Jaroslav Bachorik wrote:
On 12/02/2014 05:22 PM, shanliang wrote:
Jaroslav Bachorik wrote:
On 12/02/2014 04:22 PM, shanliang wrote:
Jaroslav Bachorik wrote:
On 12/02/2014 02:40 PM, shanliang wrote:
Jaroslav Bachorik wrote:
On 12/01/2014 02:50 PM, shanliang wrote:
Hi,
please review this test bug fix:
webrev:
http://cr.openjdk.java.net/~sjiang/JDK-8065764/00/
bug:
https://bugs.openjdk.java.net/browse/JDK-8065764
test/javax/management/monitor/CounterMonitorTest.java
L61 - observedValue could be Integer
Could be, but not make difference, observedValue is only used
with the
operation "==", like
while (value != observedValue)
In that case having a correct type would make even more sense for the
readability.
Agree in general:) but the variable "count" is declared as "Object" in
StdObservedObject, and "observedValue" is used to save observed
"count"
value, so better to keep the same type for "more readability"? and
avoid
a casting when setting "observedValue"
Any reason 'count' is declared as Object? The value is effectively an
integer value - only integer values are ever assigned to it. All the
operations silently suppose this would be an integer and yet the type
information is thrown away and the data is stored as Object. Feels
very strange ...
I think a possible reason is that the CounterMonitor supports only
Number type for comparing, and it accepts any type but detects whether
the observed variable could be "matched" to Number, pass an Object type
verifies this capability.
Hm, could you direct me to the code doing this? 'setAttribute' method
seems to be inherited from 'Monitor' class and does not do any
additional checks. Then 'Monitor.monitor()' uses 'getAttribute'
(again, not overridden) to get back to the attribute :(
ConterMonitor overrides Monitor.isComparableTypeValid(...)
This method will be called by Monitor at the monitoring time and a
Notification with the type "jmx.monitor.error.type" will be sent out if
the observed attribute is not of type "Integer".
Yes the monitor might have to do type check with the method:
Monitor.setObservedAttribute("NbObjects");
but the Javadoc declares only:
Throws: IllegalArgumentException - The specified attribute is null.
maybe it is not sure that a monitor could do type check at setting time,
for example if the MBeanInfo is null and getAttributeValue() returns null.
Shanliang
Thanks,
-JB-
L225-238 - you could replace this block with the usage of Phaser
(if
you'd do that you could completely remove 'observedValue')
Not sure that it is a good idea to remove "observedValue" by using
Phaser, yes using Phaser can tell when the monitor does an
observation,
but it is better to know which count value the monitor observed, in
case
the thread was waked up accidentally.
I don't think phaser can be confused by spurious wake-ups.
If you want to keep the current way of synchronizing then you should
make the 'count' variable volatile (L77) - it might be read and
written to from different threads.
Phaser should not make a false wakeup, but use "observedValue" can
make
sure that the observation happens on the right "count" value.
Yes "count" should be declared as "volatile".
Here is the new version:
http://cr.openjdk.java.net/~sjiang/JDK-8065764/01/
Still using 'derivedGange' instead of 'derivedGauge' :(
Oh I will change it before pushing, if no other modification.
Thanks,
Shanliang
-JB-
Thanks,
Shanliang
-JB-
Thanks,
Shanliang
-JB-
The test tested the mode "difference", according to the Javadoc:
If the counter difference mode is used, the value of the
derived
gauge is calculated as the difference between the observed counter
values for two successive observations.
The test set the first value and then waited 2 times of
granularityperiod at line 171, hoped that the monitor would get
the
first observation during this waiting time, but the test could
fail
because granularityperiod * 2 was not enough and the test did the
second
set before the monitor did the first observation.
It is easy to make the test timeout by commenting out the line
171.
The proposed solution is to get informed when the monitor did
observation on calling:
StdObservedObject.getNbObjects();
Thanks,
Shanliang
