Add the metric.IsSessionExpired metric to the exporter.

This metric reports which replicated tables have seen their Zookeeper sessions expired. This metric is labeled by database and table, plus additional labels that are added by default (e.g. ClickHouse hostname).
teralype · Oct 24, 2019 · 6ddddcf · 6ddddcf
1 parent 58e4d4d
commit 6ddddcf
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Showing 2 changed files with 29 additions and 20 deletions.
diff --git a/pkg/apis/metrics/clickhouse_fetcher.go b/pkg/apis/metrics/clickhouse_fetcher.go
@@ -68,7 +68,14 @@ const (
         'metric.DiskFreeBytes'    AS metric,
         toString(filesystemFree()) AS value,
         'Free disk space available at file system' AS description,
-        'gauge'                   AS type
+		'gauge'                   AS type
+	UNION ALL
+	SELECT
+        concat('metric.IsSessionExpired', '{', 'database=', database, ',table=', table, '}') AS metric,
+        toString(is_session_expired)                                                         AS value,
+        'Whether the Zookeeper session has expired'                                          AS description,
+        'gauge'                                                                              AS type
+    FROM system.replicas
 	`
 
 	queryTableSizesSQL = `
@@ -85,13 +92,15 @@ const (
 	GROUP BY database, table`
 )
 
+// ClickHouseFetcher describes a fetcher for a particular ClickHouse host
 type ClickHouseFetcher struct {
 	Hostname string
 	Username string
 	Password string
 	Port     int
 }
 
+// NewClickHouseFetcher creates a new fetcher to retrieve metrics from a particular ClickHouse host
 func NewClickHouseFetcher(hostname, username, password string, port int) *ClickHouseFetcher {
 	return &ClickHouseFetcher{
 		Hostname: hostname,
@@ -110,16 +119,16 @@ func (f *ClickHouseFetcher) newConn() *clickhouse.Conn {
 func (f *ClickHouseFetcher) clickHouseQueryMetrics() ([][]string, error) {
 	data := make([][]string, 0)
 	conn := f.newConn()
-	if rows, err := conn.Query(heredoc.Doc(queryMetricsSQL)); err != nil {
+	rows, err := conn.Query(heredoc.Doc(queryMetricsSQL))
+	if err != nil {
 		return nil, err
-	} else {
-		for rows.Next() {
-			var metric, value, description, _type string
-			if err := rows.Scan(&metric, &value, &description, &_type); err == nil {
-				data = append(data, []string{metric, value, description, _type})
-			} else {
-				// Skip erroneous line
-			}
+	}
+	for rows.Next() {
+		var metric, value, description, _type string
+		if err := rows.Scan(&metric, &value, &description, &_type); err == nil {
+			data = append(data, []string{metric, value, description, _type})
+		} else {
+			// Skip erroneous line
 		}
 	}
 	return data, nil
@@ -130,16 +139,16 @@ func (f *ClickHouseFetcher) clickHouseQueryMetrics() ([][]string, error) {
 func (f *ClickHouseFetcher) clickHouseQueryTableSizes() ([][]string, error) {
 	data := make([][]string, 0)
 	conn := f.newConn()
-	if rows, err := conn.Query(heredoc.Doc(queryTableSizesSQL)); err != nil {
+	rows, err := conn.Query(heredoc.Doc(queryTableSizesSQL))
+	if err != nil {
 		return nil, err
-	} else {
-		for rows.Next() {
-			var database, table, partitions, parts, bytes, uncompressed, _rows string
-			if err := rows.Scan(&database, &table, &partitions, &parts, &bytes, &uncompressed, &_rows); err == nil {
-				data = append(data, []string{database, table, partitions, parts, bytes, uncompressed, _rows})
-			} else {
-				// Skip erroneous line
-			}
+	}
+	for rows.Next() {
+		var database, table, partitions, parts, bytes, uncompressed, _rows string
+		if err := rows.Scan(&database, &table, &partitions, &parts, &bytes, &uncompressed, &_rows); err == nil {
+			data = append(data, []string{database, table, partitions, parts, bytes, uncompressed, _rows})
+		} else {
+			// Skip erroneous line
 		}
 	}
 	return data, nil

diff --git a/pkg/apis/metrics/exporter.go b/pkg/apis/metrics/exporter.go
@@ -190,7 +190,7 @@ func (e *Exporter) newFetcher(hostname string) *ClickHouseFetcher {
 	return NewClickHouseFetcher(hostname, e.chAccessInfo.Username, e.chAccessInfo.Password, e.chAccessInfo.Port)
 }
 
-// Ensure hostnames of the Pods from CHI object included into chopmetrics.Exporter state
+// UpdateWatch ensures hostnames of the Pods from CHI object included into chopmetrics.Exporter state
 func (e *Exporter) UpdateWatch(namespace, chiName string, hostnames []string) {
 	chi := &WatchedChi{
 		Namespace: namespace,