Package com.bigdata.io.writecache

Low-level write cache service.

See: Description

Interface Summary

Interface	Description
IBackingReader	A backing reader can be provided to a WriteCacheService which can use the readRaw callback method as part of an encapsulated caching strategy.
IBufferedWriter
IWriteCache	Interface for a write cache with read back and the capability to update records while they are still in the cache.
IWriteCacheCounters	Interface declaring the counters exposed by the WriteCache.
IWriteCacheServiceCounters	Interface declaring the counters exposed by the WriteCacheService .

Class Summary

Class	Description
BufferedWrite	The BufferedWrite merges/elides sorted scattered writes to minimize IO requests and maximize IO rates.
TestAll	Aggregates test suites in increasing dependency order.
TestRWWriteCacheService	Test suite for the WriteCacheService using scattered writes on a backing file.
TestWORMWriteCacheService	Test suite for the WriteCacheService using pure append writes.
TestWriteCache	Test suite for the WriteCache.
TestWriteCacheServiceLifetime	These tests exercise the lifetime semantics of a WriteCacheService.
WriteCache	This class provides a write cache with read-through for NIO writes on a FileChannel (and potentially on a remote service).
WriteCache.FileChannelScatteredWriteCache	The scattered write cache is used by the RWStore since the writes can be made to any part of the file assigned for data allocation.
WriteCache.FileChannelWriteCache	A WriteCache implementation suitable for an append-only file such as the WORMStrategy or the output file of the IndexSegmentBuilder.
WriteCache.HAPackage	Used to retrieve the HAWriteMessage AND the associated ByteBuffer.
WriteCache.ReadCache
WriteCache.RecordMetadata	The metadata associated with a record in the WriteCache.
WriteCacheCounters	Performance counters for the WriteCache.
WriteCacheService	A WriteCacheService is provisioned with some number of WriteCache buffers and a writer thread.
WriteCacheServiceCounters	Performance counters for the WriteCacheService.

Exception Summary

Exception	Description
WriteCacheService.AsynchronousCloseException	An instance of this exception is thrown if a thread notices that the WriteCacheService was closed by a concurrent process.

Package com.bigdata.io.writecache Description

Low-level write cache service. Application writes are absorbed on records destined for some byte offset on the backing persistent store. Those records are transferred into a write cache rather than writing them directly onto the backing file. The write cache service provides an abstraction supporting one or more write cache blocks so the application can write ahead of the disk. The write cache itself consists of a record map, which specifies where each record will be written onto the backing file, and a large direct ByteBuffer, which contains the raw data to be written onto the file. For the RW store, those records will be scattered. For the WORM, they will be appended (and the record map is ignored). The write cache coordinates with the journal to provide per- record checksums.

The write cache is also the basis for replicated writes in support of high availability. The entire write cache is check summed and transfered using NIO to each service in a highly available quorum.