| Interface | Description | 
|---|---|
| MetricsWALSource | 
 Interface of the source that will export metrics about the region server's WAL. 
 | 
| WALActionsListener | 
 Get notification of WAL events. 
 | 
| WALCellCodec.ByteStringCompressor | |
| WALCellCodec.ByteStringUncompressor | 
| Class | Description | 
|---|---|
| AbstractFSWAL<W extends WALProvider.WriterBase> | 
 Implementation of  
WAL to go against FileSystem; i.e. | 
| AbstractFSWAL.WalProps | |
| AbstractProtobufLogWriter | 
 Base class for Protobuf log writer. 
 | 
| AsyncFSWAL | 
 An asynchronous implementation of FSWAL. 
 | 
| AsyncProtobufLogWriter | 
 AsyncWriter for protobuf-based WAL. 
 | 
| AsyncProtobufLogWriter.OutputStreamWrapper | |
| CompressionContext | 
 Context that holds the various dictionaries for compression in WAL. 
 | 
| Compressor | 
 A set of static functions for running our custom WAL compression/decompression. 
 | 
| FSHLog | 
 The default implementation of FSWAL. 
 | 
| FSHLog.RingBufferExceptionHandler | 
 Exception handler to pass the disruptor ringbuffer. 
 | 
| FSHLog.SafePointZigZagLatch | 
 This class is used coordinating two threads holding one thread at a 'safe point' while the
 orchestrating thread does some work that requires the first thread paused: e.g. 
 | 
| FSWALEntry | 
 A WAL Entry for  
AbstractFSWAL implementation. | 
| MetricsWAL | 
 Class used to push numbers about the WAL into the metrics subsystem. 
 | 
| MetricsWALSourceImpl | 
 Class that transitions metrics from MetricsWAL into the metrics subsystem. 
 | 
| ProtobufLogReader | 
 A Protobuf based WAL has the following structure: 
 | 
| ProtobufLogReader.WALHdrContext | |
| ProtobufLogWriter | 
 Writer for protobuf-based WAL. 
 | 
| ReaderBase | |
| RingBufferTruck | 
 A 'truck' to carry a payload across the ring buffer from Handler to WAL. 
 | 
| SecureAsyncProtobufLogWriter | |
| SecureProtobufLogReader | |
| SecureProtobufLogWriter | |
| SecureWALCellCodec | 
 A WALCellCodec that encrypts the WALedits. 
 | 
| SecureWALCellCodec.EncryptedKvDecoder | |
| SecureWALCellCodec.EncryptedKvEncoder | |
| SequenceIdAccounting | 
 Accounting of sequence ids per region and then by column family. 
 | 
| SyncFuture | 
 A Future on a filesystem sync call. 
 | 
| WALCellCodec | 
 Compression in this class is lifted off Compressor/KeyValueCompression. 
 | 
| WALCellCodec.BaosAndCompressor | |
| WALCellCodec.CompressedKvDecoder | |
| WALCellCodec.CompressedKvEncoder | |
| WALCellCodec.EnsureKvEncoder | |
| WALCellCodec.NoneCompressor | |
| WALCellCodec.NoneUncompressor | |
| WALCellCodec.StatelessUncompressor | |
| WALCoprocessorHost | 
 Implements the coprocessor environment and runtime support for coprocessors
 loaded within a  
WAL. | 
| WALCoprocessorHost.WALEnvironment | 
 Encapsulation of the environment of each coprocessor 
 | 
| WALUtil | 
 Helper methods to ease Region Server integration with the Write Ahead Log (WAL). 
 | 
| Enum | Description | 
|---|---|
| CompressionContext.DictionaryIndex | |
| ProtobufLogReader.WALHdrResult | |
| RingBufferTruck.Type | |
| WALActionsListener.RollRequestReason | 
 The reason for the log roll request. 
 | 
| Exception | Description | 
|---|---|
| DamagedWALException | 
 Thrown when a failed append or sync on a WAL. 
 | 
| FailedLogCloseException | 
 Thrown when we fail close of the write-ahead-log file. 
 | 
| FailedSyncBeforeLogCloseException | 
 Thrown when we fail close of the write-ahead-log file. 
 | 
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