Add simple client for fetching AWS EC2 metadata

aws/metadata.go

@@ -0,0 +1,46 @@
+package aws
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+)
+
+type MetadataClient struct {
+	client *http.Client
+	URL    string
+}
+
+func NewMetadataClient() *MetadataClient {
+	return &MetadataClient{
+		client: &http.Client{},
+		URL:    `http://169.254.169.254/`,
+	}
+}
+
+func (m *MetadataClient) LocalIPv4() (string, error) {
+	return m.get("/latest/meta-data/local-ipv4")
+}
+
+func (m *MetadataClient) PublicIPv4() (string, error) {
+	return m.get("/latest/meta-data/public-ipv4")
+}
+
+func (m *MetadataClient) get(path string) (string, error) {
+	resp, err := m.client.Get(m.URL + path)
+	if err != nil {
+		return "", err
+	}
+
+	defer resp.Body.Close()
+
+	b, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return "", err
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("failed to request %s, got: %s", path, resp.Status)
+	}
+	return string(b), nil
+}

aws/metadata_test.go

@@ -0,0 +1,89 @@
+package aws
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func Test_NewMetadataClient(t *testing.T) {
+	c := NewMetadataClient()
+	if c == nil {
+		t.Fatalf("failed to create new Metadata client")
+	}
+}
+
+func Test_MetadataClient_LocalIPv4(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != "GET" {
+			t.Fatalf("Client did not use GET")
+		}
+		if r.URL.String() != "/latest/meta-data/local-ipv4" {
+			t.Fatalf("Request URL is wrong, got: %s", r.URL.String())
+		}
+		fmt.Fprint(w, "172.31.34.179")
+	}))
+	defer ts.Close()
+
+	c := NewMetadataClient()
+	c.URL = ts.URL
+	addr, err := c.LocalIPv4()
+	if err != nil {
+		t.Fatalf("failed to get local IPv4 address: %s", err.Error())
+	}
+	if addr != "172.31.34.179" {
+		t.Fatalf("got incorrect local IPv4 address: %s", addr)
+	}
+}
+
+func Test_MetadataClient_LocalIPv4Fail(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusBadRequest)
+	}))
+	defer ts.Close()
+
+	c := NewMetadataClient()
+	c.URL = ts.URL
+	_, err := c.LocalIPv4()
+	if err == nil {
+		t.Fatalf("failed to get error when server returned 400")
+	}
+}
+
+func Test_MetadataClient_PublicIPv4(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != "GET" {
+			t.Fatalf("Client did not use GET")
+		}
+		if r.URL.String() != "/latest/meta-data/public-ipv4" {
+			t.Fatalf("Request URL is wrong, got: %s", r.URL.String())
+		}
+		fmt.Fprint(w, "52.38.41.98")
+	}))
+	defer ts.Close()
+
+	c := NewMetadataClient()
+	c.URL = ts.URL
+	addr, err := c.PublicIPv4()
+	if err != nil {
+		t.Fatalf("failed to get local IPv4 address: %s", err.Error())
+	}
+	if addr != "52.38.41.98" {
+		t.Fatalf("got incorrect local IPv4 address: %s", addr)
+	}
+}
+
+func Test_MetadataClient_PublicIPv4Fail(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusBadRequest)
+	}))
+	defer ts.Close()
+
+	c := NewMetadataClient()
+	c.URL = ts.URL
+	_, err := c.PublicIPv4()
+	if err == nil {
+		t.Fatalf("failed to get error when server returned 400")
+	}
+}