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前言
数据格式与接入
统计站点指标
商品Top N
The End
阿里的双11销量大屏可以说是一道特殊的风景线。实时大屏(real-time dashboard)正在被越来越多的企业采用,用来及时呈现关键的数据指标。并且在实际操作中,肯定也不会仅仅计算一两个维度。由于Flink的“真·流式计算”这一特点,它比Spark Streaming要更适合大屏应用。本文从笔者的实际工作经验抽象出简单的模型,并简要叙述计算流程(当然大部分都是源码)。
简化的子订单消息体如下。
- {
- "userId": 234567,
- "orderId": 2902306918400,
- "subOrderId": 2902306918401,
- "siteId": 10219,
- "siteName": "site_blabla",
- "cityId": 101,
- "cityName": "北京市",
- "warehouseId": 636,
- "merchandiseId": 187699,
- "price": 299,
- "quantity": 2,
- "orderStatus": 1,
- "isNewOrder": 0,
- "timestamp": 1572963672217
- }
由于订单可能会包含多种商品,故会被拆分成子订单来表示,每条JSON消息表示一个子订单。现在要按照自然日来统计以下指标,并以1秒的刷新频率呈现在大屏上:
每个站点(站点ID即siteId)的总订单数、子订单数、销量与GMV;
当前销量排名前N的商品(商品ID即merchandiseId)与它们的销量。
由于大屏的最大诉求是实时性,等待迟到数据显然不太现实,因此我们采用处理时间作为时间特征,并以1分钟的频率做checkpointing。
- StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
- env.setStreamTimeCharacteristic(TimeCharacteristic.ProcessingTime);
- env.enableCheckpointing(60 * 1000, CheckpointingMode.EXACTLY_ONCE);
- env.getCheckpointConfig().setCheckpointTimeout(30 * 1000);
然后订阅Kafka的订单消息作为数据源。
- Properties consumerProps = ParameterUtil.getFromResourceFile("kafka.properties");
- DataStream<String> sourceStream = env
- .addSource(new FlinkKafkaConsumer011<>(
- ORDER_EXT_TOPIC_NAME, // topic
- new SimpleStringSchema(), // deserializer
- consumerProps // consumer properties
- ))
- .setParallelism(PARTITION_COUNT)
- .name("source_kafka_" + ORDER_EXT_TOPIC_NAME)
- .uid("source_kafka_" + ORDER_EXT_TOPIC_NAME);
给带状态的算子设定算子ID(通过调用uid()方法)是个好习惯,能够保证Flink应用从保存点重启时能够正确恢复状态现场。为了尽量稳妥,Flink官方也建议为每个算子都显式地设定ID,参考:https://ci.apache.org/projects/flink/flink-docs-stable/ops/state/savepoints.html#should-i-assign-ids-to-all-operators-in-my-job
接下来将JSON数据转化为POJO,JSON框架采用FastJSON。
- DataStream<SubOrderDetail> orderStream = sourceStream
- .map(message -> JSON.parseObject(message, SubOrderDetail.class))
- .name("map_sub_order_detail").uid("map_sub_order_detail");
JSON已经是预先处理好的标准化格式,所以POJO类SubOrderDetail的写法可以通过Lombok极大地简化。如果JSON的字段有不规范的,那么就需要手写Getter和Setter,并用@JSONField注解来指明。
- @Getter
- @Setter
- @NoArgsConstructor
- @AllArgsConstructor
- @ToString
- publicclass SubOrderDetail implements Serializable {
- privatestaticfinallong serialVersionUID = 1L;
-
- privatelong userId;
- privatelong orderId;
- privatelong subOrderId;
- privatelong siteId;
- private String siteName;
- privatelong cityId;
- private String cityName;
- privatelong warehouseId;
- privatelong merchandiseId;
- privatelong price;
- privatelong quantity;
- privateint orderStatus;
- privateint isNewOrder;
- privatelong timestamp;
- }
将子订单流按站点ID分组,开1天的滚动窗口,并同时设定ContinuousProcessingTimeTrigger触发器,以1秒周期触发计算。注意处理时间的时区问题,这是老生常谈了。
- WindowedStream<SubOrderDetail, Tuple, TimeWindow> siteDayWindowStream = orderStream
- .keyBy("siteId")
- .window(TumblingProcessingTimeWindows.of(Time.days(1), Time.hours(-8)))
- .trigger(ContinuousProcessingTimeTrigger.of(Time.seconds(1)));
接下来写个聚合函数。
- DataStream<OrderAccumulator> siteAggStream = siteDayWindowStream
- .aggregate(new OrderAndGmvAggregateFunc())
- .name("aggregate_site_order_gmv").uid("aggregate_site_order_gmv");
- publicstaticfinalclass OrderAndGmvAggregateFunc
- implements AggregateFunction<SubOrderDetail, OrderAccumulator, OrderAccumulator> {
- privatestaticfinallong serialVersionUID = 1L;
-
- @Override
- public OrderAccumulator createAccumulator() {
- returnnew OrderAccumulator();
- }
-
- @Override
- public OrderAccumulator add(SubOrderDetail record, OrderAccumulator acc) {
- if (acc.getSiteId() == 0) {
- acc.setSiteId(record.getSiteId());
- acc.setSiteName(record.getSiteName());
- }
- acc.addOrderId(record.getOrderId());
- acc.addSubOrderSum(1);
- acc.addQuantitySum(record.getQuantity());
- acc.addGmv(record.getPrice() * record.getQuantity());
- return acc;
- }
-
- @Override
- public OrderAccumulator getResult(OrderAccumulator acc) {
- return acc;
- }
-
- @Override
- public OrderAccumulator merge(OrderAccumulator acc1, OrderAccumulator acc2) {
- if (acc1.getSiteId() == 0) {
- acc1.setSiteId(acc2.getSiteId());
- acc1.setSiteName(acc2.getSiteName());
- }
- acc1.addOrderIds(acc2.getOrderIds());
- acc1.addSubOrderSum(acc2.getSubOrderSum());
- acc1.addQuantitySum(acc2.getQuantitySum());
- acc1.addGmv(acc2.getGmv());
- return acc1;
- }
- }
累加器类OrderAccumulator的实现很简单,看源码就大概知道它的结构了,因此不再多废话。唯一需要注意的是订单ID可能重复,所以需要用名为orderIds的HashSet来保存它。HashSet应付我们目前的数据规模还是没太大问题的,如果是海量数据,就考虑换用HyperLogLog吧。
接下来就该输出到Redis供呈现端查询了。这里有个问题:一秒内有数据变化的站点并不多,而ContinuousProcessingTimeTrigger每次触发都会输出窗口里全部的聚合数据,这样做了很多无用功,并且还会增大Redis的压力。所以,我们在聚合结果后再接一个ProcessFunction,代码如下。
- DataStream<Tuple2<Long, String>> siteResultStream = siteAggStream
- .keyBy(0)
- .process(new OutputOrderGmvProcessFunc(), TypeInformation.of(new TypeHint<Tuple2<Long, String>>() {}))
- .name("process_site_gmv_changed").uid("process_site_gmv_changed");
- publicstaticfinalclass OutputOrderGmvProcessFunc
- extends KeyedProcessFunction<Tuple, OrderAccumulator, Tuple2<Long, String>> {
- privatestaticfinallong serialVersionUID = 1L;
-
- private MapState<Long, OrderAccumulator> state;
-
- @Override
- public void open(Configuration parameters) throws Exception {
- super.open(parameters);
- state = this.getRuntimeContext().getMapState(new MapStateDescriptor<>(
- "state_site_order_gmv",
- Long.class,
- OrderAccumulator.class)
- );
- }
-
- @Override
- public void processElement(OrderAccumulator value, Context ctx, Collector<Tuple2<Long, String>> out) throws Exception {
- long key = value.getSiteId();
- OrderAccumulator cachedValue = state.get(key);
-
- if (cachedValue == null || value.getSubOrderSum() != cachedValue.getSubOrderSum()) {
- JSONObject result = new JSONObject();
- result.put("site_id", value.getSiteId());
- result.put("site_name", value.getSiteName());
- result.put("quantity", value.getQuantitySum());
- result.put("orderCount", value.getOrderIds().size());
- result.put("subOrderCount", value.getSubOrderSum());
- result.put("gmv", value.getGmv());
- out.collect(new Tuple2<>(key, result.toJSONString());
- state.put(key, value);
- }
- }
-
- @Override
- public void close() throws Exception {
- state.clear();
- super.close();
- }
- }
说来也简单,就是用一个MapState状态缓存当前所有站点的聚合数据。由于数据源是以子订单为单位的,因此如果站点ID在MapState中没有缓存,或者缓存的子订单数与当前子订单数不一致,表示结果有更新,这样的数据才允许输出。
最后就可以安心地接上Redis Sink了,结果会被存进一个Hash结构里。
- // 看官请自己构造合适的FlinkJedisPoolConfig
- FlinkJedisPoolConfig jedisPoolConfig = ParameterUtil.getFlinkJedisPoolConfig(false, true);
- siteResultStream
- .addSink(new RedisSink<>(jedisPoolConfig, new GmvRedisMapper()))
- .name("sink_redis_site_gmv").uid("sink_redis_site_gmv")
- .setParallelism(1);
- publicstaticfinalclass GmvRedisMapper implements RedisMapper<Tuple2<Long, String>> {
- privatestaticfinallong serialVersionUID = 1L;
- privatestaticfinal String HASH_NAME_PREFIX = "RT:DASHBOARD:GMV:";
-
- @Override
- public RedisCommandDescription getCommandDescription() {
- returnnew RedisCommandDescription(RedisCommand.HSET, HASH_NAME_PREFIX);
- }
-
- @Override
- public String getKeyFromData(Tuple2<Long, String> data) {
- return String.valueOf(data.f0);
- }
-
- @Override
- public String getValueFromData(Tuple2<Long, String> data) {
- return data.f1;
- }
-
- @Override
- public Optional<String> getAdditionalKey(Tuple2<Long, String> data) {
- return Optional.of(
- HASH_NAME_PREFIX +
- new LocalDateTime(System.currentTimeMillis()).toString(Consts.TIME_DAY_FORMAT) +
- "SITES"
- );
- }
- }
我们可以直接复用前面产生的orderStream,玩法与上面的GMV统计大同小异。这里用1秒滚动窗口就可以了。
- WindowedStream<SubOrderDetail, Tuple, TimeWindow> merchandiseWindowStream = orderStream
- .keyBy("merchandiseId")
- .window(TumblingProcessingTimeWindows.of(Time.seconds(1)));
-
- DataStream<Tuple2<Long, Long>> merchandiseRankStream = merchandiseWindowStream
- .aggregate(new MerchandiseSalesAggregateFunc(), new MerchandiseSalesWindowFunc())
- .name("aggregate_merch_sales").uid("aggregate_merch_sales")
- .returns(TypeInformation.of(new TypeHint<Tuple2<Long, Long>>() { }));
聚合函数与窗口函数的实现更加简单了,最终返回的是商品ID与商品销量的二元组。
- publicstaticfinalclass MerchandiseSalesAggregateFunc
- implements AggregateFunction<SubOrderDetail, Long, Long> {
- privatestaticfinallong serialVersionUID = 1L;
-
- @Override
- public Long createAccumulator() {
- return0L;
- }
-
- @Override
- public Long add(SubOrderDetail value, Long acc) {
- return acc + value.getQuantity();
- }
-
- @Override
- public Long getResult(Long acc) {
- return acc;
- }
-
- @Override
- public Long merge(Long acc1, Long acc2) {
- return acc1 + acc2;
- }
- }
-
-
- publicstaticfinalclass MerchandiseSalesWindowFunc
- implements WindowFunction<Long, Tuple2<Long, Long>, Tuple, TimeWindow> {
- privatestaticfinallong serialVersionUID = 1L;
-
- @Override
- public void apply(
- Tuple key,
- TimeWindow window,
- Iterable<Long> accs,
- Collector<Tuple2<Long, Long>> out) throws Exception {
- long merchId = ((Tuple1<Long>) key).f0;
- long acc = accs.iterator().next();
- out.collect(new Tuple2<>(merchId, acc));
- }
- }
既然数据最终都要落到Redis,那么我们完全没必要在Flink端做Top N的统计,直接利用Redis的有序集合(zset)就行了,商品ID作为field,销量作为分数值,简单方便。不过flink-redis-connector项目中默认没有提供ZINCRBY命令的实现(必须再吐槽一次),我们可以自己加,步骤参照之前写过的那篇加SETEX的命令的文章,不再赘述。RedisMapper的写法如下。
- publicstaticfinalclass RankingRedisMapper implements RedisMapper<Tuple2<Long, Long>> {
- privatestaticfinallong serialVersionUID = 1L;
- privatestaticfinal String ZSET_NAME_PREFIX = "RT:DASHBOARD:RANKING:";
-
- @Override
- public RedisCommandDescription getCommandDescription() {
- returnnew RedisCommandDescription(RedisCommand.ZINCRBY, ZSET_NAME_PREFIX);
- }
-
- @Override
- public String getKeyFromData(Tuple2<Long, Long> data) {
- return String.valueOf(data.f0);
- }
-
- @Override
- public String getValueFromData(Tuple2<Long, Long> data) {
- return String.valueOf(data.f1);
- }
-
- @Override
- public Optional<String> getAdditionalKey(Tuple2<Long, Long> data) {
- return Optional.of(
- ZSET_NAME_PREFIX +
- new LocalDateTime(System.currentTimeMillis()).toString(Consts.TIME_DAY_FORMAT) + ":" +
- "MERCHANDISE"
- );
- }
- }
后端取数时,用ZREVRANGE命令即可取出指定排名的数据了。只要数据规模不是大到难以接受,并且有现成的Redis,这个方案完全可以作为各类Top N需求的通用实现。
大屏的实际呈现需要保密,截图自然是没有的。以下是提交执行时Flink Web UI给出的执行计划(实际有更多的统计任务,不止3个Sink)。通过复用源数据,可以在同一个Flink job内实现更多统计需求。
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