Pulsar Terminology
Here is a glossary of terms related to Apache Pulsar:
Concepts​
Pulsar​
Pulsar is a distributed messaging system originally created by Yahoo but now under the stewardship of the Apache Software Foundation.
Namespace Bundle​
Namespace bundle is a virtual group of topics that belong to the same namespace. A namespace bundle is defined as a range between two 32-bit hashes, such as 0x00000000 and 0xffffffff.
Namespace​
Namespace is a virtual grouping of topics, under a specific
tenant. A namespace is defined
by a string name, such as my-tenant/my-namespace.
Pub-Sub​
Pub-sub is a messaging pattern in which producer processes publish messages on topics that are then consumed (processed) by consumer processes.
Reader​
Pulsar readers are message processors much like Pulsar consumers but with two crucial differences:
- you can specify where on a topic readers begin processing messages (consumers always begin with the latest available unacked message);
- readers don't retain data or acknowledge messages.
Cursor​
Cursor is the subscription position for a consumer.
Unacknowledged​
Unacknowledged means a message that has been delivered to a consumer for processing but not yet confirmed as processed by the consumer.
Retention Policy​
Retention policy is the size and time limits that you can set on a namespace to configure retention of messages that have already been acknowledged.
Multi-Tenancy​
Multi-tenancy is the ability to isolate namespaces, specify quotas, and configure authentication and authorization on a per-tenant basis.
Failure Domain​
Failure domain is a logical domain under a Pulsar cluster. Each logical domain contains a pre-configured list of brokers.
Anti-Affinity Namespaces​
Anti-affinity namespaces are a group of namespaces that have anti-affinity to each other.
Architecture​
Standalone​
Standalone is a lightweight Pulsar broker in which all components run in a single Java Virtual Machine (JVM) process. Standalone clusters can be run on a single machine and are useful for development purposes.
Topic Lookup​
Topic lookup is a service provided by Pulsar brokers that enables connecting clients to automatically determine which Pulsar cluster is responsible for a topic (and thus where message traffic for the topic needs to be routed).
Dispatcher​
Dispatcher is an asynchronous TCP server used for all data transfers in and out of a Pulsar broker. The Pulsar dispatcher uses a custom binary protocol for all communications.
Broker​
Broker is a Pulsar server that receives, acknowledges, and delivers messages to consumers. A Pulsar cluster can have one or more brokers.
Storage​
Bookie​
Bookie is the name of an individual BookKeeper server. It is effectively the storage server of Pulsar.