How to apply concurrency in golang to pass multiple app metrics to datadog

[Shatabdi Pal]

Hello,

I have a requirement to create a datadog dashboard with application metrics. The app names are read from a config.toml. The code runs only for the first app provided in the toml file and never proceeds to the second app. The structure is a follows:  

config.toml

application = ["app1", "app2", "app3"]

customer = ["abc"]

main.go

// Sending Metrics to Datadog UI

func sendMetrics(name string, channel chan string) {

// Calculates the Epoch Time for App

EpochTime1 := epochTime()

// Calculates the Epoch Time for Github

EpochTime2 := gitEpochTime()

// Lead Time from Github Commit to App Deployment

calculated_time := EpochTime1 - EpochTime2

v := versionDetails()

dd_tags := "metric_tag:" + v

tags := []string{dd_tags}

rate := float64(1)

c, err := statsd.New("127.0.0.1:18125")

if err != nil {

log.Fatal(err)

}

e := c.Gauge(name, float64(calculated_time), tags, rate)

if e != nil {

log.Println(e)

fmt.Println("name:::", name)

fmt.Println("lead time:::", leadTime)

channel <- name

}

fmt.Println("name:::", name)

fmt.Println("lead time:::", leadTime)

channel <- name

log.Printf("Metrics for %s sent successfully!!", name)

}

func main() {

channel := make(chan string)

appName, _ := getTag() //gets the appName and customerName both of which are [] string type

fmt.Println("App names: ", appName, reflect.TypeOf(appName))

for _, app := range appName {

// Calculate the Epoch Time

fmt.Println("Executing app............ ", app)

if epochTime() == 0 {

log.Println("No deployment present during the Time Frame!")

for res := range channel {

go func(app string) {

time.Sleep(3 * time.Second)

sendMetrics(app, channel)

}(res)

}

} else {

go sendMetrics(app, channel)

for res := range channel {

go func(name string) {

time.Sleep(3 * time.Second)

sendMetrics(name, channel)

}(res)

}

}

}

}

I am new to Golang and any help is highly appreciated.

Thanks,

Shatabdi

[Anderson Queiroz]

I didn't have much time to look at it, but try to rebind the `app` variable:

for _, app := range appName {

// Calculate the Epoch Time

app := app // rebidding app

a short, and not quite formal, explanation is that the loop variable is reused during the iterations, and when a loop variable is captured in a clojure, it isn't copied, so when the clojure executes the captured variable will have the value for the current loop iteration. And it happens that the clojure executed in a go routine will only run after the for loop have finished, and therefore all the goroutines referencing the loop variable will read the value for the last iteration.

here you're capturing it:

go func(app string) {

time.Sleep(3 * time.Second)

sendMetrics(app, channel)

}(res)

I hope it helps :)

Best,
Anderson