docs(inputs.dovecot): Document plugin not working for version 2.4+ (#16444)

plugins/inputs/dovecot/README.md

@@ -1,8 +1,14 @@
 # Dovecot Input Plugin
 
 This plugin uses the Dovecot [v2.1 stats protocol][stats] to gather
-metrics on configured domains of [Dovecot][dovecot] servers. You should still
-be able to use this protocol on newer versions of Dovecot.
+metrics on configured domains of [Dovecot][dovecot] servers. You can use this
+plugin on Dovecot up to and including version v2.3.x.
+
+> [!IMPORTANT]
+> Dovecot v2.4+ has the old protocol removed and this plugin will not work.
+> Please use Dovecot's [Openmetrics exporter][openmetrics] in combination with
+> the [http input plugin][http_plugin] and `openmetrics` data format for newer
+> versions of Dovecot.
 
 ⭐ Telegraf v0.10.3
 🏷️ server
@@ -10,6 +16,8 @@ be able to use this protocol on newer versions of Dovecot.
 
 [dovecot]: https://www.dovecot.org/
 [stats]: https://doc.dovecot.org/configuration_manual/stats/old_statistics/#old-statistics
+[http_plugin]: /plugins/inputs/http/README.md
+[openmetrics]: https://doc.dovecot.org/latest/core/config/statistics.html#openmetrics
 
 ## Global configuration options <!-- @/docs/includes/plugin_config.md -->
 

plugins/inputs/dovecot/dovecot_test.go

@@ -3,7 +3,6 @@ package dovecot
 import (
 	"bufio"
 	"bytes"
-	"fmt"
 	"io"
 	"net"
 	"net/textproto"
@@ -195,7 +194,7 @@ func TestDovecotContainerIntegration(t *testing.T) {
 
 	servicePort := "24242"
 	container := testutil.Container{
-		Image:        "dovecot/dovecot",
+		Image:        "dovecot/dovecot:2.3-latest",
 		ExposedPorts: []string{servicePort},
 		Files: map[string]string{
 			"/etc/dovecot/dovecot.conf": testdata,
@@ -205,14 +204,13 @@ func TestDovecotContainerIntegration(t *testing.T) {
 			wait.ForListeningPort(nat.Port(servicePort)),
 		),
 	}
+	require.NoError(t, container.Start(), "failed to start container")
 	defer container.Terminate()
 
-	err = container.Start()
-	require.NoError(t, err, "failed to start container")
-
-	d := &Dovecot{Servers: []string{
-		fmt.Sprintf("%s:%s", container.Address, container.Ports[servicePort]),
-	}, Type: "global"}
+	d := &Dovecot{
+		Servers: []string{container.Address + ":" + container.Ports[servicePort]},
+		Type:    "global",
+	}
 
 	var acc testutil.Accumulator
 	require.NoError(t, d.Gather(&acc))

testutil/container.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 
 	"github.com/docker/docker/api/types/container"
+	"github.com/docker/docker/api/types/image"
 	"github.com/docker/go-connections/nat"
 	"github.com/testcontainers/testcontainers-go"
 	"github.com/testcontainers/testcontainers-go/wait"
@@ -80,15 +81,19 @@ func (c *Container) Start() error {
 
 	c.Logs = TestLogConsumer{}
 	c.container.FollowOutput(&c.Logs)
-	err = c.container.StartLogProducer(c.ctx)
-	if err != nil {
+	if err := c.container.StartLogProducer(c.ctx); err != nil {
 		return fmt.Errorf("log producer failed: %w", err)
 	}
 
 	c.Address = "localhost"
 
-	err = c.LookupMappedPorts()
+	info, err := c.GetInfo()
 	if err != nil {
+		return fmt.Errorf("getting info failed: %w", err)
+	}
+	fmt.Println("Started container:", info)
+
+	if err := c.LookupMappedPorts(); err != nil {
 		c.Terminate()
 		return fmt.Errorf("port lookup failed: %w", err)
 	}
@@ -142,16 +147,13 @@ func (c *Container) PrintLogs() {
 }
 
 func (c *Container) Terminate() {
-	err := c.container.StopLogProducer()
-	if err != nil {
+	if err := c.container.StopLogProducer(); err != nil {
 		fmt.Println(err)
 	}
 
-	err = c.container.Terminate(c.ctx)
-	if err != nil {
+	if err := c.container.Terminate(c.ctx); err != nil {
 		fmt.Printf("failed to terminate the container: %s", err)
 	}
-
 	c.PrintLogs()
 }
 
@@ -172,3 +174,42 @@ func (c *Container) Resume() error {
 
 	return provider.Client().ContainerUnpause(c.ctx, c.container.GetContainerID())
 }
+
+func (c *Container) GetInfo() (string, error) {
+	dc, ok := c.container.(*testcontainers.DockerContainer)
+	if !ok {
+		return "not a docker container", nil
+	}
+
+	ci, err := dc.Inspect(c.ctx)
+	if err != nil {
+		return "", fmt.Errorf("inspecting container failed: %w", err)
+	}
+
+	provider, err := testcontainers.NewDockerProvider()
+	if err != nil {
+		return "", fmt.Errorf("getting provider failed: %w", err)
+	}
+
+	summaries, err := provider.Client().ImageList(c.ctx, image.ListOptions{})
+	if err != nil {
+		return "", fmt.Errorf("listing images failed: %w", err)
+	}
+
+	for _, s := range summaries {
+		if s.ID != ci.ContainerJSONBase.Image {
+			continue
+		}
+		var digest []string
+		for _, d := range s.RepoDigests {
+			if _, suffix, found := strings.Cut(d, "@"); found {
+				digest = append(digest, suffix)
+			} else {
+				digest = append(digest, d)
+			}
+		}
+		return fmt.Sprintf("%s (%s)", dc.Image, strings.Join(digest, ",")), nil
+	}
+
+	return "unknown", nil
+}