vertx kafka client consumer handler handle messages sequentially

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Young Chen

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Nov 2, 2021, 6:45:46 AM11/2/21

to vert.x

````

protected void consume(KafkaReadStream<String, JsonObject> consumer) {

consumer.handler(record -> {

// call a REST API to write a value to DB

doRestApi(record); // such as client.postAbs(...).send(...)

});

}

````

For example, records in topic like,

````

{"createtime":"2021-10-29 00:03:49.0"}

{"createtime":"2021-10-29 00:03:50.0"}

{"createtime":"2021-10-29 00:03:56.0"}

...

{"createtime":"2021-10-29 00:13:56.0"}

````

When the record `{"createtime":"2021-10-29 00:03:49.0"}` was coming, the handler did a REST api call to save the `createtime=2021-10-29 00:03:49.0` to mongodb.

when the second record came, `createtime=2021-10-29 00:03:50.0` would be saved.

Then the third record, `createtime=2021-10-29 00:03:56.0` would be saved.

And so on.

I hope these messages to be handled sequentially. As a result, the createtime in the last message `2021-10-29 00:13:56.0` would be the final value in DB.

When I ran my code, the result value was random and the former value(such as `2021-10-29 00:03:56.0`) might be the final value.