Add a config flag to allow not listwatching namespaces

The namespaces cache will be an empty store in this case. Down
the line all of the code _should_ just work for instance emitting
an error log if you try to access namespace labels.

Author: imbstack

src/sources/kubernetes_logs/mod.rs

@@ -107,6 +107,13 @@ pub struct Config {
     ))]
     extra_namespace_label_selector: String,
 
+    /// Specifies whether or not to enrich with namespace fields.
+    ///
+    /// This can be useful to make Vector not pull in namespaces to reduce load on
+    /// kube-apiserver and daemonset memory usage in clusters with  lots of namespaces.
+    ///
+    add_namespace_fields: bool,
+
     /// The name of the Kubernetes [Node][node] that is running.
     ///
     /// Configured to use an environment variable by default, to be evaluated to a value provided by
@@ -290,6 +297,7 @@ impl Default for Config {
         Self {
             extra_label_selector: "".to_string(),
             extra_namespace_label_selector: "".to_string(),
+            add_namespace_fields: true,
             self_node_name: default_self_node_name_env_template(),
             extra_field_selector: "".to_string(),
             auto_partial_merge: true,
@@ -555,6 +563,7 @@ struct Source {
     field_selector: String,
     label_selector: String,
     namespace_label_selector: String,
+    add_namespace_fields: bool,
     node_selector: String,
     self_node_name: String,
     include_paths: Vec<glob::Pattern>,
@@ -643,6 +652,7 @@ impl Source {
             field_selector,
             label_selector,
             namespace_label_selector,
+            add_namespace_fields: config.add_namespace_fields,
             node_selector,
             self_node_name,
             include_paths,
@@ -679,6 +689,7 @@ impl Source {
             field_selector,
             label_selector,
             namespace_label_selector,
+            add_namespace_fields,
             node_selector,
             self_node_name,
             include_paths,
@@ -733,27 +744,29 @@ impl Source {
 
         // -----------------------------------------------------------------
 
-        let namespaces = Api::<Namespace>::all(client.clone());
-        let ns_watcher = watcher(
-            namespaces,
-            watcher::Config {
-                label_selector: Some(namespace_label_selector),
-                list_semantic: list_semantic.clone(),
-                page_size: get_page_size(use_apiserver_cache),
-                ..Default::default()
-            },
-        )
-        .backoff(watcher::DefaultBackoff::default());
         let ns_store_w = reflector::store::Writer::default();
         let ns_state = ns_store_w.as_reader();
-        let ns_cacher = MetaCache::new();
-
-        reflectors.push(tokio::spawn(custom_reflector(
-            ns_store_w,
-            ns_cacher,
-            ns_watcher,
-            delay_deletion,
-        )));
+        if add_namespace_fields {
+            let namespaces = Api::<Namespace>::all(client.clone());
+            let ns_watcher = watcher(
+                namespaces,
+                watcher::Config {
+                    label_selector: Some(namespace_label_selector),
+                    list_semantic: list_semantic.clone(),
+                    page_size: get_page_size(use_apiserver_cache),
+                    ..Default::default()
+                },
+            )
+            .backoff(watcher::DefaultBackoff::default());
+            let ns_cacher = MetaCache::new();
+
+            reflectors.push(tokio::spawn(custom_reflector(
+                ns_store_w,
+                ns_cacher,
+                ns_watcher,
+                delay_deletion,
+            )));
+        }
 
         // -----------------------------------------------------------------