2013-05-07 16:53:12 -04:00
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## Introduction
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Druid can use Cassandra as a deep storage mechanism. Segments and their metadata are stored in Cassandra in two tables:
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`index_storage` and `descriptor_storage`. Underneath the hood, the Cassandra integration leverages Astyanax. The
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index storage table is a [Chunked Object](https://github.com/Netflix/astyanax/wiki/Chunked-Object-Store) repository. It contains
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2013-05-16 13:04:46 -04:00
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compressed segments for distribution to compute nodes. Since segments can be large, the Chunked Object storage allows the integration to multi-thread
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the write to Cassandra, and spreads the data across all the nodes in a cluster. The descriptor storage table is a normal C* table that
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stores the segment metadatak.
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## Schema
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Below are the create statements for each:
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CREATE TABLE index_storage ( key text, chunk text, value blob, PRIMARY KEY (key, chunk)) WITH COMPACT STORAGE;
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CREATE TABLE descriptor_storage ( key varchar, lastModified timestamp, descriptor varchar, PRIMARY KEY (key) ) WITH COMPACT STORAGE;
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## Getting Started
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First create the schema above. (I use a new keyspace called `druid`)
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Then, add the following properties to your properties file to enable a Cassandra
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backend.
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druid.pusher.cassandra=true
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druid.pusher.cassandra.host=localhost:9160
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druid.pusher.cassandra.keyspace=druid
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Use the `druid-development@googlegroups.com` mailing list if you have questions,
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or feel free to reach out directly: `bone@alumni.brown.edu`.
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