Add label aggregation for innodb buffer metrics

Add label aggregation for innodb_metrics buffer subsystem.
* Total can be ignored as it is an aggregation of data+misc+free
* Dirty pages are not aggregateable, keep as a separate metric.

collector/info_schema_innodb_metrics.go

@@ -30,10 +30,23 @@ var (
 		"Total number of buffer pages written total.",
 		[]string{"type"}, nil,
 	)
+	infoSchemaBufferPoolPagesDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, informationSchema, "innodb_metrics_buffer_pool_pages"),
+		"Total number of buffer pool pages by state.",
+		[]string{"state"}, nil,
+	)
+	infoSchemaBufferPoolPagesDirtyDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, informationSchema, "innodb_metrics_buffer_pool_dirty_pages"),
+		"Total number of dirty pages in the buffer pool.",
+		nil, nil,
+	)
 )
 
 // Regexp for matching metric aggregations.
-var bufferPageRE = regexp.MustCompile(`^buffer_page_(read|written)_(.*)$`)
+var (
+	bufferRE     = regexp.MustCompile(`^buffer_(pool_pages)_(.*)$`)
+	bufferPageRE = regexp.MustCompile(`^buffer_page_(read|written)_(.*)$`)
+)
 
 // ScrapeInnodbMetrics collects from `information_schema.innodb_metrics`.
 func ScrapeInnodbMetrics(db *sql.DB, ch chan<- prometheus.Metric) error {
@@ -73,6 +86,30 @@ func ScrapeInnodbMetrics(db *sql.DB, ch chan<- prometheus.Metric) error {
 			}
 			continue
 		}
+		if subsystem == "buffer" {
+			match := bufferRE.FindStringSubmatch(name)
+			// Many buffer substem metrics are not matched, fall through to generic metric.
+			if match != nil {
+				switch match[1] {
+				case "pool_pages":
+					switch match[2] {
+					case "total":
+						// Ignore total, it is an aggregation of the rest.
+						continue
+					case "dirty":
+						// Dirty pages are a separate metric, not in the total.
+						ch <- prometheus.MustNewConstMetric(
+							infoSchemaBufferPoolPagesDirtyDesc, prometheus.GaugeValue, value,
+						)
+					default:
+						ch <- prometheus.MustNewConstMetric(
+							infoSchemaBufferPoolPagesDesc, prometheus.GaugeValue, value, match[2],
+						)
+					}
+				}
+				continue
+			}
+		}
 		metricName := "innodb_metrics_" + subsystem + "_" + name
 		// MySQL returns counters named two different ways. "counter" and "status_counter"
 		// value >= 0 is necessary due to upstream bugs: http://bugs.mysql.com/bug.php?id=75966

collector/info_schema_innodb_metrics_test.go

@@ -30,7 +30,10 @@ func TestScrapeInnodbMetrics(t *testing.T) {
 		AddRow("buffer_pool_size", "server", "value", "Server buffer pool size (all buffer pools) in bytes", 2).
 		AddRow("buffer_page_read_system_page", "buffer_page_io", "counter", "Number of System Pages read", 3).
 		AddRow("buffer_page_written_undo_log", "buffer_page_io", "counter", "Number of Undo Log Pages written", 4).
-		AddRow("NOPE", "buffer_page_io", "counter", "An invalid buffer_page_io metric", 5)
+		AddRow("buffer_pool_pages_dirty", "buffer", "gauge", "Number of Undo Log Pages written", 5).
+		AddRow("buffer_pool_pages_data", "buffer", "gauge", "Number of Undo Log Pages written", 6).
+		AddRow("buffer_pool_pages_total", "buffer", "gauge", "Number of Undo Log Pages written", 7).
+		AddRow("NOPE", "buffer_page_io", "counter", "An invalid buffer_page_io metric", 999)
 	mock.ExpectQuery(sanitizeQuery(infoSchemaInnodbMetricsQuery)).WillReturnRows(rows)
 
 	ch := make(chan prometheus.Metric)
@@ -47,6 +50,8 @@ func TestScrapeInnodbMetrics(t *testing.T) {
 		{labels: labelMap{}, value: 2, metricType: dto.MetricType_GAUGE},
 		{labels: labelMap{"type": "system_page"}, value: 3, metricType: dto.MetricType_COUNTER},
 		{labels: labelMap{"type": "undo_log"}, value: 4, metricType: dto.MetricType_COUNTER},
+		{labels: labelMap{}, value: 5, metricType: dto.MetricType_GAUGE},
+		{labels: labelMap{"state": "data"}, value: 6, metricType: dto.MetricType_GAUGE},
 	}
 	convey.Convey("Metrics comparison", t, func() {
 		for _, expect := range metricExpected {