What's wrong with my aggs nestification

Hi all

ES give me a error when I run the aggs as below

"aggs":{
		"groupby_day":{
			"date_histogram":{
				"field":"reqtime",
				"format": "yyyyMMdd",
				"interval":"day"
			},
			"aggs":{
				"groupby_minute":{
					"date_histogram":{
						"field":"reqtime",
						"format": "yyyyMMddHHmm",
						"interval":"1m"
					}
				},
				"aggs":{
					"req_count":{
						"value_count":{
							"field":"rowkey"
						}
					}
				}
			}
		}
	}

Pls help ~

error message: Could not find aggregator type [req_count] in [aggs]

I didn't test but look like the last aggs is not nested correctly, try this one.