Show latest config in /v1/agent/self (#18714)

* Show latest config in /v1/agent/self

* remove license string in backport

.changelog/18681.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+api: Fix `/v1/agent/self` not returning latest configuration 
+```

GNUmakefile

@@ -335,6 +335,7 @@ deep-copy:
 	@$(SHELL) $(CURDIR)/agent/structs/deep-copy.sh
 	@$(SHELL) $(CURDIR)/agent/proxycfg/deep-copy.sh
 	@$(SHELL) $(CURDIR)/agent/consul/state/deep-copy.sh
+	@$(SHELL) $(CURDIR)/agent/config/deep-copy.sh
 
 version:
 	@echo -n "Version:                    "

agent/agent.go

@@ -4195,6 +4195,9 @@ func (a *Agent) reloadConfigInternal(newCfg *config.RuntimeConfig) error {
 	a.enableDebug.Store(newCfg.EnableDebug)
 	a.config.EnableDebug = newCfg.EnableDebug
 
+	// update Agent config with new config
+	a.config = newCfg.DeepCopy()
+
 	return nil
 }
 

agent/agent_endpoint_test.go

@@ -8031,3 +8031,59 @@ func TestAgent_Services_ExposeConfig(t *testing.T) {
 	}
 	require.Equal(t, srv1.Proxy.ToAPI(), actual.Proxy)
 }
+
+func TestAgent_Self_Reload(t *testing.T) {
+	if testing.Short() {
+		t.Skip("too slow for testing.Short")
+	}
+
+	t.Parallel()
+
+	// create new test agent
+	a := NewTestAgent(t, `
+		log_level = "info"
+		raft_snapshot_threshold = 100
+	`)
+	defer a.Shutdown()
+
+	testrpc.WaitForTestAgent(t, a.RPC, "dc1")
+	req, _ := http.NewRequest("GET", "/v1/agent/self", nil)
+	resp := httptest.NewRecorder()
+	a.srv.h.ServeHTTP(resp, req)
+
+	dec := json.NewDecoder(resp.Body)
+	val := &Self{}
+	require.NoError(t, dec.Decode(val))
+
+	require.Equal(t, "info", val.DebugConfig["Logging"].(map[string]interface{})["LogLevel"])
+	require.Equal(t, float64(100), val.DebugConfig["RaftSnapshotThreshold"].(float64))
+
+	// reload with new config
+	shim := &delegateConfigReloadShim{delegate: a.delegate}
+	a.delegate = shim
+	newCfg := TestConfig(testutil.Logger(t), config.FileSource{
+		Name:   "Reload",
+		Format: "hcl",
+		Data: `
+			data_dir = "` + a.Config.DataDir + `"
+			log_level = "debug"
+			raft_snapshot_threshold = 200	
+		`,
+	})
+	if err := a.reloadConfigInternal(newCfg); err != nil {
+		t.Fatalf("got error %v want nil", err)
+	}
+	require.Equal(t, 200, shim.newCfg.RaftSnapshotThreshold)
+
+	// validate new config is reflected in API response
+	req, _ = http.NewRequest("GET", "/v1/agent/self", nil)
+	resp = httptest.NewRecorder()
+	a.srv.h.ServeHTTP(resp, req)
+
+	dec = json.NewDecoder(resp.Body)
+	val = &Self{}
+	require.NoError(t, dec.Decode(val))
+	require.Equal(t, "debug", val.DebugConfig["Logging"].(map[string]interface{})["LogLevel"])
+	require.Equal(t, float64(200), val.DebugConfig["RaftSnapshotThreshold"].(float64))
+
+}