...

• preGetOp
• prePut
• preDelete
• preScannerOpen
• postScannerOpen
• preFlush
• preCompact

 Queue Coprocessors

...

Queue Coprocessors

CDAP flow-queue has two coprocessors on HBase region servers.

1. Source: HBaseQueueRegionObserver.java 
   
   • Responsibles for eviction of consumed data
   • Overrides the preFlush and preCompact methods
     • Returns an InternalScanner that will skip over cells that are already processed based on the queue logic
2. Source: DequeueScanObserver.java
   • Responsibles for scan time filtering based on transaction information provided by the client
   • Overrides the preScannerOpen method
     • Returns a RegionScanner that will skip over cells that are not yet committed based on the transaction information