feat: add vector-cron-sink for scheduled cron task output

Scheduled cron task output previously reached only the `dokku` user's cron mail, and could not be redirected because `app.json` rejects bare shell operators in a cron `command`. Setting `vector-cron-sink` on an app or globally routes that output to a dedicated sink instead, on both the `docker-local` and `k3s` schedulers, which keeps log destinations under operator control rather than in a deployed repository. Cron events carry `dokku_app` and `dokku_cron_id` fields so a sink can give each task its own destination. This also fixes a `k3s` bug where configuring a global `vector-sink` silently removed the vector prometheus exporter sink.

plugins/logs/functions_test.go

@@ -0,0 +1,174 @@
+package logs
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+func appScope(sink string, cronSink string) vectorAppSinks {
+	return vectorAppSinks{
+		SourceID:      "docker-source:myapp",
+		IncludeLabels: []string{"com.dokku.app-name=myapp"},
+		SinkID:        "docker-sink:myapp",
+		CronSinkID:    "docker-cron-sink:myapp",
+		RouterID:      "docker-router:myapp",
+		CronRemapID:   "docker-cron-remap:myapp",
+		Sink:          sink,
+		CronSink:      cronSink,
+	}
+}
+
+func marshalConfig(t *testing.T, scopes []vectorAppSinks) (string, map[string]interface{}) {
+	t.Helper()
+
+	config, err := buildVectorConfig(scopes)
+	if err != nil {
+		t.Fatalf("buildVectorConfig() error = %v", err)
+	}
+
+	b, err := json.MarshalIndent(config, "", "  ")
+	if err != nil {
+		t.Fatalf("MarshalIndent() error = %v", err)
+	}
+
+	var decoded map[string]interface{}
+	if err := json.Unmarshal(b, &decoded); err != nil {
+		t.Fatalf("Unmarshal() error = %v", err)
+	}
+
+	return string(b), decoded
+}
+
+func lookup(t *testing.T, decoded map[string]interface{}, path ...string) interface{} {
+	t.Helper()
+
+	var current interface{} = decoded
+	for _, key := range path {
+		asMap, ok := current.(map[string]interface{})
+		if !ok {
+			t.Fatalf("path %v: %q is not a map", path, key)
+		}
+		current, ok = asMap[key]
+		if !ok {
+			t.Fatalf("path %v: missing key %q", path, key)
+		}
+	}
+
+	return current
+}
+
+// TestBuildVectorConfigOmitsTransforms is the backwards compatibility guard:
+// a config without a cron sink must marshal exactly as it did before cron
+// routing existed, which means no transforms key at all.
+func TestBuildVectorConfigOmitsTransforms(t *testing.T) {
+	raw, decoded := marshalConfig(t, []vectorAppSinks{appScope("console://?encoding[codec]=json", "")})
+
+	if strings.Contains(raw, "transforms") {
+		t.Errorf("config should not contain a transforms key:\n%s", raw)
+	}
+
+	inputs := lookup(t, decoded, "sinks", "docker-sink:myapp", "inputs")
+	if got := inputs.([]interface{})[0]; got != "docker-source:myapp" {
+		t.Errorf("sink inputs[0] = %v, want docker-source:myapp", got)
+	}
+}
+
+func TestBuildVectorConfigCronSinkOnly(t *testing.T) {
+	_, decoded := marshalConfig(t, []vectorAppSinks{appScope("", "console://?encoding[codec]=json")})
+
+	if got := lookup(t, decoded, "transforms", "docker-router:myapp", "type"); got != "route" {
+		t.Errorf("router type = %v, want route", got)
+	}
+
+	// nothing consumes the unmatched output when there is no plain sink
+	if got := lookup(t, decoded, "transforms", "docker-router:myapp", "reroute_unmatched"); got != false {
+		t.Errorf("reroute_unmatched = %v, want false", got)
+	}
+
+	condition := lookup(t, decoded, "transforms", "docker-router:myapp", "route", "cron", "source")
+	want := `.label."com.dokku.container-type" == "cron"`
+	if condition != want {
+		t.Errorf("route condition = %v, want %v", condition, want)
+	}
+
+	remapSource := lookup(t, decoded, "transforms", "docker-cron-remap:myapp", "source").(string)
+	for _, fragment := range []string{".dokku_app", ".dokku_cron_id", `.label."com.dokku.cron-id"`} {
+		if !strings.Contains(remapSource, fragment) {
+			t.Errorf("remap source %q missing %q", remapSource, fragment)
+		}
+	}
+
+	inputs := lookup(t, decoded, "sinks", "docker-cron-sink:myapp", "inputs")
+	if got := inputs.([]interface{})[0]; got != "docker-cron-remap:myapp" {
+		t.Errorf("cron sink inputs[0] = %v, want docker-cron-remap:myapp", got)
+	}
+
+	sinks := lookup(t, decoded, "sinks").(map[string]interface{})
+	if _, ok := sinks["docker-sink:myapp"]; ok {
+		t.Error("plain sink should not exist when only a cron sink is set")
+	}
+}
+
+func TestBuildVectorConfigBothSinks(t *testing.T) {
+	_, decoded := marshalConfig(t, []vectorAppSinks{
+		appScope("console://?encoding[codec]=json", "console://?encoding[codec]=text"),
+	})
+
+	if got := lookup(t, decoded, "transforms", "docker-router:myapp", "reroute_unmatched"); got != true {
+		t.Errorf("reroute_unmatched = %v, want true", got)
+	}
+
+	inputs := lookup(t, decoded, "sinks", "docker-sink:myapp", "inputs")
+	if got := inputs.([]interface{})[0]; got != "docker-router:myapp._unmatched" {
+		t.Errorf("plain sink inputs[0] = %v, want docker-router:myapp._unmatched", got)
+	}
+
+	cronInputs := lookup(t, decoded, "sinks", "docker-cron-sink:myapp", "inputs")
+	if got := cronInputs.([]interface{})[0]; got != "docker-cron-remap:myapp" {
+		t.Errorf("cron sink inputs[0] = %v, want docker-cron-remap:myapp", got)
+	}
+}
+
+func TestBuildVectorConfigGlobalScope(t *testing.T) {
+	_, decoded := marshalConfig(t, []vectorAppSinks{{
+		SourceID:      "docker-global-source",
+		IncludeLabels: []string{"com.dokku.app-name"},
+		SinkID:        "docker-global-sink",
+		CronSinkID:    "docker-global-cron-sink",
+		RouterID:      "docker-global-router",
+		CronRemapID:   "docker-global-cron-remap",
+		Sink:          "console://?encoding[codec]=json",
+		CronSink:      "console://?encoding[codec]=text",
+	}})
+
+	lookup(t, decoded, "transforms", "docker-global-router")
+	lookup(t, decoded, "transforms", "docker-global-cron-remap")
+	lookup(t, decoded, "sinks", "docker-global-cron-sink")
+
+	inputs := lookup(t, decoded, "sinks", "docker-global-sink", "inputs")
+	if got := inputs.([]interface{})[0]; got != "docker-global-router._unmatched" {
+		t.Errorf("global sink inputs[0] = %v, want docker-global-router._unmatched", got)
+	}
+}
+
+func TestBuildVectorConfigNoSinks(t *testing.T) {
+	raw, decoded := marshalConfig(t, []vectorAppSinks{appScope("", "")})
+
+	if strings.Contains(raw, "transforms") {
+		t.Errorf("config should not contain a transforms key:\n%s", raw)
+	}
+
+	lookup(t, decoded, "sources", "docker-null-source")
+
+	inputs := lookup(t, decoded, "sinks", "docker-null-sink", "inputs")
+	if got := inputs.([]interface{})[0]; got != "docker-null-source" {
+		t.Errorf("null sink inputs[0] = %v, want docker-null-source", got)
+	}
+}
+
+func TestBuildVectorConfigInvalidSink(t *testing.T) {
+	if _, err := buildVectorConfig([]vectorAppSinks{appScope("console://?sinks=nope", "")}); err == nil {
+		t.Fatal("buildVectorConfig() expected an error for an invalid sink DSN")
+	}
+}