[extension/opamp] Add support for polling interval in HTTP client (op…

…en-telemetry#34811)

**Description:** <Describe what has changed.>
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->

Adds support for configuring polling interval for the OpAMP HTTP client.

**Link to tracking Issue:** open-telemetry#34749

**Testing:** Adjusted unit test, manually tested

**Documentation:** Added to README

---------

Signed-off-by: Matej Gera <matejgera@gmail.com>
Co-authored-by: Evan Bradley <11745660+evan-bradley@users.noreply.github.com>

.chloggen/opampextension_add_http_polling_interval.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: opampextension
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Adds the ability to configure the polling interval for the HTTP client.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [34749]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

extension/opampextension/README.md

@@ -19,12 +19,23 @@ The following settings are required:
   - `ws`: The OpAMP websocket transport settings.
     - `endpoint` (no default): The OpAMP server websocket endpoint (URL).
 
-The following settings are optional:
+The following settings are optional for the websocket client:
 
 - `server`: The OpAMP server connection settings.
   - `ws`: The OpAMP websocket transport settings.
     - `tls`: TLS settings.
     - `headers`: HTTP headers to set.
+
+The following settings are optional for the HTTP client:
+
+- `server`: The OpAMP server connection settings.
+  - `http`: The OpAMP websocket transport settings.
+    - `tls`: TLS settings.
+    - `headers`: HTTP headers to set.
+    - `polling_interval`: The interval at which the extension will poll the server. Defaults to 30s.
+
+The following settings are optional for both transports:
+
 - `instance_uid`: A UUIDv7 formatted as a 36 character string in canonical
   representation. Auto-generated on start if missing. Setting this ensures the
   instance UID remains constant across process restarts.

extension/opampextension/config.go

@@ -15,6 +15,10 @@ import (
 	"go.uber.org/zap"
 )
 
+// Default value for HTTP client's polling interval, set to 30 seconds in
+// accordance with the OpAMP spec.
+const httpPollingIntervalDefault = 30 * time.Second
+
 // Config contains the configuration for the opamp extension. Trying to mirror
 // the OpAMP supervisor config for some consistency.
 type Config struct {
@@ -68,12 +72,6 @@ type commonFields struct {
 	Headers    map[string]configopaque.String `mapstructure:"headers,omitempty"`
 }
 
-// OpAMPServer contains the OpAMP transport configuration.
-type OpAMPServer struct {
-	WS   *commonFields `mapstructure:"ws,omitempty"`
-	HTTP *commonFields `mapstructure:"http,omitempty"`
-}
-
 func (c *commonFields) Scheme() string {
 	uri, err := url.ParseRequestURI(c.Endpoint)
 	if err != nil {
@@ -89,11 +87,38 @@ func (c *commonFields) Validate() error {
 	return nil
 }
 
+type httpFields struct {
+	commonFields `mapstructure:",squash"`
+
+	PollingInterval time.Duration `mapstructure:"polling_interval"`
+}
+
+func (h *httpFields) Validate() error {
+	if err := h.commonFields.Validate(); err != nil {
+		return err
+	}
+
+	if h.PollingInterval < 0 {
+		return errors.New("polling interval must be 0 or greater")
+	}
+
+	return nil
+}
+
+// OpAMPServer contains the OpAMP transport configuration.
+type OpAMPServer struct {
+	WS   *commonFields `mapstructure:"ws,omitempty"`
+	HTTP *httpFields   `mapstructure:"http,omitempty"`
+}
+
 func (s OpAMPServer) GetClient(logger *zap.Logger) client.OpAMPClient {
 	if s.WS != nil {
 		return client.NewWebSocket(newLoggerFromZap(logger.With(zap.String("client", "ws"))))
 	}
-	return client.NewHTTP(newLoggerFromZap(logger.With(zap.String("client", "http"))))
+
+	httpClient := client.NewHTTP(newLoggerFromZap(logger.With(zap.String("client", "http"))))
+	httpClient.SetPollingInterval(s.GetPollingInterval())
+	return httpClient
 }
 
 func (s OpAMPServer) GetHeaders() map[string]configopaque.String {
@@ -123,6 +148,14 @@ func (s OpAMPServer) GetEndpoint() string {
 	return ""
 }
 
+func (s OpAMPServer) GetPollingInterval() time.Duration {
+	if s.HTTP != nil && s.HTTP.PollingInterval > 0 {
+		return s.HTTP.PollingInterval
+	}
+
+	return httpPollingIntervalDefault
+}
+
 // Validate checks if the extension configuration is valid
 func (cfg *Config) Validate() error {
 	switch {

extension/opampextension/config_test.go

@@ -53,8 +53,11 @@ func TestUnmarshalHttpConfig(t *testing.T) {
 	assert.Equal(t,
 		&Config{
 			Server: &OpAMPServer{
-				HTTP: &commonFields{
-					Endpoint: "https://127.0.0.1:4320/v1/opamp",
+				HTTP: &httpFields{
+					commonFields: commonFields{
+						Endpoint: "https://127.0.0.1:4320/v1/opamp",
+					},
+					PollingInterval: 1 * time.Minute,
 				},
 			},
 			InstanceUID: "01BX5ZZKBKACTAV9WEVGEMMVRZ",
@@ -115,13 +118,15 @@ func TestConfig_Getters(t *testing.T) {
 			name: "HTTP valid endpoint and valid instance id",
 			fields: fields{
 				Server: &OpAMPServer{
-					HTTP: &commonFields{
-						Endpoint: "https://127.0.0.1:4320/v1/opamp",
-						Headers: map[string]configopaque.String{
-							"test": configopaque.String("test"),
-						},
-						TLSSetting: configtls.ClientConfig{
-							Insecure: true,
+					HTTP: &httpFields{
+						commonFields: commonFields{
+							Endpoint: "https://127.0.0.1:4320/v1/opamp",
+							Headers: map[string]configopaque.String{
+								"test": configopaque.String("test"),
+							},
+							TLSSetting: configtls.ClientConfig{
+								Insecure: true,
+							},
 						},
 					},
 				},
@@ -194,7 +199,7 @@ func TestConfig_Validate(t *testing.T) {
 			name: "HTTP must have endpoint",
 			fields: fields{
 				Server: &OpAMPServer{
-					HTTP: &commonFields{},
+					HTTP: &httpFields{},
 				},
 			},
 			wantErr: func(t assert.TestingT, err error, _ ...any) bool {
@@ -205,8 +210,10 @@ func TestConfig_Validate(t *testing.T) {
 			name: "HTTP valid endpoint and invalid instance id",
 			fields: fields{
 				Server: &OpAMPServer{
-					HTTP: &commonFields{
-						Endpoint: "https://127.0.0.1:4320/v1/opamp",
+					HTTP: &httpFields{
+						commonFields: commonFields{
+							Endpoint: "https://127.0.0.1:4320/v1/opamp",
+						},
 					},
 				},
 				InstanceUID: "01BX5ZZKBKACTAV9WEVGEMMVRZFAIL",
@@ -219,14 +226,33 @@ func TestConfig_Validate(t *testing.T) {
 			name: "HTTP valid endpoint and valid instance id",
 			fields: fields{
 				Server: &OpAMPServer{
-					HTTP: &commonFields{
-						Endpoint: "https://127.0.0.1:4320/v1/opamp",
+					HTTP: &httpFields{
+						commonFields: commonFields{
+							Endpoint: "https://127.0.0.1:4320/v1/opamp",
+						},
 					},
 				},
 				InstanceUID: "01BX5ZZKBKACTAV9WEVGEMMVRZ",
 			},
 			wantErr: assert.NoError,
 		},
+		{
+			name: "HTTP invalid polling interval",
+			fields: fields{
+				Server: &OpAMPServer{
+					HTTP: &httpFields{
+						commonFields: commonFields{
+							Endpoint: "https://127.0.0.1:4320/v1/opamp",
+						},
+						PollingInterval: -1,
+					},
+				},
+				InstanceUID: "01BX5ZZKBKACTAV9WEVGEMMVRZ",
+			},
+			wantErr: func(t assert.TestingT, err error, _ ...any) bool {
+				return assert.Equal(t, "polling interval must be 0 or greater", err.Error())
+			},
+		},
 		{
 			name: "neither config set",
 			fields: fields{
@@ -241,7 +267,7 @@ func TestConfig_Validate(t *testing.T) {
 			fields: fields{
 				Server: &OpAMPServer{
 					WS:   &commonFields{},
-					HTTP: &commonFields{},
+					HTTP: &httpFields{},
 				},
 			},
 			wantErr: func(t assert.TestingT, err error, _ ...any) bool {

extension/opampextension/testdata/config_http.yaml

@@ -1,4 +1,5 @@
 server:
   http:
     endpoint: https://127.0.0.1:4320/v1/opamp
+    polling_interval: 1m
 instance_uid: 01BX5ZZKBKACTAV9WEVGEMMVRZ