[Event Hubs] Add a sample for buffered producer (Azure#18674)

* [Event Hubs] Add a sample for buffered producer

* edit

* Apply suggestions from code review

Ramya's feedback

Co-authored-by: Ramya Rao <ramya.rao.a@outlook.com>

* address feedback

* unpublish the sample for now

* address feedback

* fix format

* address feedback

* document the sending behavior

* update comment for maxWaitTimeInMs

* update formatting

* address feedback

* remove unused imports

Co-authored-by: Ramya Rao <ramya.rao.a@outlook.com>

Author: deyaaeldeen

sdk/eventhub/event-hubs/samples-dev/sendBufferedEvents.ts

@@ -0,0 +1,72 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT Licence.
+
+/**
+ @summary Demonstrates how to send events to an Event Hub using the `EventHubBufferedProducerClient`.
+ * This sample is different from the one in `sendEvent.ts` in that the client manages batching of events and sending
+ * after a given amount of time or after a given amount of events are in a batch instead of you managing the same explicitly.
+ *
+ * @azsdk-weight 60
+ */
+
+import { EventHubBufferedProducerClient, OnSendEventsErrorContext } from "@azure/event-hubs";
+
+// Load the .env file if it exists
+import * as dotenv from "dotenv";
+dotenv.config();
+
+const connectionString = process.env["EVENTHUB_CONNECTION_STRING"] || "";
+
+async function handleError(ctx: OnSendEventsErrorContext): Promise<void> {
+  console.log(`The following error occurred:`);
+  console.log(JSON.stringify(ctx.error, undefined, 2));
+  console.log(
+    `The following events were not sent as a result to the partition with ID ${ctx.partitionId}:`
+  );
+  for (const event of ctx.events) {
+    console.log(JSON.stringify(event, undefined, 2));
+    console.log("\n");
+  }
+}
+
+export async function main(): Promise<void> {
+  console.log(`Running sendBufferedEvents sample`);
+
+  /**
+   * Create a buffered client that batches the enqueued events and sends it either
+   * after 750ms or after batching 1000 events, whichever occurs first.
+   */
+  const client = new EventHubBufferedProducerClient(connectionString, {
+    /** An error handler must be provided */
+    onSendEventsErrorHandler: handleError,
+
+    /** wait for up to 750 milliseconds before sending a batch */
+    maxWaitTimeInMs: 750,
+
+    /** buffer up to 1000 events per partition before sending */
+    maxEventBufferLengthPerPartition: 1000,
+  });
+
+  function createData(count: number): number[] {
+    return [...Array(count).keys()];
+  }
+
+  console.log("Enqueuing events...");
+
+  for (const item of createData(2000)) {
+    client.enqueueEvent({ body: item });
+  }
+
+  /**
+   * Flushing ensures buffered events that were not sent yet will be sent before
+   * closing the connection. Flushing can also be invoked directly using
+   * client.flush().
+   */
+  await client.close({ flush: true });
+  console.log(`Exiting sendBufferedEvents sample`);
+}
+
+main().catch((error) => {
+  console.error("Error running sample:", error);
+  process.exit(1);
+});