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Re: Multiple hosts for a single connection


Hmm yes, it appears that the `airflow connections` CLI doesn't let you create multiple connections of the same conn_id. What the WebUI can do the CLI should be able to do also! It should allow that in some way (behind a `--allow-multiple` flag perhaps? I can see an argument for not allowing set multiple by default as it is often not what people want.)

-ash

> On 7 Aug 2018, at 15:17, Deng Xiaodong <xd.deng.r@xxxxxxxxx> wrote:
> 
> Hi Ben,
> 
> If you would like to set multiple connections with the same *conn_id*, you
> can only do that in Web UI. That is, you need to build multiple entries
> with different host, but with the same *conn_id*.
> 
> The method of setting connection in environment variables can only help set
> one connection for each *conn_id*.
> 
> (Of course Web UI stores your connections in the metadata database. So if
> you really need to avoid manual interventions and need multiple connections
> for one single conn_id, hacking into the metadata database may be an
> option? even thought not recommended)
> 
> Other guys please correct me if I'm wrong in any parts. Thanks.
> 
> 
> Regards,
> XD
> 
> On Tue, Aug 7, 2018 at 9:43 PM Ben Laird <br.laird@xxxxxxxxx> wrote:
> 
>> Hello -
>> 
>> I'd like to define multiple connections for the `webhdfs_default` conn_id,
>> as we have a primary and backup host for the hadoop namenode. This is for
>> use with the WebHDFSHook, which queries for connections and seemingly can
>> accept a list of them from the database.
>> 
>> ```
>>        nn_connections = self.get_connections(self.webhdfs_conn_id)
>>        for nn in nn_connections:
>> ```
>> 
>> https://github.com/apache/incubator-airflow/blob/master/airflow/hooks/webhdfs_hook.py#L54-L55
>> 
>> I can manually add 2 entries for `webhdfs_default` in the Web UI, one for
>> each hostname, however with the CLI and adding the entries to the
>> airflow.cfg I get errors that a connection already exists.
>> 
>> It seems WebHDFSHook doesn't support reading multiple hosts from one entry.
>> Is this a bug? Or is there a different way to accomplish without manually
>> adding via the UI?
>> 
>> Thanks!
>> Ben Laird
>>