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From Christian Schneider <>
Subject Re: [discuss] implementing Locks in Camel
Date Wed, 07 Sep 2011 16:25:01 GMT
Well my case is a little different as the locking or synchronization is 
not per object.
In my case it was the connection to a backend system (a Stock Exchange) 
where only one instance should be connected to the
exchange but several were needed as fallbacks.

So the main difference is that in my case the producer of the route had 
to be enabled / disabled instead of a processing step inside the route.
Still many aspects are common and I can imagine that hazelcast would 
also work for me.


Am 07.09.2011 18:10, schrieb boday:
> Christian, my use case is that I have multiple apps that update the same data
> (PurchaseOrders) and we periodically see some stale writes.  We have a
> combination of Camel/CXF web services (load balanced across 2 machines) and
> batch processing in Camel routes (in a separate app) and are evaluating
> using Hazelcast distributed locking to make sure only one thread works on a
> PO at any given time.
> Its simple enough to just manually add the Hazelcast locking in as pre/post
> processors in routes, it just got me thinking about how it could fit into
> Camel natively (since we already have a Hazelcast component, etc).  As
> suggested by others, maybe the term "lock" is confusing and we should term
> it "synchronized" or "exclusive" or something...
> Christian Schneider wrote:
>> I am not sure if this is the same use case that I had some years ago.
>> We wanted to have several instances of an integration running but only
>> one of them should be active at any time.
>> At the time there was no easy solution for this problem.
>> So in that use case you would have several instances of camel each on
>> its own machine.
>> They could have the same route but only one should be active.
>> In the dsl this could also be expressed with a lock or perhaps exclusive
>> element.
>> from("some source ").exclusive("some id")....
>> So the question in this case is: What lib or backend would be suitable
>> to impement this and what parameters would we need?
>> Does Hazelcast support this scenario?
>> Would we start and stop the route when it gets or looses the lock?
>> Christian
>> Am 06.09.2011 22:16, schrieb boday:
>>> hey guys, while working on a solution for a client, I ran into the need
>>> to
>>> "synchronize" multiple routes that modify the same data (users, orders,
>>> etc)
>>> to prevent collisions (stale writes, etc).  Is there an existing way to
>>> do
>>> this that I've overlooked?
>>> In the past, I've relied on
>>> AMQ message groups  for JMS based routes and Hazelcast to span
>>> routes/containers.  I feel this would be a good fit for the Camel DSL.
>>> Has
>>> anyone looked into this in the past?
>>> After doing some quick research, it seems like Java
>>> Lock  seems to be the way to go.  Also, Hazelcast can extend this to be
>>> distributed across VMs.
>>> So, I've been playing around with adding distributed locking support with
>>> Hazelcast (see
>>> CAMEL-4397
>>> ) and wanted to get some feedback on doing this.  In particular, I'm
>>> using a
>>> Lock instance stored in a ThreadLocal variable (to ensure that the same
>>> thread releases the lock).  Does anyone see any issue with this approach?
>>> If all goes well with this, I was planning on also adding a DSL API to
>>> provide a basic support for (non distributed)
>>> ReentrantLocks .
>>> something like this...
>>> from(route1).lock(userId).process(processor1).unlock();
>>> from(route2).lock(userId).process(processor2).unlock();
>>> Any advice/comments are welcome...thanks
>>> -----
>>> Ben O'Day
>>> IT Consultant -
>>> --
>>> View this message in context:
>>> Sent from the Camel Development mailing list archive at
>> -- 
>> Christian Schneider
>> Open Source Architect
> -----
> Ben O'Day
> IT Consultant -
> --
> View this message in context:
> Sent from the Camel Development mailing list archive at

Christian Schneider

Open Source Architect

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