[loadbalancingexporter]Allow specifying port when using DNS resolver (#…

…1650)

* [loadbalancingexporter]Allow specifying port when using DNS resolver

* Edit README message for newly added port field

exporter/loadbalancingexporter/README.md

@@ -17,6 +17,7 @@ Refer to [config.yaml](./testdata/config.yaml) for detailed examples on using th
 * The `otlp` property configures the template used for building the OTLP exporter. Refer to the OTLP Exporter documentation for information on which options are available. Note that the `endpoint` property should not be set and will be overridden by this exporter with the backend endpoint.
 * The `resolver` accepts either a `static` node, or a `dns`. If both are specified, `dns` takes precedence.
 * The `hostname` property inside a `dns` node specifies the hostname to query in order to obtain the list of IP addresses.
+* The `dns` node also accepts an optional property `port` to specify the port to be used for exporting the traces to the IP addresses resolved from `hostname`. If `port` is not specified, the default port 55680 is used.
 
 
 Simple example

exporter/loadbalancingexporter/config.go

@@ -45,4 +45,5 @@ type StaticResolver struct {
 // DNSResolver defines the configuration for the DNS resolver
 type DNSResolver struct {
  Hostname string `mapstructure:"hostname"`
+ Port string `mapstructure:"port"`
 }

exporter/loadbalancingexporter/exporter.go

@@ -88,7 +88,7 @@ func newExporter(params component.ExporterCreateParams, cfg configmodels.Exporte
  dnsLogger := params.Logger.With(zap.String("resolver", "dns"))
 
  var err error
- res, err = newDNSResolver(dnsLogger, oCfg.Resolver.DNS.Hostname)
+ res, err = newDNSResolver(dnsLogger, oCfg.Resolver.DNS.Hostname, oCfg.Resolver.DNS.Port)
  if err != nil {
  return nil, err
  }

exporter/loadbalancingexporter/resolver_dns.go

@@ -41,6 +41,7 @@ type dnsResolver struct {
  logger *zap.Logger
 
  hostname string
+ port string
  resolver netResolver
  resInterval time.Duration
  resTimeout time.Duration
@@ -58,14 +59,15 @@ type netResolver interface {
  LookupIPAddr(ctx context.Context, host string) ([]net.IPAddr, error)
 }
 
-func newDNSResolver(logger *zap.Logger, hostname string) (*dnsResolver, error) {
+func newDNSResolver(logger *zap.Logger, hostname string, port string) (*dnsResolver, error) {
  if len(hostname) == 0 {
  return nil, errNoHostname
  }
 
  return &dnsResolver{
  logger: logger,
  hostname: hostname,
+ port: port,
  resolver: &net.Resolver{},
  resInterval: defaultResInterval,
  resTimeout: defaultResTimeout,
@@ -134,6 +136,12 @@ func (r *dnsResolver) resolve(ctx context.Context) ([]string, error) {
  // it's an IPv6 address
  backend = fmt.Sprintf("[%s]", ip.String())
  }
+
+ // if a port is specified in the configuration, add it
+ if r.port != "" {
+ backend = fmt.Sprintf("%s:%s", backend, r.port)
+ }
+
  backends = append(backends, backend)
  }
 

exporter/loadbalancingexporter/resolver_dns_test.go

@@ -29,7 +29,7 @@ import (
 
 func TestInitialDNSResolution(t *testing.T) {
  // prepare
- res, err := newDNSResolver(zap.NewNop(), "service-1")
+ res, err := newDNSResolver(zap.NewNop(), "service-1", "")
  require.NoError(t, err)
 
  res.resolver = &mockDNSResolver{
@@ -57,9 +57,39 @@ func TestInitialDNSResolution(t *testing.T) {
  }
 }
 
+func TestInitialDNSResolutionWithPort(t *testing.T) {
+ // prepare
+ res, err := newDNSResolver(zap.NewNop(), "service-1", "55690")
+ require.NoError(t, err)
+
+ res.resolver = &mockDNSResolver{
+ onLookupIPAddr: func(context.Context, string) ([]net.IPAddr, error) {
+ return []net.IPAddr{
+ {IP: net.IPv4(127, 0, 0, 1)},
+ {IP: net.IPv4(127, 0, 0, 2)},
+ {IP: net.IPv6loopback},
+ }, nil
+ },
+ }
+
+ // test
+ var resolved []string
+ res.onChange(func(endpoints []string) {
+ resolved = endpoints
+ })
+ res.start(context.Background())
+ defer res.shutdown(context.Background())
+
+ // verify
+ assert.Len(t, resolved, 3)
+ for i, value := range []string{"127.0.0.1:55690", "127.0.0.2:55690", "[::1]:55690"} {
+ assert.Equal(t, value, resolved[i])
+ }
+}
+
 func TestErrNoHostname(t *testing.T) {
  // test
- res, err := newDNSResolver(zap.NewNop(), "")
+ res, err := newDNSResolver(zap.NewNop(), "", "")
 
  // verify
  assert.Nil(t, res)
@@ -68,7 +98,7 @@ func TestErrNoHostname(t *testing.T) {
 
 func TestCantResolve(t *testing.T) {
  // prepare
- res, err := newDNSResolver(zap.NewNop(), "service-1")
+ res, err := newDNSResolver(zap.NewNop(), "service-1", "")
  require.NoError(t, err)
 
  expectedErr := errors.New("some expected error")
@@ -87,7 +117,7 @@ func TestCantResolve(t *testing.T) {
 
 func TestOnChange(t *testing.T) {
  // prepare
- res, err := newDNSResolver(zap.NewNop(), "service-1")
+ res, err := newDNSResolver(zap.NewNop(), "service-1", "")
  require.NoError(t, err)
 
  resolve := []net.IPAddr{
@@ -150,7 +180,7 @@ func TestEqualStringSlice(t *testing.T) {
 
 func TestPeriodicallyResolve(t *testing.T) {
  // prepare
- res, err := newDNSResolver(zap.NewNop(), "service-1")
+ res, err := newDNSResolver(zap.NewNop(), "service-1", "")
  require.NoError(t, err)
 
  counter := 0
@@ -195,7 +225,7 @@ func TestPeriodicallyResolve(t *testing.T) {
 
 func TestPeriodicallyResolveFailure(t *testing.T) {
  // prepare
- res, err := newDNSResolver(zap.NewNop(), "service-1")
+ res, err := newDNSResolver(zap.NewNop(), "service-1", "")
  require.NoError(t, err)
 
  expectedErr := errors.New("some expected error")
@@ -237,7 +267,7 @@ func TestPeriodicallyResolveFailure(t *testing.T) {
 
 func TestShutdownClearsCallbacks(t *testing.T) {
  // prepare
- res, err := newDNSResolver(zap.NewNop(), "service-1")
+ res, err := newDNSResolver(zap.NewNop(), "service-1", "")
  require.NoError(t, err)
 
  res.resolver = &mockDNSResolver{}

exporter/loadbalancingexporter/testdata/config.yaml

@@ -14,16 +14,25 @@ exporters:
  resolver:
  static:
  hostnames:
- - endpoint-1 # assumes 55678 as the default port
+ - endpoint-1 # assumes 55680 as the default port
  - endpoint-2:55678
  loadbalancing/2:
  protocol:
  otlp:
 
+ # how to get the list of backends: DNS
+ resolver:
+ dns:
+ hostname: service-1 # assumes 55680 as the default port for the resolved IP addresses
+ loadbalancing/3:
+ protocol:
+ otlp:
+
  # how to get the list of backends: DNS
  resolver:
  dns:
  hostname: service-1
+ port: 55690
 
 service:
  pipelines: