,

Song

________________________________
From: Song Liu <songliu@xxxxxxxxxxx>
Sent: Saturday, May 12, 2018 7:58:43 PM
To: dev@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
Subject: About the DAG discovering not synced between scheduler and webserver

Hi,

When add a new dag, sometimes we can see:

```
This DAG isn't available in the web server's DagBag object. It shows up in this list because the scheduler marked it as active in the metadata database.
```

In the views.py, it will collect DAGs under "DAGS_FOLDER" by instantiate a DagBag object as bellow:

```
dagbag = models.DagBag(settings.DAGS_FOLDER)
```

So that webserver will depends on its own timing to collect DAGs, but why not just simply to query metadata db ? since if a DAG is active in DB now it can be visible in web at the time.

Could someone share something behind this design ?

Thanks,
Song