K8s/Client: Add watch support (#99060)

* add watch client

* add watch client

* add support for selectors

* parse labels

* always send watch

* reuse decoder

* Update public/app/features/apiserver/client.ts

Co-authored-by: Alex Khomenko <Clarity-89@users.noreply.github.com>

* Update public/app/features/apiserver/client.ts

Co-authored-by: Alex Khomenko <Clarity-89@users.noreply.github.com>

* Update public/app/features/apiserver/client.ts

Co-authored-by: Alex Khomenko <Clarity-89@users.noreply.github.com>

---------

Co-authored-by: Alex Khomenko <Clarity-89@users.noreply.github.com>

public/app/core/services/backend_srv.ts

@@ -198,13 +198,14 @@ export class BackendSrv implements BackendService {
             }
           }
           process()
-            .catch((e) => {
-              console.log(requestId, 'catch', e);
-            }) // from abort
             .then(() => {
               console.log(requestId, 'complete');
               observer.complete();
-            }); // runs in background
+            }) // runs in background
+            .catch((e) => {
+              console.log(requestId, 'catch', e);
+              observer.error(e);
+            }); // from abort
         },
         error: (e) => {
           observer.error(e);

public/app/features/apiserver/client.ts

@@ -1,3 +1,5 @@
+import { Observable, from, retry, catchError, filter, map, mergeMap } from 'rxjs';
+
 import { config, getBackendSrv } from '@grafana/runtime';
 import { contextSrv } from 'app/core/core';
 
@@ -11,8 +13,10 @@ import {
   ResourceList,
   ResourceClient,
   ObjectMeta,
+  WatchOptions,
   K8sAPIGroupList,
   AnnoKeySavedFromUI,
+  ResourceEvent,
 } from './types';
 
 export interface GroupVersionResource {
@@ -34,6 +38,44 @@ export class ScopedResourceClient<T = object, S = object, K = string> implements
     return getBackendSrv().get<Resource<T, S, K>>(`${this.url}/${name}`);
   }
 
+  public watch(opts?: WatchOptions): Observable<ResourceEvent<T, S, K>> {
+    const decoder = new TextDecoder();
+    const params = {
+      ...opts,
+      watch: true,
+      labelSelector: this.parseListOptionsSelector(opts?.labelSelector),
+      fieldSelector: this.parseListOptionsSelector(opts?.fieldSelector),
+    };
+    return getBackendSrv()
+      .chunked({
+        url: params.name ? `${this.url}/${params.name}` : this.url,
+        params,
+      })
+      .pipe(
+        filter((response) => response.ok && response.data instanceof Uint8Array),
+        map((response) => {
+          const text = decoder.decode(response.data);
+          return text.split('\n');
+        }),
+        mergeMap((text) => from(text)),
+        filter((line) => line.length > 0),
+        map((line) => {
+          try {
+            return JSON.parse(line);
+          } catch (e) {
+            console.warn('Invalid JSON in watch stream:', e);
+            return null;
+          }
+        }),
+        filter((event): event is ResourceEvent<T, S, K> => event !== null),
+        retry({ count: 3, delay: 1000 }),
+        catchError((error) => {
+          console.error('Watch stream error:', error);
+          throw error;
+        })
+      );
+  }
+
   public async subresource<S>(name: string, path: string): Promise<S> {
     return getBackendSrv().get<S>(`${this.url}/${name}/${path}`);
   }

public/app/features/apiserver/types.ts

@@ -8,6 +8,8 @@
  *
  */
 
+import { Observable } from 'rxjs';
+
 /** The object type and version */
 export interface TypeMeta<K = string> {
   apiVersion: string;
@@ -152,6 +154,25 @@ export interface ListOptions {
 
   // Limit the response count
   limit?: number;
+
+  // Watch for changes
+  watch?: boolean;
+}
+
+export interface WatchOptions {
+  // A specific resource
+  name?: string;
+
+  // Start watching from a given resource version
+  resourceVersion?: string;
+
+  // Query by labels
+  // https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#label-selectors
+  labelSelector?: ListOptionsLabelSelector;
+
+  // Query by fields
+  // https://kubernetes.io/docs/concepts/overview/working-with-objects/field-selectors/
+  fieldSelector?: ListOptionsFieldSelector;
 }
 
 export interface MetaStatus {
@@ -171,9 +192,15 @@ export interface MetaStatus {
   details?: object;
 }
 
+export interface ResourceEvent<T = object, S = object, K = string> {
+  type: 'ADDED' | 'DELETED' | 'MODIFIED';
+  object: Resource<T, S, K>;
+}
+
 export interface ResourceClient<T = object, S = object, K = string> {
   create(obj: ResourceForCreate<T, K>): Promise<Resource<T, S, K>>;
   get(name: string): Promise<Resource<T, S, K>>;
+  watch(opts?: WatchOptions): Observable<ResourceEvent<T, S, K>>;
   subresource<S>(name: string, path: string): Promise<S>;
   list(opts?: ListOptions): Promise<ResourceList<T, S, K>>;
   update(obj: ResourceForCreate<T, K>): Promise<Resource<T, S, K>>;