@Override
    public void appendFrom(ReadableByteChannel channel, long size) throws StoreException {
      ByteBuffer buf = ByteBuffer.allocate((int) size);
      int sizeRead = 0;
      try {
        while (sizeRead < size) {
          sizeRead += channel.read(buf);
        }
      } catch (IOException e) {
        StoreErrorCodes errorCode = StoreException.resolveErrorCode(e);
        throw new StoreException(errorCode.toString() + " while writing into dummy log", e, errorCode);
      }
      buf.flip();
      storeBuf(buf);
    }
Log that stores all data in memory.
ambry-replication/src/test/java/com/github/ambry/replication/InMemoryStore.java