cli: improve debug error messages (#11507)

Improves `nomad debug` error messages when contacting agents that do not have /v1/agent/host endpoints (the endpoint was added in v0.12.0) Part of #9568 and manually tested against Nomad v0.8.7. Hopefully isRedirectError can be reused for more cases listed in #9568
hashicorp · Jan 17, 2022 · dc81f26 · dc81f26
1 parent ac18d71
commit dc81f26
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diff --git a/.changelog/11507.txt b/.changelog/11507.txt
@@ -0,0 +1,3 @@
+```improvement
+cli: improve `nomad operator debug` error messages
+```
diff --git a/command/operator_debug.go b/command/operator_debug.go
@@ -707,6 +707,11 @@ func (c *OperatorDebugCommand) collectAgentHost(path, id string, client *api.Cli
 		host, err = client.Agent().Host("", id, c.queryOpts())
 	}
 
+	if isRedirectError(err) {
+		c.Ui.Warn(fmt.Sprintf("%s/%s: /v1/agent/host unavailable on this agent", path, id))
+		return
+	}
+
 	if err != nil {
 		c.Ui.Error(fmt.Sprintf("%s/%s: Failed to retrieve agent host data, err: %v", path, id, err))
 
@@ -1428,3 +1433,13 @@ func defaultHttpClient() *http.Client {
 
 	return httpClient
 }
+
+// isRedirectError returns true if an error is a redirect error.
+func isRedirectError(err error) bool {
+	if err == nil {
+		return false
+	}
+
+	const redirectErr string = `invalid character '<' looking for beginning of value`
+	return strings.Contains(err.Error(), redirectErr)
+}
diff --git a/command/operator_debug_test.go b/command/operator_debug_test.go
@@ -3,8 +3,11 @@ package command
 import (
 	"fmt"
 	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 
@@ -741,6 +744,35 @@ func TestDebug_CollectVault(t *testing.T) {
 	require.FileExists(t, filepath.Join(testDir, "test", "vault-sys-health.json"))
 }
 
+// TestDebug_RedirectError asserts that redirect errors are detected so they
+// can be translated into more understandable output.
+func TestDebug_RedirectError(t *testing.T) {
+	// Create a test server that always returns the error many versions of
+	// Nomad return instead of a 404 for unknown paths.
+	// 1st request redirects to /ui/
+	// 2nd request returns UI's HTML
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if strings.HasSuffix(r.URL.String(), "/ui/") {
+			fmt.Fprintln(w, `<html>Fake UI HTML</html>`)
+			return
+		}
+
+		w.Header().Set("Location", "/ui/")
+		w.WriteHeader(307)
+		fmt.Fprintln(w, `<a href="/ui/">Temporary Redirect</a>.`)
+	}))
+	defer ts.Close()
+
+	config := api.DefaultConfig()
+	config.Address = ts.URL
+	client, err := api.NewClient(config)
+	require.NoError(t, err)
+
+	resp, err := client.Agent().Host("abc", "", nil)
+	assert.Nil(t, resp)
+	assert.True(t, isRedirectError(err), err.Error())
+}
+
 // TestDebug_StaleLeadership verifies that APIs that are required to
 // complete a debug run have their query options configured with the
 // -stale flag