thread in script based component not working

When I comment out the thread related code below, the submission to the slack API works as expected. However, when I attempt to process the submission within a thread command, the submission never goes through.

Am I doing something wrong? Running in Railo 4

// push to slack!
public function push(options = {}) {

    var http = new http();
    var data = {
        "text": "Default message",
        "channel": "activity"
    };

    structAppend(data, options);

    // thread
    //  action="run" {

        sleep(5000);

        http.setMethod("post");
        http.setUrl(variables.slackWebhookUrl);
        http.addParam(
            type = "formField",
            name = "payload",
            value = serializeJson(data)
        );

        http.send();

    // }

}

Credit goes to Adam Cameron for pointing me in the right direction. As it turns out, scoping is quite tricky with cfthreads.

For the sake of brevity, I will just say that I will follow these rules when using threads in the future:

1. do not reference any variables from scopes outside the "thread block"
2. explicitly pass into the thread any "parent scope" data you need to reference
3. basically treat the cfthread as a cfmodule (passing data through attributes)

This is working code:

    // push to slack!   
    public function push(options = {}) {

        var data = {
            "text": "Default message",
            "channel": "activity"
        };

        structAppend(data, options);

        thread
            action="run"
            data="#data#"
            slackUrl="#variables.slackWebhookUrl#" {

            var http = new http();

            http.setMethod("post");
            http.setUrl(attributes.slackUrl);
            http.addParam(
                type = "formField",
                name = "payload",
                value = serializeJson(attributes.data)
            );

            http.send();

        }

    }