如何使用生成返回Mono的包装调用来创建Flux
我有一个例子，我想使用Flos.Generate，因为我不想进行昂贵的阻塞调用，除非/直到订阅者请求它。具体地说，我会多次调用Elasticearch(有效地进行分页)，直到没有更多的匹配。我已经使用Iterator<SearchResponse>中的标准阻塞调用实现了这一点。其中，对生成的lambda块和通量的每次调用都以.subscribeOn(Schedulers.boundedElastic())结束。但是，我想使用Spring的ReactiveElasticsearchClient，它返回一个Mono<SearchResponse>，但仍然希望一次返回一个。
以下是使用阻止的前一段代码：
public Iterator<SearchResponse> createDeepQueryIterator(@NonNull PITSearchInput input){
return new PointInTimeIterator(elasticClient, input);
}
public Flux<SearchResponse> createDeepQueryFlux(@NonNull PITSearchInput input){
return Flux.<SearchResponse, PointInTimeIterator>generate(
() -> new PointInTimeIterator(elasticClient, input),
(deepQueryIterator, sink) -> {
if (deepQueryIterator.hasNext()) {
sink.next(deepQueryIterator.next());
}else{
sink.complete();
}
return deepQueryIterator;
},
(deepQueryIterator) -> deepQueryIterator.shutdown())
.subscribeOn(Schedulers.boundedElastic());
}
上面的工作很好，因为它会等待对ES的下一次调用，直到订户准备好接收下一块数据。
在下面，我尝试使用Spring的ReactiveElasticsearchClient，但问题是在订阅者处理第一个调用之前，对ES进行了多次调用。
public Flux<SearchResponse> createDeepQuery(PointInTimeIteratorFactory.PITSearchInput input) {
log.info("Creating flux");
AtomicReference<PitId> pitId = new AtomicReference<>();
AtomicInteger count = new AtomicInteger();
Mono<PitId> pitIdMono =
Mono.fromCallable(
() -> {
pitId.set(createPIT(input));
return pitId.get();
})
.subscribeOn(Schedulers.boundedElastic());
Mono<SearchResponse> searchResponseMono =
pitIdMono.flatMap(
p -> {
log.info("Calling search");
return reactiveElasticsearchClient.searchForResponse(createSearchRequestFrom(p, input));
});
Flux<SearchResponse> expand =
searchResponseMono
.expand(
(searchResponse -> {
int hitCount = searchResponse.getHits().getHits().length;
count.addAndGet(hitCount);
log.info("Previous returned {} hits totaling {}", hitCount, count.get());
if (count.get() > input.getMaxTotalSize()
|| hitCount < input.getMaxSizePerQuery()){
log.info("Returning empty");
return Mono.empty();
}
log.info("Calling search");
pitId.set(new PitId(searchResponse.pointInTimeId()));
return reactiveElasticsearchClient.searchForResponse(
createSearchRequestFrom(searchResponse, input));
}))
.doFinally(
p -> {
deletePIT(pitId.get());
});
return expand;
}
因此，问题不是使用被动客户端在Flux中返回Mono<SearchResponse>的能力，而是根据订阅者的需要一次只返回一个。
下面是上面的Flux->Mono方法的日志记录，PitTest日志记录来自通量的测试onNext()。
2021-12-02 13:13:37.300 INFO 13704 --- [ main] a.a.t.ReactivePointInTimeIteratorFactory : Creating flux
2021-12-02 13:13:37.346 INFO 13704 --- [oundedElastic-1] a.a.t.ReactivePointInTimeIteratorFactory : Creating PIT
2021-12-02 13:13:37.407 INFO 13704 --- [oundedElastic-1] a.a.t.ReactivePointInTimeIteratorFactory : Calling search
2021-12-02 13:13:38.176 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Previous returned 50 hits totaling 50
2021-12-02 13:13:38.177 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Calling search
2021-12-02 13:13:38.177 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Setting searchAfter to 1634877306267
2021-12-02 13:13:38.228 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Previous returned 50 hits totaling 100
2021-12-02 13:13:38.228 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Calling search
2021-12-02 13:13:38.228 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Setting searchAfter to 1634877606162
2021-12-02 13:13:38.271 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Previous returned 50 hits totaling 150
2021-12-02 13:13:38.271 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Calling search
2021-12-02 13:13:38.272 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Setting searchAfter to 1634877606362
2021-12-02 13:13:38.311 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Previous returned 50 hits totaling 200
2021-12-02 13:13:38.312 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Calling search
2021-12-02 13:13:38.312 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Setting searchAfter to 1634877906244
2021-12-02 13:13:38.344 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Previous returned 50 hits totaling 250
2021-12-02 13:13:38.345 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Returning empty
2021-12-02 13:13:38.345 INFO 13704 --- [or-http-epoll-2] a.a.t.ReactivePointInTimeIteratorFactory : Closing PIT ReactivePointInTimeIteratorFactory.PitId(id=m_2xAwENYWN0aXZpdHlzdG9yZRZQQkRGWldmclI2cWZITEpoWDI1cGlRABZCZU8xbm55ZlFabXREYmNEdThESG1RAAAAAAAAWQcTFm5BcXdPU2xTUWE2bEU4dkVPVkpkWFEBFlBCREZaV2ZyUjZxZkhMSmhYMjVwaVEAAA==)
2021-12-02 13:13:40.171 INFO 13704 --- [ parallel-1] p.actss.activity.store.PitTest : [1634877306066]
2021-12-02 13:13:42.172 INFO 13704 --- [ parallel-2] p.actss.activity.store.PitTest : [1634877306272]
2021-12-02 13:13:44.172 INFO 13704 --- [ parallel-3] p.actss.activity.store.PitTest : [1634877606166]
2021-12-02 13:13:46.173 INFO 13704 --- [ parallel-4] p.actss.activity.store.PitTest : [1634877906057]
2021-12-02 13:13:48.174 INFO 13704 --- [ parallel-1] p.actss.activity.store.PitTest : [1634877906248]
2021-12-02 13:13:48.174 INFO 13704 --- [ parallel-1] p.actss.activity.store.PitTest : Complete
2021-12-02 13:13:48.174 INFO 13704 --- [ main] p.actss.activity.store.PitTest : blah
2021-12-02 13:13:48.175 INFO 13704 --- [ parallel-1] p.actss.activity.store.PitTest : onComplete
更新：添加PitTest代码以确保完整性：
@Test
void testReactoiveFluxIt() throws InterruptedException {
Flux<SearchResponse> deepQuery = reactivePointInTimeIteratorFactory.createDeepQuery(...);
deepQuery
.delayElements(Duration.ofMillis(2000))
.doOnNext(p -> log.info(Arrays.toString(p.getHits().getHits()[0].getSortValues()))) //
.doOnComplete(() -> log.info("Complete")) //
.doFinally(p -> log.info(p.toString()))
.blockLast();
log.info("blah");
Thread.sleep(5000);
}
解决方案
delayElements切换到并行调度程序并将每个发出的元素延迟2秒。这就是以后打印排序值的原因。
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