Failed transactions

[Ross Rick]

If read the previous thread correctly...   a transaction is journaled to the disk prior to execution on the model.  

If the transaction fails, does the journaled transaction always get removed from disk?   It would appear that the transaction is removed from disk under normal circumstances, but under catastrophic failure, it's less clear.     In fact, I doubt that it is entirely possible to ensure any such thing.   How do the rest of you handle this?   When you come back up your system will attempt the transaction again, even if it works, that is not the expected state of the system.   The expected state is the state just prior to attempting the bad transaction.   

How am I doing on the understanding here?   I appreciate everyone's help very much.

R

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[Klaus Wuestefeld]

There is a more general question that you have to answer anyway,
regardless of how you do your persistence, Prevayler or otherwise:

"My system is in a state that will crash given some common basic user
action. What now?"

See you, Klaus.



On Fri, Jul 31, 2009 at 5:28 PM, Ross Rick<rick@...> wrote:

> If read the previous thread correctly...   a transaction is journaled to the
> disk prior to execution on the model.
> If the transaction fails, does the journaled transaction always get removed
> from disk?   It would appear that the transaction is removed from disk under
> normal circumstances, but under catastrophic failure, it's less clear.
> In fact, I doubt that it is entirely possible to ensure any such thing.
> How do the rest of you handle this?   When you come back up your system will
> attempt the transaction again, even if it works, that is not the expected
> state of the system.   The expected state is the state just prior to
> attempting the bad transaction.
> How am I doing on the understanding here?   I appreciate everyone's help
> very much.
>
> R
> ------------------------------------------------------------------------------
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[Ross Rick]

Klaus,

I am discussing the likelihood that I will someday be faced with out  
of memory problems and yes, once you've popped your memory, you have  
no idea what your app will do for any given user action, no doubt  
about it.  That is precisely why I am bringing it up, the scenario is  
very real.  My customers will quickly eat up all the memory / data  
space I give them and then demand more.  My responsibility is to do  
the maximum possible to protect my customers data.  At the same time,  
I would like to give them as much speed as possible, hence my being  
here.

If a computer goes down during a db transaction you lose the  
transaction and it is not re-attemped when you come back.  That is a  
perfectly reasonable expectation.   With Prevayler, the failed  
transaction will reattempt unless I tell the system otherwise.

If the last transaction fails due to a lack of available memory,  it  
is reasonable to assume that the same thing could happen if I come  
back up and re-run the transaction.  I am going to have to manage that  
somehow and I ask again, how (if at all) has anyone out there prepared  
for this scenario?   All systems have strengths and weaknesses, and I  
don't mind dealing with prevayler's weaknesses to get it's benefits,  
but I do need to understand them in gory detail.

Thanks,

R

On Jul 31, 2009, at 2:50 PM, Klaus Wuestefeld wrote:

> There is a more general question that you have to answer anyway,
> regardless of how you do your persistence, Prevayler or otherwise:
>
> "My system is in a state that will crash given some common basic user
> action. What now?"
>
> See you, Klaus.
>
>
>
> On Fri, Jul 31, 2009 at 5:28 PM, Ross Rick<rick@...> wrote:
>> If read the previous thread correctly...   a transaction is  
>> journaled to the
>> disk prior to execution on the model.
>> If the transaction fails, does the journaled transaction always get  
>> removed
>> from disk?   It would appear that the transaction is removed from  
>> disk under
>> normal circumstances, but under catastrophic failure, it's less  
>> clear.
>> In fact, I doubt that it is entirely possible to ensure any such  
>> thing.
>> How do the rest of you handle this?   When you come back up your  
>> system will
>> attempt the transaction again, even if it works, that is not the  
>> expected
>> state of the system.   The expected state is the state just prior to
>> attempting the bad transaction.
>> How am I doing on the understanding here?   I appreciate everyone's  
>> help
>> very much.
>>
>> R
>> ------------------------------------------------------------------------------
>> Let Crystal Reports handle the reporting - Free Crystal Reports  
>> 2008 30-Day
>> trial. Simplify your report design, integration and deployment -  
>> and focus
>> on
>> what you do best, core application coding. Discover what's new with
>> Crystal Reports now.  http://p.sf.net/sfu/bobj-july
>> _______________________________________________
>> To unsubscribe go to the end of this page:
>> http://lists.sourceforge.net/lists/listinfo/prevayler-discussion
>> _______________________________________________
>> "Databases in Memoriam" -- http://www.prevayler.org
>>
>>
>
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[Klaus Wuestefeld]

The only remedy against OutOfMemoryError is to restart the system
giving it more RAM, as you suspected.

Even if you had discarded the last transaction, your system would just
sit there waiting to blow up at the next transaction.

Sneer, the current desktop system I am developing, presents a MemMeter
showing how much RAM is being used and what the max is.

You don't necessarily need a visible meter, but it would be wise to
popup messages at certain thresholds.

See you, Klaus.


On Fri, Jul 31, 2009 at 9:44 PM, Ross Rick<rick@...> wrote:

> Klaus,
>
> I am discussing the likelihood that I will someday be faced with out
> of memory problems and yes, once you've popped your memory, you have
> no idea what your app will do for any given user action, no doubt
> about it.  That is precisely why I am bringing it up, the scenario is
> very real.  My customers will quickly eat up all the memory / data
> space I give them and then demand more.  My responsibility is to do
> the maximum possible to protect my customers data.  At the same time,
> I would like to give them as much speed as possible, hence my being
> here.
>
> If a computer goes down during a db transaction you lose the
> transaction and it is not re-attemped when you come back.  That is a
> perfectly reasonable expectation.   With Prevayler, the failed
> transaction will reattempt unless I tell the system otherwise.
>
> If the last transaction fails due to a lack of available memory,  it
> is reasonable to assume that the same thing could happen if I come
> back up and re-run the transaction.  I am going to have to manage that
> somehow and I ask again, how (if at all) has anyone out there prepared
> for this scenario?   All systems have strengths and weaknesses, and I
> don't mind dealing with prevayler's weaknesses to get it's benefits,
> but I do need to understand them in gory detail.
>
> Thanks,
>
> R
>
> On Jul 31, 2009, at 2:50 PM, Klaus Wuestefeld wrote:
>
>> There is a more general question that you have to answer anyway,
>> regardless of how you do your persistence, Prevayler or otherwise:
>>
>> "My system is in a state that will crash given some common basic user
>> action. What now?"
>>
>> See you, Klaus.
>>
>>
>>
>> On Fri, Jul 31, 2009 at 5:28 PM, Ross Rick<rick@...> wrote:
>>> If read the previous thread correctly...   a transaction is
>>> journaled to the
>>> disk prior to execution on the model.
>>> If the transaction fails, does the journaled transaction always get
>>> removed
>>> from disk?   It would appear that the transaction is removed from
>>> disk under
>>> normal circumstances, but under catastrophic failure, it's less
>>> clear.
>>> In fact, I doubt that it is entirely possible to ensure any such
>>> thing.
>>> How do the rest of you handle this?   When you come back up your
>>> system will
>>> attempt the transaction again, even if it works, that is not the
>>> expected
>>> state of the system.   The expected state is the state just prior to
>>> attempting the bad transaction.
>>> How am I doing on the understanding here?   I appreciate everyone's
>>> help
>>> very much.
>>>
>>> R
>>> ------------------------------------------------------------------------------
>>> Let Crystal Reports handle the reporting - Free Crystal Reports
>>> 2008 30-Day
>>> trial. Simplify your report design, integration and deployment -
>>> and focus
>>> on
>>> what you do best, core application coding. Discover what's new with
>>> Crystal Reports now.  http://p.sf.net/sfu/bobj-july
>>> _______________________________________________
>>> To unsubscribe go to the end of this page:
>>> http://lists.sourceforge.net/lists/listinfo/prevayler-discussion
>>> _______________________________________________
>>> "Databases in Memoriam" -- http://www.prevayler.org
>>>
>>>
>>
>> ------------------------------------------------------------------------------
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>> 30-Day
>> trial. Simplify your report design, integration and deployment - and
>> focus on
>> what you do best, core application coding. Discover what's new with
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>> _______________________________________________
>> To unsubscribe go to the end of this page: http://lists.sourceforge.net/lists/listinfo/prevayler-discussion
>> _______________________________________________
>> "Databases in Memoriam" -- http://www.prevayler.org
>>
>
>
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[Ross Rick]

As expected.   I wonder that no has quibbled about this before, as it  
is very surprising that the transaction is still there and will run.  
But hardly an insurmountable problem.

Looks like I'm going into the JMX stuff, unless you happen to be  
working on an open source project right now?

R

On Jul 31, 2009, at 7:09 PM, Klaus Wuestefeld wrote:

> The only remedy against OutOfMemoryError is to restart the system
> giving it more RAM, as you suspected.
>
> Even if you had discarded the last transaction, your system would just
> sit there waiting to blow up at the next transaction.
>
> Sneer, the current desktop system I am developing, presents a MemMeter
> showing how much RAM is being used and what the max is.
>
> You don't necessarily need a visible meter, but it would be wise to
> popup messages at certain thresholds.
>
> See you, Klaus.
>
>
> On Fri, Jul 31, 2009 at 9:44 PM, Ross Rick<rick@...> wrote:
>> Klaus,
>>
>> I am discussing the likelihood that I will someday be faced with out
>> of memory problems and yes, once you've popped your memory, you have
>> no idea what your app will do for any given user action, no doubt
>> about it.  That is precisely why I am bringing it up, the scenario is
>> very real.  My customers will quickly eat up all the memory / data
>> space I give them and then demand more.  My responsibility is to do
>> the maximum possible to protect my customers data.  At the same time,
>> I would like to give them as much speed as possible, hence my being
>> here.
>>
>> If a computer goes down during a db transaction you lose the
>> transaction and it is not re-attemped when you come back.  That is a
>> perfectly reasonable expectation.   With Prevayler, the failed
>> transaction will reattempt unless I tell the system otherwise.
>>
>> If the last transaction fails due to a lack of available memory,  it
>> is reasonable to assume that the same thing could happen if I come
>> back up and re-run the transaction.  I am going to have to manage  
>> that
>> somehow and I ask again, how (if at all) has anyone out there  
>> prepared
>> for this scenario?   All systems have strengths and weaknesses, and I
>> don't mind dealing with prevayler's weaknesses to get it's benefits,
>> but I do need to understand them in gory detail.
>>
>> Thanks,
>>
>> R
>>
>> On Jul 31, 2009, at 2:50 PM, Klaus Wuestefeld wrote:
>>
>>> There is a more general question that you have to answer anyway,
>>> regardless of how you do your persistence, Prevayler or otherwise:
>>>
>>> "My system is in a state that will crash given some common basic  
>>> user
>>> action. What now?"
>>>
>>> See you, Klaus.
>>>
>>>
>>>
>>> On Fri, Jul 31, 2009 at 5:28 PM, Ross Rick<rick@...> wrote:
>>>> If read the previous thread correctly...   a transaction is
>>>> journaled to the
>>>> disk prior to execution on the model.
>>>> If the transaction fails, does the journaled transaction always get
>>>> removed
>>>> from disk?   It would appear that the transaction is removed from
>>>> disk under
>>>> normal circumstances, but under catastrophic failure, it's less
>>>> clear.
>>>> In fact, I doubt that it is entirely possible to ensure any such
>>>> thing.
>>>> How do the rest of you handle this?   When you come back up your
>>>> system will
>>>> attempt the transaction again, even if it works, that is not the
>>>> expected
>>>> state of the system.   The expected state is the state just prior  
>>>> to
>>>> attempting the bad transaction.
>>>> How am I doing on the understanding here?   I appreciate everyone's
>>>> help
>>>> very much.
>>>>
>>>> R
>>>> ------------------------------------------------------------------------------
>>>> Let Crystal Reports handle the reporting - Free Crystal Reports
>>>> 2008 30-Day
>>>> trial. Simplify your report design, integration and deployment -
>>>> and focus
>>>> on
>>>> what you do best, core application coding. Discover what's new with
>>>> Crystal Reports now.  http://p.sf.net/sfu/bobj-july
>>>> _______________________________________________
>>>> To unsubscribe go to the end of this page:
>>>> http://lists.sourceforge.net/lists/listinfo/prevayler-discussion
>>>> _______________________________________________
>>>> "Databases in Memoriam" -- http://www.prevayler.org
>>>>
>>>>
>>>
>>> ------------------------------------------------------------------------------
>>> Let Crystal Reports handle the reporting - Free Crystal Reports 2008
>>> 30-Day
>>> trial. Simplify your report design, integration and deployment - and
>>> focus on
>>> what you do best, core application coding. Discover what's new with
>>> Crystal Reports now.  http://p.sf.net/sfu/bobj-july
>>> _______________________________________________
>>> To unsubscribe go to the end of this page: http://lists.sourceforge.net/lists/listinfo/prevayler-discussion
>>> _______________________________________________
>>> "Databases in Memoriam" -- http://www.prevayler.org
>>>
>>
>>
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[Klaus Wuestefeld]

> Looks like I'm going into the JMX stuff, unless you happen to be
> working on an open source project right now?

What do you mean?

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[Klaus Wuestefeld]

Yes. My project is open source.

On Sat, Aug 1, 2009 at 6:49 PM, Klaus
Wuestefeld<klauswuestefeld@...> wrote:
>> Looks like I'm going into the JMX stuff, unless you happen to be
>> working on an open source project right now?
>
> What do you mean?
>

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[mikael-12]

Hi.

I would just like to give my view of this.

Let's assume we have perfectly fine transactions without bugs causing OOM.
(This is theory, ok? ;-)

What makes you think the last transaction is "bad"? Is it wrong because it
happend to cause the OOM error?
In my view it's just as valid as all previous transactions. Why would you
remove it?

As Justin said, Prevayler will not proceed if you get the OOM error, so no
need to worry about an inconsistent state of the model.

If it continues to blow up when restoring the model, then you have
insufficient ram to run your program.

Have I misunderstood?

/Mikael

> As expected.   I wonder that no has quibbled about this before, as it
> is very surprising that the transaction is still there and will run.
> But hardly an insurmountable problem.
>
> Looks like I'm going into the JMX stuff, unless you happen to be
> working on an open source project right now?
>
> R
>
> On Jul 31, 2009, at 7:09 PM, Klaus Wuestefeld wrote:
>
>> The only remedy against OutOfMemoryError is to restart the system
>> giving it more RAM, as you suspected.
>>
>> Even if you had discarded the last transaction, your system would just
>> sit there waiting to blow up at the next transaction.
>>
>> Sneer, the current desktop system I am developing, presents a MemMeter
>> showing how much RAM is being used and what the max is.
>>
>> You don't necessarily need a visible meter, but it would be wise to
>> popup messages at certain thresholds.
>>
>> See you, Klaus.
>>
>>
>> On Fri, Jul 31, 2009 at 9:44 PM, Ross Rick<rick@...> wrote:
>>> Klaus,
>>>
>>> I am discussing the likelihood that I will someday be faced with out
>>> of memory problems and yes, once you've popped your memory, you have
>>> no idea what your app will do for any given user action, no doubt
>>> about it.  That is precisely why I am bringing it up, the scenario is
>>> very real.  My customers will quickly eat up all the memory / data
>>> space I give them and then demand more.  My responsibility is to do
>>> the maximum possible to protect my customers data.  At the same time,
>>> I would like to give them as much speed as possible, hence my being
>>> here.
>>>
>>> If a computer goes down during a db transaction you lose the
>>> transaction and it is not re-attemped when you come back.  That is a
>>> perfectly reasonable expectation.   With Prevayler, the failed
>>> transaction will reattempt unless I tell the system otherwise.
>>>
>>> If the last transaction fails due to a lack of available memory,  it
>>> is reasonable to assume that the same thing could happen if I come
>>> back up and re-run the transaction.  I am going to have to manage
>>> that
>>> somehow and I ask again, how (if at all) has anyone out there
>>> prepared
>>> for this scenario?   All systems have strengths and weaknesses, and I
>>> don't mind dealing with prevayler's weaknesses to get it's benefits,
>>> but I do need to understand them in gory detail.
>>>
>>> Thanks,
>>>
>>> R
>>>
>>> On Jul 31, 2009, at 2:50 PM, Klaus Wuestefeld wrote:
>>>
>>>> There is a more general question that you have to answer anyway,
>>>> regardless of how you do your persistence, Prevayler or otherwise:
>>>>
>>>> "My system is in a state that will crash given some common basic
>>>> user
>>>> action. What now?"
>>>>
>>>> See you, Klaus.
>>>>
>>>>
>>>>
>>>> On Fri, Jul 31, 2009 at 5:28 PM, Ross Rick<rick@...> wrote:
>>>>> If read the previous thread correctly...   a transaction is
>>>>> journaled to the
>>>>> disk prior to execution on the model.
>>>>> If the transaction fails, does the journaled transaction always get
>>>>> removed
>>>>> from disk?   It would appear that the transaction is removed from
>>>>> disk under
>>>>> normal circumstances, but under catastrophic failure, it's less
>>>>> clear.
>>>>> In fact, I doubt that it is entirely possible to ensure any such
>>>>> thing.
>>>>> How do the rest of you handle this?   When you come back up your
>>>>> system will
>>>>> attempt the transaction again, even if it works, that is not the
>>>>> expected
>>>>> state of the system.   The expected state is the state just prior
>>>>> to
>>>>> attempting the bad transaction.
>>>>> How am I doing on the understanding here?   I appreciate everyone's
>>>>> help
>>>>> very much.
>>>>>
>>>>> R
>>>>> ------------------------------------------------------------------------------
>>>>> Let Crystal Reports handle the reporting - Free Crystal Reports
>>>>> 2008 30-Day
>>>>> trial. Simplify your report design, integration and deployment -
>>>>> and focus
>>>>> on
>>>>> what you do best, core application coding. Discover what's new with
>>>>> Crystal Reports now.  http://p.sf.net/sfu/bobj-july
>>>>> _______________________________________________
>>>>> To unsubscribe go to the end of this page:
>>>>> http://lists.sourceforge.net/lists/listinfo/prevayler-discussion
>>>>> _______________________________________________
>>>>> "Databases in Memoriam" -- http://www.prevayler.org
>>>>>
>>>>>
>>>>
>>>> ------------------------------------------------------------------------------
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>>>> 30-Day
>>>> trial. Simplify your report design, integration and deployment - and
>>>> focus on
>>>> what you do best, core application coding. Discover what's new with
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>>>>
>>>
>>>
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[Ross Rick]

As discussed in an earlier thread, we have a couple different error  
scenarios..  OOM is serious and may require manual intervention.  Ok.  
fine.

The other types, "deterministic" are like when a parameter that must  
be validated at transaction time fails.  Existence of a dependent  
object for example.  I have to test within the execution of  
transaction to guarantee state.   When that fails, I wonder what the  
expected state of the journal is.

R


On Aug 1, 2009, at 4:02 PM, mikael@... wrote:

> Hi.
>
> I would just like to give my view of this.
>
> Let's assume we have perfectly fine transactions without bugs  
> causing OOM.
> (This is theory, ok? ;-)
>
> What makes you think the last transaction is "bad"? Is it wrong  
> because it
> happend to cause the OOM error?
> In my view it's just as valid as all previous transactions. Why  
> would you
> remove it?
>
> As Justin said, Prevayler will not proceed if you get the OOM error,  
> so no
> need to worry about an inconsistent state of the model.
>
> If it continues to blow up when restoring the model, then you have
> insufficient ram to run your program.
>
> Have I misunderstood?
>
> /Mikael
>
>> As expected.   I wonder that no has quibbled about this before, as it
>> is very surprising that the transaction is still there and will run.
>> But hardly an insurmountable problem.
>>
>> Looks like I'm going into the JMX stuff, unless you happen to be
>> working on an open source project right now?
>>
>> R
>>
>> On Jul 31, 2009, at 7:09 PM, Klaus Wuestefeld wrote:
>>
>>> The only remedy against OutOfMemoryError is to restart the system
>>> giving it more RAM, as you suspected.
>>>
>>> Even if you had discarded the last transaction, your system would  
>>> just
>>> sit there waiting to blow up at the next transaction.
>>>
>>> Sneer, the current desktop system I am developing, presents a  
>>> MemMeter
>>> showing how much RAM is being used and what the max is.
>>>
>>> You don't necessarily need a visible meter, but it would be wise to
>>> popup messages at certain thresholds.
>>>
>>> See you, Klaus.
>>>
>>>
>>> On Fri, Jul 31, 2009 at 9:44 PM, Ross Rick<rick@...> wrote:
>>>> Klaus,
>>>>
>>>> I am discussing the likelihood that I will someday be faced with  
>>>> out
>>>> of memory problems and yes, once you've popped your memory, you  
>>>> have
>>>> no idea what your app will do for any given user action, no doubt
>>>> about it.  That is precisely why I am bringing it up, the  
>>>> scenario is
>>>> very real.  My customers will quickly eat up all the memory / data
>>>> space I give them and then demand more.  My responsibility is to do
>>>> the maximum possible to protect my customers data.  At the same  
>>>> time,
>>>> I would like to give them as much speed as possible, hence my being
>>>> here.
>>>>
>>>> If a computer goes down during a db transaction you lose the
>>>> transaction and it is not re-attemped when you come back.  That  
>>>> is a
>>>> perfectly reasonable expectation.   With Prevayler, the failed
>>>> transaction will reattempt unless I tell the system otherwise.
>>>>
>>>> If the last transaction fails due to a lack of available memory,  
>>>> it
>>>> is reasonable to assume that the same thing could happen if I come
>>>> back up and re-run the transaction.  I am going to have to manage
>>>> that
>>>> somehow and I ask again, how (if at all) has anyone out there
>>>> prepared
>>>> for this scenario?   All systems have strengths and weaknesses,  
>>>> and I
>>>> don't mind dealing with prevayler's weaknesses to get it's  
>>>> benefits,
>>>> but I do need to understand them in gory detail.
>>>>
>>>> Thanks,
>>>>
>>>> R
>>>>
>>>> On Jul 31, 2009, at 2:50 PM, Klaus Wuestefeld wrote:
>>>>
>>>>> There is a more general question that you have to answer anyway,
>>>>> regardless of how you do your persistence, Prevayler or otherwise:
>>>>>
>>>>> "My system is in a state that will crash given some common basic
>>>>> user
>>>>> action. What now?"
>>>>>
>>>>> See you, Klaus.
>>>>>
>>>>>
>>>>>
>>>>> On Fri, Jul 31, 2009 at 5:28 PM, Ross Rick<rick@...> wrote:
>>>>>> If read the previous thread correctly...   a transaction is
>>>>>> journaled to the
>>>>>> disk prior to execution on the model.
>>>>>> If the transaction fails, does the journaled transaction always  
>>>>>> get
>>>>>> removed
>>>>>> from disk?   It would appear that the transaction is removed from
>>>>>> disk under
>>>>>> normal circumstances, but under catastrophic failure, it's less
>>>>>> clear.
>>>>>> In fact, I doubt that it is entirely possible to ensure any such
>>>>>> thing.
>>>>>> How do the rest of you handle this?   When you come back up your
>>>>>> system will
>>>>>> attempt the transaction again, even if it works, that is not the
>>>>>> expected
>>>>>> state of the system.   The expected state is the state just prior
>>>>>> to
>>>>>> attempting the bad transaction.
>>>>>> How am I doing on the understanding here?   I appreciate  
>>>>>> everyone's
>>>>>> help
>>>>>> very much.
>>>>>>
>>>>>> R
>>>>>> ------------------------------------------------------------------------------
>>>>>> Let Crystal Reports handle the reporting - Free Crystal Reports
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>>>>>> _______________________________________________
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>>>>>> http://lists.sourceforge.net/lists/listinfo/prevayler-discussion
>>>>>> _______________________________________________
>>>>>> "Databases in Memoriam" -- http://www.prevayler.org
>>>>>>
>>>>>>
>>>>>
>>>>> ------------------------------------------------------------------------------
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>>>>> _______________________________________________
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>>>>> _______________________________________________
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>>>>>
>>>>
>>>>
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>>>>
>>>
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>>
>>
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>
>
>
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[Klaus Wuestefeld]

> The other types, "deterministic" are like when a parameter that must
> be validated at transaction time fails.  Existence of a dependent
> object for example.  I have to test within the execution of
> transaction to guarantee state.   When that fails, I wonder what the
> expected state of the journal is.

The transaction is written to the journal before being applied to the
system (to ensure durability of reads) and never removed.

The food taster turned on (Justin please confirm) will prevent such
faulty transactions from being written to the log.

The food taster is rebuilt in RAM as a copy of the actual system.
Piped serialization in RAM is used to make the copy. All transactions
are blocked while that happens.

This is how I measure used RAM:

        static private final Runtime RUNTIME = Runtime.getRuntime();

        private int measureUsedMemory() {
                long total, total2, free;
                do {
                        total = RUNTIME.totalMemory();
                        free = RUNTIME.freeMemory();
                        total2 = RUNTIME.totalMemory();
                } while (total != total2);
                       
                return total - free;
        }

And calling RUNTIME.maxMemory() you get the max given to the VM. I
wouldn't resort to JMX unless I wanted to monitor remotely, and maybe
not even then.

See you, Klaus.

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[Ross Rick]

Thanks very much for the clarifications, and the code.


R


On Aug 1, 2009, at 8:54 PM, Klaus Wuestefeld wrote:

>> The other types, "deterministic" are like when a parameter that must
>> be validated at transaction time fails.  Existence of a dependent
>> object for example.  I have to test within the execution of
>> transaction to guarantee state.   When that fails, I wonder what the
>> expected state of the journal is.
>
> The transaction is written to the journal before being applied to the
> system (to ensure durability of reads) and never removed.
>
> The food taster turned on (Justin please confirm) will prevent such
> faulty transactions from being written to the log.
>
> The food taster is rebuilt in RAM as a copy of the actual system.
> Piped serialization in RAM is used to make the copy. All transactions
> are blocked while that happens.
>
> This is how I measure used RAM:
>
> static private final Runtime RUNTIME = Runtime.getRuntime();
>
> private int measureUsedMemory() {
> long total, total2, free;
> do {
> total = RUNTIME.totalMemory();
> free = RUNTIME.freeMemory();
> total2 = RUNTIME.totalMemory();
> } while (total != total2);
>
> return total - free;
> }
>
> And calling RUNTIME.maxMemory() you get the max given to the VM. I
> wouldn't resort to JMX unless I wanted to monitor remotely, and maybe
> not even then.
>
> See you, Klaus.
>
> ------------------------------------------------------------------------------
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[mikael-12]

> And calling RUNTIME.maxMemory() you get the max given to the VM. I
> wouldn't resort to JMX unless I wanted to monitor remotely, and maybe
> not even then.


I am very fond of all the powers of JMX.
Any specific reason why you don't use it?

/Mikael


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[Klaus Wuestefeld]

I used JMX once only. I just not all that familiar with all its powers.


On Sun, Aug 2, 2009 at 3:37 AM, Mikael Nordenberg<mikael@...> wrote:

>
>> And calling RUNTIME.maxMemory() you get the max given to the VM. I
>> wouldn't resort to JMX unless I wanted to monitor remotely, and maybe
>> not even then.
>
>
> I am very fond of all the powers of JMX.
> Any specific reason why you don't use it?
>
> /Mikael
>
>
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