feat: allow specifying base64-encoded values in vector-sink DSN urls

This will allow Vector templating to work when using Kubernetes as the scheduler.

docs/deployment/logs.md

@@ -234,6 +234,19 @@ For some sinks - such as the `http` sink - it may be useful to use special chara
 dokku logs:set test vector-sink "http://?uri=https%3A//loggerservice.com%3A1234/%3Ftoken%3Dabc1234%26type%3Dvector"
 ```
 
+For kubernetes, it may be necessary to use template syntax - `{{ .parent.child }}` - in the sink configuration. Naively using brackets will fail due to the Helm chart install process assuming that the template should be interpreted at Helm install time vs by Vector itself. To avoid this, use `base64enc:` values (available only for top-level properties at this time). The following example shows how to use `{{ pod }}` as a value.
+
+```shell
+# encode the value with a Helm `print` statement wrapper
+encoded="$(echo '{{ print "{{ pod }}" }}' | base64)"
+# the value of encoded should be: e3sgcHJpbnQgInt7IHBvZCB9fSIgfX0K
+
+# set the value 
+dokku logs:set test vector-sink "http://?process=base64enc%3A${encoded}"
+```
+
+This will transform the value to it's encoded form when configuring Vector sinks for Kubernetes.
+
 Please read the [sink documentation](https://vector.dev/docs/reference/configuration/sinks/) for your sink of choice to configure the sink as desired.
 
 ##### Configuring the app label

docs/deployment/schedulers/k3s.md

@@ -611,6 +611,7 @@ Next, run the `scheduler-k3s:ensure-charts` command with the `vector` chart to f
 ```shell
 dokku scheduler-k3s:ensure-charts --charts vector
 ```
+Please see the [vector logs documentation](/docs/deployment/logs.md#configuring-a-log-sink) for more information on specifying vector sinks.
 
 ### Supported Resource Management Properties
 

plugins/logs/logs.go

@@ -2,6 +2,7 @@ package logs
 
 import (
 	"embed"
+	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -102,5 +103,21 @@ func SinkValueToConfig(appName string, sinkValue string) (VectorSink, error) {
 		data["inputs"] = []string{"docker-null-source"}
 	}
 
+	// add special support for `base64enc:VAL` fields
+	for key, value := range data {
+		valueString, ok := value.(string)
+		if !ok {
+			continue
+		}
+
+		if encodedValue, found := strings.CutPrefix(valueString, "base64enc:"); found {
+			decodedValue, err := base64.StdEncoding.DecodeString(encodedValue)
+			if err != nil {
+				return data, fmt.Errorf("Error decoding base64: %w", err)
+			}
+			data[key] = strings.TrimSpace(string(decodedValue))
+		}
+	}
+
 	return data, nil
 }

tests/unit/scheduler-k3s-3.bats

@@ -52,6 +52,37 @@ teardown_() {
   assert_output "2"
 }
 
+@test "(scheduler-k3s) deploy kustomize with vector sink" {
+  if [[ -z "$DOCKERHUB_USERNAME" ]] || [[ -z "$DOCKERHUB_TOKEN" ]]; then
+    skip "skipping due to missing docker.io credentials DOCKERHUB_USERNAME:DOCKERHUB_TOKEN"
+  fi
+
+  INGRESS_CLASS=nginx install_k3s
+
+  encoded="$(echo '{{ print "{{ pod }}" }}' | base64)"
+  run /bin/bash -c "echo $encoded"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output "e3sgcHJpbnQgInt7IHBvZCB9fSIgfX0K"
+
+  run /bin/bash -c "dokku logs:set --global vector-sink 'http://?process=base64enc%3A${encoded}'"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "dokku scheduler-k3s:ensure-charts --charts vector"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "kubectl get cm -n vector vector -o yaml"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output_contains "process: '{{ pod }}'"
+}
+
 inject_kustomization_yaml() {
   local APP="$1"
   local APP_REPO_DIR="$2"