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Allow adjustable number of rendering workers via MAX_WORKERS envar #306

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Allow adjustable number of rendering workers via MAX_WORKERS envar #306

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c3b9b31
allow adjustable number of rendering workers via MAX_WORKERS envar
Aug 9, 2021
b70b07b
Cleanup worker assignment
marklr Aug 9, 2021
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19 changes: 17 additions & 2 deletions report/report.go
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Original file line number Diff line number Diff line change
Expand Up @@ -20,9 +20,12 @@ import (
"fmt"
"io"
"log"
"math"
"os"
"os/exec"
"path/filepath"
"runtime"
"strconv"
"sync"
"text/template"

Expand Down Expand Up @@ -72,6 +75,15 @@ func new(g grafana.Client, dashName string, time grafana.TimeRange, texTemplate
return &report{g, time, texTemplate, dashName, tmpDir, ""}
}

func (rep *report) getWorkerNum() int {
var (
desiredWorkers, _ = strconv.Atoi(os.Getenv("MAX_WORKERS"))
maxWorkers = runtime.NumCPU()
)
desiredWorkers = int(math.Max(1, math.Min(float64(desiredWorkers), float64(maxWorkers))))
return desiredWorkers
}

// Generate returns the report.pdf file. After reading this file it should be Closed()
// After closing the file, call report.Clean() to delete the file as well the temporary build files
func (rep *report) Generate() (pdf io.ReadCloser, err error) {
Expand Down Expand Up @@ -130,6 +142,10 @@ func (rep *report) texPath() string {
}

func (rep *report) renderPNGsParallel(dash grafana.Dashboard) error {
var (
wg sync.WaitGroup
workers = rep.getWorkerNum()
)
//buffer all panels on a channel
panels := make(chan grafana.Panel, len(dash.Panels))
for _, p := range dash.Panels {
Expand All @@ -140,8 +156,7 @@ func (rep *report) renderPNGsParallel(dash grafana.Dashboard) error {
//fetch images in parrallel form Grafana sever.
//limit concurrency using a worker pool to avoid overwhelming grafana
//for dashboards with many panels.
var wg sync.WaitGroup
workers := 5

wg.Add(workers)
errs := make(chan error, len(dash.Panels)) //routines can return errors on a channel
for i := 0; i < workers; i++ {
Expand Down