Wrong commit order when using autoCommit=false in HighlevelConsumer - node.js

Question

I'm using a HighlevelProducer and HighlevelConsumer to send and receive Messages. The HighlevelConsumer is configured with autoCommit=false as I want to commit Messages only when it was produced successfully. The problem is, that the first message never really gets commited.
Example:
Send Messages 1-10.
Receive Message 1
Receive Message 2
Commit Message 2
...
Receive Message 10
Commit Message 10
Commit Message 1
If I restart my Consumer, all messages from 1 to 10 are processed again. Only if I send new messages to the consumer, the old messages get committed. This happens for any number of messages.
My Code reads as follows:
var kafka = require('kafka-node'),
HighLevelConsumer = kafka.HighLevelConsumer,
client = new kafka.Client("localhost:2181/");
consumer = new HighLevelConsumer(
client,
[
{ topic: 'mytopic' }
],
{
groupId: 'my-group',
id: "my-consumer-1",
autoCommit: false
}
);
consumer.on('message', function (message) {
console.log("consume: " + message.offset);
consumer.commit(function (err, data) {
console.log("commited:" + message.offset);
});
console.log("consumed:" + message.offset);
});
process.on('SIGINT', function () {
consumer.close(true, function () {
process.exit();
});
});
process.on('exit', function () {
consumer.close(true, function () {
process.exit();
});
});
var messages = 10;
var kafka = require('kafka-node'),
HighLevelProducer = kafka.HighLevelProducer,
client = new kafka.Client("localhost:2181/");
var producer = new HighLevelProducer(client, { partitionerType: 2, requireAcks: 1 });
producer.on('error', function (err) { console.log(err) });
producer.on('ready', function () {
for (i = 0; i < messages; i++) {
payloads = [{ topic: 'mytopic', messages: "" }];
producer.send(payloads, function (err, data) {
err ? console.log(i + "err", err) : console.log(i + "data", data);
});
}
});
Am I doing something wrong or is this a bug in kafka-node?

Answer 1

A commit of message 2 is an implicit commit of message 1.
As you commits are done asynchronously, and commit of message 1 and message 2 are done quick after each other (ie, committing 2 happens before the consumer did send the commit of 1), the first commit will not happen explicitly and only a single commit of message 2 will be sent.