Flink启动报错could not be determined automatically

今天发布Flink应用，报如下错误：

The return type of function 'main(RyeCollectorLauncher.java:77)' could not be determined automatically, due to type erasure. You can give type information hints by using the returns(...) method on the result of the transformation call, or by letting your function implement the 'ResultTypeQueryable' interface.
	org.apache.flink.streaming.api.transformations.StreamTransformation.getOutputType(StreamTransformation.java:420)
	org.apache.flink.streaming.api.datastream.DataStream.getType(DataStream.java:175)
	org.apache.flink.streaming.api.datastream.DataStream.union(DataStream.java:217)
	com.mogujie.traffic.rye.anchor.flink.collector.RyeCollectorLauncher.main(RyeCollectorLauncher.java:104)

根据错误信心定位到出错位置：

根据错误信息You can give type information hints by using the returns，只需要在后面调用returns方法，然后指明其返回类型即可解决。

问题已经解决，这里简单记录下，希望可以帮到各位朋友！！！

补充：
报错：

2019-07-30 11:36:46,193 ERROR org.apache.flink.runtime.entrypoint.ClusterEntrypoint         - Could not start cluster entrypoint YarnJobClusterEntrypoint.
org.apache.flink.runtime.entrypoint.ClusterEntrypointException: Failed to initialize the cluster entrypoint YarnJobClusterEntrypoint.
	at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.startCluster(ClusterEntrypoint.java:181)
	at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.runClusterEntrypoint(ClusterEntrypoint.java:517)
	at org.apache.flink.yarn.entrypoint.YarnJobClusterEntrypoint.main(YarnJobClusterEntrypoint.java:102)
Caused by: java.lang.Exception: Could not create actor system
	at org.apache.flink.runtime.clusterframework.BootstrapTools.startActorSystem(BootstrapTools.java:276)
	at org.apache.flink.runtime.clusterframework.BootstrapTools.startActorSystem(BootstrapTools.java:162)
	at org.apache.flink.runtime.clusterframework.BootstrapTools.startActorSystem(BootstrapTools.java:121)
	at org.apache.flink.runtime.clusterframework.BootstrapTools.startActorSystem(BootstrapTools.java:96)
	at org.apache.flink.runtime.rpc.akka.AkkaRpcServiceUtils.createRpcService(AkkaRpcServiceUtils.java:78)
	at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.createRpcService(ClusterEntrypoint.java:284)
	at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.initializeServices(ClusterEntrypoint.java:255)
	at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.runCluster(ClusterEntrypoint.java:207)
	at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.lambda$startCluster$0(ClusterEntrypoint.java:163)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:422)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1754)
	at org.apache.flink.runtime.security.HadoopSecurityContext.runSecured(HadoopSecurityContext.java:41)
	at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.startCluster(ClusterEntrypoint.java:162)
	... 2 more
Caused by: java.lang.NoSuchMethodError: scala.Predef$.refArrayOps([Ljava/lang/Object;)Lscala/collection/mutable/ArrayOps;
	at org.apache.flink.runtime.akka.AkkaUtils$.getRemoteAkkaConfig(AkkaUtils.scala:471)
	at org.apache.flink.runtime.akka.AkkaUtils$.getAkkaConfig(AkkaUtils.scala:218)
	at org.apache.flink.runtime.akka.AkkaUtils.getAkkaConfig(AkkaUtils.scala)
	at org.apache.flink.runtime.clusterframework.BootstrapTools.startActorSystem(BootstrapTools.java:256)
	... 15 more

出现这种问题是程序中的Scala版本和线上集群使用的版本产生冲突，因此只需要更换Scala版本即可。