我正在尝试使用 golang sdk 将对象上传到 AWS S3，而无需在我的系统中创建文件(尝试仅上传字符串)。但我很难做到这一点。谁能举例说明如何在无需创建文件的情况下上传到 AWS S3？

关于如何上传文件的 AWS 示例:

// Creates a S3 Bucket in the region configured in the shared config
// or AWS_REGION environment variable.
//
// Usage:
//    go run s3_upload_object.go BUCKET_NAME FILENAME
func main() {
    if len(os.Args) != 3 {
        exitErrorf("bucket and file name required\nUsage: %s bucket_name filename",
            os.Args[0])
    }

    bucket := os.Args[1]
    filename := os.Args[2]

    file, err := os.Open(filename)
    if err != nil {
        exitErrorf("Unable to open file %q, %v", err)
    }

    defer file.Close()

    // Initialize a session in us-west-2 that the SDK will use to load
    // credentials from the shared credentials file ~/.aws/credentials.
    sess, err := session.NewSession(&aws.Config{
        Region: aws.String("us-west-2")},
    )

    // Setup the S3 Upload Manager. Also see the SDK doc for the Upload Manager
    // for more information on configuring part size, and concurrency.
    //
    // http://docs.aws.amazon.com/sdk-for-go/api/service/s3/s3manager/#NewUploader
    uploader := s3manager.NewUploader(sess)

    // Upload the file's body to S3 bucket as an object with the key being the
    // same as the filename.
    _, err = uploader.Upload(&s3manager.UploadInput{
        Bucket: aws.String(bucket),

        // Can also use the `filepath` standard library package to modify the
        // filename as need for an S3 object key. Such as turning absolute path
        // to a relative path.
        Key: aws.String(filename),

        // The file to be uploaded. io.ReadSeeker is preferred as the Uploader
        // will be able to optimize memory when uploading large content. io.Reader
        // is supported, but will require buffering of the reader's bytes for
        // each part.
        Body: file,
    })
    if err != nil {
        // Print the error and exit.
        exitErrorf("Unable to upload %q to %q, %v", filename, bucket, err)
    }

    fmt.Printf("Successfully uploaded %q to %q\n", filename, bucket)
}

我已经尝试以编程方式创建文件，但它正在我的系统上创建文件，然后将其上传到 S3。

最佳答案

在这个答案中，我将发布与这个问题相关的所有对我有用的东西。非常感谢@ThunderCat 和@Flimzy 提醒我上传请求的 body 参数已经是一个 io.Reader。我将发布一些示例代码来评论我从这个问题中学到的东西以及它如何帮助我解决这个问题。也许这会帮助像我和@AlokKumarSingh 这样的人。

情况 1:您已经将数据存储在内存中(例如，从 Kafka、Kinesis 或 SQS 等流媒体/消息服务接收数据)

func main() {
    if len(os.Args) != 3 {
        fmt.Printf(
            "bucket and file name required\nUsage: %s bucket_name filename",
            os.Args[0],
        )
    }

    bucket := os.Args[1]
    filename := os.Args[2]

    // this is your data that you have in memory
    // in this example it is hard coded but it may come from very distinct
    // sources, like streaming services for example.
    data := "Hello, world!"

    // create a reader from data data in memory
    reader := strings.NewReader(data)

    sess, err := session.NewSession(&aws.Config{
        Region: aws.String("us-east-1")},
    )
    uploader := s3manager.NewUploader(sess)

    _, err = uploader.Upload(&s3manager.UploadInput{
        Bucket: aws.String(bucket),
        Key: aws.String(filename),
        // here you pass your reader
        // the aws sdk will manage all the memory and file reading for you
        Body: reader,
    })
    if err != nil {.
        fmt.Printf("Unable to upload %q to %q, %v", filename, bucket, err)
    }

    fmt.Printf("Successfully uploaded %q to %q\n", filename, bucket)
}

情况 2:您已经有一个持久化文件并且您想要上传它但您不想在内存中维护整个文件:

func main() {
    if len(os.Args) != 3 {
        fmt.Printf(
            "bucket and file name required\nUsage: %s bucket_name filename",
            os.Args[0],
        )
    }

    bucket := os.Args[1]
    filename := os.Args[2]

    // open your file
    // the trick here is that the method os.Open just returns for you a reader
    // for the desired file, so you will not maintain the whole file in memory.
    // I know this might sound obvious, but for a starter (as I was at the time
    // of the question) it is not.
    fileReader, err := os.Open(filename)
    if err != nil {
        fmt.Printf("Unable to open file %q, %v", err)
    }
    defer fileReader.Close()

    sess, err := session.NewSession(&aws.Config{
        Region: aws.String("us-east-1")},
    )
    uploader := s3manager.NewUploader(sess)

    _, err = uploader.Upload(&s3manager.UploadInput{
        Bucket: aws.String(bucket),
        Key:    aws.String(filename),
        // here you pass your reader
        // the aws sdk will manage all the memory and file reading for you
        Body: fileReader,
    })
    if err != nil {
        fmt.Printf("Unable to upload %q to %q, %v", filename, bucket, err)
    }

    fmt.Printf("Successfully uploaded %q to %q\n", filename, bucket)
}

案例 3:这就是我在我的系统的最终版本上实现它的方式，但为了理解我为什么这样做，我必须给你一些背景知识。

我的用例有所改进。上传代码将成为 Lambda 中的一个函数，结果文件变得很大。此更改意味着什么:如果我通过附加到 Lambda 函数的 API 网关中的入口点上传文件，我将不得不等待整个文件在 Lambda 中完成上传。由于 lambda 是根据调用的持续时间和内存使用情况定价的，这可能是一个非常大的问题。

因此，为了解决这个问题，我使用了预签名的帖子 URL 进行上传。这对架构/工作流程有何影响？

我没有从我的后端代码上传到 S3，我只是创建并验证一个 URL 以在后端将对象发布到 S3，然后将此 URL 发送到前端。这样，我就实现了到该 URL 的分段上传。我知道这比问题具体得多，但发现这个解决方案并不容易，所以我认为最好在此处为其他人记录下来。

这是一个示例，说明如何在 nodejs 中创建该预签名 URL。

const AWS = require('aws-sdk');

module.exports.upload = async (event, context, callback) => {

  const s3 = new AWS.S3({ signatureVersion: 'v4' });
  const body = JSON.parse(event.body);

  const params = {
    Bucket: process.env.FILES_BUCKET_NAME,
    Fields: {
      key: body.filename,
    },
    Expires: 60 * 60
  }

  let promise = new Promise((resolve, reject) => {
    s3.createPresignedPost(params, (err, data) => {
      if (err) {
        reject(err);
      } else {
        resolve(data);
      }
    });
  })

  return await promise
    .then((data) => {
      return {
        statusCode: 200,
        body: JSON.stringify({
          message: 'Successfully created a pre-signed post url.',
          data: data,
        })
      }
    })
    .catch((err) => {
      return {
        statusCode: 400,
        body: JSON.stringify({
          message: 'An error occurred while trying to create a pre-signed post url',
          error: err,
        })
      }
    });
};

如果你想用go也是一样的思路，你只需要改一下de sdk即可。

关于go - 使用 aws-sdk-go 将对象上传到 AWS S3 而无需创建文件，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47621804/