(1) When building Flink, Maven sometimes is not able to shade away dependencies well. It is possible that ./build.sh throws errors like:
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.0:compile (default-compile) on project flink-statebackend-rocksdb_2.11: Compilation failure: Compilation failure:
[ERROR] /home/shennig/cepless/flink/flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/ttl/RocksDbTtlCompactFiltersManager.java:[86,24] cannot find symbol
The easiest way to resolve this is to navigate to the corresponding sub-project (in this case flink-statebackend-rocksdb) and issue the maven build command again with: mvn package -DskipTests -Dfast
After this completed successfully the build can be started again in the flink root director with ./build.sh
(2) CEP engine or Kafka producer prints message:
kafka cannot find topic "metadata"
This usually means that either CEP engine or Kafka producer is not able to access the Kafka server. To resolve this, verify that Kafka server and CEP engine/Kafka producer are communicating on the same IP address.