szpak opened a new pull request #10062:
URL: https://github.com/apache/kafka/pull/10062
That method intends to increase a chance to have KeyValueIterator closed
after usage, by providing a convenient performAndClose() default method which
executes a given operation and guarantee to automatically close the iterator
right after.
### Rationality
I decided to create that PR observing in different projects how often an
iterator is left open after performing operations such as
`.forEachRemaining(...)` (who reads JavaDoc after all? ;-) ). For people
aware of the problem, instead of verbose try-with-resources constructions
repeated in every place in code:
```
try (KeyValueIterator<String, Order> ordersKeyValueIterator =
streamsBuilderFactoryBean
.getKafkaStreams()
.store(StoreQueryParameters.fromNameAndType(ORDERS_STORE,
QueryableStoreTypes.<String, Order>keyValueStore()))
.all()) {
ordersKeyValueIterator
.forEachRemaining(kv -> {
...
});
}
```
(or hidden in in-house built utility classes)
a developer using Kafka Streams has a built-in clear way to perform
operations on elements contained in an iterator (and have that stream closed
after that automatically):
```
streamsBuilderFactoryBean
.getKafkaStreams()
.store(StoreQueryParameters.fromNameAndType(ORDERS_STORE,
QueryableStoreTypes.<String, OrderRequest>keyValueStore()))
.all()
.performAndClose(iterator -> iterator
.forEachRemaining(kv -> {
...
})
);
```
I believe it can increase a rate of closed iterator in user projects.
### Testing approach
Being a default method in KeyValueIterator, I decided to test it using
KeyValueIteratorFacade which already provides a nice unit testing
infrastructure with mocked iterator. I don't know the implementation details,
but I expect to have it behaved similarly in other implementations.
I might miss some extra cases, so feel free to point them and I will happily
cover them with tests.
### Rejected extensions
For some time past, I was thinking also about covering operations that
returns some value. However, at least in projects I've been observing the usage
of Kafka Streams, performing side effects is more popular and implementation
for that use cases might be more tricky and I decided to start with pure
Consumer.
### Other information
Naming is not my area of expertise. Feel free to propose any better name or
any other possible enhancements to my MR :-).
### Committer Checklist (excluded from commit message)
- [ ] Verify design and implementation
- [ ] Verify test coverage and CI build status
- [ ] Verify documentation (including upgrade notes)
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