I'm facing a problem in which I don't get results from my query in Flink-SQL.
I have some informations stored in two Kafka Topics, I want to store them in two tables and perform a join between them in a streaming way.
These are my flink instructions :
StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
StreamTableEnvironment tableEnv = TableEnvironment.getTableEnvironment(env);
// configure Kafka consumer
Properties props = new Properties();
props.setProperty("bootstrap.servers", "localhost:9092"); // Broker default host:port
props.setProperty("group.id", "flink-consumer"); // Consumer group ID
FlinkKafkaConsumer011<Blocks> flinkBlocksConsumer = new FlinkKafkaConsumer011<>(args[0], new BlocksSchema(), props);
flinkBlocksConsumer.setStartFromEarliest();
FlinkKafkaConsumer011<Transactions> flinkTransactionsConsumer = new FlinkKafkaConsumer011<>(args[1], new TransactionsSchema(), props);
flinkTransactionsConsumer.setStartFromEarliest();
DataStream<Blocks> blocks = env.addSource(flinkBlocksConsumer);
DataStream<Transactions> transactions = env.addSource(flinkTransactionsConsumer);
tableEnv.registerDataStream("blocksTable", blocks);
tableEnv.registerDataStream("transactionsTable", transactions);
Here is my SQL query :
Table sqlResult
= tableEnv.sqlQuery(
"SELECT block_timestamp,count(tx_hash) " +
"FROM blocksTable " +
"JOIN transactionsTable " +
"ON blocksTable.block_hash=transactionsTable.tx_hash " +
"GROUP BY blocksTable.block_timestamp");
DataStream<Test> resultStream = tableEnv
.toRetractStream(sqlResult,Row.class)
.map(t -> {
Row r = t.f1;
String field2 = r.getField(0).toString();
long count = Long.valueOf(r.getField(1).toString());
return new Test(field2,count);
})
.returns(Test.class);
Then, I print the results :
resultStream.print();
But I don't get any answers, my program is stuck...
For the schema used for serialization and deserialization, here is my test class which stores the result of my query (two fields a string and a long for respectively the block_timestamp and the count) :
public class TestSchema implements DeserializationSchema<Test>, SerializationSchema<Test> {
@Override
public Test deserialize(byte[] message) throws IOException {
return Test.fromString(new String(message));
}
@Override
public boolean isEndOfStream(Test nextElement) {
return false;
}
@Override
public byte[] serialize(Test element) {
return element.toString().getBytes();
}
@Override
public TypeInformation<Test> getProducedType() {
return TypeInformation.of(Test.class);
}
}
This is the same principle for BlockSchema
and TransactionsSchema
classes.
Do you know why I can't get the result of my query ? Should I test with BatchExecutionEnvironment
?