Persistent queue channel backed by a transactional jdbc messagestore blocks sender.

Hi,

Summary:
Persistent queue based channel, backed by a transactional jdbc message-store blocks sending messages to channel when messages are read from the channel.

A little more explanation:
I want to do something really simple: I want to send messages asynchronously(in order to not block the sender) and want messages to be persisted. And I want the messages to be retained in channel queue if something goes wrong at the consumer (so I set up transaction).
Here is my Spring integration configuration:


<int:gateway id="myMailSender" service-interface="com.serkan.MyMailSender"/>

<int:channel id="mailChannel" >
<int:queue message-store="messageStore" />
</int:channel>

<int-jdbc:message-store id="messageStore" data-source="myDataSource" />

<int:service-activator input-channel="mailChannel" ref="myMailManager" method="sendMail">
<int:poller fixed-rate="1000">
<int:transactional transaction-manager="transactionManager" isolation="READ_COMMITTED" propagation="REQUIRED" timeout="3000"/>
</int:poller>
</int:service-activator>

<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSou rceTransactionManager">
<property name="dataSource">
<ref bean="myDataSource"/>
</property>
</bean>

This looks like working but there is a problem: When the consumer receives a message and working on it, sender cannot put another message into the channel. It just blocks until the consumer is done. If I remove transaction configuration this problem disappears. I have tried 2 different databases: Oracle and PostgreSQL with almost all possible isolation levels and it is always same.

Anyone have any idea how I can overcome this?

Thanks in advance,