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DiskBlockObjectWriter is a custom that BlockManager offers for writing data blocks to disk.

DiskBlockObjectWriter is used when:

Creating Instance

DiskBlockObjectWriter takes the following to be created:

DiskBlockObjectWriter is created when:

  • BlockManager is requested for one


DiskBlockObjectWriter manages a SerializationStream for writing a key-value record:


DiskBlockObjectWriter can be in one of the following states (that match the state of the underlying output streams):

  • Initialized
  • Open
  • Closed

Writing Out Record

  key: Any,
  value: Any): Unit

write opens the underlying stream unless open already.

write requests the SerializationStream to write the key and then the value.

In the end, write updates the write metrics.

write is used when:


commitAndGet(): FileSegment


commitAndGet is used when...FIXME

Committing Writes and Closing Resources

close(): Unit


close is used when...FIXME


revertPartialWritesAndClose(): File


revertPartialWritesAndClose is used when...FIXME

Writing Bytes (From Byte Array Starting From Offset)

  kvBytes: Array[Byte],
  offs: Int,
  len: Int): Unit


write is used when...FIXME

Opening DiskBlockObjectWriter

open(): DiskBlockObjectWriter

open opens the DiskBlockObjectWriter, i.e. initializes and re-sets bs and objOut internal output streams.

Internally, open makes sure that DiskBlockObjectWriter is not closed (hasBeenClosed flag is disabled). If it was, open throws a IllegalStateException:

Writer already closed. Cannot be reopened.

Unless DiskBlockObjectWriter has already been initialized (initialized flag is enabled), open initializes it (and turns initialized flag on).

Regardless of whether DiskBlockObjectWriter was already initialized or not, open requests SerializerManager to wrap mcs output stream for encryption and compression (for blockId) and sets it as bs.

open requests the SerializerInstance to serialize bs output stream and sets it as objOut.


open uses the SerializerInstance that was used to create the DiskBlockObjectWriter.

In the end, open turns streamOpen flag on.

open is used when DiskBlockObjectWriter writes out a record or bytes from a specified byte array and the stream is not open yet.

Internal Properties

initialized Flag

hasBeenClosed Flag