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DAS indexer is implemented using Apache Lucene which is a full text search library. Users can index records and search for records later via Lucene queries. Events received by DAS are converted to a list of records and inserted into FileSystem based queues. These queues are created in <DAS_HOME>/repository/data/index_staging_queues directory. With a background thread, these queues are consumed and records are indexed. The indexed data is stored in the <DAS_HOME>/repository/data/index_data directory. The DAS index consists of smaller indexes known as shards. A shard can be accessed nly by one index writer at a given time. (Index writer is the lucene class visible to outside world which is that is used to write lucene documents to a file system based index).Therefore having multiple shards can increase the write throughput (however, the write throughput can be limited by Disk IO operations). By default, DAS is configured to have six shards and one replica.
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