@Override
    public void stop() {
        if (throttler != null)
            throttler.wakeup();
    }
A connector primarily intended for system tests. The connector simply generates as many tasks as requested. The
tasks print metadata in the form of JSON to stdout for each message generated, making externally visible which
messages have been sent. Each message is also assigned a unique, increasing seqno that is passed to Kafka Connect; when
tasks are started on new nodes, this seqno is used to resume where the task previously left off, allowing for
testing of distributed Kafka Connect.
<p>
If logging is left enabled, log output on stdout can be easily ignored by checking whether a given line is valid JSON.
connect/test-plugins/src/main/java/org/apache/kafka/connect/tools/VerifiableSourceTask.java