Pulsar

Pulsar 是一个分布式消息系统，最初由 Yahoo 创建，现在是 Apache 软件基金会的一个孵化器项目。

消息

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

Topic

A named channel used to pass messages published by to consumers who process those .

Partitioned Topic

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

Namespace

A grouping mechanism for related .

Namespace Bundle

A virtual group of that belong to the same namespace. A namespace bundle is 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 established by a group of consumers. Pulsar has three subscription modes (exclusive, shared, and failover).

Pub-Sub

A messaging pattern in which producer proccesses publish messages on that are then consumed (processed) by consumer processes.

Producer

Consumer

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

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

The subscription position for a consumer.

Acknowledgment (ack)

A message sent to a Pulsar broker by a consumer 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 Pulsar to signal that the message should be replayed at a later timer. (By default, failed messages are replayed 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 namespace to configure retention of that have already been acknowledged.

Multi-Tenancy

The ability to isolate namespaces, specify quotas, and configure authentication and authorization on a per- basis.

Standalone

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.

Cluster

Instance

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

Geo-Replication

Replication of messages across Pulsar , potentially in different datacenters or geographical regions.

Configuration Store

Pulsar’s configuration store (previously known as configuration store) is a ZooKeeper quorum that is used for configuration-specific tasks. A multi-cluster Pulsar installation requires just one configuration store across all .

Topic Lookup

A service provided by Pulsar that enables connecting clients to automatically determine which Pulsar cluster is responsible for a (and thus where message traffic for the topic needs to be routed).

Service Discovery

A mechanism provided by Pulsar that enables connecting clients to use just a single URL to interact with all the in a cluster.

Broker

A stateless component of Pulsar clusters that runs two other components: an HTTP server exposing a REST interface for administration and topic lookup and a that handles 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 . The Pulsar dispatcher uses a custom binary protocol for all communications.

BookKeeper

is a scalable, low-latency persistent log storage service 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.