Stackoverflow: 79734079

config.go

package main

import (
	"fmt"
	"log/slog"
	"math/rand/v2"
	"os"

	"cloud.google.com/go/run/apiv2/runpb"
)

type config struct {
	project   string
	region    string
	service   string
	revisions map[string]string
}

func new() config {
	return config{
		project: os.Getenv("PROJECT"),
		region:  os.Getenv("REGION"),
		service: os.Getenv("SERVICE"),
		revisions: map[string]string{
			"blue":   os.Getenv("BLUE"),
			"green":  os.Getenv("GREEN"),
			"purple": os.Getenv("PURPLE"),
		},
	}
}
func (c config) name() string {
	name := fmt.Sprintf("projects/%s/locations/%s/services/%s",
		c.project,
		c.region,
		c.service,
	)

	return name
}

// traffic is a method that returns a Cloud RUn Service's TrafficTarget
// It uses a random number, initially 100%, that reduces for each target
// The last target must always consume the remaining percentage
// So that the total of all the revisions is 100%
func (c config) traffic() []*runpb.TrafficTarget {
	// Create TrafficTargets for each config revision
	num := len(c.revisions)
	targets := make([]*runpb.TrafficTarget, num)

	// Generate random traffic percent to avoid collisions
	// Start with 1..100
	var remaining int32 = 100
	var percent int32

	// Iterator
	i := 0
	for tag, revision := range c.revisions {
		// The last branch must consume the remaining percent so that the branches total 100%
		if i == num-1 {
			percent = remaining
		} else {
			percent = rand.N(int32(remaining + 1))
		}

		slog.Info("Generating traffic",
			"tag", tag,
			"revision", revision,
			"percent", percent,
		)
		targets[i] = &runpb.TrafficTarget{
			Type:     runpb.TrafficTargetAllocationType_TRAFFIC_TARGET_ALLOCATION_TYPE_REVISION,
			Revision: revision,
			Percent:  percent,
			Tag:      tag,
		}

		// Increment the iterator
		i = i + 1
		remaining = remaining - percent
	}

	return targets
}

go.mod

module github.com/DazWilkin/stackoverflow/79734079

go 1.25.0

require (
	cloud.google.com/go/run v1.12.0
	google.golang.org/protobuf v1.36.7
)

require (
	cloud.google.com/go v0.120.0 // indirect
	cloud.google.com/go/auth v0.16.3 // indirect
	cloud.google.com/go/auth/oauth2adapt v0.2.8 // indirect
	cloud.google.com/go/compute/metadata v0.7.0 // indirect
	cloud.google.com/go/iam v1.5.2 // indirect
	cloud.google.com/go/longrunning v0.6.7 // indirect
	github.com/felixge/httpsnoop v1.0.4 // indirect
	github.com/go-logr/logr v1.4.3 // indirect
	github.com/go-logr/stdr v1.2.2 // indirect
	github.com/google/s2a-go v0.1.9 // indirect
	github.com/googleapis/enterprise-certificate-proxy v0.3.6 // indirect
	github.com/googleapis/gax-go/v2 v2.15.0 // indirect
	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.61.0 // indirect
	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.61.0 // indirect
	go.opentelemetry.io/otel v1.36.0 // indirect
	go.opentelemetry.io/otel/metric v1.36.0 // indirect
	go.opentelemetry.io/otel/trace v1.36.0 // indirect
	golang.org/x/crypto v0.40.0 // indirect
	golang.org/x/net v0.42.0 // indirect
	golang.org/x/oauth2 v0.30.0 // indirect
	golang.org/x/sync v0.16.0 // indirect
	golang.org/x/sys v0.34.0 // indirect
	golang.org/x/text v0.27.0 // indirect
	golang.org/x/time v0.12.0 // indirect
	google.golang.org/api v0.246.0 // indirect
	google.golang.org/genproto v0.0.0-20250603155806-513f23925822 // indirect
	google.golang.org/genproto/googleapis/api v0.0.0-20250804133106-a7a43d27e69b // indirect
	google.golang.org/genproto/googleapis/rpc v0.0.0-20250804133106-a7a43d27e69b // indirect
	google.golang.org/grpc v1.74.2 // indirect
)

main.go

package main

import (
	"context"
	"log/slog"
	"os"

	run "cloud.google.com/go/run/apiv2"
	"cloud.google.com/go/run/apiv2/runpb"
	"google.golang.org/protobuf/types/known/fieldmaskpb"
)

func main() {
	ctx := context.Background()
	client, err := run.NewServicesClient(ctx)
	if err != nil {
		panic(err)
	}
	defer func() {
		if err := client.Close(); err != nil {
			slog.Error("Failed to close client", "err", err.Error())
			os.Exit(1)
		}
	}()

	c := new()

	// Get the Service
	var resp *runpb.Service
	{
		rqst := &runpb.GetServiceRequest{
			Name: c.name(),
		}

		var err error
		resp, err = client.GetService(ctx, rqst)
		if err != nil {
			panic(err)
		}

		slog.Info("Response", "resp", resp)
	}

	// Update the Service
	{
		// Update the Service's traffic
		resp.Traffic = c.traffic()

		rqst := &runpb.UpdateServiceRequest{
			UpdateMask: &fieldmaskpb.FieldMask{
				Paths: []string{
					"traffic",
				},
			},
			Service: resp,
		}
		resp, err := client.UpdateService(ctx, rqst)
		if err != nil {
			panic(err)
		}

		slog.Info("Response", "resp", resp)
	}
}