当对象上传到我的 GCS 存储桶时，我如何收到通知?

问题描述

我有一个应用可以定期将照片上传到 GCS 存储桶.上传这些照片后，我需要添加缩略图并进行一些分析.如何为存储分区设置通知?

I have an app that uploads photos regularly to a GCS bucket. When those photos are uploaded, I need to add thumbnails and do some analysis. How do I set up notifications for the bucket?

推荐答案

这样做的方法是为新对象创建一个 Cloud Pub/Sub 主题，并配置您的 GCS 存储桶以在新对象出现时向该主题发布消息已创建.

The way to do this is to create a Cloud Pub/Sub topic for new objects and to configure your GCS bucket to publish messages to that topic when new objects are created.

首先，让我们创建一个存储桶 PHOTOBUCKET:

First, let's create a bucket PHOTOBUCKET:

$ gsutil mb gs://PHOTOBUCKET

现在，请确保您已激活云发布/订阅 API.

接下来，让我们创建一个 Cloud Pub/Sub 主题并使用 gsutil 将其连接到我们的 GCS 存储桶:

Next, let's create a Cloud Pub/Sub topic and wire it to our GCS bucket with gsutil:

$ gsutil notification create
    -t uploadedphotos -f json
    -e OBJECT_FINALIZE gs://PHOTOBUCKET

-t 指定 Pub/Sub 主题.如果该主题尚不存在，gsutil 将为您创建它.

The -t specifies the Pub/Sub topic. If the topic doesn't already exist, gsutil will create it for you.

-e 指定您只对 OBJECT_FINALIZE 消息(正在创建的对象)感兴趣.否则，您将收到主题中的各种消息.

The -e specifies that you're only interested in OBJECT_FINALIZE messages (objects being created). Otherwise you'll get every kind of message in your topic.

-f 指定您希望消息的有效负载为 JSON API 的对象元数据.

The -f specifies that you want the payload of the messages to be the object metadata for the JSON API.

请注意，这需要最新版本的 gsutil，因此请务必更新到最新版本的 gcloud，如果您使用独立的 gsutil，请运行 gsutil update.

Note that this requires a recent version of gsutil, so be sure to update to the latest version of gcloud, or run gsutil update if you use a standalone gsutil.

现在我们已经配置并发送通知，但我们希望看到它们.让我们创建一个 Pub/Sub 订阅:

Now we have notifications configured and pumping, but we'll want to see them. Let's create a Pub/Sub subscription:

$ gcloud beta pubsub 订阅创建 processphotos --topic=uploadedphotos

$ gcloud beta pubsub subscriptions create processphotos --topic=uploadedphotos

现在我们只需要阅读这些消息.这是一个 Python 示例就是这样做.以下是相关位:

Now we just need to read these messages. Here's a Python example of doing just that. Here are the relevant bits:

def poll_notifications(subscription_id):
    client = pubsub.Client()
    subscription = pubsub.subscription.Subscription(
        subscription_id, client=client)
    while True:
        pulled = subscription.pull(max_messages=100)
        for ack_id, message in pulled:
            print('Received message {0}:
{1}'.format(
                message.message_id, summarize(message)))
            subscription.acknowledge([ack_id])

def summarize(message):
    # [START parse_message]
    data = message.data
    attributes = message.attributes

    event_type = attributes['eventType']
    bucket_id = attributes['bucketId']
    object_id = attributes['objectId']
    return "A user uploaded %s, we should do something here." % object_id

这里有更多关于这个系统如何工作的阅读:

Here is some more reading on how this system works:

https://cloud.google.com/storage/docs/reporting-changeshttps://cloud.google.com/storage/docs/pubsub-notifications

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