运行线程时的异常处理

Question

I have a an application which has a kafka consumer and updates Elastic search according to the data it receives.

My issue is that when ever ES goes down, the kafka consumer stops completely and doesn't restart.

I believe its due to how my ES code is running:

public CompletionStage<SearchResponse> executeSearch(SearchRequest searchRequest) {
        CompletableFuture<SearchResponse> f = new CompletableFuture<>();

        client.searchAsync(searchRequest, RequestOptions.DEFAULT, new ActionListener<SearchResponse>() {
            @Override
            public void onResponse(SearchResponse searchResponse) {
                f.complete(searchResponse);
            }

            @Override
            public void onFailure(Exception e) {

                throw new Exception();  // I am guessing because of this
            }
        });
        return f;
} 

If I change my onFailure method to:

            public void onFailure(Exception e) {

                f.complete(null);
            }

It works perfectly but I dont understand why throwing an exception leads to this.

Any help would be greatly appreciated.

Answer 1

For those that need a solution, I changed my code to below for it to work with exception:

public void onFailure(Exception e) {
    f.completeExceptionally(new Exception());
}

Answer 2

Also potentially relevant are the exceptionally method and the handle method from CompletableFuture

CompletableFuture.exceptionally((ex)-> ) - https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CompletableFuture.html#exceptionally-java.util.function.Function-

https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CompletableFuture.html#handle-java.util.function.BiFunction-