Details
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New Feature
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Status: Resolved
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Major
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Resolution: Implemented
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Description
The TopicStream is a publish/subscribe messaging service built on top of SolrCloud. The TopicStream returns all new documents for a specific query. Version numbers will be used as checkpoints for Topics to ensure single delivery of each document. When combined with the DaemonStream (SOLR-8550), Topics can provide continuous streaming. Sample syntax:
topic(checkpointCollection, dataCollection, id="topicA", q="awesome stuff" checkpointEvery="1000")
The checkpoint collection will be used to persist the topic checkpoints.
Example combined with the DaemonStream:
daemon(topic(...)...)
When combined with SOLR-7739 this allows for messaging based on machine learned classifications.
The TopicStream supports 3 models of publish/subscribe messaging:
1) Request & response: In this model a topic(...) expression can be saved and executed at any time. In this scenario the TopicStream will always retrieve it's checkpoints and start from where it left off.
2) Continuous pull streaming: In this model you would wrap the TopicStream in a DaemonStream and call read() in a loop inside a java program. This would provide a continuous stream of new content as it arrives in the index.
3) Continuous push streaming: In this model you would send an expression like this to the /stream handler: daemon(update(topic(...)...)...). This daemon process would run inside Solr and continuously stream new documents from the topic and push them to another SolrCloud collection. Other pushing expressions can be created to push documents in different ways or take other types of actions.
