Apache Pulsar: Distributed Pub-Sub Messaging System

Apache Pulsar is an open-source distributed pub-sub messaging system originally created at Yahoo and part of the Apache Software Foundation. Pulsar is a mult...

Furkan Kamaci

Jan. 27, 18 · Big Data Zone · Tutorial

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Apache Pulsar is an open-source distributed pub-sub messaging system originally created at Yahoo! that is part of the Apache Software Foundation.

Pulsar is a multi-tenant, high-performance solution for server-to-server messaging.

Pulsar's key features include:

Native support for multiple clusters in a Pulsar instance, with seamless geo-replication of messages across clusters
Very low publish and end-to-end latency
Seamless scalability out to over a million topics
A simple client API with bindings for Java, Python, and C++
Multiple subscription modes for topics (exclusive, shared, and failover)
Guaranteed message delivery with persistent message storage provided by Apache BookKeeper

Architecture Overview

At the highest level, a Pulsar instance is composed of one or more Pulsar clusters. Clusters within an instance can replicate data amongst themselves.

The diagram below provides an illustration of a Pulsar cluster:

Pulsar Comparison With Apache Kafka

The table below lists the similarities and differences between Apache Pulsar and Apache Kafka:

	Kafka	Pulsar
Concepts	Producer-topic-consumer group-consumer	Producer-topic-subscription-consumer
Consumption	More focused on streaming, exclusive messaging on partitions. No shared consumption.	Unified messaging model and API. Streaming via exclusive, failover subscription Queuing via shared subscription
Acking	Simple offset management Prior to Kafka 0.8, offsets are stored in ZooKeeper After Kafka 0.8, offsets are stored on offset topics	Unified messaging model and API. Streaming via exclusive, failover subscription Queuing via shared subscription
Retention	Messages are deleted based on retention. If a consumer doesn’t read messages before retention period, it will lose data.	Messages are only deleted after all subscriptions consumed them. No data loss even the consumers of a subscription are down for a long time. Messages are allowed to keep for a configured retention period time even after all subscriptions consume them.
TTL	No TTL support	Supports message TTL

Conclusion

Apache Pulsar is an effort undergoing incubation at The Apache Software Foundation (ASF) sponsored by the Apache Incubator PMC. It seems that it will be a competitive alternative to Apache Kafka due to its unique features.

References

Topics:

big data, apache pulsar, tutorial, pub-sub, architecture

Published at DZone with permission of Furkan Kamaci, DZone MVB. See the original article here.

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