Merge pull request #12 from statsbomb/region_from_ec2imds

Allow for explicitly setting the region and add EC2 IMDS as a fallback

README.md

@@ -61,6 +61,11 @@ $ ./prometheus-msk-discovery -scrape-interval 10s -filter 'primary'
 
 An example output file can be found [here](examples/msk_file_sd.yml)
 
+## Region Precedence
+When no region is specified with the `-region` flag the process first attempts to load the default SDK configuration checking for an `AWS_REGION` environment variable or reading any region specified in the standard [configuration file](https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-files.html). If no region is found it will attempt to retrieve it from the EC2 Instance Metadata Service.
+
+**Explicitly setting a region with the** `-region` **flag takes precedence over everything else.**
+
 ## Integration with kube-prometheus-stack
 
 The [Docker image](https://hub.docker.com/r/statsbomb/prometheus-msk-discovery) for this project can be used to inject a container into the Prometheus Spec of a [kube-prometheus-stack](https://github.com/prometheus-community/helm-charts/tree/main/charts/kube-prometheus-stack) installation by using the following snippet in `values.yaml`:

main.go

@@ -16,13 +16,18 @@ import (
 	"gopkg.in/yaml.v2"
 )
 
-const jmxExporterPort = 11001
-const nodeExporterPort = 11002
+const (
+	jmxExporterPort  = 11001
+	nodeExporterPort = 11002
+)
 
-var outFile = flag.String("output", "msk_file_sd.yml", "path of the file to write MSK discovery information to")
-var interval = flag.Duration("scrape-interval", 5*time.Minute, "interval at which to scrape the AWS API for MSK cluster information")
-var jobPrefix = flag.String("job-prefix", "msk", "string with which to prefix each job label")
-var clusterFilter = flag.String("filter", "", "a regex pattern to filter cluster names from the results")
+var (
+	outFile       = flag.String("output", "msk_file_sd.yml", "path of the file to write MSK discovery information to")
+	interval      = flag.Duration("scrape-interval", 5*time.Minute, "interval at which to scrape the AWS API for MSK cluster information")
+	jobPrefix     = flag.String("job-prefix", "msk", "string with which to prefix each job label")
+	clusterFilter = flag.String("filter", "", "a regex pattern to filter cluster names from the results")
+	awsRegion     = flag.String("region", "", "the aws region in which to scan for MSK clusters")
+)
 
 type kafkaClient interface {
 	ListClusters(ctx context.Context, params *kafka.ListClustersInput, optFns ...func(*kafka.Options)) (*kafka.ListClustersOutput, error)
@@ -171,7 +176,7 @@ func GetStaticConfigs(svc kafkaClient, opt_filter ...regexp.Regexp) ([]Prometheu
 func main() {
 	flag.Parse()
 
-	cfg, err := config.LoadDefaultConfig(context.TODO())
+	cfg, err := config.LoadDefaultConfig(context.TODO(), config.WithRegion(*awsRegion), config.WithEC2IMDSRegion())
 	if err != nil {
 		fmt.Println(err)
 		return
@@ -180,7 +185,6 @@ func main() {
 	client := kafka.NewFromConfig(cfg)
 
 	work := func() {
-
 		regexpFilter, err := regexp.Compile(*clusterFilter)
 		if err != nil {
 			fmt.Println(err)
@@ -216,5 +220,4 @@ func main() {
 		}
 		work()
 	}
-
 }