netbalancer: more consistent handling of empty host list

esiqveland · Apr 9, 2019 · 2ea2d75 · 2ea2d75
1 parent 91b5a71
commit 2ea2d75
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Showing 2 changed files with 13 additions and 15 deletions.
diff --git a/netbalancer/netbalancer.go b/netbalancer/netbalancer.go
@@ -16,8 +16,11 @@ import (
 // We can not use TTL from dns because TTL is not exposed by the Go calls.
 func New(host string, port int, updateInterval, timeout time.Duration) (balancer.Balancer, error) {
  initialHosts, err := lookupTimeout(timeout, host, port)
+ if err != nil {
+ return nil, err
+ }
  if len(initialHosts) == 0 {
- return nil, errors.Wrapf(err, "Error no ips found for host=%v", host)
+ return nil, balancer.ErrNoHosts
  }
 
  bal := &dnsBalancer{
@@ -74,7 +77,7 @@ func (b *dnsBalancer) update() {
  // TODO: set hostList to empty?
  // TODO: log?
  } else {
- if len(nextHostList) > 0 {
+ if nextHostList != nil {
  log.Printf("[DnsBalancer] reloaded dns=%v hosts=%v", b.lookupAddress, nextHostList)
  b.lock.Lock()
  b.hosts = nextHostList
@@ -97,16 +100,13 @@ func lookupTimeout(timeout time.Duration, host string, port int) ([]balancer.Hos
 }
 
 func lookup(ctx context.Context, host string, port int) ([]balancer.Host, error) {
+ hosts := []balancer.Host{}
+
  ips, err := net.DefaultResolver.LookupIPAddr(ctx, host)
  if err != nil {
- return nil, errors.Wrapf(err, "Error looking up initial list for host=%v", host)
+ return hosts, errors.Wrapf(err, "Error looking up host=%v", host)
  }
 
- if len(ips) == 0 {
- return nil, balancer.ErrNoHosts
- }
-
- hosts := []balancer.Host{}
  for k := range ips {
  entry := balancer.Host{
  Address: ips[k].IP,

diff --git a/netbalancer/srvbalancer.go b/netbalancer/srvbalancer.go
@@ -9,7 +9,6 @@ import (
  "time"
 
  "github.com/esiqveland/balancer"
- "github.com/pkg/errors"
 )
 
 type dnsSrvBalancer struct {
@@ -24,16 +23,15 @@ type dnsSrvBalancer struct {
  Timeout time.Duration
 }
 
-// NewNetBalancer returns a Balancer that uses dns lookups from net.Lookup* to reload a set of hosts every updateInterval.
-// We can not use TTL from dns because TTL is not exposed by the Go calls.
+// NewSRV returns a Balancer that uses dns lookups from net.LookupSRV to reload a set of hosts every updateInterval.
+// We can not use TTL from dns because TTL is not exposed by the Go stdlib.
 func NewSRV(servicename, proto, host string, updateInterval time.Duration, dnsTimeout time.Duration) (balancer.Balancer, error) {
  initialHosts, err := lookupSRVTimeout(dnsTimeout, servicename, proto, host)
  if err != nil {
  return nil, err
  }
-
  if len(initialHosts) == 0 {
- return nil, errors.Wrapf(err, "Error no ips found for host=%v", host)
+ return nil, balancer.ErrNoHosts
  }
 
  bal := &dnsSrvBalancer{
@@ -119,8 +117,8 @@ func (b *dnsSrvBalancer) update() {
  // TODO: set hostList to empty?
  // TODO: log?
  } else {
- if len(nextHostList) > 0 {
- log.Printf("[DnsBalancer] reloaded dns=%v hosts=%v", b.host, nextHostList)
+ if nextHostList != nil {
+ log.Printf("[SRVBalancer] reloaded dns=%v hosts=%v", b.host, nextHostList)
  b.lock.Lock()
  b.hosts = nextHostList
  b.lock.Unlock()