Change k8sattribute to return error if unset envvar is used for node_from_env_var

.chloggen/ret-error-k8s.yaml

@@ -0,0 +1,28 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: breaking
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: processor/k8sattributes
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Change processor/k8sattributes to return error if unset envvar is used for `node_from_env_var`
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [39447]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: Before this was a valid configuration, but had an unexpected behavior to monitor the entire cluster. |
+  To keep the same behavior simply do not set the `node_from_env_var` value or use empty string.
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

processor/k8sattributesprocessor/config.go

@@ -5,6 +5,7 @@ package k8sattributesprocessor // import "github.com/open-telemetry/opentelemetr
 
 import (
 	"fmt"
+	"os"
 	"regexp"
 	"time"
 
@@ -259,6 +260,15 @@ type FilterConfig struct {
 	Labels []FieldFilterConfig `mapstructure:"labels"`
 }
 
+func (cfg *FilterConfig) Validate() error {
+	if cfg.NodeFromEnvVar != "" {
+		if _, ok := os.LookupEnv(cfg.NodeFromEnvVar); !ok {
+			return fmt.Errorf("`node_from_env_var` is configured but envvar %q is not set", cfg.NodeFromEnvVar)
+		}
+	}
+	return nil
+}
+
 // FieldFilterConfig allows specifying exactly one filter by a field.
 // It can be used to represent a label or generic field filter.
 type FieldFilterConfig struct {

processor/k8sattributesprocessor/config_test.go

@@ -20,8 +20,6 @@ import (
 )
 
 func TestLoadConfig(t *testing.T) {
-	t.Parallel()
-
 	tests := []struct {
 		id       component.ID
 		expected component.Config
@@ -173,6 +171,8 @@ func TestLoadConfig(t *testing.T) {
 			require.NoError(t, err)
 			require.NoError(t, sub.Unmarshal(cfg))
 
+			// Set "K8S_NODE" to pass validation.
+			t.Setenv("K8S_NODE", "ip-111.us-west-2.compute.internal")
 			if tt.expected == nil {
 				err = xconfmap.Validate(cfg)
 				assert.Error(t, err)
@@ -183,3 +183,13 @@ func TestLoadConfig(t *testing.T) {
 		})
 	}
 }
+
+func TestFilterConfigInvalidEnvVar(t *testing.T) {
+	f := FilterConfig{
+		Namespace:      "ns2",
+		NodeFromEnvVar: "K8S_NODE",
+		Labels:         []FieldFilterConfig{},
+		Fields:         []FieldFilterConfig{},
+	}
+	assert.Error(t, xconfmap.Validate(f))
+}