Remove response body from websocket error

If a websocket connection errors we currently return the error with a
copy of the response body. The response body from the websocket can
often times be completely illegible so remove it from the error string.

make alloc id empty for more reliable failure

un-gzip if content encoding header present

api/allocations_test.go

 package api
 
 import (
+	"context"
+	"os"
 	"reflect"
 	"sort"
 	"testing"
@@ -247,6 +249,58 @@ func TestAllocations_RescheduleInfo(t *testing.T) {
 
 }
 
+// TestAllocations_ExecErrors ensures errors are properly formatted
+func TestAllocations_ExecErrors(t *testing.T) {
+	c, s := makeClient(t, nil, nil)
+	defer s.Stop()
+	a := c.Allocations()
+
+	job := &Job{
+		Name:      stringToPtr("foo"),
+		Namespace: stringToPtr(DefaultNamespace),
+		ID:        stringToPtr("bar"),
+		ParentID:  stringToPtr("lol"),
+		TaskGroups: []*TaskGroup{
+			{
+				Name: stringToPtr("bar"),
+				Tasks: []*Task{
+					{
+						Name: "task1",
+					},
+				},
+			},
+		},
+	}
+	job.Canonicalize()
+
+	uuidGen := func() string {
+		ret, err := uuid.GenerateUUID()
+		if err != nil {
+			t.Fatal(err)
+		}
+		return ret
+	}
+
+	alloc := &Allocation{
+		ID:        "",
+		Namespace: DefaultNamespace,
+		EvalID:    uuidGen(),
+		Name:      "foo-bar[1]",
+		NodeID:    uuidGen(),
+		TaskGroup: *job.TaskGroups[0].Name,
+		JobID:     *job.ID,
+		Job:       job,
+	}
+	// Querying when no allocs exist returns nothing
+	sizeCh := make(chan TerminalSize, 1)
+
+	// make a request that will result in an error
+	// ensure the error is what we expect
+	_, err := a.Exec(context.Background(), alloc, "bar", false, []string{"command"}, os.Stdin, os.Stdout, os.Stderr, sizeCh, nil)
+	require.Contains(t, err.Error(), "Unexpected response code: 301")
+	require.Contains(t, err.Error(), "Moved Permanently")
+}
+
 func TestAllocations_ShouldMigrate(t *testing.T) {
 	t.Parallel()
 	require.True(t, DesiredTransition{Migrate: boolToPtr(true)}.ShouldMigrate())

api/api.go

@@ -742,7 +742,16 @@ func (c *Client) websocket(endpoint string, q *QueryOptions) (*websocket.Conn, *
 	// check resp status code, as it's more informative than handshake error we get from ws library
 	if resp != nil && resp.StatusCode != 101 {
 		var buf bytes.Buffer
-		io.Copy(&buf, resp.Body)
+
+		if resp.Header.Get("Content-Encoding") == "gzip" {
+			greader, err := gzip.NewReader(resp.Body)
+			if err != nil {
+				return nil, nil, fmt.Errorf("Unexpected response code: %d", resp.StatusCode)
+			}
+			io.Copy(&buf, greader)
+		} else {
+			io.Copy(&buf, resp.Body)
+		}
 		resp.Body.Close()
 
 		return nil, nil, fmt.Errorf("Unexpected response code: %d (%s)", resp.StatusCode, buf.Bytes())