| `KAFKA_BROKER` | **Yes** | The address of the Kafka broker. | `127.0.0.1:29092` |
| `KAFKA_CONCURRENCY` | **Yes** | The concurrency of the Kafka connection. | `3` |
| `KAFKA_SSL` | No | Whether an SSL connection should be established to the kafka service. | `1` (enabled) or `0` (disabled) |
| `KAFKA_SSL_CA_PATH` | No | Refer to [TLS create secure context](https://nodejs.org/dist/latest-v8.x/docs/api/tls.html#tls_tls_createsecurecontext_options) for more information | `./path_to_ca` |
| `KAFKA_SSL_CERT_PATH` | No | Refer to [TLS create secure context](https://nodejs.org/dist/latest-v8.x/docs/api/tls.html#tls_tls_createsecurecontext_options) for more information | `./path_to_cert` |
| `KAFKA_SSL_KEY_PATH` | No | Refer to [TLS create secure context](https://nodejs.org/dist/latest-v8.x/docs/api/tls.html#tls_tls_createsecurecontext_options) for more information | `./path_to_key` |
| `KAFKA_SASL_MECHANISM` | No | The mechanism used for doing SASL authentication | `plain` or `scram-sha-256` or `scram-sha-512` |
| `KAFKA_SASL_USERNAME` | No (Yes, if `KAFKA_SASL_MECHANISM` is defined) | The username for the SASL authentication | `letmein` |
| `KAFKA_SASL_PASSWORD` | No (Yes, if `KAFKA_SASL_MECHANISM` is defined) | Whether an SSL connection should be established to the kafka service. | `letmein` |
| `CLICKHOUSE_PROTOCOL` | **Yes** | The ClickHouse protocol. | `http` or `https` |