Segfault while closing the consumer while consume loop is running

[milindl]

Reproduction code:

function runConsumer() {
    const consumer = new RdKafka.KafkaConsumer({
        'group.id': 'test-group' + Math.random(),
        'bootstrap.servers': 'localhost:9092',
    }, {
        'auto.offset.reset': 'earliest',
    });

    consumer.connect();

    consumer.on('ready', () => {
        console.log("Consumer is ready");
        consumer.subscribe(['test-topic']);
        consumer.consume(); // consume loop
    });

    consumer.on('data', (data) => {
        console.log("Received data");
        console.log(data);
        consumer.disconnect();
    });

    consumer.on('event.error', (err) => {
        console.error(err);
    });
}

Cause: NodeKafka::Workers::KafkaConsumerConsumeLoop::HandleMessageCallback is called after KafkaConsumerConsumerLoop:Close and the callback has been cleared by that time so callback->Call causes a segfault.

[constantind]

This is because of the worker.WorkComplete() added in kafka_consumer.cc/NodeDisconnect in 2.16.1 , can be reproduced on double disconnect or pause and disconnect, connect/disconnect at the same time.

Another note here is that if getMetadata fails (timeout) it will call disconnect on its own here: /lib/client.js#L165 so if you call disconnect as well it will cause double disconnect.
could be caused by GC on javascript side, since v8::Persistent can be GC'ed if the callback passed goes out of scope.

The fix would be to check (callback && !callback->IsEmpty()) here: /src/workers.cc#L770 as that can still run after worker->WorkComplete() has been called.

Blizzard/node-rdkafka#1136

[FroYo425]

Thank you @constantind for the nice explanation.

As it took me some time to find the exact references, the following might help others to save some time:

• the changes in the package "node-rdkafka" from v2.16.0 to v2.16.1 introduced a cleanup of the async worker in kafka_consumer.cc
• the mentioned WorkComplete() can in this package be found in kafka-consumer.cc#L1483
• the line of the client disconnect also references "node-rdkafka" and can be found in this package in client.js#L267
• the suggested fix with the callback check should here then be done in workers.cc#L771