Hi Craig,
I like the proposal. It solves the issue of having different timeout
values for read and write operation and the wording makes clear that the
scope of the timeout value is the datastore operation.
About the exception thrown in case of a timeout. I agree with what is
written in the minutes of the JDO TCK conference call: it is ok to throw
a JDODatastoreException, no need for a specific exception.
Regards Michael
Hi Michael,
Good summary.
The original request for this feature was to allow queries that were
either stuck (possible deadlock) or running away (query too complex
for the server to complete timely).
Then, Jörg added a request for updates to time out if they were stuck.
And others wanted to know whether the timeout applied to memory
operations or just database operations.
I'd like to propose something completely different that attempts to
resolve all of the above issues.
Define two new properties and associated apis:
DatastoreReadTimeoutMillis and DatastoreWriteTimeoutMillis. Get rid of
the QueryTimeoutMillis property.
DatastoreReadTimeoutMillis applies to all operations on the datastore
that are associated with reading data, including getObjectById,
queries, refresh, navigation, and lazy loading of fields or properties.
DatastoreWriteTimeoutMillis applies to all operations on the datastore
that are associated with writing data, including flush, commit, delete
by query.
If multiple datastore operations are involved in satisfying a user
request, the timeout applies individually to each of them.
The rules for specifying the timeout are the same as in the original
proposal: if specified on a query, the timeout applies only to that
query, with the default coming from the PM. If the operation is
related to a PM operation, the timeout comes from the PM api, with the
default coming from the PMF.
Whether there is a timeout is determined by the optional features
property. I don't know of a datastore that supports read and write
timeouts separately, so the feature can simply be called
DatastoreTimeout and it either is supported or not.
Craig
On Nov 17, 2009, at 12:05 AM, Michael Bouschen wrote:
Hi,
the current spec allows specifying a query timeout on a Query, a PM
or a PMF. The PM defines the default for all Query instances of the
PM and the PMF defines the default value for all PMs of that PMF.
However, there are still three open issue in the query timeout area:
(1) query timeout as an optional feature
I propose to add query timeout as an optional feature. This means the
collection returned by the PMF method supportedOptions includes the
string "javax.jdo.option.QueryTimeout", if the JDO implementation and
the datastore bound to the PMF supports query timeout. This would be
a change in chapter 11.6 "Optional Feature Support" of the spec.
(2) Scope of the query timeout value
I propose that a query timeout value set for a PM applies to all
"datastore query" operations issued by the PM. This includes
relationship navigation, findByObjectId and lasy loading of collections.
But how about modifying operations such as update, delete and insert?
Does it make sense to apply the PM's query timeout for these
operationsas well? I think this makes sense, but it might be less
obvious, because these operations are part of the transaction commit.
See also Jörg's recent email with subject "update timeout". This
would be a change in chapter 12 PersistenceManager. Today chapter
12.6.3 "Query factory interface" specifies method setQueryTimeout. If
we broaden the scope of a query timeout set on a PM, it might make
sense to specify this in its own section, e.g. 12.6.9 "Query Timeout".
(3) Definition of query timeout: datastore operation or JDO method?
Does the query timeout apply to the underlying datastore operation or
does it define the maximum execution time of the JDO method such as
Query.execute?
I propose the former, meaning use the query timeout value for the
datastore operation. Otherwise, the JDO implementation would need to
calculate the timeout for the datastore operation and need o guess
the time needed to post-process the query result. If the datastore
has the JDBC standard second resolution, and there is less than 1000
millis left in the timeout, what should be the timeout set on the
datastore query statement?
What do you think?
Regards Michael
--
*Michael Bouschen*
*Prokurist*
akquinet t...@spree GmbH
Bülowstr. 66, D-10783 Berlin
Fon: +49 30 235 520-33
Fax: +49 30 217 520-12
Email: [email protected]
Url: www.akquinet.de <http://www.akquinet.de>
akquinet t...@spree GmbH, Berlin
Geschäftsführung: Martin Weber, Prof. Dr. Christian Roth
Amtsgericht Berlin-Charlottenburg HRB 86780 B
USt.-Id. Nr.: DE 225 964 680
--
*Michael Bouschen*
*Prokurist*
akquinet t...@spree GmbH
Bülowstr. 66, D-10783 Berlin
Fon: +49 30 235 520-33
Fax: +49 30 217 520-12
Email: [email protected]
Url: www.akquinet.de <http://www.akquinet.de>
akquinet t...@spree GmbH, Berlin
Geschäftsführung: Martin Weber, Prof. Dr. Christian Roth
Amtsgericht Berlin-Charlottenburg HRB 86780 B
USt.-Id. Nr.: DE 225 964 680
--
*Michael Bouschen*
*Prokurist*
akquinet t...@spree GmbH
Bülowstr. 66, D-10783 Berlin
Fon: +49 30 235 520-33
Fax: +49 30 217 520-12
Email: [email protected]
Url: www.akquinet.de <http://www.akquinet.de>
akquinet t...@spree GmbH, Berlin
Geschäftsführung: Martin Weber, Prof. Dr. Christian Roth
Amtsgericht Berlin-Charlottenburg HRB 86780 B
USt.-Id. Nr.: DE 225 964 680
Craig L Russell
Architect, Sun Java Enterprise System http://db.apache.org/jdo
408 276-5638 mailto:[email protected]
P.S. A good JDO? O, Gasp!
--
*Michael Bouschen*
*Prokurist*
akquinet t...@spree GmbH
Bülowstr. 66, D-10783 Berlin
Fon: +49 30 235 520-33
Fax: +49 30 217 520-12
Email: [email protected]
Url: www.akquinet.de <http://www.akquinet.de>
akquinet t...@spree GmbH, Berlin
Geschäftsführung: Martin Weber, Prof. Dr. Christian Roth
Amtsgericht Berlin-Charlottenburg HRB 86780 B
USt.-Id. Nr.: DE 225 964 680
