Pulsar Terminology

    Pulsar

    Pulsar is a distributed messaging system originally created by Yahoo but now under the stewardship of the Apache Software Foundation.

    Message

    Messages are the basic unit of Pulsar. They're what producers publish to and what consumers then consume from topics.

    Topic

    A named channel used to pass messages published by producers to whoprocess those messages.

    Partitioned Topic

    A topic that is served by multiple Pulsar brokers, which enables higher throughput.

    Namespace

    A grouping mechanism for related topics.

    Namespace Bundle

    A virtual group of topics that belong to the same . A namespace bundleis defined as a range between two 32-bit hashes, such as 0x00000000 and 0xffffffff.

    Tenant

    An administrative unit for allocating capacity and enforcing an authentication/authorization scheme.

    Subscription

    A lease on a topic established by a group of . Pulsar has three subscriptionmodes (exclusive, shared, and failover).

    Pub-Sub

    A messaging pattern in which proccesses publish messages on topics thatare then consumed (processed) by processes.

    Producer

    Consumer

    A process that establishes a subscription to a Pulsar topic and processes messages publishedto that topic by .

    Reader

    Pulsar readers are message processors much like Pulsar but with two crucial differences:

    • you can specify where on a topic readers begin processing messages (consumers always begin with the latestavailable unacked message);

    Cursor

    The subscription position for a .

    Acknowledgment (ack)

    A message sent to a Pulsar broker by a that a message has been successfully processed.An acknowledgement (ack) is Pulsar's way of knowing that the message can be deleted from the system;if no acknowledgement, then the message will be retained until it's processed.

    Negative Acknowledgment (nack)

    When an application fails to process a particular message, it can sends a "negative ack" to Pulsarto signal that the message should be replayed at a later timer. (By default, failed messages arereplayed after a 1 minute delay)

    Unacknowledged

    A message that has been delivered to a consumer for processing but not yet confirmed as processed by the consumer.

    Retention Policy

    Size and/or time limits that you can set on a to configure retention of messagesthat have already been .

    Multi-Tenancy

    The ability to isolate , specify quotas, and configure authentication and authorizationon a per-tenant basis.

    Standalone

    A lightweight Pulsar broker in which all components run in a single Java Virtual Machine (JVM) process. Standaloneclusters can be run on a single machine and are useful for development purposes.

    Cluster

    Instance

    A group of Pulsar clusters that act together as a single unit.

    Geo-Replication

    Replication of messages across Pulsar clusters, potentially in different datacentersor geographical regions.

    Configuration Store

    Pulsar's configuration store (previously known as configuration store) is a ZooKeeper quorum thatis used for configuration-specific tasks. A multi-cluster Pulsar installation requires just oneconfiguration store across all clusters.

    Topic Lookup

    A service provided by Pulsar brokers that enables connecting clients to automatically determinewhich Pulsar is responsible for a topic (and thus where message traffic forthe topic needs to be routed).

    Service Discovery

    A mechanism provided by Pulsar that enables connecting clients to use just a single URL to interactwith all the brokers in a .

    Broker

    A stateless component of Pulsar that runs two other components: an HTTP serverexposing a REST interface for administration and topic lookup and a dispatcher thathandles all message transfers. Pulsar clusters typically consist of multiple brokers.

    Dispatcher

    An asynchronous TCP server used for all data transfers in-and-out a Pulsar broker. The Pulsardispatcher uses a custom binary protocol for all communications.

    BookKeeper

    Apache BookKeeper is a scalable, low-latency persistent log storageservice that Pulsar uses to store data.

    Bookie

    Bookie is the name of an individual BookKeeper server. It is effectively the storage server of Pulsar.

    Ledger

    Pulsar Functions are lightweight functions that can consume messages from Pulsar topics, apply custom processing logic, and, if desired, publish results to topics.