Apache Flink: could not find implicit value for evidence parameter of type This is a common error when transforming streams in Apache Flink based applications. The solution is simple. We just need to import the following: Which should import the necessary types for the operations.
com.esotericsoftware.kryo.KryoException: Unusual solution upgrading Flink While upgrading from Flink from 1.4 to a newer version 1.6.1, there are a few build issues. After we fix the issues, suddenly we started getting KryoException. Why are we getting this and how it this related to the upgrade? Let’s start with the exception message. If you try to… Continue reading »
Flink – Interactive Scala Shell Interactive scala shell is available in Flink download package. It allows us to run flink streams and batch processing statements in scala by building and executing the jobs directly created from the shell. We can simply call execute() method, which should request to run the job. The shell supports including… Continue reading »
Apache Flink – mapWithState on KeyedStream mapWithState operator provides a syntactic ease for keeping ValueState for map operations on KeyedStreams in Apache Flink. It is specially useful for doing a running count on the data. That is exactly what we are going to try in this post. Just remember that you don’t have to return… Continue reading »
Downloading Flink You can download flink from it’s Apache’s site. We are downloading Flink 1.6, which is the latest version available. https://flink.apache.org/downloads.html It requires Java version 8. Running Flink Cluster Let’s start the cluster. We can just run it directly from bin folder using start-cluster.sh utility available with the download. Alternatively we can run it… Continue reading »
Apache Flink – Collections & Streams While developing a streaming application, it is often necessary to use some inputs as collections. This can be specially useful for testing purposes. In this post we are trying to discuss how we can create a DataStream from a collection. After applying some operators on the stream, we are… Continue reading »
![Apache Flink – Class Not found [org/apache/flink/streaming/api/scala/DataStream]](http://www.alternatestack.com/wp-content/uploads/2018/09/Screen-Shot-2018-09-16-at-5.29.04-PM-200x140.png)
Apache Flink – Class Not found [org/apache/flink/streaming/api/scala/DataStream] If you are developing a Flink app following examples on the web, you can most likely encounter the following error: Generally, the problem is resolved by correctly setting the source folder in a scala project in IntelliJ but the weird thing is that it is happening for a… Continue reading »
Apache Flink – Change Port for web front end Apache Flink runs the dashboard on port 8081. Since this is a common port there might be conflict with some other services running on the same machines. You might encounter this scenario especially during development when many services are running on the your development machine. But… Continue reading »