Установите параллелизм в аннотации @JmsListener
:
/**
* The concurrency limits for the listener, if any. Overrides the value defined
* by the container factory used to create the listener container.
* <p>The concurrency limits can be a "lower-upper" String — for example,
* "5-10" — or a simple upper limit String — for example, "10", in
* which case the lower limit will be 1.
* <p>Note that the underlying container may or may not support all features.
* For instance, it may not be able to scale, in which case only the upper limit
* is used.
*/
String concurrency() default "";
Похоже, что Javadocs неверны, хотя
Overrides the value defined
* by the container factory used to create the listener container.