Add health check endpoint

.github/workflows/ci.yml

@@ -73,6 +73,8 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - uses: actions/checkout@0ad4b8fadaa221de15dcec353f45205ec38ea70b # v4.1.4
+        with:
+          fetch-depth: 0
       - uses: actions/setup-go@0c52d547c9bc32b1aa3301fd7a9cb496313a4491 # v5.0.0
         with:
           go-version-file: 'go.mod'
@@ -144,6 +146,8 @@ jobs:
           version: "bookworm-slim"
     steps:
       - uses: actions/checkout@0ad4b8fadaa221de15dcec353f45205ec38ea70b # v4.1.4
+        with:
+          fetch-depth: 0
       - uses: actions/setup-go@0c52d547c9bc32b1aa3301fd7a9cb496313a4491 # v5.0.0
         with:
           go-version-file: 'go.mod'

docs/swagger.json

@@ -3,6 +3,23 @@
   "info": {},
   "host": "localhost:8081",
   "paths": {
+    "/health": {
+      "get": {
+        "tags": [
+          "nginx-agent"
+        ],
+        "summary": "Check the health of the NGINX Agent",
+        "operationId": "health-check",
+        "responses": {
+          "200": {
+            "description": "HealthResponse",
+            "schema": {
+              "$ref": "#/definitions/HealthResponse"
+            }
+          }
+        }
+      }
+    },
     "/metrics/": {
       "get": {
         "description": "# Returns prometheus metrics",
@@ -127,6 +144,12 @@
             "schema": {
               "$ref": "#/definitions/AgentAPIConfigApplyStatusResponse"
             }
+          },
+          "500": {
+            "description": "AgentAPICommonResponse",
+            "schema": {
+              "$ref": "#/definitions/AgentAPICommonResponse"
+            }
           }
         }
       }
@@ -195,6 +218,44 @@
       },
       "x-go-package": "github.com/nginx/agent/v2/src/plugins"
     },
+    "HealthResponse": {
+      "type": "object",
+      "properties": {
+        "checks": {
+          "description": "Array of health checks",
+          "type": "array",
+          "items": {
+            "$ref": "#/definitions/HealthStatusCheck"
+          },
+          "x-go-name": "Checks"
+        },
+        "status": {
+          "description": "Overall health status",
+          "type": "string",
+          "x-go-name": "Status",
+          "example": "OK"
+        }
+      },
+      "x-go-package": "github.com/nginx/agent/v2/src/plugins"
+    },
+    "HealthStatusCheck": {
+      "type": "object",
+      "properties": {
+        "name": {
+          "description": "Health check name",
+          "type": "string",
+          "x-go-name": "Name",
+          "example": "commandConnection"
+        },
+        "status": {
+          "description": "Health check status",
+          "type": "string",
+          "x-go-name": "Status",
+          "example": "OK"
+        }
+      },
+      "x-go-package": "github.com/nginx/agent/v2/src/plugins"
+    },
     "NginxDetails": {
       "type": "object",
       "properties": {

main.go

@@ -73,10 +73,7 @@ func main() {
 		controller, commander, reporter := core.CreateGrpcClients(ctx, loadedConfig)
 
 		if controller != nil {
-			if err := controller.Connect(); err != nil {
-				log.Warnf("Unable to connect to control plane: %v", err)
-				return
-			}
+			go controller.Connect()
 		}
 
 		binary := core.NewNginxBinary(env, loadedConfig)

sdk/client/client.go

@@ -78,7 +78,7 @@ type (
 		WithClient(Client) Controller
 		Context() context.Context
 		WithContext(context.Context) Controller
-		Connect() error
+		Connect()
 		Close() error
 	}
 )

sdk/client/commander.go

@@ -10,6 +10,7 @@ package client
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"sync"
@@ -74,11 +75,15 @@ func (c *commander) Connect(ctx context.Context) error {
 	log.Debugf("Commander connecting to %s", c.server)
 
 	c.ctx = ctx
+
+	c.retryLock.Lock()
 	err := backoff.WaitUntil(
 		c.ctx,
 		c.backoffSettings,
 		c.createClient,
 	)
+	c.retryLock.Unlock()
+
 	if err != nil {
 		return err
 	}
@@ -163,6 +168,11 @@ func (c *commander) Send(ctx context.Context, message Message) error {
 			return err
 		}
 
+		if c.channel == nil {
+			c.setIsRetrying(true)
+			return c.handleGrpcError("Commander Channel Send", errors.New("command channel client not created yet"))
+		}
+
 		if err := c.channel.Send(cmd); err != nil {
 			c.setIsRetrying(true)
 			return c.handleGrpcError("Commander Channel Send", err)

sdk/client/controller.go

@@ -10,6 +10,8 @@ package client
 import (
 	"context"
 	"fmt"
+
+	log "github.com/sirupsen/logrus"
 )
 
 func NewClientController() Controller {
@@ -33,19 +35,12 @@ func (c *ctrl) WithContext(ctx context.Context) Controller {
 	return c
 }
 
-func (c *ctrl) Connect() error {
-	var retErr error
+func (c *ctrl) Connect() {
 	for _, client := range c.clients {
 		if err := client.Connect(c.ctx); err != nil {
-			if retErr == nil {
-				retErr = fmt.Errorf("%s failed to connect: %w", client.Server(), err)
-			} else {
-				retErr = fmt.Errorf("%v\n%s failed to connect: %w", retErr, client.Server(), err)
-			}
+			log.Warnf("%s failed to connect: %v", client.Server(), err)
 		}
 	}
-
-	return retErr
 }
 
 func (c *ctrl) Close() error {

sdk/client/controller_test.go

@@ -45,8 +45,7 @@ func TestControllerConnect(t *testing.T) {
 	controller.WithClient(metricsReportClient)
 	controller.WithContext(ctx)
 
-	err := controller.Connect()
-	assert.Nil(t, err)
+	controller.Connect()
 
 	commanderClient.AssertNumberOfCalls(t, "Connect", 1)
 	metricsReportClient.AssertNumberOfCalls(t, "Connect", 1)
@@ -75,8 +74,7 @@ func TestControllerConnect_error(t *testing.T) {
 	controller.WithClient(metricsReportClient)
 	controller.WithContext(ctx)
 
-	err := controller.Connect()
-	assert.NotNil(t, err)
+	controller.Connect()
 
 	commanderClient.AssertNumberOfCalls(t, "Connect", 1)
 	metricsReportClient.AssertNumberOfCalls(t, "Connect", 1)

sdk/client/metric_reporter.go

@@ -9,6 +9,7 @@ package client
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"sync"
@@ -28,6 +29,7 @@ func NewMetricReporterClient() MetricReporter {
 	return &metricReporter{
 		connector:       newConnector(),
 		backoffSettings: DefaultBackoffSettings,
+		isRetrying:      false,
 	}
 }
 
@@ -39,6 +41,8 @@ type metricReporter struct {
 	ctx             context.Context
 	mu              sync.Mutex
 	backoffSettings backoff.BackoffSettings
+	isRetrying      bool
+	retryLock       sync.Mutex
 }
 
 func (r *metricReporter) WithInterceptor(interceptor interceptors.Interceptor) Client {
@@ -57,11 +61,14 @@ func (r *metricReporter) Connect(ctx context.Context) error {
 	log.Debugf("Metric Reporter connecting to %s", r.server)
 
 	r.ctx = ctx
+
+	r.retryLock.Lock()
 	err := backoff.WaitUntil(
 		r.ctx,
 		r.backoffSettings,
 		r.createClient,
 	)
+	r.retryLock.Unlock()
 	if err != nil {
 		return err
 	}
@@ -151,18 +158,19 @@ func (r *metricReporter) Send(ctx context.Context, message Message) error {
 			return fmt.Errorf("MetricReporter expected a metrics report message, but received %T", message.Data())
 		}
 
-		isRetrying := false
-
 		err = backoff.WaitUntil(r.ctx, r.backoffSettings, func() error {
-			if isRetrying {
-				log.Infof("Metric Reporter Channel Send: retrying to connect to %s", r.grpc.Target())
-				err := r.createClient()
-				if err != nil {
-					return err
-				}
+			err := r.checkClientConnection()
+			if err != nil {
+				return err
+			}
+
+			if r.channel == nil {
+				r.isRetrying = true
+				return r.handleGrpcError("Metric Reporter Channel Send", errors.New("metric service stream client not created yet"))
 			}
+
 			if err := r.channel.Send(report); err != nil {
-				isRetrying = true
+				r.isRetrying = true
 				return r.handleGrpcError("Metric Reporter Channel Send", err)
 			}
 
@@ -176,18 +184,14 @@ func (r *metricReporter) Send(ctx context.Context, message Message) error {
 			return fmt.Errorf("MetricReporter expected an events report message, but received %T", message.Data())
 		}
 
-		isRetrying := false
-
 		err = backoff.WaitUntil(r.ctx, r.backoffSettings, func() error {
-			if isRetrying {
-				log.Infof("Metric Reporter Channel Send: retrying to connect to %s", r.grpc.Target())
-				err = r.createClient()
-				if err != nil {
-					return err
-				}
+			err := r.checkClientConnection()
+			if err != nil {
+				return err
 			}
+
 			if err := r.eventsChannel.Send(report); err != nil {
-				isRetrying = true
+				r.isRetrying = true
 				return r.handleGrpcError("Metric Reporter Events Channel Send", err)
 			}
 
@@ -202,6 +206,21 @@ func (r *metricReporter) Send(ctx context.Context, message Message) error {
 	return err
 }
 
+func (r *metricReporter) checkClientConnection() error {
+	r.retryLock.Lock()
+	defer r.retryLock.Unlock()
+
+	if r.isRetrying {
+		log.Infof("Metric Reporter Channel Send: retrying to connect to %s", r.grpc.Target())
+		err := r.createClient()
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 func (r *metricReporter) closeConnection() error {
 	var err error
 	if r.channel != nil {

src/core/topics.go

@@ -10,7 +10,6 @@ package core
 const (
 	UNKNOWN                         = "unknown"
 	RegistrationPrefix              = "registration."
-	RegistrationCompletedTopic      = RegistrationPrefix + "completed"
 	CommNginxConfig                 = "nginx.config"
 	NginxConfigUpload               = "nginx.config.upload"
 	NginxReload                     = "nginx.reload"
@@ -49,4 +48,6 @@ const (
 	EnableExtension                 = "enable.extension"
 	EnableFeature                   = "enable.feature"
 	AgentAPIConfigApplyResponse     = "agent.api.config.apply.response"
+	CommandSent                     = "command.sent"
+	MetricReportSent                = "metrics.report.sent"
 )