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From Claus Ibsen <>
Subject Re: [DISCUSS - CAMEL 2.0] - About Producers and thread safety
Date Mon, 25 May 2009 13:10:10 GMT

I have looked into this a bit more.

With this we can support correlation for concurrent request/response
with mina as well. A feature that was generelly lacking there.

So this is definitely a great step in a good direction for Camel.

This feature has been tracked here:

On Mon, May 25, 2009 at 10:19 AM, Claus Ibsen <> wrote:
> Hi
> A recent bug was reported in ticket CAMEL-1641
> The issue is in Camel 2.0 the FTP producer is not thread safe, in the
> sense that you cannot concurrently send at the same time to the same
> FTP endpoint.
> I have digged into this issue and discovered the issue lies in the
> fact that the FtpProducer cannot be singleton scoped. It uses a local
> FTPClient that is used for the FTP communication.
> A given endpoint producer is however stored in either a producer cache
> or as a class instance variable in SendProcessor.
> This causes the issue that a non singleton producer will be reused for
> concurrent threads.
> So to remedy this I have done some code as a prototype that I usually
> do during my findings.
> We extend the concept of IsSingleton from Endpoint to Producer as
> well. Then we can set it as false for FtpProducer.
> We let the producer cache detect the IsSingleton and only cache singletons.
> I have also added a ProducerCallback interface that resembles the
> Spring resource patterns for its JmsTemplate, JdbcTemplate etc with
> its doInXXXX
> public interface ProducerCallback<T> {
>    /**
>     * Performs operation on the given producer to send the given exchange.
>     *
>     * @param producer  the producer, is newer <tt>null</tt>
>     * @param exchange  the exchange, can be <tt>null</tt> if so then
> create a new exchange from the producer
>     * @param exchangePattern the exchange pattern, can be <tt>null</tt>
>     * @return the response
>     * @throws Exception if an internal processing error has occurred.
>     */
>    T doInProducer(Producer producer, Exchange exchange,
> ExchangePattern exchangePattern) throws Exception;
> }
> With this callback it allows a producer client to safely use the
> producer without having to worry about how to start and stop the
> resource whether its singleton or not.
> And in the future we can incorporate a pooling as well so Camel can
> leverage pooling with this pattern. So Camel can safely obtain a
> producer from the pool, invoke this callback where the client/user can
> use it to do what is needed, usually to send an exchange. And
> afterwards Camel can safely return the producer back to the pool.
> However I know this is kinda expanding Camel out of its current scope.
> There is a tiny concept of IoC or resource/lifecycle handling in here.
> Another idea is also to denote the ProducerCache as a higher role. We
> could let CamelContext be able to hold a per context producer cache
> and let it provide this cache where its needed in: ProducerTemplate,
> SendToProcessor and a few other areas. This allows us to reuse this
> cache instead of having a per local cache.
> Well a few concepts to grasp. I will create a ticket for this and
> attach a patch for people to look at.
> Any thoughts?
> --
> Claus Ibsen
> Apache Camel Committer
> Open Source Integration:
> Blog:
> Twitter:

Claus Ibsen
Apache Camel Committer

Open Source Integration:

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