BlockInfo
= BlockInfo
BlockInfo is a metadata of storage:BlockId.md[memory block] -- the memory block's <
BlockInfo has a storage:StorageLevel.md[], ClassTag and tellMaster flag.
== [[size]] Size
size attribute is the size of the memory block. It starts with 0.
It represents the number of bytes that storage:BlockManager.md#putBytes[BlockManager saved] or storage:BlockManager.md#doPutIterator[BlockManager.doPutIterator].
== [[readerCount]] Reader Count -- readerCount Counter
readerCount counter is the number of readers of the memory block, i.e. the number of read locks. It starts with 0.
readerCount is incremented when a storage:BlockInfoManager.md#lockForReading[read lock is acquired] and decreases when the following happens:
-
The storage:BlockManager.md#unlock[memory block is unlocked]
-
storage:BlockInfoManager.md#releaseAllLocksForTask[All locks for the memory block obtained by a task are released].
-
storage:BlockInfoManager.md#removeBlock[memory block is removed]
-
storage:BlockInfoManager.md#clear[Clearing the current state of
BlockInfoManager].
== [[writerTask]] Writer Task -- writerTask Attribute
writerTask attribute is the task that owns the write lock for the memory block.
A writer task can be one of the three possible identifiers:
-
[[NO_WRITER]]
NO_WRITER(i.e.-1) to denote no writers and hence no write lock in use. -
[[NON_TASK_WRITER]]
NON_TASK_WRITER(i.e.-1024) for non-task threads, e.g. by a driver thread or by unit test code. -
the task attempt id of the task which currently holds the write lock for this block.
The writer task is assigned in the following scenarios:
-
A storage:BlockInfoManager.md#lockForWriting[write lock is requested for a memory block (with no writer and readers)]
-
A storage:BlockInfoManager.md#unlock[memory block is unlocked]
-
storage:BlockInfoManager.md#releaseAllLocksForTask[All locks obtained by a task are released]
-
A storage:BlockInfoManager.md#removeBlock[memory block is removed]
-
storage:BlockInfoManager.md#clear[Clearing the current state of
BlockInfoManager].