Fix some self-review notes

src/plugins/telemetry/server/event_based_telemetry/event_based_telemetry_service.test.ts

@@ -123,7 +123,7 @@ describe('EventBasedTelemetryService', () => {
             test: { type: 'keyword', _meta: { description: 'Always OK because tests never fail' } },
           },
         })
-      ).toThrowError('Channels can only be lifecycle step.');
+      ).toThrowError('Channels can only be registered during the setup lifecycle step.');
 
       // Checking the validator is registered for the channel
       expect(

src/plugins/telemetry/server/event_based_telemetry/event_based_telemetry_service.ts

@@ -59,7 +59,7 @@ export class EventBasedTelemetryService {
 
   public registerChannel(pluginName: string, channelOptions: EventChannelOptions) {
     if (this.started) {
-      throw new Error(`Channels can only be lifecycle step.`);
+      throw new Error(`Channels can only be registered during the setup lifecycle step.`);
     }
     const { name: channelName, schema, quotaPercentage } = channelOptions;
     this.logger.debug(`Registering channel "${channelName}" from plugin "${pluginName}"`);

src/plugins/telemetry/server/event_based_telemetry/leaky_bucket.ts

@@ -76,14 +76,20 @@ export class LeakyBucket {
 
   private async sendIfFull(sender: HTTPSender) {
     if (this.isFullQueue()) {
-      // To don't go over our "threshold bytes per second", we need to wait 1s before consuming from queues again.
-      // Doing a Promise.all because we don't want to add the sending time to the max_frequency_of_requests wait.
-      await Promise.all([
+      // To don't go over our "threshold bytes per second", we need to wait
+      // {max_frequency_of_requests} before consuming from queues again.
+      // Using Promise.allSettled because we don't want to add the sending
+      // time to the {max_frequency_of_requests} wait, but we still want to wait if we fail to send.
+      const [sendResults] = await Promise.allSettled([
         this.send(sender),
         new Promise((resolve) =>
           setTimeout(resolve, this.config.max_frequency_of_requests.asMilliseconds())
         ),
       ]);
+
+      if (sendResults.status === 'rejected') {
+        throw sendResults.reason;
+      }
     }
   }