Tasklet transaction-manager and chunk transaction - spring-batch

Question

I specified a tasklet with a chunk orientated procssing.
<batch:step id="midxStep" parent="stepParent">
<batch:tasklet transaction-manager="transactionManager">
<batch:chunk
reader="processDbItemReaderJdbc"
processor="midxItemProcessor"
writer="midxCompositeItemWriter"
processor-transactional="false"
reader-transactional-queue="false"
skip-limit="${cmab.batch.skip.limit}"
commit-interval="#{jobParameters['toProcess']==T(de.axa.batch.ecmcm.cmab.util.CmabConstants).TYPE_POSTAUSGANG ? '${consumer.global.pa.midx.commitSize}' : '${consumer.global.pe.midx.commitSize}' }"
cache-capacity="20">
<batch:skippable-exception-classes>
<batch:include class="de.axa.batch.ecmcm.cmab.util.CmabProcessMidxException" />
<batch:exclude class="java.lang.IllegalArgumentException" />
</batch:skippable-exception-classes>
<batch:retryable-exception-classes>
<batch:include class="de.axa.batch.ecmcm.cmab.util.CmabTechnicalMidxException" />
<batch:include class="de.axa.batch.ecmcm.cmab.util.CmabTechnicalException" />
</batch:retryable-exception-classes>
<batch:retry-listeners>
<batch:listener ref="logRetryListener"/>
</batch:retry-listeners>
<batch:listeners>
<batch:listener>
<bean id="midxProcessSkipListener" class="de.axa.batch.ecmcm.cmab.core.batch.listener.CmabDbSkipListener" scope="step">
<constructor-arg index="0" value="#{jobParameters['errorStatus']}" type="java.lang.String"/>
</bean>
</batch:listener>
</batch:listeners>
</batch:chunk>
<batch:transaction-attributes isolation="SERIALIZABLE" propagation="MANDATORY" timeout="${cmab.jta.usertransaction.timeout}"/>
<batch:listeners>
<batch:listener ref="midxStepListener"/>
<batch:listener>
<bean id="cmabChunkListener" class="de.axa.batch.ecmcm.cmab.core.batch.listener.CmabChunkListener" scope="step"/>
</batch:listener>
</batch:listeners>
</batch:tasklet>
</batch:step>
The tasklet runs with a JtaTransaction manger (Atomikos, name="transactionManager").
Now my question:
Is this transaction manager "delegate" to the chunk-process?
Why I'm asking this? If I set the transaction-attributes (see chunk) to propagation level "MANDATORY" the chunk process aborted with the error that no transaction is available.
Therefore it left me confused because I thought that the tasklet transaction specification implies that the chunk running within this tasklet transaction, too.
Furthermore I intended to run the application within a cloud system with more than one pod. The processDbIemReaderJdbs fetches via a StoredProcedureItemReader Items with a "FOR UPDATE SKIP LOCKED" from a PostgresDB.
So my intention is to run the hole chunk, means also the reader, within one transaction in order to block the reader resultSet to other POD-Processes.

Answer 1

The transaction attributes are for the transaction that Spring Batch will create to run your step with the transaction manager that you set on the step. Those are the attributes of the transaction itself, not the transaction manager (that does not make sense).
All batch artifacts are executed within the scope of that same transaction, including the reader and the writer. The only exception to that is the JdbcCursorItemReader, which by default does not participate in the transaction, unless useSharedExtendedConnection is set.