flink-cep | flink-cep | Stream Processing library

With pattern.get("first") you are selecting a pattern named "first" from the pattern sequence, but the pattern sequence only has one pattern, which is named "start". Trying changing "first" to "start".

Also, CEP has to be able to sort the stream into temporal order in order to do pattern matching. You should define a watermark strategy. For processing time semantics you can use WatermarkStrategy.noWatermarks().

Your application is using event time, so you will need to arrange for a sufficiently large Watermark to be generated despite the lack of incoming events. You could use this example if you want to artificially advance the current watermark when the source is idle.

Given that your events don't have event-time timestamps, why don't you simply use processing time instead, and thereby avoid this problem? (Note, however, the limitation mentioned in https://stackoverflow.com/a/50357721/2000823).

The error appears when flink-clients is not in the classpath. Can you double-check if your profile is working as expected by inspecting the actual classpath? Btw for IntelliJ you don't need the profile at all. Just tick the option to include provided dependencies in the Run/Debug dialog.

For an unknown reason, setting the classloader.resolve-order property to parent-first as mentioned in the Apache Flink mailing list resolves the issue. I am still baffled as to why it works, as there should be no dependency clashes between the child and parent classloader loading different versions of this dependency (as it is not provided out of the box with the flink-dist I am using).

In the Flink documentation under "Debugging Classloading", there's a section which talks about this parent-child relationship:

In setups where dynamic classloading is involved (plugin components, Flink jobs in session setups), there is a hierarchy of typically two ClassLoaders: (1) Java’s application classloader, which has all classes in the classpath, and (2) the dynamic plugin/user code classloader. for loading classes from the plugin or the user-code jar(s). The dynamic ClassLoader has the application classloader as its parent.

By default, Flink inverts classloading order, meaning it looks into the dynamic classloader first, and only looks into the parent (application classloader) if the class is not part of the dynamically loaded code.

The benefit of inverted classloading is that plugins and jobs can use different library versions than Flink’s core itself, which is very useful when the different versions of the libraries are not compatible. The mechanism helps to avoid the common dependency conflict errors like IllegalAccessError or NoSuchMethodError. Different parts of the code simply have separate copies of the classes (Flink’s core or one of its dependencies can use a different copy than the user code or plugin code). In most cases, this works well and no additional configuration from the user is needed.

I have yet to understand why loading ProducerRecord happens more than once, or what this "different type" in the exception message refers to (greping on the result of -verbose:class yielded only a single path for ProducerRecord).

Try this: