console: add an API to get flow rate

console/widgets.go

@@ -0,0 +1,85 @@
+package console
+
+import (
+	"net/http"
+	"reflect"
+
+	"github.com/gin-gonic/gin"
+)
+
+func (c *Component) widgetFlowLastHandlerFunc(gc *gin.Context) {
+	ctx := c.t.Context(gc.Request.Context())
+	rows, err := c.d.ClickHouseDB.Conn.Query(ctx,
+		`SELECT * FROM flows WHERE TimeReceived = (SELECT MAX(TimeReceived) FROM flows) LIMIT 1`)
+	if err != nil {
+		c.r.Err(err).Msg("unable to query database")
+		gc.JSON(http.StatusInternalServerError, gin.H{"message": "Unable to query database."})
+		return
+	}
+
+	if !rows.Next() {
+		gc.JSON(http.StatusNotFound, gin.H{"message": "no flow currently in database."})
+		return
+	}
+	defer rows.Close()
+
+	var (
+		response    = gin.H{}
+		columnTypes = rows.ColumnTypes()
+		vars        = make([]interface{}, len(columnTypes))
+	)
+	for i := range columnTypes {
+		vars[i] = reflect.New(columnTypes[i].ScanType()).Interface()
+	}
+	if err := rows.Scan(vars...); err != nil {
+		c.r.Err(err).Msg("unable to parse flow")
+		gc.JSON(http.StatusInternalServerError, gin.H{"message": "Unable to parse flow."})
+		return
+	}
+	for index, column := range rows.Columns() {
+		response[column] = vars[index]
+	}
+	gc.IndentedJSON(http.StatusOK, response)
+}
+
+func (c *Component) widgetFlowRateHandlerFunc(gc *gin.Context) {
+	ctx := c.t.Context(gc.Request.Context())
+	row := c.d.ClickHouseDB.Conn.QueryRow(ctx,
+		`SELECT COUNT(*)/300 AS rate FROM flows WHERE TimeReceived > date_sub(minute, 5, now())`)
+	if err := row.Err(); err != nil {
+		c.r.Err(err).Msg("unable to query database")
+		gc.JSON(http.StatusInternalServerError, gin.H{"message": "Unable to query database."})
+		return
+	}
+	var result float64
+	if err := row.Scan(&result); err != nil {
+		c.r.Err(err).Msg("unable to parse result")
+		gc.JSON(http.StatusInternalServerError, gin.H{"message": "Unable to parse result."})
+		return
+	}
+	gc.IndentedJSON(http.StatusOK, gin.H{
+		"rate":   result,
+		"period": "second",
+	})
+}
+
+func (c *Component) widgetExportersHandlerFunc(gc *gin.Context) {
+	ctx := c.t.Context(gc.Request.Context())
+
+	exporters := []struct {
+		ExporterName string
+	}{}
+	err := c.d.ClickHouseDB.Conn.Select(ctx, &exporters,
+		`SELECT ExporterName FROM exporters GROUP BY ExporterName ORDER BY ExporterName`)
+	if err != nil {
+		c.r.Err(err).Msg("unable to query database")
+		gc.JSON(http.StatusInternalServerError, gin.H{"message": "Unable to query database."})
+		return
+	}
+	exporterList := make([]string, len(exporters))
+	for idx, exporter := range exporters {
+		exporterList[idx] = exporter.ExporterName
+	}
+
+	gc.IndentedJSON(http.StatusOK, gin.H{"exporters": exporterList})
+}