Interface StagedSnapshotCapability

All Superinterfaces:

LogCapability

public interface StagedSnapshotCapability
extends LogCapability

A log capability that allows snapshot creation in two phases: staging and committing.

The caller writes snapshot data to the OutputStream returned by stage(), then atomically promotes it with commit(OutputStream).

Since:

2.0

Author:

José Bolina

Method Summary

Modifier and Type	Method	Description
void	commit(OutputStream staged)	Atomically installs a previously staged snapshot as the active snapshot.
OutputStream	stage()	Creates a new staging area for a snapshot and returns a stream to write into it.

Method Details

stage

OutputStream stage()
            throws IOException

Creates a new staging area for a snapshot and returns a stream to write into it.

The returned stream must be closed before calling commit(OutputStream). Closing the stream flushes all data to durable storage.

Returns:

an output stream for writing snapshot data

Throws:

IOException - if the staging area cannot be created

commit

void commit(OutputStream staged)
     throws IOException

Atomically installs a previously staged snapshot as the active snapshot.

Must be called from the RAFT event loop.

Parameters:

staged - the stream previously returned by stage(), already closed

Throws:

IOException - if the snapshot cannot be installed