Cache handling with RXJava

I'm trying to implement this workflow with rxJava but i'm sure if i'm misusing or doing stuff wrong.

• User asks to login
• If a loginResult is available in cache then "emit" the cached LoginResult
• Else actually perform the request to the webservice and cache the result if everything is successfull
• If an error occurs retry at most 3 times and if there is a 4th time then purge the cache.

Here is my full snippet of code.

public class LoginTask extends BaseBackground<LoginResult> {
  private static CachedLoginResult cachedLoginResult = new CachedLoginResult();
  private XMLRPCClient xmlrpcClient;
  private UserCredentialsHolder userCredentialsHolder;

  @Inject
  public LoginTask(XMLRPCClient client, UserCredentialsHolder userCredentialsHolder) {
    this.xmlrpcClient = client;
    this.userCredentialsHolder = userCredentialsHolder;
  }

  @Override
  public LoginResult performRequest() throws Exception {
    return UserApi.login(
        xmlrpcClient,
        userCredentialsHolder.getUserName(),
        userCredentialsHolder.getPlainPassword());


  }

  @Override
  public Observable<LoginResult> getObservable() {
    return cachedLoginResult.getObservable()
        .onErrorResumeNext(
            Observable.create(
                ((Observable.OnSubscribe<LoginResult>) subscriber -> {
                  try {
                    if (!subscriber.isUnsubscribed()) {
                      subscriber.onNext(performRequest()); // actually performRequest
                    }
                    subscriber.onCompleted();
                  } catch (Exception e) {
                    subscriber.onError(e);
                  }
                })
            )
                .doOnNext(cachedLoginResult::setLoginResult)
                .retry((attempts, t) -> attempts < 3)
                .doOnError(throwable -> cachedLoginResult.purgeCache())
        );
  }


  private static class CachedLoginResult {
    private LoginResult lr = null;
    private long when = 0;

    private CachedLoginResult() {
    }

    public boolean hasCache() {
      return lr != null && when + TimeUnit.MILLISECONDS.convert(30, TimeUnit.MINUTES) < System.currentTimeMillis();
    }

    public void setLoginResult(LoginResult lr) {
      if (lr != null) {
        if (this.lr == null) {
          this.lr = lr;
          this.when = System.currentTimeMillis();
        }
      }
    }

    public void purgeCache() {
      this.lr = null;
      this.when = 0;
    }

    public Observable<LoginResult> getObservable() {
      return Observable.create(new Observable.OnSubscribe<LoginResult>() {
        @Override
        public void call(Subscriber<? super LoginResult> subscriber) {
          if (!subscriber.isUnsubscribed()) {
            if (hasCache()) {
              subscriber.onNext(lr);
              subscriber.onCompleted();
            } else {
              subscriber.onError(new RuntimeException("No cache"));
            }
          }
        }
      });
    }
  }
}

Since i wan't able to find any similar examples and i started "playing" with rxjava just 1 day ago i'm unsure of my implementation.

Thank you for your time.