| # Apache Aries Journaled events |
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| [](https://builds.apache.org/job/Aries-journaled-events/) |
| [](https://travis-ci.org/apache/aries-journaled-events) |
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| This subproject provides an API (possibly as spec) and backends for journaled streams of events. These extend the publish/subscribe model with means to start consume from an point in the stored event stream history. |
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| ## Goals |
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| * Provide traditional publish / subscribe semantics |
| * Allow consuming a stream from any point in the history (given it is not yet evicted) |
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| ## Non goals (to be discussed) |
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| * No coverage of extreme scaling like Apache Kafka. So no sharding support in the API (like partitions). |
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| ## Requirements |
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| * Messages sent to a topic must be journaled and must be available to all consumers |
| * Consumers must be able to start consuming messages from any point in the history that is still available |
| * If a consumer specifies a position that is not available anymore then it must start with the oldest message |
| * Each consumer must receive messages in the same order they were sent |
| * The journal of each topic may evict messages that are older than a certain retention time |
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