I've successfully created and started a rollup job but it never runs. I've tried removing the delay, setting the cron expression to every minute (0 * 0 ? * * *) still it always shows "documents_processed: 0" and there are no docs in the rollup-test index. The log shows no issues and we definitely have loads of data in our access-test index.
{
    "jobs": [
        {
            "config": {
                "id": "accessPerformance4",
                "index_pattern": "access-test",
                "rollup_index": "rollup-test",
                "cron": "0 * 0 ? * * *",
                "groups": {
                    "date_histogram": {
                        "interval": "1d",
                        "field": "timestamp",
                        "time_zone": "UTC"
                    },
                    "terms": {
                        "fields": [
                            "category",
                            "subcategory",
                            "method"
                        ]
                    }
                },
                "metrics": [
                    {
                        "field": "timeTaken",
                        "metrics": [
                            "min",
                            "max",
                            "avg"
                        ]
                    }
                ],
                "timeout": "20s",
                "page_size": 100
            },
            "status": {
                "job_state": "started"
            },
            "stats": {
                "pages_processed": 0,
                "documents_processed": 0,
                "rollups_indexed": 0,
                "trigger_count": 0
            }
        }
    ]
}