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From akaptsan <akapt...@mail.ru>
Subject RE: Is there limitation on Semaphores and Queues?
Date Sat, 09 Jan 2016 08:30:34 GMT


Thank you so much for helping me!

But none of your suggestions really work for me L.


I can’t now switch my application to Ignate as primary storage. But I do have this idea
in remote plans.


I can’t use native RDBMS replication, because databases are not 100% identical (in fact
probably less then 50% of DB objects are identical). 

I do need application-level capturing and applying of changes. 


And main reason why I can’t use Kafka or similar messaging system is: I need to eliminate
simultaneous change of one object in the two DBs. If it happened, then the object state in
DBs would be inconsistent.

That’s why I want to use Ignite semaphore




From: Denis Magda [via Apache Ignite Users] [mailto:ml-node+s70518n2453h58@n6.nabble.com]

Sent: Saturday, January 09, 2016 9:26 AM
To: akaptsan
Subject: Re: Is there limitation on Semaphores and Queues?



Please properly subscribe to the user list (this way we will not have to 
manually approve your emails and you will get answers on your questions quicker). All you
need to do is send an email to “ 
user-subscribe@ignite.apache.org” and follow simple instructions in the 

Since the content in the databases is almost identical and you have a load balancer that directs
queries to one of the systems I would review current architecture design and probably switch
to the following one. You can still have a single Ignite in-memory cluster that will persist
data [1] in one or several databases depending on your requirements and configuration. In
such a design all business model related queries will go directly to the cluster and you don't
need to care about replication cause everything will be already there. Ignite supports ANSI-99
SQL so your SQL queries should work fine as well[2]. 

If your systems are web applications then you may want to use web session clustering in addition

On the other hand, if you can't switch to such an architecture then basing on your description
you are trying to implement a replication between the databases and probably solutions like
Kafka Connect [4] should work perfectly fine for you. Also different RDBMS vendors provide
native tools for replication between their databases. As an example replication between Oracle
databases can be done using Oracle Golden Gate product. I don't get why you need to lock an
Ignite object when you're applying changes, stored in queues, from one database to another
that's why consider that Kafka or RDBMS native replication tool will be enough. 

Does any of suggestions work for you? 

[1] https://apacheignite.readme.io/docs/persistent-store
[2] https://apacheignite.readme.io/docs/sql-queries
[3] https://apacheignite.readme.io/docs/web-session-clustering
[4] http://kafka.apache.org/documentation.html 


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