fix: apply app-label-alias to shipped events

The alias was only ever used to build the `include_labels` filter on the generated vector source, while dokku labels containers with `com.dokku.app-name` unconditionally. Setting the property therefore pointed the source at a label no container carries, and log collection stopped without any error. The source now always filters the label dokku applies, and a generated remap renames the field on its way to the sink, which is what the property was documented to do. An app whose own alias differs from the global one gets a branch in the global pipeline, so a per-app value is honored even when the app ships through the global sink.

Closes #8916.

plugins/logs/functions.go

@@ -8,6 +8,7 @@ import (
 	"html/template"
 	"os"
 	"path/filepath"
+	"sort"
 	"strings"
 
 	"github.com/dokku/dokku/plugins/common"
@@ -232,6 +233,19 @@ type vectorAppSinks struct {
 	// CronRemapID is the component id for the remap transform on the cron branch
 	CronRemapID string
 
+	// RelabelID is the component id for the remap transform renaming the app
+	// label on the non-cron branch
+	RelabelID string
+
+	// LabelAlias is the label key the app name is shipped under for this scope.
+	// It is the AppLabelAlias constant unless the app-label-alias property is set
+	LabelAlias string
+
+	// LabelAliasOverrides holds the apps within this scope whose own alias
+	// differs from LabelAlias. Only the global scope carries these, since a
+	// per-app source only ever covers one app
+	LabelAliasOverrides []vectorLabelAliasOverride
+
 	// Sink is the DSN for non-cron logs, empty when unset
 	Sink string
 
@@ -239,6 +253,16 @@ type vectorAppSinks struct {
 	CronSink string
 }
 
+// vectorLabelAliasOverride is the alias a single app ships its name under when
+// it differs from the alias of the scope collecting it
+type vectorLabelAliasOverride struct {
+	// AppName is the app the override applies to
+	AppName string
+
+	// Alias is the label key the app name is shipped under
+	Alias string
+}
+
 // cronRouteTransforms returns the route and remap pair that splits a source
 // into cron and non-cron branches. The remap flattens the cron labels into
 // top-level fields because vector drops any event whose sink template
@@ -247,12 +271,22 @@ type vectorAppSinks struct {
 // The route carries a single condition, so an event either matches it or falls
 // through to the reserved _unmatched output. A second route added later would
 // need a mutually exclusive condition, since route fans out to every match.
-func cronRouteTransforms(routerID string, remapID string, sourceID string, hasSink bool) map[string]any {
+//
+// Any label rename is appended to the remap rather than given a component of
+// its own, so that dokku_app is captured from the literal label before the
+// rename runs and keeps its value regardless of the configured alias.
+func cronRouteTransforms(scope vectorAppSinks, relabel string) map[string]any {
+	source := fmt.Sprintf(".dokku_app = to_string(%s) ?? \"\"\n.dokku_cron_id = to_string(%s) ?? \"\"",
+		vrlLabelPath(AppLabelAlias), vrlLabelPath(CronIDLabel))
+	if relabel != "" {
+		source = fmt.Sprintf("%s\n%s", source, relabel)
+	}
+
 	return map[string]any{
-		routerID: vectorRouteTransform{
+		scope.RouterID: vectorRouteTransform{
 			Type:             "route",
-			Inputs:           []string{sourceID},
-			RerouteUnmatched: hasSink,
+			Inputs:           []string{scope.SourceID},
+			RerouteUnmatched: scope.Sink != "",
 			Route: map[string]vectorCondition{
 				CronRouteName: {
 					Type:   "vrl",
@@ -260,11 +294,10 @@ func cronRouteTransforms(routerID string, remapID string, sourceID string, hasSi
 				},
 			},
 		},
-		remapID: vectorRemapTransform{
+		scope.CronRemapID: vectorRemapTransform{
 			Type:   "remap",
-			Inputs: []string{fmt.Sprintf("%s.%s", routerID, CronRouteName)},
-			Source: fmt.Sprintf(".dokku_app = to_string(%s) ?? \"\"\n.dokku_cron_id = to_string(%s) ?? \"\"",
-				vrlLabelPath(AppLabelAlias), vrlLabelPath(CronIDLabel)),
+			Inputs: []string{fmt.Sprintf("%s.%s", scope.RouterID, CronRouteName)},
+			Source: source,
 		},
 	}
 }
@@ -275,6 +308,92 @@ func vrlLabelPath(label string) string {
 	return fmt.Sprintf(".label.%q", label)
 }
 
+// vrlRenameLabel renders the assignment moving the dokku app label onto the
+// supplied alias
+func vrlRenameLabel(alias string) string {
+	return fmt.Sprintf("%s = del(%s)", vrlLabelPath(alias), vrlLabelPath(AppLabelAlias))
+}
+
+// vrlClause is one branch of a generated VRL conditional. An empty Condition
+// renders as a trailing else
+type vrlClause struct {
+	Condition string
+	Statement string
+}
+
+// vrlIfChain renders clauses as a single if/else if/else statement
+func vrlIfChain(clauses []vrlClause) string {
+	if len(clauses) == 1 && clauses[0].Condition == "" {
+		return clauses[0].Statement
+	}
+
+	var chain strings.Builder
+	for i, clause := range clauses {
+		if i > 0 {
+			chain.WriteString(" else ")
+		}
+		if clause.Condition != "" {
+			chain.WriteString(fmt.Sprintf("if %s ", clause.Condition))
+		}
+		chain.WriteString(fmt.Sprintf("{\n  %s\n}", clause.Statement))
+	}
+
+	return chain.String()
+}
+
+// relabelVRL renders the program renaming the dokku app label to the alias
+// configured for the scope, or an empty string when there is nothing to rename.
+//
+// The rename happens on the event rather than on the container because dokku
+// only ever labels containers com.dokku.app-name: pointing the source filter at
+// any other label - which is what this property used to do - matches nothing at
+// all and silently collects no logs.
+//
+// The global scope collects every app, so an app whose own alias differs from
+// the global one gets a branch of its own here. Without that, a per-app alias
+// would be silently ignored for any app shipping through the global sink.
+func relabelVRL(scope vectorAppSinks) string {
+	alias := scope.LabelAlias
+	if alias == "" {
+		alias = AppLabelAlias
+	}
+
+	if len(scope.LabelAliasOverrides) == 0 {
+		if alias == AppLabelAlias {
+			return ""
+		}
+
+		return vrlRenameLabel(alias)
+	}
+
+	clauses := []vrlClause{}
+	retained := []string{}
+	for _, override := range scope.LabelAliasOverrides {
+		if override.Alias == AppLabelAlias {
+			retained = append(retained, fmt.Sprintf("app != %q", override.AppName))
+			continue
+		}
+
+		clauses = append(clauses, vrlClause{
+			Condition: fmt.Sprintf("app == %q", override.AppName),
+			Statement: vrlRenameLabel(override.Alias),
+		})
+	}
+
+	if alias != AppLabelAlias {
+		clauses = append(clauses, vrlClause{
+			Condition: strings.Join(retained, " && "),
+			Statement: vrlRenameLabel(alias),
+		})
+	}
+
+	if len(clauses) == 0 {
+		return ""
+	}
+
+	return fmt.Sprintf("app = to_string(%s) ?? \"\"\n%s", vrlLabelPath(AppLabelAlias), vrlIfChain(clauses))
+}
+
 // buildVectorConfig assembles the vector configuration for the supplied scopes.
 // It performs no IO so that the generated shape can be asserted directly.
 func buildVectorConfig(scopes []vectorAppSinks) (vectorConfig, error) {
@@ -293,12 +412,14 @@ func buildVectorConfig(scopes []vectorAppSinks) (vectorConfig, error) {
 			IncludeLabels: scope.IncludeLabels,
 		}
 
+		relabel := relabelVRL(scope)
+
 		sinkInputs := []string{scope.SourceID}
 		if scope.CronSink != "" {
 			if data.Transforms == nil {
 				data.Transforms = map[string]any{}
 			}
-			for id, transform := range cronRouteTransforms(scope.RouterID, scope.CronRemapID, scope.SourceID, scope.Sink != "") {
+			for id, transform := range cronRouteTransforms(scope, relabel) {
 				data.Transforms[id] = transform
 			}
 
@@ -316,6 +437,21 @@ func buildVectorConfig(scopes []vectorAppSinks) (vectorConfig, error) {
 		}
 
 		if scope.Sink != "" {
+			// the cron branch renames within its own remap, so this transform
+			// only exists when there is a non-cron sink downstream to consume it
+			if relabel != "" {
+				if data.Transforms == nil {
+					data.Transforms = map[string]any{}
+				}
+				data.Transforms[scope.RelabelID] = vectorRemapTransform{
+					Type:   "remap",
+					Inputs: sinkInputs,
+					Source: relabel,
+				}
+
+				sinkInputs = []string{scope.RelabelID}
+			}
+
 			sink, err := SinkValueToConfig(SinkValueToConfigInput{
 				SinkValue: scope.Sink,
 				Inputs:    sinkInputs,
@@ -355,30 +491,50 @@ func buildVectorConfig(scopes []vectorAppSinks) (vectorConfig, error) {
 // vectorScopes collects the sink configuration for every app plus the global scope
 func vectorScopes() []vectorAppSinks {
 	apps, _ := common.UnfilteredDokkuApps()
+	globalAlias := reportComputedAppLabelAlias("--global")
+
 	scopes := []vectorAppSinks{}
+	overrides := []vectorLabelAliasOverride{}
 	for _, appName := range apps {
 		inflectedAppName := strings.ReplaceAll(appName, ".", "-")
+		appAlias := reportComputedAppLabelAlias(appName)
+		if appAlias != globalAlias {
+			overrides = append(overrides, vectorLabelAliasOverride{
+				AppName: appName,
+				Alias:   appAlias,
+			})
+		}
+
 		scopes = append(scopes, vectorAppSinks{
 			SourceID:      fmt.Sprintf("docker-source:%s", inflectedAppName),
-			IncludeLabels: []string{fmt.Sprintf("%s=%s", reportComputedAppLabelAlias(appName), appName)},
+			IncludeLabels: []string{fmt.Sprintf("%s=%s", AppLabelAlias, appName)},
 			SinkID:        fmt.Sprintf("docker-sink:%s", inflectedAppName),
 			CronSinkID:    fmt.Sprintf("docker-cron-sink:%s", inflectedAppName),
 			RouterID:      fmt.Sprintf("docker-router:%s", inflectedAppName),
 			CronRemapID:   fmt.Sprintf("docker-cron-remap:%s", inflectedAppName),
+			RelabelID:     fmt.Sprintf("docker-relabel:%s", inflectedAppName),
+			LabelAlias:    appAlias,
 			Sink:          common.PropertyGet("logs", appName, "vector-sink"),
 			CronSink:      common.PropertyGet("logs", appName, "vector-cron-sink"),
 		})
 	}
 
+	sort.Slice(overrides, func(i int, j int) bool {
+		return overrides[i].AppName < overrides[j].AppName
+	})
+
 	return append(scopes, vectorAppSinks{
-		SourceID:      "docker-global-source",
-		IncludeLabels: []string{reportComputedAppLabelAlias("global")},
-		SinkID:        "docker-global-sink",
-		CronSinkID:    "docker-global-cron-sink",
-		RouterID:      "docker-global-router",
-		CronRemapID:   "docker-global-cron-remap",
-		Sink:          common.PropertyGet("logs", "--global", "vector-sink"),
-		CronSink:      common.PropertyGet("logs", "--global", "vector-cron-sink"),
+		SourceID:            "docker-global-source",
+		IncludeLabels:       []string{AppLabelAlias},
+		SinkID:              "docker-global-sink",
+		CronSinkID:          "docker-global-cron-sink",
+		RouterID:            "docker-global-router",
+		CronRemapID:         "docker-global-cron-remap",
+		RelabelID:           "docker-global-relabel",
+		LabelAlias:          globalAlias,
+		LabelAliasOverrides: overrides,
+		Sink:                common.PropertyGet("logs", "--global", "vector-sink"),
+		CronSink:            common.PropertyGet("logs", "--global", "vector-cron-sink"),
 	})
 }