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From "Jacques Le Roux" <jacques.le.r...@les7arts.com>
Subject Re: EntitySync issues & suggestions ( was EntitySync RMI error )
Date Mon, 26 Oct 2009 07:38:34 GMT
Thanks Pankaj,

I had not the time to read all your message, very useful I guess.
I will post all this (with Deyan's remark too) on Wiki after having done my own opinion...

Jacques

From: <Pankaj.Jain@lntinfotech.com>
> Hi Deyan n others
> 
> I have also worked & solved many sync problems in ofbiz in my application:
> 
> 1) As you said while sync is in progress if server crashes, the status in 
> EntitySync table gets in running state and we can't sync further until we 
> manually change it even if we restart server it remains in running state
> To solve this problem:  I created a new entity SyncStatus on client side 
> to maintain the status of sync, in that ist status is Not Started, when 
> service runEntitySync or runPullEntitySync starts I set the status of 
> field as running and when service returns (whether fail or successful) I 
> updated status to finish. 
> I also added code, that if server restarts and if this field status is 
> running change it to not started, By this I solved the above problem:
> 
> *) If client crashes, then after restart, status in SyncStatus table will 
> be Not Started.
> *) If  server crashes, then service will be failed and status will be 
> finished and no further problem.
> 
> 2) There were other problems like if sync(push or pull) is running, and 
> one other job of same service is also created then we get exception "An 
> instance is already running" By using above status in SyncStatus table 
> when A job of sync is running, I just cancelled out all other jobs of same 
> type.
> 
> 3) I also solved "Connection refused" problem by same method even I 
> displayed message on screen rather than giving exception on console. 
> 
> 4) I did not get your point of updating time stamp, I did not get this 
> problem because In push or pull sync the successful timestamp is updated 
> on EntitySync table on client or MCS side only if sync is successful, if 
> server crashes or sync fails this field is not updated, but yes there are 
> some issues:
> *) If we have 2 hours of sync, n sync fails on last minute. then in next 
> sync as sync successful status has not been revisesd, next sync will pick 
> the status of previous one, as a solution I think we need to keep updating 
> syn status in EntitySync table after particular intervals. but how to 
> decide these intervals b'coz tables are linked with foreign key 
> constriants.
> *) One problem with connection refused in push and pull case is that, In 
> pull sync first connection is established then data is prepared for sync 
> while in push sync first data is prepared and then conncetion is 
> established. So in pull sync we get connection refused problem in earlier 
> stage than push sync. We can say in push sync if there is no MCS (Or MCS 
> IP address is wrong), Our code is doing efforts in preparing data that 
> effort is of no use.
> 
> 5) If we place order on POS side and try to perform push sync, some time I 
> was getting random exceptions due to order header or Order Status table, I 
> solved the problem. 
> Explain: In placing order (or others) if you have used a database trigger 
> (eecas) like if an entry is created on A table create an entry on B table. 
> Now wile sync if MCS is also having same trigger then as a entry is 
> created (by sync) on A table , trigger is fired and an entry for B is 
> created. Now for one A, B will be having two entries that creates random 
> exception
> So I want to ask, that mean for sync there should not be ant trigger on 
> opposite side(means for push MCS and for pull POS), how we will maintain 
> that ???
> 
> I did not get your concept of using XML file inspite of RMI. Could you 
> please give some details regarding that????  Even I agree with the fact 
> that RMI takes long time.
> 
> 
> Regards:
> 
> Pankaj Jain
> 
> 
> 
> ______________________________________________________________________


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