|
Home > Archive > Apache JDO Project > February 2007 > [DISCUSS} Server TimeZone
You are viewing an archived Text-only version of the thread.
To view this thread in it's original format and/or if you want to reply to
this thread please [click here]
| Author |
[DISCUSS} Server TimeZone
|
|
| Craig L Russell 2007-02-08, 7:11 pm |
| | |
| Erik Bengtson 2007-02-09, 7:11 am |
| Craig, I understand that server means the backend database server. what it we
have multiple backend db servers?
Use case with multiple dbs:
SELECT FROM db1.classA WHERE classA.time > datetime() && classB.time >
datetime() VARIABLES db2.classB
The first datetime() is evaluated by db1, while the second by db2.
Quoting Craig L Russell <Craig.Russell@Sun.COM>:
> Here is a proposal to add the ability of a user to get the time at
> the server in a portable way.
>
> This should allow an application to avoid time skew by using the time
> as seen by a single source, the server to which the
> PersistenceManagerFactory is connected.
>
> <proposed>
> 11.1
> ...
> ServerTimeZoneID: the time zone ID of the server to which this
> PersistenceManagerFactory is connected, for use with the
> PersistenceManager method getServerDate
> If ServerTimeZoneID is specified, the value must correspond to a
> valid time zone ID as returned by TimeZone.getAvailableIDs(). The
> implementation uses the ServerTimeZoneID to implement the
> getServerDate method. If ServerTimeZoneID is not specified, the
> implementation might use proprietary methods to determine the time
> zone in which the server is located. If ServerTimeZoneID is not
> specified, and the implementation cannot or does not use proprietary
> methods to determine the server time zone, then the default time zone
> ID of the Java VM is used.
>
> 12.17 Server Date
> java.util.Date getServerDate();
>
> Time skew is a phenomenon in which machines connected together in
> client/server configurations might have clocks that are not perfectly
> synchronized, and the time as seen by different clients might differ.
> In order for the application to avoid time skew, this method can be
> used to acquire a Date instance corresponding to the UTC Date as seen
> by the server. Clients using this method can order their operations
> according to a single time source.
> Implementations use the setting of the server time zone to prepare a
> Date instance that represents UTC time on the server.
> </proposed>
>
> Craig Russell
> Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
> 408 276-5638 mailto:Craig.Russell@sun.com
> P.S. A good JDO? O, Gasp!
>
>
| |
| Joerg von Frantzius 2007-02-09, 7:11 am |
| Hello Erik,
this seems to be connected to thread Transaction Manager and JCA
<http://www.jpox.org/servlet/forum/v...ead?thread=4099>, where it
seems you proposed to associate a single PersistenceManagerFactory with
multiple DBs. As a PMF only has properties to connect and authenticate
with a single DB (URL, username/pw), I think the spec implicitly defines
that a PMF can be connected to a single DB only.
So it seems to me your question implies some fundamental conceptual change?
Regards,
Jörg
Erik Bengtson wrote:
> Craig, I understand that server means the backend database server. what it we
> have multiple backend db servers?
>
> Use case with multiple dbs:
>
> SELECT FROM db1.classA WHERE classA.time > datetime() && classB.time >
> datetime() VARIABLES db2.classB
>
> The first datetime() is evaluated by db1, while the second by db2.
>
> Quoting Craig L Russell <Craig.Russell@Sun.COM>:
>
>
>
>
>
>
>
>
| |
| Erik Bengtson 2007-02-09, 1:11 pm |
| I don't think the spec prohibits multiple dbs in the backend, so my
concern is to not difficult it
Quoting Joerg von Frantzius <joerg.von.frantzius@artnology.com>:
> Hello Erik,
>
> this seems to be connected to thread Transaction Manager and JCA
> <http://www.jpox.org/servlet/forum/v...ead?thread=4099>, where it
> seems you proposed to associate a single PersistenceManagerFactory with
> multiple DBs. As a PMF only has properties to connect and authenticate
> with a single DB (URL, username/pw), I think the spec implicitly defines
> that a PMF can be connected to a single DB only.
>
> So it seems to me your question implies some fundamental conceptual change?
>
> Regards,
> Jörg
>
> Erik Bengtson wrote:
> we
>
>
| |
| Joerg von Frantzius 2007-02-09, 1:11 pm |
| Erik Bengtson wrote:
> I don't think the spec prohibits multiple dbs in the backend, so my
> concern is to not difficult it
>
The spec allows for multiple DBs in the backend, with a single PMF for
each of them (or what backend were you referring to?)
How do you want to configure multiple database connections per PMF
without extending the spec?
> Quoting Joerg von Frantzius <joerg.von.frantzius@artnology.com>:
>
>
>
>
>
>
>
>
| |
| Erik Bengtson 2007-02-09, 1:11 pm |
| Joerg,
> How do you want to configure multiple database connections per PMF
> without extending the spec?
Agreed, this has to discussed/specified in JPOX. After completed the
implementation, I see this as a potential feature to be proposed to JDO
standard
Quoting Joerg von Frantzius <joerg.von.frantzius@artnology.com>:
> Erik Bengtson wrote:
> The spec allows for multiple DBs in the backend, with a single PMF for
> each of them (or what backend were you referring to?)
>
> How do you want to configure multiple database connections per PMF
> without extending the spec?
> change?
> it
>
>
| |
| Joerg von Frantzius 2007-02-09, 1:11 pm |
| Maybe I got something wrong here, but don't we run into a whole lot of
other questions here? Like, when we execute a query, what DB will it be
run on? When invoking operations on a PersistenceManager from a PMF with
multiple databases, which DB will the resulting SQL be sent to?
Erik Bengtson wrote:
> Joerg,
>
>
>
> Agreed, this has to discussed/specified in JPOX. After completed the
> implementation, I see this as a potential feature to be proposed to JDO
> standard
>
> Quoting Joerg von Frantzius <joerg.von.frantzius@artnology.com>:
>
>
>
>
>
>
>
>
|
|
|
|
|