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聊聊flink的Queryable State

@Test
    public void testValueStateForQuery() throws Exception {
        StreamExecutionEnvironment env = StreamExecutionEnvironment
                .createRemoteEnvironment("192.168.99.100", 8081, SubmitTest.JAR_FILE);
        env.addSource(new RandomTuple2Source())
                .keyBy(0) //key by first value of tuple
                .flatMap(new CountWindowAverage())
                .print();
        JobExecutionResult result = env.execute("testQueryableState");
        LOGGER.info("submit job result:{}",result);
    }
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这里运行一个job，它对tuple的第一个值作为key，然后flatMap操作使用的是CountWindowAverage

CountWindowAverage

public class CountWindowAverage extends RichFlatMapFunction<Tuple2<Long, Long>, Tuple2<Long, Long>> {

    private transient ValueState<Tuple2<Long, Long>> sum; // a tuple containing the count and the sum

    @Override
    public void flatMap(Tuple2<Long, Long> input, Collector<Tuple2<Long, Long>> out) throws Exception {
        Tuple2<Long, Long> currentSum = sum.value();
        if(currentSum == null){
            currentSum = Tuple2.of(1L,input.f1);
        }else{
            currentSum.f0 += 1;
            currentSum.f1 += input.f1;
        }

        sum.update(currentSum);

        if (currentSum.f0 >= 2) {
            out.collect(new Tuple2<>(input.f0, currentSum.f1 / currentSum.f0));
            sum.clear();
        }
    }

    @Override
    public void open(Configuration config) {
        ValueStateDescriptor<Tuple2<Long, Long>> descriptor =
                new ValueStateDescriptor<>(
                        "average", // the state name
                        TypeInformation.of(new TypeHint<Tuple2<Long, Long>>() {})); // type information
        descriptor.setQueryable("query-name");
        sum = getRuntimeContext().getState(descriptor);
    }
}
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CountWindowAverage通过ValueStateDescriptor的setQueryable("query-name")方法，将state声明为是queryable的

QueryableStateClient

@Test
    public void testQueryStateByJobId() throws InterruptedException, IOException {
        //get jobId from flink ui running job page
        JobID jobId = JobID.fromHexString("793edfa93f354aa0274f759cb13ce79e");
        long key = 1L;
        //flink-core-1.7.0-sources.jar!/org/apache/flink/configuration/QueryableStateOptions.java
        QueryableStateClient client = new QueryableStateClient("192.168.99.100", 9069);

        // the state descriptor of the state to be fetched.
        ValueStateDescriptor<Tuple2<Long, Long>> descriptor =
                new ValueStateDescriptor<>(
                        "average",
                        TypeInformation.of(new TypeHint<Tuple2<Long, Long>>() {}));

        CompletableFuture<ValueState<Tuple2<Long, Long>>> resultFuture =
                client.getKvState(jobId, "query-name", key, BasicTypeInfo.LONG_TYPE_INFO, descriptor);

        LOGGER.info("get kv state return future, waiting......");
        // org.apache.flink.queryablestate.exceptions.UnknownKeyOrNamespaceException: Queryable State Server : No state for the specified key/namespace.
        ValueState<Tuple2<Long, Long>> res = resultFuture.join();
        LOGGER.info("query result:{}",res.value());
        client.shutdownAndWait();
    }
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