fix potential race condition in API client

.circleci/config.yml

@@ -293,11 +293,15 @@ jobs:
       goarch:
         type: string
         default: "amd64"
+      enable_race_testing:
+        type: string
+        default: ""
     environment:
       GOTEST_PKGS_EXCLUDE: "<< parameters.exclude_packages >>"
       GOTEST_PKGS: "<< parameters.test_packages >>"
       GOTEST_MOD: "<< parameters.test_module >>"
       GOTESTARCH: "<< parameters.goarch >>"
+      ENABLE_RACE: "<< parameters.enable_race_testing >>"
     steps:
       - checkout
       - install-golang
@@ -616,6 +620,7 @@ workflows:
           name: "test-api"
           test_module: "api"
           filters: *backend_test_branches_filter
+          enable_race_testing: "1"
       - test-container:
           name: "test-devices"
           test_packages: "./devices/..."

CHANGELOG.md

@@ -17,6 +17,7 @@ IMPROVEMENTS:
 
 BUG FIXES:
  * agent: Only allow querying Prometheus formatted metrics if Prometheus is enabled within the config [[GH-10140](https://github.com/hashicorp/nomad/pull/10140)]
+ * api: Fixed race condition around headers in API client [[GH-10302](https://github.com/hashicorp/nomad/issues/10302)]
  * api: Added missing devices block to AllocatedTaskResources [[GH-10064](https://github.com/hashicorp/nomad/pull/10064)]
  * cli: Fixed a bug where non-int proxy port would panic CLI [[GH-10072](https://github.com/hashicorp/nomad/issues/10072)]
  * cli: Fixed a bug where `nomad operator debug` incorrectly parsed https Consul API URLs. [[GH-10082](https://github.com/hashicorp/nomad/pull/10082)]

api/api.go

@@ -685,8 +685,8 @@ func (c *Client) newRequest(method, path string) (*request, error) {
 		}
 	}
 
-	if c.config.Headers != nil {
-		r.header = c.config.Headers
+	for key, values := range c.config.Headers {
+		r.header[key] = values
 	}
 
 	return r, nil

api/api_test.go

@@ -13,9 +13,10 @@ import (
 	"testing"
 	"time"
 
-	"github.com/hashicorp/nomad/api/internal/testutil"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"github.com/hashicorp/nomad/api/internal/testutil"
 )
 
 type configCallback func(c *Config)
@@ -538,3 +539,28 @@ func TestCloneHttpClient(t *testing.T) {
 	})
 
 }
+
+func TestClient_HeaderRaceCondition(t *testing.T) {
+	require := require.New(t)
+
+	conf := DefaultConfig()
+	conf.Headers = map[string][]string{
+		"test-header": {"a"},
+	}
+	client, err := NewClient(conf)
+	require.NoError(err)
+
+	c := make(chan int)
+
+	go func() {
+		req, _ := client.newRequest("GET", "/any/path/will/do")
+		r, _ := req.toHTTP()
+		c <- len(r.Header)
+	}()
+	req, _ := client.newRequest("GET", "/any/path/will/do")
+	r, _ := req.toHTTP()
+
+	require.Len(r.Header, 2, "local request should have two headers")
+	require.Equal(2, <-c, "goroutine  request should have two headers")
+	require.Len(conf.Headers, 1, "config headers should not mutate")
+}