Flow Windows service: Support environment variables

CHANGELOG.md

@@ -14,6 +14,10 @@ Main (unreleased)
 
 - Agent Management: Introduce support for templated configuration. (@jcreixell)
 
+### Enhancements
+
+- Flow Windows service: Support environment variables. (@jkroepke)
+
 ### Bugfixes
 
 - Permit `X-Faro-Session-ID` header in CORS requests for the `faro.receiver`

cmd/grafana-agent-service/config_windows.go

@@ -16,6 +16,11 @@ type config struct {
 	// not included.
 	Args []string
 
+	// Environment holds environment variables for the Grafana Agent service.
+	// Each item represents an environment variable in form "key=value".
+	// All environments variables from the current process with be merged into Environment
+	Environment []string
+
 	// WorkingDirectory points to the working directory to run the Grafana Agent
 	// binary from.
 	WorkingDirectory string
@@ -42,9 +47,15 @@ func loadConfig() (*config, error) {
 		return nil, fmt.Errorf("failed to retrieve key Arguments: %w", err)
 	}
 
+	env, _, err := agentKey.GetStringsValue("Environment")
+	if err != nil {
+		return nil, fmt.Errorf("failed to retrieve key Environment: %w", err)
+	}
+
 	return &config{
 		ServicePath:      servicePath,
 		Args:             args,
+		Environment:      env,
 		WorkingDirectory: filepath.Dir(servicePath),
 	}, nil
 }

cmd/grafana-agent-service/main_windows.go

@@ -29,9 +29,10 @@ func main() {
 	}
 
 	cfg := serviceManagerConfig{
-		Path: managerConfig.ServicePath,
-		Args: managerConfig.Args,
-		Dir:  managerConfig.WorkingDirectory,
+		Path:        managerConfig.ServicePath,
+		Args:        managerConfig.Args,
+		Environment: managerConfig.Environment,
+		Dir:         managerConfig.WorkingDirectory,
 
 		// Send logs directly to the event logger.
 		Stdout: logger,

cmd/grafana-agent-service/service.go

@@ -24,6 +24,9 @@ type serviceManagerConfig struct {
 	// Args of the binary to run, not including the command itself.
 	Args []string
 
+	// Environment of the binary to run, including the command environment itself.
+	Environment []string
+
 	// Dir specifies the working directory to run the binary from. If Dir is
 	// empty, the working directory of the current process is used.
 	Dir string
@@ -84,5 +87,7 @@ func (svc *serviceManager) buildCommand(ctx context.Context) *exec.Cmd {
 	cmd.Dir = svc.cfg.Dir
 	cmd.Stdout = svc.cfg.Stdout
 	cmd.Stderr = svc.cfg.Stderr
+	cmd.Env = os.Environ()
+	cmd.Env = append(cmd.Env, svc.cfg.Environment...)
 	return cmd
 }

cmd/grafana-agent-service/service_test.go

@@ -30,8 +30,9 @@ func Test_serviceManager(t *testing.T) {
 		listenHost := getListenHost(t)
 
 		mgr := newServiceManager(l, serviceManagerConfig{
-			Path: serviceBinary,
-			Args: []string{"-listen-addr", listenHost},
+			Path:        serviceBinary,
+			Args:        []string{"-listen-addr", listenHost},
+			Environment: []string{"LISTEN=" + listenHost},
 		})
 		go mgr.Run(componenttest.TestContext(t))
 
@@ -40,6 +41,12 @@ func Test_serviceManager(t *testing.T) {
 			require.NoError(t, err)
 			require.Equal(t, []byte("Hello, world!"), resp)
 		})
+
+		util.Eventually(t, func(t require.TestingT) {
+			resp, err := makeServiceRequest(listenHost, "/echo/env", nil)
+			require.NoError(t, err)
+			require.Contains(t, string(resp), "LISTEN="+listenHost)
+		})
 	})
 
 	t.Run("terminates service binary", func(t *testing.T) {

cmd/grafana-agent-service/testdata/example_service.go

@@ -7,6 +7,7 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"strings"
 )
 
 func main() {
@@ -46,6 +47,9 @@ func run() error {
 	mux.HandleFunc("/echo/response", func(w http.ResponseWriter, r *http.Request) {
 		_, _ = io.Copy(w, r.Body)
 	})
+	mux.HandleFunc("/echo/env", func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write([]byte(strings.Join(os.Environ(), "\n")))
+	})
 
 	srv := &http.Server{Handler: mux}
 	_ = srv.Serve(lis)

docs/sources/flow/setup/install/windows.md

@@ -57,6 +57,14 @@ To do a silent install of Grafana Agent on Windows, perform the following steps.
 * `/CONFIG=<path>` Path to the configuration file. Default: `$INSTDIR\config.river`
 * `/DISABLEREPORTING=<yes|no>` Disable [data collection][]. Default: `no`
 * `/DISABLEPROFILING=<yes|no>` Disable profiling endpoint. Default: `no`
+* `/ENVIRONMENT="KEY=VALUE\0KEY2=VALUE2"` Define environment variables for Windows Service. Default: ``
+
+## Service Configuration
+
+Grafana Agent uses the Windows Registry `HKLM\Software\Grafana\Grafana Agent Flow` for service configuration.
+
+* `Arguments` (Type `REG_MULTI_SZ`) Each value represents a binary argument for grafana-agent-flow binary.
+* `Environment` (Type `REG_MULTI_SZ`) Each value represents a environment value `KEY=VALUE` for grafana-agent-flow binary.
 
 ## Uninstall
 

packaging/grafana-agent-flow/windows/install_script.nsis

@@ -31,6 +31,7 @@ OutFile     "${OUT}"
 Var PassedInParameters
 Var Config
 Var ConfigFlag
+Var Environment
 Var DisableReporting
 Var DisableReportingFlag
 Var DisableProfiling
@@ -51,6 +52,7 @@ Section "install"
   ${GetParameters} $PassedInParameters
   ${GetOptions} $PassedInParameters "/DISABLEPROFILING=" $DisableProfiling
   ${GetOptions} $PassedInParameters "/DISABLEREPORTING=" $DisableReporting
+  ${GetOptions} $PassedInParameters "/ENVIRONMENT=" $Environment
   ${GetOptions} $PassedInParameters "/CONFIG=" $Config
 
   # Calls to functions like nsExec::ExecToLog below push the exit code to the
@@ -146,6 +148,11 @@ Function InitializeRegistry
     Pop $0 # Ignore return result
   ${EndIf}
 
+  # Define the environment key, which holds environment variables to pass to the
+  # service.
+  nsExec::ExecToLog 'Reg.exe add "${REGKEY}" /reg:64 /v Environment /t REG_MULTI_SZ /d "$Environment"'
+  Pop $0 # Ignore return result
+
   Return
 FunctionEnd