Add collector to get table stats grouped by schema (#354)

* Add collector to get table stats grouped by schema

Signed-off-by: Ricardo Rodríguez <rrodriguez@tuenti.com>

CHANGELOG.md

@@ -16,6 +16,7 @@ The minimum supported MySQL version is now 5.5.
 * [FEATURE] Add by_user and by_host metrics to info_schema.processlist collector (PR #333) #334
 * [FEATURE] Add wsrep_evs_repl_latency metric collecting. (PR #338)
 * [FEATURE] Add collector for mysql.user (PR #341)
+* [FEATURE] Add collector to get table stats grouped by schema (PR #354)
 
 ## 0.11.0 / 2018-06-29
 

README.md

@@ -68,6 +68,7 @@ collect.info_schema.query_response_time                | 5.5           | Collect
 collect.info_schema.tables                             | 5.1           | Collect metrics from information_schema.tables (Enabled by default)
 collect.info_schema.tables.databases                   | 5.1           | The list of databases to collect table stats for, or '`*`' for all.
 collect.info_schema.tablestats                         | 5.1           | If running with userstat=1, set to true to collect table statistics.
+collect.info_schema.schemastats                        | 5.1           | If running with userstat=1, set to true to collect schema statistics
 collect.info_schema.userstats                          | 5.1           | If running with userstat=1, set to true to collect user statistics.
 collect.perf_schema.eventsstatements                   | 5.6           | Collect metrics from performance_schema.events_statements_summary_by_digest.
 collect.perf_schema.eventsstatements.digest_text_limit | 5.6           | Maximum length of the normalized statement text. (default: 120)

collector/info_schema_schemastats.go

@@ -0,0 +1,128 @@
+// Copyright 2018 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Scrape `information_schema.table_statistics`.
+
+package collector
+
+import (
+	"context"
+	"database/sql"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/common/log"
+)
+
+const schemaStatQuery = `
+		SELECT 
+			TABLE_SCHEMA, 
+			SUM(ROWS_READ) AS ROWS_READ, 
+			SUM(ROWS_CHANGED) AS ROWS_CHANGED, 
+			SUM(ROWS_CHANGED_X_INDEXES) AS ROWS_CHANGED_X_INDEXES 
+		FROM information_schema.TABLE_STATISTICS 
+		GROUP BY TABLE_SCHEMA;
+		`
+
+// Metric descriptors.
+var (
+	infoSchemaStatsRowsReadDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, informationSchema, "schema_statistics_rows_read_total"),
+		"The number of rows read from the schema.",
+		[]string{"schema"}, nil,
+	)
+	infoSchemaStatsRowsChangedDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, informationSchema, "schema_statistics_rows_changed_total"),
+		"The number of rows changed in the schema.",
+		[]string{"schema"}, nil,
+	)
+	infoSchemaStatsRowsChangedXIndexesDesc = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, informationSchema, "schema_statistics_rows_changed_x_indexes_total"),
+		"The number of rows changed in the schema, multiplied by the number of indexes changed.",
+		[]string{"schema"}, nil,
+	)
+)
+
+// ScrapeSchemaStat collects from `information_schema.table_statistics` grouped by schema.
+type ScrapeSchemaStat struct{}
+
+// Name of the Scraper. Should be unique.
+func (ScrapeSchemaStat) Name() string {
+	return "info_schema.schemastats"
+}
+
+// Help describes the role of the Scraper.
+func (ScrapeSchemaStat) Help() string {
+	return "If running with userstat=1, set to true to collect schema statistics"
+}
+
+// Version of MySQL from which scraper is available.
+func (ScrapeSchemaStat) Version() float64 {
+	return 5.1
+}
+
+// Scrape collects data from database connection and sends it over channel as prometheus metric.
+func (ScrapeSchemaStat) Scrape(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric) error {
+	var varName, varVal string
+
+	err := db.QueryRowContext(ctx, userstatCheckQuery).Scan(&varName, &varVal)
+	if err != nil {
+		log.Debugln("Detailed schema stats are not available.")
+		return nil
+	}
+	if varVal == "OFF" {
+		log.Debugf("MySQL @@%s is OFF.", varName)
+		return nil
+	}
+
+	informationSchemaTableStatisticsRows, err := db.QueryContext(ctx, schemaStatQuery)
+	if err != nil {
+		return err
+	}
+	defer informationSchemaTableStatisticsRows.Close()
+
+	var (
+		tableSchema         string
+		rowsRead            uint64
+		rowsChanged         uint64
+		rowsChangedXIndexes uint64
+	)
+
+	for informationSchemaTableStatisticsRows.Next() {
+		err = informationSchemaTableStatisticsRows.Scan(
+			&tableSchema,
+			&rowsRead,
+			&rowsChanged,
+			&rowsChangedXIndexes,
+		)
+
+		if err != nil {
+			return err
+		}
+		ch <- prometheus.MustNewConstMetric(
+			infoSchemaStatsRowsReadDesc, prometheus.CounterValue, float64(rowsRead),
+			tableSchema,
+		)
+		ch <- prometheus.MustNewConstMetric(
+			infoSchemaStatsRowsChangedDesc, prometheus.CounterValue, float64(rowsChanged),
+			tableSchema,
+		)
+		ch <- prometheus.MustNewConstMetric(
+			infoSchemaStatsRowsChangedXIndexesDesc, prometheus.CounterValue, float64(rowsChangedXIndexes),
+			tableSchema,
+		)
+	}
+	return nil
+}
+
+// check interface
+var _ Scraper = ScrapeSchemaStat{}

collector/info_schema_schemastats_test.go

@@ -0,0 +1,68 @@
+// Copyright 2018 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package collector
+
+import (
+	"context"
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/smartystreets/goconvey/convey"
+	"gopkg.in/DATA-DOG/go-sqlmock.v1"
+)
+
+func TestScrapeSchemaStat(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("error opening a stub database connection: %s", err)
+	}
+	defer db.Close()
+
+	mock.ExpectQuery(sanitizeQuery(userstatCheckQuery)).WillReturnRows(sqlmock.NewRows([]string{"Variable_name", "Value"}).
+		AddRow("userstat", "ON"))
+
+	columns := []string{"TABLE_SCHEMA", "ROWS_READ", "ROWS_CHANGED", "ROWS_CHANGED_X_INDEXES"}
+	rows := sqlmock.NewRows(columns).
+		AddRow("mysql", 238, 0, 8).
+		AddRow("default", 99, 1, 0)
+	mock.ExpectQuery(sanitizeQuery(schemaStatQuery)).WillReturnRows(rows)
+
+	ch := make(chan prometheus.Metric)
+	go func() {
+		if err = (ScrapeSchemaStat{}).Scrape(context.Background(), db, ch); err != nil {
+			t.Errorf("error calling function on test: %s", err)
+		}
+		close(ch)
+	}()
+
+	expected := []MetricResult{
+		{labels: labelMap{"schema": "mysql"}, value: 238},
+		{labels: labelMap{"schema": "mysql"}, value: 0},
+		{labels: labelMap{"schema": "mysql"}, value: 8},
+		{labels: labelMap{"schema": "default"}, value: 99},
+		{labels: labelMap{"schema": "default"}, value: 1},
+		{labels: labelMap{"schema": "default"}, value: 0},
+	}
+	convey.Convey("Metrics comparison", t, func() {
+		for _, expect := range expected {
+			got := readMetric(<-ch)
+			convey.So(expect, convey.ShouldResemble, got)
+		}
+	})
+
+	// Ensure all SQL queries were executed
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("there were unfulfilled exceptions: %s", err)
+	}
+}

mysqld_exporter.go

@@ -79,6 +79,7 @@ var scrapers = map[collector.Scraper]bool{
 	collector.ScrapeUserStat{}:                        false,
 	collector.ScrapeClientStat{}:                      false,
 	collector.ScrapeTableStat{}:                       false,
+	collector.ScrapeSchemaStat{}:                      false,
 	collector.ScrapeInnodbCmp{}:                       true,
 	collector.ScrapeInnodbCmpMem{}:                    true,
 	collector.ScrapeQueryResponseTime{}:               true,