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Spring Reactive. How wait for all monos to finish?

I have the following code where I call external APIs via webclient and return Mono.
I need to execute some logic when I receive data. And after all, requests are processed, execute one logic for all gathered data. I can collect all Monos and put them to flux and then execute some logic at the end. But I have serviceName filed which is accessible only in the loop, so I need to execute logic for mono in loop and here I'm stuck and don't know how to wait for all data to complete and do it in a reactive way.
#Scheduled(fixedDelay = 50000)
public void refreshSwaggerConfigurations() {
log.debug("Starting Service Definition Context refresh");
List<SwaggerServiceData> allServicesApi = new ArrayList<>();
swaggerProperties.getUrls().forEach((serviceName, serviceSwaggerUrl) -> {
log.debug("Attempting service definition refresh for Service : {} ", serviceName);
Mono<SwaggerServiceData> swaggerData = getSwaggerDefinitionForAPI(serviceName,
serviceSwaggerUrl);
swaggerData.subscribe(swaggerServiceData -> {
if (swaggerServiceData != null) {
allServicesApi.add(swaggerServiceData);
String content = getJSON(swaggerServiceData);
definitionContext.addServiceDefinition(serviceName, content);
} else {
log.error("Skipping service id : {} Error : Could not get Swagger definition from API ",
serviceName);
}
});
});
//I need to wait here for all monos to complete and after that proceed for All gathered data...
//Now it's empty And I know why, just don't know how to make it.
Optional<SwaggerServiceData> swaggerAllServicesData = getAllServicesApiSwagger(allServicesApi);
if (swaggerAllServicesData.isPresent()) {
String allApiContent = getJSON(swaggerAllServicesData.get());
definitionContext.addServiceDefinition("All", allApiContent);
}
}
private Mono<SwaggerServiceData> getSwaggerDefinitionForAPI(String serviceName, String url) {
log.debug("Accessing the SwaggerDefinition JSON for Service : {} : URL : {} ", serviceName,
url);
Mono<SwaggerServiceData> swaggerServiceDataMono = webClient.get()
.uri(url)
.exchangeToMono(clientResponse -> clientResponse.bodyToMono(SwaggerServiceData.class));
return swaggerServiceDataMono;
}

I would add a temporary class to group data and serivce name :
record SwaggerService(SwaggerServiceData swaggerServiceData, String serviceName) {
boolean hasData() {
return swaggerServiceData != null;
}
}
And then change your pipeline :
Flux.fromStream(swaggerProperties.getUrls().entrySet().stream())
.flatMap((e) -> {
Mono<SwaggerServiceData> swaggerDefinitionForAPI = getSwaggerDefinitionForAPI(e.getKey(),
e.getValue());
return swaggerDefinitionForAPI.map(swaggerServiceData -> new SwaggerService(swaggerServiceData, e.getKey()));
})
.filter(SwaggerService::hasData)
.map(swaggerService -> {
String content = getJSON(swaggerService.swaggerServiceData());
definitionContext.addServiceDefinition(swaggerService.serviceName(), content);
return swaggerService.swaggerServiceData();
})
// here we will collect all datas and they will be emmited as single Mono with list of SwaggerServiceData
.collectList()
.map(this::getAllServicesApiSwagger)
.filter(Optional::isPresent)
.map(Optional::get)
.subscribe(e -> {
String allApiContent = getJSON(e);
definitionContext.addServiceDefinition("All", allApiContent);
});
This does not deal with logging error when SwaggerServiceData is null but you can further change it if you want. Also I assume that DefinitionContext is thread safe.
Solution with error logging (using flatMap and Mono.empty()) :
Flux.fromStream(swaggerProperties.getUrls().entrySet().stream())
.flatMap((e) -> {
Mono<SwaggerServiceData> swaggerDefinitionForAPI = getSwaggerDefinitionForAPI(e.getKey(),
e.getValue());
return swaggerDefinitionForAPI
.flatMap(swaggerServiceData -> {
if(swaggerServiceData != null) {
return Mono.just(new SwaggerService(swaggerServiceData, e.getKey()));
} else {
log.error("Skipping service id : {} Error : Could not get Swagger definition from API ",
e.getKey());
return Mono.empty();
}
});
})
.map(swaggerService -> {
String content = getJSON(swaggerService.swaggerServiceData());
definitionContext.addServiceDefinition(swaggerService.serviceName(), content);
return swaggerService.swaggerServiceData();
}).collectList()
.map(this::getAllServicesApiSwagger)
.filter(Optional::isPresent)
.map(Optional::get)
.subscribe(e -> {
String allApiContent = getJSON(e);
definitionContext.addServiceDefinition("All", allApiContent);
});
You can also wrap those lambads into some meaningful methods to improve readibility.

How to wait for #Async annotated method to complete execution completely for all the elements of List<String> which has 130k element then execute next

I have used ThreadPoolTaskExecutor class to call my #Async annotated method as number of api calls are more then 130k+ so I am trying to achieve it through async api calls using executor framework, but once the list through which I am streaming and making async calls gets completed then next flow is getting executed, but here I want to wait until for all async calls gets completed. Which means I want to wait until I will get api response for all 130k+ call which has been made async while streaming the list
public void downloadData(Map.Entry<String, String> entry, String downloadPath,
Locale locale, ApiClient apiClient, Task task,
Set<Locale> downloadFailedLocales) {
String targetFileName = entry.getKey() + ".xml";
Path filePath = null;
try {
filePath = getTargetDestination(downloadPath, "2", entry.getKey(), targetFileName);
MultiValueMap<String, String> queryParameters = restelApiClient.fetchQueryParameters();
if (downloadPath != null && !downloadFileService.localFileExists(filePath)) {
fetchCountryAndHotelList(entry.getValue(), filePath, task, downloadFailedLocales, locale, queryParameters);
//After fetching hotelList proceed for fetching hotelInfo from hotelList xml Data
if (entry.getKey().equals(HotelConstants.HOTEL_LIST)) {
//fetching hotelCodes from downloaded xml of hotelList, to make API calls for hotelInfo
List<String> hotelInfoArray = getHotelCodeList(filePath);
AtomicInteger hotelCounter = new AtomicInteger();
String hotelInfoXml = apiClient.getApiClientSettings().getEndpoints()
.get(HotelConstants.HOTEL_INFO);
/*Fetching data from HotelInfo API Async but once it will stream the hotelinfo list then next flow of code execute and it won't wait all api calls to be made and get the response back. */
hotelInfoArray.stream().forEach(hotel -> {
StringBuilder fileName = new StringBuilder();
fileName.append(HotelConstants.HOTEL_INFO).append(hotelCounter.getAndIncrement()).append(".xml");
Path path = getTargetDestination(downloadPath, "2", HotelConstants.HOTEL_INFO,
fileName.toString());
StringBuilder hotelCode = new StringBuilder();
hotelCode.append("<codigo>").append(hotel).append("</codigo>");
String xml = String.format(hotelInfoXml).replace("<codigo></codigo>", hotelCode);
try {
hotelDataFetchThreadService.fetchHotelInfo(xml, path, task, downloadFailedLocales, locale, queryParameters);
} catch (DownloadFailedException e) {
log.info("Download failed for hotel code {} with exception {}", hotel, e);
downloadFileService.deleteIncompleteFiles(path);
}
});
}
} else {
log.info("file already exist skipping downloading again");
}
} catch (DownloadException e) {
downloadFileService.deleteIncompleteFiles(filePath);
log.info("Download failed for endpoint {} with exception {}", entry.getKey(), e);
} catch (DownloadFailedException e) {
throw new RuntimeException(e);
}
}
/*
This method make api call and write the xml response in local file in async way
*/
#Async("TestExecutor")
public void fetchHotelInfo(String xml, Path path, Task task, Set<Locale> downloadFailedLocales, Locale locale,
MultiValueMap<String, String> queryParameters) throws DownloadFailedException {
Flux<DataBuffer> bufferedData;
try {
// log.info("using thread {}", Thread.currentThread().getName());
bufferedData = apiClient.getWebClient()
.uri(uriBuilder -> uriBuilder
.queryParams(queryParameters)
.queryParam(HotelConstants.XML, xml.trim())
.build()
).retrieve()
.bodyToFlux(DataBuffer.class)
.retryWhen(Retry.fixedDelay(maxRetryAttempts, Duration.ofSeconds(maxRetryDelay))
.onRetryExhaustedThrow(
(RetryBackoffSpec retryBackoffSpec, Retry.RetrySignal retrySignal) -> {
throw new DownloadException(
"External Service failed to process after max retries");
}));
writeBufferDataToFile(bufferedData, path);
} catch (DownloadException e) {
downloadFileService.deleteIncompleteFiles(path);
downloadFailedLocales.add(locale);
if (locale.equals(task.getJob().getProvider().getDefaultLocale().getLocale())) {
throw new DownloadFailedException(
String.format("Network issue during download, Max retry reached: %s", e.getMessage()), e);
}
log.info("Download failed for with exception ", e);
}
}

Vert.x request handler and blocking db queries

How can i translate this piece of code correctly in vert.x?
normally, in spring or in a simple sevlet with a template engine to output an html response i'll do like this
function test(request, response) {
templatecontext tc = getContext();
init conditions
if (condition1) {
retrieve data from db ({
asyncresult -> {
tc.put("data1", data1)
})
} else if (condition2) {
other code
if (condition 2.1) {
retrieve data from db ({
asyncresult -> {
tc.put("data2", data2)
})
}
}
get other data from db and put in context
template.eval("templatefile", tc)
write to response
}
the problem is, retrieving data from database is an handler of asyncresult, so i cannot grant that template evaluation is made with data1 or data2, because retrieving of async without falling in a callback hell.
I've not really understood rxjava2, but i feel i'm trying to kill a bean with a spoon.

You can use futures and composition. See the ComposeExample in vertx-examples repo:
public class ComposeExample extends AbstractVerticle {
#Override
public void start() throws Exception {
Future<String> future = anAsyncAction();
future.compose(this::anotherAsyncAction)
.setHandler(ar -> {
if (ar.failed()) {
System.out.println("Something bad happened");
ar.cause().printStackTrace();
} else {
System.out.println("Result: " + ar.result());
}
});
}
private Future<String> anAsyncAction() {
Future<String> future = Future.future();
// mimic something that take times
vertx.setTimer(100, l -> future.complete("world"));
return future;
}
private Future<String> anotherAsyncAction(String name) {
Future<String> future = Future.future();
// mimic something that take times
vertx.setTimer(100, l -> future.complete("hello " + name));
return future;
}
}

Transform Observable onError and emit an item

In my Android App I have a generated (Swagger) ApiClient which gets initialized with a Token to identify the User.
This Token (which comes from the Server) can expire.
I get Observable´s with Data from my WebService via myApiClient.myServiceMethod(params)
When I get 401 from the Server it means my Token is expired and I have to initialize myApiClient again (to get it with an unexpired Token).
How myApiClient is initialized. It is returned by getMyApiClient()
//getOkHttpClientWithToken() first issues another Server call to get an
//unexpired Token and then returns an OkHttpClient with that Token set.
myApiClient = new ApiClient()
.getAdapterBuilder()
.baseUrl(url)
.client(getOkHttpClientWithToken())
.build()
.create(MyApiClient.class);
I get the Observable from myApiClient calls
Observable<Result> getResultObservable(Type param1, Type param2) {
return Observable.just(getMyApiClient())
.flatMap(myApiClient ->
myApiClient.getResult(param1, param2).cache()
);
}
What I tried is
//How to recreate myApiClient and Retry call on new myApiClient when an Error occurs
getResultObservable(param1, param2)
.take(1)
.subscribe(result -> {
doSomethingWithResult();
}
});
Works but is done on every error, not just 401 and may never end
I need something like
getResultObservable(param1, param2)
.take(1)
.subscribe(result -> {
doSomethingWithResult();
}, e -> {
if(e.getMessage.equals("HTTP 401")) {
"Transform this Observable to getResultObservable with new myApiClient and emit Result in onNext"
} else {
"Other error inform User and stop."
}
}
});

You may use Observable#onErrorResumeNext to provide an fallback-observable. You can check the exception for typ and return a fallback-observable, if given condition is met or just wrap the exception with Observable#error.
Please have a look at the test, how #onErrorResumNext is used, to provide an fallback-observable, when some exception happens.
#Test
void nameX() {
Observable<String> stringObservable = get();
Observable<String> fallback$ =
stringObservable
.doOnError(s -> System.out.println("fail -> " + s.getMessage()))
.onErrorResumeNext(
throwable -> {
if (throwable instanceof MyException) {
return fallBack().doOnNext(s -> System.out.println("use fallback value " + s));
} else {
return Observable.error(throwable);
}
});
fallback$
.test()
.assertNotComplete()
.assertValueCount(1)
.assertValueAt(0, s -> "Wurst".equals(s));
}
private Observable<String> get() {
return Observable.error(new MyException("Fail"));
}
private Observable<String> fallBack() {
return Observable.just("Wurst").mergeWith(Observable.never());
}
private static final class MyException extends Exception {
MyException(String message) {
super(message);
}
}

Rxjava Android how to use the Zip operator

I am having a lot of trouble understanding the zip operator in RxJava for my android project.
Problem
I need to be able to send a network request to upload a video
Then i need to send a network request to upload a picture to go with it
finally i need to add a description and use the responses from the previous two requests to upload the location urls of the video and picture along with the description to my server.
I assumed that the zip operator would be perfect for this task as I understood we could take the response of two observables (video and picture requests) and use them for my final task.
But I cant seem to get this to occur how I envision it.
I am looking for someone to answer how this can be done conceptually with a bit of psuedo code.
Thank you

Zip operator strictly pairs emitted items from observables. It waits for both (or more) items to arrive then merges them. So yes this would be suitable for your needs.
I would use Func2 to chain the result from the first two observables.
Notice this approach would be simpler if you use Retrofit since its api interface may return an observable. Otherwise you would need to create your own observable.
// assuming each observable returns response in the form of String
Observable<String> movOb = Observable.create(...);
// if you use Retrofit
Observable<String> picOb = RetrofitApiManager.getService().uploadPic(...),
Observable.zip(movOb, picOb, new Func2<String, String, MyResult>() {
#Override
public MyResult call(String movieUploadResponse, String picUploadResponse) {
// analyze both responses, upload them to another server
// and return this method with a MyResult type
return myResult;
}
}
)
// continue chaining this observable with subscriber
// or use it for something else

A small example:
val observableOne = Observable.just("Hello", "World")
val observableTwo = Observable.just("Bye", "Friends")
val zipper = BiFunction<String, String, String> { first, second -> "$first - $second" }
Observable.zip(observableOne, observableTwo, zipper)
.subscribe { println(it) }
This will print:
Hello - Bye
World - Friends
In BiFunction<String, String, String> the first String the type of the first observable, the second String is the type of the second observable, the third String represents the type of the return of your zipper function.
I made a small example that calls two real endpoints using zip in this blog post

Here I have an example that I did using Zip in asynchronous way, just in case you´re curious
/**
* Since every observable into the zip is created to subscribeOn a diferent thread, it´s means all of them will run in parallel.
* By default Rx is not async, only if you explicitly use subscribeOn.
*/
#Test
public void testAsyncZip() {
scheduler = Schedulers.newThread();
scheduler1 = Schedulers.newThread();
scheduler2 = Schedulers.newThread();
long start = System.currentTimeMillis();
Observable.zip(obAsyncString(), obAsyncString1(), obAsyncString2(), (s, s2, s3) -> s.concat(s2)
.concat(s3))
.subscribe(result -> showResult("Async in:", start, result));
}
/**
* In this example the the three observables will be emitted sequentially and the three items will be passed to the pipeline
*/
#Test
public void testZip() {
long start = System.currentTimeMillis();
Observable.zip(obString(), obString1(), obString2(), (s, s2, s3) -> s.concat(s2)
.concat(s3))
.subscribe(result -> showResult("Sync in:", start, result));
}
public void showResult(String transactionType, long start, String result) {
System.out.println(result + " " +
transactionType + String.valueOf(System.currentTimeMillis() - start));
}
public Observable<String> obString() {
return Observable.just("")
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> "Hello");
}
public Observable<String> obString1() {
return Observable.just("")
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> " World");
}
public Observable<String> obString2() {
return Observable.just("")
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> "!");
}
public Observable<String> obAsyncString() {
return Observable.just("")
.observeOn(scheduler)
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> "Hello");
}
public Observable<String> obAsyncString1() {
return Observable.just("")
.observeOn(scheduler1)
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> " World");
}
public Observable<String> obAsyncString2() {
return Observable.just("")
.observeOn(scheduler2)
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> "!");
}
You can see more examples here https://github.com/politrons/reactive

zip operator allow you to compose a result from results of two different observable.
You 'll have to give am lambda that will create a result from datas emitted by each observable.
Observable<MovieResponse> movies = ...
Observable<PictureResponse> picture = ...
Observable<Response> response = movies.zipWith(picture, (movie, pic) -> {
return new Response("description", movie.getName(), pic.getUrl());
});

i have been searching for a simple answer on how to use the Zip operator, and what to do with the Observables i create to pass them to it, i was wondering if i should call subscribe() for every observable or not, non of these answers were simple to find, i had to figure it out by my self, so here is a simple example for using Zip operator on 2 Observables :
#Test
public void zipOperator() throws Exception {
List<Integer> indexes = Arrays.asList(0, 1, 2, 3, 4);
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
Observable<Integer> indexesObservable = Observable.fromIterable(indexes);
Observable<String> lettersObservable = Observable.fromIterable(letters);
Observable.zip(indexesObservable, lettersObservable, mergeEmittedItems())
.subscribe(printMergedItems());
}
#NonNull
private BiFunction<Integer, String, String> mergeEmittedItems() {
return new BiFunction<Integer, String, String>() {
#Override
public String apply(Integer index, String letter) throws Exception {
return "[" + index + "] " + letter;
}
};
}
#NonNull
private Consumer<String> printMergedItems() {
return new Consumer<String>() {
#Override
public void accept(String s) throws Exception {
System.out.println(s);
}
};
}
the printed result is :
[0] a
[1] b
[2] c
[3] d
[4] e
the final answers to the questions that where in my head were as follows
the Observables passed to the zip() method just need to be created only, they do not need to have any subscribers to them, only creating them is enough ... if you want any observable to run on a scheduler, you can specify this for that Observable ... i also tried the zip() operator on Observables where they should wait for there result, and the Consumable of the zip() was triggered only when both results where ready (which is the expected behavior)

This is my implementation using Single.zip and rxJava2
I tried to make it as easy to understand as possible
//
// API Client Interface
//
#GET(ServicesConstants.API_PREFIX + "questions/{id}/")
Single<Response<ResponseGeneric<List<ResponseQuestion>>>> getBaseQuestions(#Path("id") int personId);
#GET(ServicesConstants.API_PREFIX + "physician/{id}/")
Single<Response<ResponseGeneric<List<ResponsePhysician>>>> getPhysicianInfo(#Path("id") int personId);
//
// API middle layer - NOTE: I had feedback that the Single.create is not needed (but I haven't yet spent the time to improve it)
//
public Single<List<ResponsePhysician>> getPhysicianInfo(int personId) {
return Single.create(subscriber -> {
apiClient.getPhysicianInfo(appId)
.subscribeOn(Schedulers.io())
.observeOn(Schedulers.io())
.subscribe(response -> {
ResponseGeneric<List<ResponsePhysician>> responseBody = response.body();
if(responseBody != null && responseBody.statusCode == 1) {
if (!subscriber.isDisposed()) subscriber.onSuccess(responseBody.data);
} else if(response.body() != null && response.body().status != null ){
if (!subscriber.isDisposed()) subscriber.onError(new Throwable(response.body().status));
} else {
if (!subscriber.isDisposed()) subscriber.onError(new Throwable(response.message()));
}
}, throwable -> {
throwable.printStackTrace();
if(!subscriber.isDisposed()) subscriber.onError(throwable);
});
});
}
public Single<List<ResponseQuestion>> getHealthQuestions(int personId){
return Single.create(subscriber -> {
apiClient.getBaseQuestions(personId)
.subscribeOn(Schedulers.io())
.observeOn(Schedulers.io())
.subscribe(response -> {
ResponseGeneric<List<ResponseQuestion>> responseBody = response.body();
if(responseBody != null && responseBody.data != null) {
if (!subscriber.isDisposed()) subscriber.onSuccess(response.body().data);
} else if(response.body() != null && response.body().status != null ){
if (!subscriber.isDisposed()) subscriber.onError(new Throwable(response.body().status));
} else {
if (!subscriber.isDisposed()) subscriber.onError(new Throwable(response.message()));
}
}, throwable -> {
throwable.printStackTrace();
if(!subscriber.isDisposed()) subscriber.onError(throwable);
});
});
}
//please note that ResponseGeneric is just an outer wrapper of the returned data - common to all API's in this project
public class ResponseGeneric<T> {
#SerializedName("Status")
public String status;
#SerializedName("StatusCode")
public float statusCode;
#SerializedName("Data")
public T data;
}
//
// API end-use layer - this gets close to the UI so notice the oberver is set for main thread
//
private static class MergedResponse{// this is just a POJO to store all the responses in one object
public List<ResponseQuestion> listQuestions;
public List<ResponsePhysician> listPhysicians;
public MergedResponse(List<ResponseQuestion> listQuestions, List<ResponsePhysician> listPhysicians){
this.listQuestions = listQuestions;
this.listPhysicians = listPhysicians;
}
}
// example of Single.zip() - calls getHealthQuestions() and getPhysicianInfo() from API Middle Layer
private void downloadHealthQuestions(int personId) {
addRxSubscription(Single
.zip(getHealthQuestions(personId), getPhysicianInfo(personId), MergedResponse::new)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(response -> {
if(response != null) {
Timber.i(" - total health questions downloaded %d", response.listQuestions.size());
Timber.i(" - physicians downloaded %d", response.listPhysicians.size());
if (response.listPhysicians != null && response.listPhysicians.size()>0) {
// do your stuff to process response data
}
if (response.listQuestions != null && response.listQuestions.size()>0) {
// do your stuff to process response data
}
} else {
// process error - show message
}
}, error -> {
// process error - show network error message
}));
}

You use the zip from rxjava with Java 8:
Observable<MovieResponse> movies = ...
Observable<PictureResponse> picture = ...
Observable<ZipResponse> response = Observable.zip(movies, picture, ZipResponse::new);
class ZipResponse {
private MovieResponse movieResponse;
private PictureResponse pictureResponse;
ZipResponse(MovieResponse movieResponse, PictureResponse pictureResponse) {
this.movieResponse = movieResponse;
this.pictureResponse = pictureResponse;
}
public MovieResponse getMovieResponse() {
return movieResponse;
}
public void setMovieResponse(MovieResponse movieResponse) {
this.movieResponse= movieResponse;
}
public PictureResponse getPictureResponse() {
return pictureResponse;
}
public void setPictureResponse(PictureResponse pictureResponse) {
this.pictureResponse= pictureResponse;
}
}

You can use .zipWith operator for Observable chains.
If uploadMovies() and uploadPictures() return Observable,
uploadMovies()
.zipWith(uploadPictures()) { m, p ->
"$m with $p were uploaded"
}
.subscribe { print(it) }