Can't make API call urlfetch.Fetch in a thread that is neither the original request thread nor a thread created by ThreadManager - google-app-engine

Question

I am currently playing with kotlin, Spring social and Google app engine. I am trying to get back a number of followers every second.
Here is my code :
#Service
class SubscribeService {
var subscriber : Disposable? = null
var twitter : Twitter = TwitterTemplate(
"XXXAUTHXXX",
"XXXAUTHXXX",
"XXXAUTHXXX",
"XXXAUTHXXX")
fun subscribe() {
subscriber = Observable.interval(1, TimeUnit.SECONDS).subscribe {println(twitter.userOperations().getUserProfile("azeaze").followersCount)}
}
fun unsubscribe() {
subscriber?.dispose()
}
}
I get this exception when I execute subscribe function :
[INFO] io.reactivex.exceptions.OnErrorNotImplementedException: Can't make API call urlfetch.Fetch in a thread that is neither the original request thread nor a thread created by ThreadManager
[INFO] at io.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:704)
[INFO] at io.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:701)
[INFO] at io.reactivex.internal.observers.LambdaObserver.onError(LambdaObserver.java:74)
[INFO] at io.reactivex.internal.observers.LambdaObserver.onNext(LambdaObserver.java:64)
[INFO] at io.reactivex.internal.operators.observable.ObservableInterval$IntervalObserver.run(ObservableInterval.java:83)
[INFO] at io.reactivex.internal.schedulers.ScheduledDirectPeriodicTask.run(ScheduledDirectPeriodicTask.java:39)
[INFO] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
[INFO] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
[INFO] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
[INFO] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
[INFO] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
[INFO] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
[INFO] at java.lang.Thread.run(Thread.java:748)
[INFO] Caused by: com.google.apphosting.api.ApiProxy$CallNotFoundException: Can't make API call urlfetch.Fetch in a thread that is neither the original request thread nor a thread created by ThreadManager
[INFO] at com.google.apphosting.api.ApiProxy$CallNotFoundException.foreignThread(ApiProxy.java:844)
[INFO] at com.google.apphosting.api.ApiProxy.makeSyncCall(ApiProxy.java:116)
[INFO] at com.google.appengine.api.urlfetch.URLFetchServiceImpl.fetch(URLFetchServiceImpl.java:40)
[INFO] at com.google.apphosting.utils.security.urlfetch.URLFetchServiceStreamHandler$Connection.fetchResponse(URLFetchServiceStreamHandler.java:543)
[INFO] at com.google.apphosting.utils.security.urlfetch.URLFetchServiceStreamHandler$Connection.getInputStream(URLFetchServiceStreamHandler.java:422)
[INFO] at com.google.apphosting.utils.security.urlfetch.URLFetchServiceStreamHandler$Connection.getResponseCode(URLFetchServiceStreamHandler.java:275)
[INFO] at org.springframework.http.client.SimpleBufferingClientHttpRequest.executeInternal(SimpleBufferingClientHttpRequest.java:84)
[INFO] at org.springframework.http.client.AbstractBufferingClientHttpRequest.executeInternal(AbstractBufferingClientHttpRequest.java:48)
[INFO] at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:53)
[INFO] at org.springframework.http.client.InterceptingClientHttpRequest$InterceptingRequestExecution.execute(InterceptingClientHttpRequest.java:99)
[INFO] at org.springframework.social.oauth1.OAuth1RequestInterceptor.intercept(OAuth1RequestInterceptor.java:48)
[INFO] at org.springframework.http.client.InterceptingClientHttpRequest$InterceptingRequestExecution.execute(InterceptingClientHttpRequest.java:86)
[INFO] at org.springframework.http.client.InterceptingClientHttpRequest.executeInternal(InterceptingClientHttpRequest.java:70)
[INFO] at org.springframework.http.client.AbstractBufferingClientHttpRequest.executeInternal(AbstractBufferingClientHttpRequest.java:48)
[INFO] at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:53)
[INFO] at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:652)
[INFO] at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:628)
[INFO] at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:303)
[INFO] at org.springframework.social.twitter.api.impl.UserTemplate.getUserProfile(UserTemplate.java:60)
[INFO] at tbetous.SubscribeService$test$1.accept(SubscribeService.kt:20)
[INFO] at tbetous.SubscribeService$test$1.accept(SubscribeService.kt:11)
[INFO] at io.reactivex.internal.observers.LambdaObserver.onNext(LambdaObserver.java:60)
[INFO] ... 9 more
[INFO] Exception in thread "RxComputationThreadPool-1" io.reactivex.exceptions.OnErrorNotImplementedException: Can't make API call urlfetch.Fetch in a thread that is neither the original request thread nor a thread created by ThreadManager
[INFO] at io.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:704)
[INFO] at io.reactivex.internal.functions.Functions$OnErrorMissingConsumer.accept(Functions.java:701)
[INFO] at io.reactivex.internal.observers.LambdaObserver.onError(LambdaObserver.java:74)
[INFO] at io.reactivex.internal.observers.LambdaObserver.onNext(LambdaObserver.java:64)
[INFO] at io.reactivex.internal.operators.observable.ObservableInterval$IntervalObserver.run(ObservableInterval.java:83)
[INFO] at io.reactivex.internal.schedulers.ScheduledDirectPeriodicTask.run(ScheduledDirectPeriodicTask.java:39)
[INFO] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
[INFO] at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
[INFO] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
[INFO] at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
[INFO] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
[INFO] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
[INFO] at java.lang.Thread.run(Thread.java:748)
[INFO] Caused by: com.google.apphosting.api.ApiProxy$CallNotFoundException: Can't make API call urlfetch.Fetch in a thread that is neither the original request thread nor a thread created by ThreadManager
[INFO] at com.google.apphosting.api.ApiProxy$CallNotFoundException.foreignThread(ApiProxy.java:844)
[INFO] at com.google.apphosting.api.ApiProxy.makeSyncCall(ApiProxy.java:116)
[INFO] at com.google.appengine.api.urlfetch.URLFetchServiceImpl.fetch(URLFetchServiceImpl.java:40)
[INFO] at com.google.apphosting.utils.security.urlfetch.URLFetchServiceStreamHandler$Connection.fetchResponse(URLFetchServiceStreamHandler.java:543)
[INFO] at com.google.apphosting.utils.security.urlfetch.URLFetchServiceStreamHandler$Connection.getInputStream(URLFetchServiceStreamHandler.java:422)
[INFO] at com.google.apphosting.utils.security.urlfetch.URLFetchServiceStreamHandler$Connection.getResponseCode(URLFetchServiceStreamHandler.java:275)
[INFO] at org.springframework.http.client.SimpleBufferingClientHttpRequest.executeInternal(SimpleBufferingClientHttpRequest.java:84)
[INFO] at org.springframework.http.client.AbstractBufferingClientHttpRequest.executeInternal(AbstractBufferingClientHttpRequest.java:48)
[INFO] at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:53)
[INFO] at org.springframework.http.client.InterceptingClientHttpRequest$InterceptingRequestExecution.execute(InterceptingClientHttpRequest.java:99)
[INFO] at org.springframework.social.oauth1.OAuth1RequestInterceptor.intercept(OAuth1RequestInterceptor.java:48)
[INFO] at org.springframework.http.client.InterceptingClientHttpRequest$InterceptingRequestExecution.execute(InterceptingClientHttpRequest.java:86)
[INFO] at org.springframework.http.client.InterceptingClientHttpRequest.executeInternal(InterceptingClientHttpRequest.java:70)
[INFO] at org.springframework.http.client.AbstractBufferingClientHttpRequest.executeInternal(AbstractBufferingClientHttpRequest.java:48)
[INFO] at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:53)
[INFO] at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:652)
[INFO] at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:628)
[INFO] at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:303)
[INFO] at org.springframework.social.twitter.api.impl.UserTemplate.getUserProfile(UserTemplate.java:60)
[INFO] at tbetous.SubscribeService$test$1.accept(SubscribeService.kt:20)
[INFO] at tbetous.SubscribeService$test$1.accept(SubscribeService.kt:11)
[INFO] at io.reactivex.internal.observers.LambdaObserver.onNext(LambdaObserver.java:60)
[INFO] ... 9 more
I am pretty sure it is something about google app engine. When I run my application I use mvn appengine:devserver. Can anyone help me ?

Answer 1

I found my solution. Thanks to this link. GAE does not work with RxJava beacause It does not respect thred restriction of Google standard environnent. I had to specify how RxJava have to create thread.
Here is my code :
val scheduler : Scheduler = Schedulers.from(ScheduledThreadPoolExecutor(3, ThreadManager.backgroundThreadFactory()))
RxJavaPlugins.setComputationSchedulerHandler { scheduler }
After that I can use RxJava :
subscriber = Observable.interval(1, TimeUnit.SECONDS)
.map { twitter.userOperations().getUserProfile("azeazeaz").followersCount }
.subscribe {it -> println(it)}