NewClient creates a new pulsar client.

NewNackBackoffPolicy creates a new NackBackoffPolicy or returns an error if the parameters are invalid.

maxDeliveryAttempts before sending to DLQ - 0 means no DLQ by default, maxDeliveryAttempts is 5.

topic persistency prefix.

NackBackoffPolicy implements pulsar's NackBackoffPolicy interface NackBackoffPolicy is a redelivery backoff mechanism which we can achieve redelivery with different delays according to the number of times the message is retried.