从事件中心获取消息到变量

Question

I am absolutely new to Azure Event Hub. I checked documentation and see that messages are set to console log.

    async function main() {
    console.log(`Running receiveEvents sample`);

    const consumerClient = new EventHubConsumerClient(consumerGroup, connectionString);

    const subscription = consumerClient.subscribe(
        {
            // The callback where you add your code to process incoming events
            processEvents: async (events, context) => {
                // Note: It is possible for `events` to be an empty array.
                // This can happen if there were no new events to receive
                // in the `maxWaitTimeInSeconds`, which is defaulted to
                // 60 seconds.
                // The `maxWaitTimeInSeconds` can be changed by setting
                // it in the `options` passed to `subscribe()`.
                for (const event of events) {
                    console.log(
                        `Received event: '${JSON.stringify(event.body)}' from partition: '${context.partitionId}' and consumer group: '${context.consumerGroup}'`
                    );
                }
            },
            processError: async (err, context) => {
                console.log(`Error : ${err}`);
            }
        },
        { startPosition: earliestEventPosition }
    );

    // Wait for a bit before cleaning up the sample
    setTimeout(async () => {
        await subscription.close();
        await consumerClient.close();
        console.log(`Exiting receiveEvents sample`);
    }, 30 * 1000);
}

main().catch((error) => {
    console.error("Error running sample:", error);
});

I would like to have this one `Received event:

${JSON.stringify(event.body)}

in variable and then operate it in thenable.

How can I do this? Also is any possibility to filter events? I haven't found any example.

Answer 1

What I understood from your question, you want a thenable (promise) async processing of the event. You can do something like below.

async function main() {
  console.log(`Running receiveEvents sample`);

  const consumerClient = new EventHubConsumerClient(consumerGroup, connectionString, eventHubName);

  const subscription = consumerClient.subscribe(
    {
      // The callback where you add your code to process incoming events
      processEvents: async (events, context) => {
        // Note: It is possible for `events` to be an empty array.
        // This can happen if there were no new events to receive
        // in the `maxWaitTimeInSeconds`, which is defaulted to
        // 60 seconds.
        // The `maxWaitTimeInSeconds` can be changed by setting
        // it in the `options` passed to `subscribe()`.
        for (const event of events) {
          console.log(
            `Received event: '${JSON.stringify(event.body)}' from partition: '${context.partitionId}' and consumer group: '${context.consumerGroup}'`
          );
          processAsync(event)
            .then(e => {
              console.log('Done processing event');
            });
        }
      },
      processError: async (err, context) => {
        console.log(`Error : ${err}`);
      }
    },
    { startPosition: earliestEventPosition }
  );

  const processAsync = async (event) => {
    // do something
    // you have access to the full event object

    return event;
  };

  // Wait for a bit before cleaning up the sample
  setTimeout(async () => {
    await subscription.close();
    await consumerClient.close();
    console.log(`Exiting receiveEvents sample`);
  }, 86400 * 1000);
}

main().catch((error) => {
  console.error("Error running sample:", error);
});