fix: ensure the vector container does not exit when no configured sinks are in place

docs/deployment/logs.md

@@ -73,8 +73,6 @@ dokku logs:vector-start
 
 This will start a new container named `vector` with Dokku's vector config mounted and ready for use. If a running container already exists, this command will do nothing. Additionally, if a container exists but is not running, this command will attempt to start the container.
 
-By default, the vector container will do nothing and may exit immediately. It is necessary to configure a sink in order to ensure the vector container runs as necessary.
-
 While the default vector image is hardcoded, users may specify an alternative via the `--vector-image` flag:
 
 ```shell
@@ -101,8 +99,6 @@ The `vector` container will be stopped and removed from the system. If the conta
 
 #### Configuring a log sink
 
-> If no sinks are specified, the vector container will exit.
-
 Vector uses the concept of log "sinks" to send logs to a given endpoint. Log sinks may be configured globally or on a per-app basis by specifying a `sink` in DSN form with the `logs:set` command. Specifying a sink value will reload any running vector container.
 
 ```shell
@@ -131,8 +127,6 @@ As with app-specific sink settings, the global value may also be cleared by sett
 dokku logs:set --global sink
 ```
 
-If no sink is specified, the vector container may exit prematurely.
-
 ##### Log Sink DSN Format
 
 The DSN form of a sink is as follows:

plugins/logs/functions.go

@@ -123,6 +123,10 @@ func valueToConfig(appName string, value string) (vectorSink, error) {
 	if appName == "--global" {
 		i = "inputs[]=docker-global-source"
 	}
+	if appName == "--null" {
+		i = "inputs[]=docker-null-source"
+	}
+
 	initialQuery := fmt.Sprintf("%s&%s", t, i)
 	query := u.RawQuery
 	if query == "" {
@@ -189,6 +193,24 @@ func writeVectorConfig() error {
 		data.Sinks["docker-global-sink"] = sink
 	}
 
+	if len(data.Sources) == 0 {
+		// pull from no containers
+		data.Sources["docker-null-source"] = vectorSource{
+			Type:          "docker_logs",
+			IncludeLabels: []string{"com.dokku.vector-null"},
+		}
+	}
+
+	if len(data.Sinks) == 0 {
+		// write logs to a blackhole
+		sink, err := valueToConfig("--null", "blackhole://?print_amount=1")
+		if err != nil {
+			return err
+		}
+
+		data.Sinks["docker-null-sink"] = sink
+	}
+
 	b, err := json.MarshalIndent(data, "", "  ")
 	if err != nil {
 		return err

plugins/logs/subcommands.go

@@ -104,6 +104,11 @@ func CommandVectorLogs() error {
 func CommandVectorStart(vectorImage string) error {
 	common.LogInfo2("Starting vector container")
 	if !common.ContainerExists(vectorContainerName) {
+		common.LogVerbose("Ensuring vector configuration exists")
+		if err := writeVectorConfig(); err != nil {
+			return err
+		}
+
 		return startVectorContainer(vectorImage)
 	}