聊聊rocketmq的QueryMessageProcessor

public interface NettyRequestProcessor {
    RemotingCommand processRequest(ChannelHandlerContext ctx, RemotingCommand request)
        throws Exception;

    boolean rejectRequest();
}

public class QueryMessageProcessor implements NettyRequestProcessor {
    private static final InternalLogger log = InternalLoggerFactory.getLogger(LoggerName.BROKER_LOGGER_NAME);

    private final BrokerController brokerController;

    public QueryMessageProcessor(final BrokerController brokerController) {
        this.brokerController = brokerController;
    }

    @Override
    public RemotingCommand processRequest(ChannelHandlerContext ctx, RemotingCommand request)
        throws RemotingCommandException {
        switch (request.getCode()) {
            case RequestCode.QUERY_MESSAGE:
                return this.queryMessage(ctx, request);
            case RequestCode.VIEW_MESSAGE_BY_ID:
                return this.viewMessageById(ctx, request);
            default:
                break;
        }

        return null;
    }

    @Override
    public boolean rejectRequest() {
        return false;
    }

    //......
}

public class QueryMessageProcessor implements NettyRequestProcessor {

    //......

    public RemotingCommand queryMessage(ChannelHandlerContext ctx, RemotingCommand request)
        throws RemotingCommandException {
        final RemotingCommand response =
            RemotingCommand.createResponseCommand(QueryMessageResponseHeader.class);
        final QueryMessageResponseHeader responseHeader =
            (QueryMessageResponseHeader) response.readCustomHeader();
        final QueryMessageRequestHeader requestHeader =
            (QueryMessageRequestHeader) request
                .decodeCommandCustomHeader(QueryMessageRequestHeader.class);

        response.setOpaque(request.getOpaque());

        String isUniqueKey = request.getExtFields().get(MixAll.UNIQUE_MSG_QUERY_FLAG);
        if (isUniqueKey != null && isUniqueKey.equals("true")) {
            requestHeader.setMaxNum(this.brokerController.getMessageStoreConfig().getDefaultQueryMaxNum());
        }

        final QueryMessageResult queryMessageResult =
            this.brokerController.getMessageStore().queryMessage(requestHeader.getTopic(),
                requestHeader.getKey(), requestHeader.getMaxNum(), requestHeader.getBeginTimestamp(),
                requestHeader.getEndTimestamp());
        assert queryMessageResult != null;

        responseHeader.setIndexLastUpdatePhyoffset(queryMessageResult.getIndexLastUpdatePhyoffset());
        responseHeader.setIndexLastUpdateTimestamp(queryMessageResult.getIndexLastUpdateTimestamp());

        if (queryMessageResult.getBufferTotalSize() > 0) {
            response.setCode(ResponseCode.SUCCESS);
            response.setRemark(null);

            try {
                FileRegion fileRegion =
                    new QueryMessageTransfer(response.encodeHeader(queryMessageResult
                        .getBufferTotalSize()), queryMessageResult);
                ctx.channel().writeAndFlush(fileRegion).addListener(new ChannelFutureListener() {
                    @Override
                    public void operationComplete(ChannelFuture future) throws Exception {
                        queryMessageResult.release();
                        if (!future.isSuccess()) {
                            log.error("transfer query message by page cache failed, ", future.cause());
                        }
                    }
                });
            } catch (Throwable e) {
                log.error("", e);
                queryMessageResult.release();
            }

            return null;
        }

        response.setCode(ResponseCode.QUERY_NOT_FOUND);
        response.setRemark("can not find message, maybe time range not correct");
        return response;
    }

    //......
}

public class QueryMessageProcessor implements NettyRequestProcessor {

    //......

    public RemotingCommand viewMessageById(ChannelHandlerContext ctx, RemotingCommand request)
        throws RemotingCommandException {
        final RemotingCommand response = RemotingCommand.createResponseCommand(null);
        final ViewMessageRequestHeader requestHeader =
            (ViewMessageRequestHeader) request.decodeCommandCustomHeader(ViewMessageRequestHeader.class);

        response.setOpaque(request.getOpaque());

        final SelectMappedBufferResult selectMappedBufferResult =
            this.brokerController.getMessageStore().selectOneMessageByOffset(requestHeader.getOffset());
        if (selectMappedBufferResult != null) {
            response.setCode(ResponseCode.SUCCESS);
            response.setRemark(null);

            try {
                FileRegion fileRegion =
                    new OneMessageTransfer(response.encodeHeader(selectMappedBufferResult.getSize()),
                        selectMappedBufferResult);
                ctx.channel().writeAndFlush(fileRegion).addListener(new ChannelFutureListener() {
                    @Override
                    public void operationComplete(ChannelFuture future) throws Exception {
                        selectMappedBufferResult.release();
                        if (!future.isSuccess()) {
                            log.error("Transfer one message from page cache failed, ", future.cause());
                        }
                    }
                });
            } catch (Throwable e) {
                log.error("", e);
                selectMappedBufferResult.release();
            }

            return null;
        } else {
            response.setCode(ResponseCode.SYSTEM_ERROR);
            response.setRemark("can not find message by the offset, " + requestHeader.getOffset());
        }

        return response;
    }

    //......
}