codemirror-promql: add method to fetch flags in prometheus client (#11090)

Signed-off-by: Augustin Husson <husson.augustin@gmail.com>

web/ui/module/codemirror-promql/src/client/prometheus.ts

@@ -36,6 +36,8 @@ export interface PrometheusClient {
   // Note that the returned list can be a superset of those suggestions for the prefix (i.e., including ones without the
   // prefix), as codemirror will filter these out when displaying suggestions to the user.
   metricNames(prefix?: string): Promise<string[]>;
+  // flags returns flag values that prometheus was configured with.
+  flags(): Promise<Record<string, string>>;
 }
 
 export interface CacheConfig {
@@ -209,6 +211,15 @@ export class HTTPPrometheusClient implements PrometheusClient {
     return this.labelValues('__name__');
   }
 
+  flags(): Promise<Record<string, string>> {
+    return this.fetchAPI<Record<string, string>>(this.flagsEndpoint()).catch((error) => {
+      if (this.errorHandler) {
+        this.errorHandler(error);
+      }
+      return {};
+    });
+  }
+
   private fetchAPI<T>(resource: string, init?: RequestInit): Promise<T> {
     return this.fetchFn(this.url + resource, init)
       .then((res) => {
@@ -254,6 +265,10 @@ export class HTTPPrometheusClient implements PrometheusClient {
   private metricMetadataEndpoint(): string {
     return `${this.apiPrefix}/metadata`;
   }
+
+  private flagsEndpoint(): string {
+    return `${this.apiPrefix}/status/flags`;
+  }
 }
 
 class Cache {
@@ -263,6 +278,7 @@ class Cache {
   private metricMetadata: Record<string, MetricMetadata[]>;
   private labelValues: LRUCache<string, string[]>;
   private labelNames: string[];
+  private flags: Record<string, string>;
 
   constructor(config?: CacheConfig) {
     const maxAge = config && config.maxAge ? config.maxAge : 5 * 60 * 1000;
@@ -270,6 +286,7 @@ class Cache {
     this.metricMetadata = {};
     this.labelValues = new LRUCache<string, string[]>(maxAge);
     this.labelNames = [];
+    this.flags = {};
     if (config?.initialMetricList) {
       this.setLabelValues('__name__', config.initialMetricList);
     }
@@ -297,6 +314,14 @@ class Cache {
     });
   }
 
+  setFlags(flags: Record<string, string>): void {
+    this.flags = flags;
+  }
+
+  getFlags(): Record<string, string> {
+    return this.flags;
+  }
+
   setMetricMetadata(metadata: Record<string, MetricMetadata[]>): void {
     this.metricMetadata = metadata;
   }
@@ -388,7 +413,7 @@ export class CachedPrometheusClient implements PrometheusClient {
 
     return this.client.metricMetadata().then((metadata) => {
       this.cache.setMetricMetadata(metadata);
-      return this.cache.getMetricMetadata();
+      return metadata;
     });
   }
 
@@ -402,4 +427,16 @@ export class CachedPrometheusClient implements PrometheusClient {
   metricNames(): Promise<string[]> {
     return this.labelValues('__name__');
   }
+
+  flags(): Promise<Record<string, string>> {
+    const cachedFlags = this.cache.getFlags();
+    if (cachedFlags && Object.keys(cachedFlags).length > 0) {
+      return Promise.resolve(cachedFlags);
+    }
+
+    return this.client.flags().then((flags) => {
+      this.cache.setFlags(flags);
+      return flags;
+    });
+  }
 }