[wildfly-dev] A few questions about the NoSQL MongoDB client subsystem configuration...

[Scott Marlow]

On 06/09/2016 06:27 AM, Gunnar Morling wrote:
> Hi,
>
> My concern with the current proposal and its usage of dedicated
> elements/attributes for specific options such as write concern is that
> it easily leads into a catch-up game with datastore vendors as they keep
> adding new options. That might create a constant effort for maintaining
> this subsystem.
>
> How about having a more generic approach which only has typed elements
> for common properties/settings such as user, password, database name and
> then allows to set custom things as part of the connection URL:
>
>     <subsystem xmlns="urn:jboss:domain:nosql:1.0">
>         <nosql-datasource jndi-name="java:jboss/nosql/mongodb_test">
>
> <connection-url>nosql:mongdb:localhost:27017,otherhost:27017/somedatabase?writeConcern=ACKNOWLEDGED&readPreference=MAJORITY&...</connection-url>
>             <security>
>                 <user-name>bob</user-name>
>                 <password>secret</password>
>             </security>
>         </datasource>
>     </subsystem>
>
> Here, the connection-url would be analyzed to load the right driver and
> pass any configured settings to it.
>
> While compact, that URL syntax might be confused with existing URI
> schemes of specific stores, so an alternative might be this (a bit more
> verbose, though):
>
>     <subsystem xmlns="urn:jboss:domain:nosql:1.0">
>         <nosql-datasource jndi-name="java:jboss/nosql/mongodb_test">
>             <driver>mongodb</driver>
>             <end-points>localhost:27017,otherhost:27017</end-points>

We cannot include hostname + port numbers directly, instead we reference 
host names/port pairs defined in the outbound-socket-binding section of 
standalone.xml.

>             <database>somedatabase</database>
>             <security>
>                 <user-name>bob</user-name>
>                 <password>secret</password>
>             </security>
>             <properties>
>                 <property name="writeConcern">ACKNOWLEDGED</property>
>                 <property name="readPreference">MAJORITY</property>
>             </properties>
>         </datasource>
>     </subsystem>
>

+1 for the separate properties idea!

> Both alternatives don't address custom write concerns, but I think you
> foresee CDI producer methods for more advanced customizations, so that
> might be fine. That'd also be needed for some other non-primitive
> options (dbDecoderFactory, codecRegistry etc.), unless you provide a way
> to configure classes here and have them instantiated.

I'm still learning more about how to use advance customizations in the 
CDI producer but yes, we definitely want to do this, to simplify 
application program use of NoSQL.

>
> These more generic approaches will make it more robust towards new
> options being added, but of course you also loose type-safety and I
> suppose usability in the console which might provide dedicated editors
> for real types such as boolean etc.

I think that about summarizes the difference.  Eventually, when the 
configuration options stabilize, it might be better to switch to 
dedicated editors, which would be a big one-off upgrade, I think.  If we 
used dedicated editors now, we will have several big (NoSQL subsystem 
configuration) upgrades, as the NoSQL database options may change over time.

Thanks,
Scott

>
> --Gunnar
>
>
>
>
> 2016-06-08 22:18 GMT+02:00 Brian Stansberry <brian.stansberry at redhat.com
> <mailto:brian.stansberry at redhat.com>>:
>
>     On 6/8/16 9:44 AM, Jesper Pedersen wrote:
>     > On 06/08/2016 10:39 AM, Scott Marlow wrote:
>     >> For those not reading [1], we also can support one of the predefined
>     >> write-concern constants via:
>     >>
>     >> <mongo ... write-concern="ACKNOWLEDGED">
>     >>     ...
>     >> </mongo>
>     >>
>     >
>     > I would choose this approach, and support the predefined constants.
>     >
>     > Exposing MongoDB internal API details in the configuration seems to be
>     > overkill, and put extra effort on your part when they change the API.
>     >
>
>     This is good input. If this ends up in WildFly or EAP, we have stringent
>     compatibility guarantees, so be cautious about exposing things in
>     your API.
>
>     >
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>     >
>
>
>     --
>     Brian Stansberry
>     Senior Principal Software Engineer
>     JBoss by Red Hat
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