Make backoff MaxInterval and MaxElapsedTime configurable (#33)

This makes the max interval and max elapsed time configurabe for the
exponential backoff used when getting a role based on source IP.

The defaults are still the same e.g. 1 minute for MaxInterval and 15
minutes for the MaxElapsedTime.

Fix #28

* Use sane max interval & max elapsed time defaults

cmd/server.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"net/http/httputil"
 	"strings"
+	"time"
 
 	log "github.com/Sirupsen/logrus"
 	"github.com/cenk/backoff"
@@ -15,22 +16,24 @@ import (
 // Server encapsulates all of the parameters necessary for starting up
 // the server. These can either be set via command line or directly.
 type Server struct {
-	APIServer       string
-	APIToken        string
-	AppPort         string
-	BaseRoleARN     string
-	DefaultIAMRole  string
-	IAMRoleKey      string
-	MetadataAddress string
-	HostInterface   string
-	HostIP          string
-	AddIPTablesRule bool
-	Insecure        bool
-	Verbose         bool
-	Version         bool
-	iam             *iam
-	k8s             *k8s
-	store           *store
+	APIServer             string
+	APIToken              string
+	AppPort               string
+	BaseRoleARN           string
+	DefaultIAMRole        string
+	IAMRoleKey            string
+	MetadataAddress       string
+	HostInterface         string
+	HostIP                string
+	BackoffMaxInterval    time.Duration
+	BackoffMaxElapsedTime time.Duration
+	AddIPTablesRule       bool
+	Insecure              bool
+	Verbose               bool
+	Version               bool
+	iam                   *iam
+	k8s                   *k8s
+	store                 *store
 }
 
 type appHandler func(http.ResponseWriter, *http.Request)
@@ -63,7 +66,11 @@ func (s *Server) getRole(IP string) (string, error) {
 		return err
 	}
 
-	err = backoff.Retry(operation, backoff.NewExponentialBackOff())
+	expBackoff := backoff.NewExponentialBackOff()
+	expBackoff.MaxInterval = s.BackoffMaxInterval
+	expBackoff.MaxElapsedTime = s.BackoffMaxElapsedTime
+
+	err = backoff.Retry(operation, expBackoff)
 	if err != nil {
 		return "", err
 	}

main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"runtime"
+	"time"
 
 	log "github.com/Sirupsen/logrus"
 	"github.com/spf13/pflag"
@@ -11,6 +12,11 @@ import (
 	"github.com/jtblin/kube2iam/version"
 )
 
+const (
+	defaultMaxInterval    = 1 * time.Second
+	defaultMaxElapsedTime = 2 * time.Second
+)
+
 func main() {
 	runtime.GOMAXPROCS(runtime.NumCPU())
 	s := cmd.NewServer()
@@ -49,6 +55,8 @@ func addFlags(s *cmd.Server, fs *pflag.FlagSet) {
 	fs.BoolVar(&s.AddIPTablesRule, "iptables", false, "Add iptables rule (also requires --host-ip)")
 	fs.StringVar(&s.HostInterface, "host-interface", "docker0", "Host interface for proxying AWS metadata")
 	fs.StringVar(&s.HostIP, "host-ip", s.HostIP, "IP address of host")
+	fs.DurationVar(&s.BackoffMaxInterval, "backoff-max-interval", defaultMaxInterval, "Max interval for backoff when querying for role.")
+	fs.DurationVar(&s.BackoffMaxElapsedTime, "backoff-max-elapsed-time", defaultMaxElapsedTime, "Max elapsed time for backoff when querying for role.")
 	fs.BoolVar(&s.Verbose, "verbose", false, "Verbose")
 	fs.BoolVar(&s.Version, "version", false, "Print the version and exits")
 }