[Usage Collection] Ensure no type duplicates

src/plugins/usage_collection/README.md

@@ -59,7 +59,7 @@ All you need to provide is a `type` for organizing your fields, `schema` field t
 
       // create usage collector
       const myCollector = usageCollection.makeUsageCollector<Usage>({
-        type: MY_USAGE_TYPE,
+        type: 'MY_USAGE_TYPE',
         schema: {
           my_objects: {
             total: 'long',
@@ -84,7 +84,11 @@ All you need to provide is a `type` for organizing your fields, `schema` field t
     }
     ```
 
-Some background: The `callCluster` that gets passed to the `fetch` method is created in a way that's a bit tricky, to support multiple contexts the `fetch` method could be called. Your `fetch` method could get called as a result of an HTTP API request: in this case, the `callCluster` function wraps `callWithRequest`, and the request headers are expected to have read privilege on the entire `.kibana` index. The use case for this is stats pulled from a Kibana Metricbeat module, where the Beat calls Kibana's stats API in Kibana to invoke collection.
+Some background: 
+
+- `MY_USAGE_TYPE` can be any string. It usually matches the plugin name. As a safety mechanism, we double check there are no duplicates at the moment of registering the collector.
+- The `fetch` method needs to support multiple contexts in which it is called. For example, when stats are pulled from a Kibana Metricbeat module, the Beat calls Kibana's stats API to invoke usage collection.
+In this case, the `fetch` method is called as a result of an HTTP API request and `callCluster` wraps `callWithRequest`, where the request headers are expected to have read privilege on the entire `.kibana' index.
 
 Note: there will be many cases where you won't need to use the `callCluster` function that gets passed in to your `fetch` method at all. Your feature might have an accumulating value in server memory, or read something from the OS, or use other clients like a custom SavedObjects client. In that case it's up to the plugin to initialize those clients like the example below:
 

src/plugins/usage_collection/server/collector/collector_set.test.ts

@@ -41,7 +41,7 @@ describe('CollectorSet', () => {
       loggerSpies.warn.mockRestore();
     });
 
-    const mockCallCluster = () => Promise.resolve({ passTest: 1000 });
+    const mockCallCluster = jest.fn().mockResolvedValue({ passTest: 1000 });
 
     it('should throw an error if non-Collector type of object is registered', () => {
       const collectors = new CollectorSet({ logger });
@@ -58,6 +58,23 @@ describe('CollectorSet', () => {
       );
     });
 
+    it('should throw when 2 collectors with the same type are registered', () => {
+      const collectorSet = new CollectorSet({ logger });
+      collectorSet.registerCollector(
+        new Collector(logger, { type: 'test_duplicated', fetch: () => 1, isReady: () => true })
+      );
+      expect(() =>
+        collectorSet.registerCollector(
+          // Even for Collector vs. UsageCollector
+          new UsageCollector(logger, {
+            type: 'test_duplicated',
+            fetch: () => 2,
+            isReady: () => false,
+          })
+        )
+      ).toThrowError(`Usage collector's type "test_duplicated" is duplicated.`);
+    });
+
     it('should log debug status of fetching from the collector', async () => {
       const collectors = new CollectorSet({ logger });
       collectors.registerCollector(
@@ -68,7 +85,7 @@ describe('CollectorSet', () => {
         })
       );
 
-      const result = await collectors.bulkFetch(mockCallCluster as any);
+      const result = await collectors.bulkFetch(mockCallCluster);
       expect(loggerSpies.debug).toHaveBeenCalledTimes(1);
       expect(loggerSpies.debug).toHaveBeenCalledWith(
         'Fetching data from MY_TEST_COLLECTOR collector'
@@ -93,7 +110,7 @@ describe('CollectorSet', () => {
 
       let result;
       try {
-        result = await collectors.bulkFetch(mockCallCluster as any);
+        result = await collectors.bulkFetch(mockCallCluster);
       } catch (err) {
         // Do nothing
       }
@@ -111,7 +128,7 @@ describe('CollectorSet', () => {
         })
       );
 
-      const result = await collectors.bulkFetch(mockCallCluster as any);
+      const result = await collectors.bulkFetch(mockCallCluster);
       expect(result).toStrictEqual([
         {
           type: 'MY_TEST_COLLECTOR',
@@ -129,7 +146,7 @@ describe('CollectorSet', () => {
         } as any)
       );
 
-      const result = await collectors.bulkFetch(mockCallCluster as any);
+      const result = await collectors.bulkFetch(mockCallCluster);
       expect(result).toStrictEqual([
         {
           type: 'MY_TEST_COLLECTOR',
@@ -152,7 +169,7 @@ describe('CollectorSet', () => {
         })
       );
 
-      const result = await collectors.bulkFetch(mockCallCluster as any);
+      const result = await collectors.bulkFetch(mockCallCluster);
       expect(result).toStrictEqual([
         {
           type: 'MY_TEST_COLLECTOR',

src/plugins/usage_collection/server/collector/collector_set.ts

@@ -32,10 +32,10 @@ export class CollectorSet {
   private _waitingForAllCollectorsTimestamp?: number;
   private readonly logger: Logger;
   private readonly maximumWaitTimeForAllCollectorsInS: number;
-  private collectors: Array<Collector<any, any>> = [];
+  private readonly collectors: Map<string, Collector<any, any>>;
   constructor({ logger, maximumWaitTimeForAllCollectorsInS, collectors = [] }: CollectorSetConfig) {
     this.logger = logger;
-    this.collectors = collectors;
+    this.collectors = new Map(collectors.map((collector) => [collector.type, collector]));
     this.maximumWaitTimeForAllCollectorsInS = maximumWaitTimeForAllCollectorsInS || 60;
   }
 
@@ -55,7 +55,11 @@ export class CollectorSet {
       throw new Error('CollectorSet can only have Collector instances registered');
     }
 
-    this.collectors.push(collector);
+    if (this.collectors.get(collector.type)) {
+      throw new Error(`Usage collector's type "${collector.type}" is duplicated.`);
+    }
+
+    this.collectors.set(collector.type, collector);
 
     if (collector.init) {
       this.logger.debug(`Initializing ${collector.type} collector`);
@@ -64,7 +68,7 @@ export class CollectorSet {
   };
 
   public getCollectorByType = (type: string) => {
-    return this.collectors.find((c) => c.type === type);
+    return [...this.collectors.values()].find((c) => c.type === type);
   };
 
   public isUsageCollector = (x: UsageCollector | any): x is UsageCollector => {
@@ -81,7 +85,7 @@ export class CollectorSet {
 
     const collectorTypesNotReady: string[] = [];
     let allReady = true;
-    for (const collector of collectorSet.collectors) {
+    for (const collector of collectorSet.collectors.values()) {
       if (!(await collector.isReady())) {
         allReady = false;
         collectorTypesNotReady.push(collector.type);
@@ -113,10 +117,10 @@ export class CollectorSet {
 
   public bulkFetch = async (
     callCluster: LegacyAPICaller,
-    collectors: Array<Collector<any, any>> = this.collectors
+    collectors: Map<string, Collector<any, any>> = this.collectors
   ) => {
     const responses = [];
-    for (const collector of collectors) {
+    for (const collector of collectors.values()) {
       this.logger.debug(`Fetching data from ${collector.type} collector`);
       try {
         responses.push({
@@ -136,7 +140,7 @@ export class CollectorSet {
    * @return {new CollectorSet}
    */
   public getFilteredCollectorSet = (filter: (col: Collector) => boolean) => {
-    const filtered = this.collectors.filter(filter);
+    const filtered = [...this.collectors.values()].filter(filter);
     return this.makeCollectorSetFromArray(filtered);
   };
 
@@ -188,12 +192,12 @@ export class CollectorSet {
 
   // TODO: remove
   public map = (mapFn: any) => {
-    return this.collectors.map(mapFn);
+    return [...this.collectors.values()].map(mapFn);
   };
 
   // TODO: remove
   public some = (someFn: any) => {
-    return this.collectors.some(someFn);
+    return [...this.collectors.values()].some(someFn);
   };
 
   private makeCollectorSetFromArray = (collectors: Collector[]) => {