Apache Kafka listeners
Charmed Apache Kafka comes with a set of listeners that can be enabled for inter- and intra-cluster communication.
Internal listeners are used for internal traffic and exchange of information between Apache Kafka brokers, whereas external listeners are used for external clients to be optionally enabled based on the relations created on particular charm endpoints. Each listener is characterized by a specific port, scope and protocol.
In the following table, we summarize the protocols, the port and
the relation that each listener is bound to. Note that based on whether a certificates
relation is present, one of two mutually exclusive types of listeners can be
opened.
| Listener name | Driving endpoints | Protocol | Port | Scope |
|---|---|---|---|---|
| SASL_INTERNAL | cluster |
SASL_PLAINTEXT | 19092 |
internal |
| SASL_INTERNAL | cluster + certificates |
SASL_SSL | 19093 |
internal |
| SASL_EXTERNAL | kafka-client |
SASL_PLAINTEXT | 9092 |
external |
| SASL_EXTERNAL | kafka-client + certificates |
SASL_SSL | 9093 |
external |
| SSL_EXTERNAL | trusted-certificate + certificates |
SSL | 9094 |
external |
| SSL_EXTERNAL | trusted-ca + certificates |
SSL | 9094 |
external |
Since cluster is a peer relation, the SASL_INTERNAL listener is always enabled.