Add an 'isConnected' Custom metric to the operators

[Deleted user]

The isConnected custom metric has a special treatment in the cloud. It creates a warning when it has the value 0.

As the Kafka Java API is very high-level, and does not provide connection handling to the user, we could derive the isConnected state from the kafka metric connection-count:

Pseudo code:

isConnected = connection-count > 0? 1: 0;

Care must be taken to avoid a false warning when the producer has not yet produced, or the consumer has not yet assigned partitions. This can happen when the consumer input port is used, or when a pattern subscription is configured, and no topic is matching the pattern.

This issue tracks the implementation of the enhancement in IBMStreams/streamsx.messagehub#93

[Deleted user]

Streams in public cloud is not a priority any more.