public class MultiStreamStateHandle extends Object implements StreamStateHandle
StreamStateHandle
and makes them look like a single one. This is done by
providing a contiguous view on all the streams of the inner handles through a wrapper stream and by summing up all
all the meta data.Constructor and Description |
---|
MultiStreamStateHandle(List<StreamStateHandle> stateHandles) |
Modifier and Type | Method and Description |
---|---|
void |
discardState()
Discards the state referred to and solemnly owned by this handle, to free up resources in
the persistent storage.
|
long |
getStateSize()
Returns the size of the state in bytes.
|
FSDataInputStream |
openInputStream()
Returns an
FSDataInputStream that can be used to read back the data that
was previously written to the stream. |
String |
toString() |
public MultiStreamStateHandle(List<StreamStateHandle> stateHandles)
public FSDataInputStream openInputStream() throws IOException
StreamStateHandle
FSDataInputStream
that can be used to read back the data that
was previously written to the stream.openInputStream
in interface StreamStateHandle
IOException
public void discardState() throws Exception
StateObject
discardState
in interface StateObject
Exception
public long getStateSize()
StateObject
0
.
The values produced by this method are only used for informational purposes and for metrics/monitoring. If this method returns wrong values, the checkpoints and recovery will still behave correctly. However, efficiency may be impacted (wrong space pre-allocation) and functionality that depends on metrics (like monitoring) will be impacted.
Note for implementors: This method should not perform any I/O operations
while obtaining the state size (hence it does not declare throwing an IOException
).
Instead, the state size should be stored in the state object, or should be computable from
the state stored in this object.
The reason is that this method is called frequently by several parts of the checkpointing
and issuing I/O requests from this method accumulates a heavy I/O load on the storage
system at higher scale.
getStateSize
in interface StateObject
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