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）。但我很难实现这一目标。任何人都可以举例说明如何在不需要创建文件的情况下上传到AWS S3？
AWS如何上传文件的示例：
@Document(collection = "prospects")
public class Prospect {
@Id private String prospectId;
@TextIndexed() private String businessName;
public String getProspectId() {
return prospectId;
}
public void setProspectId(String prospectId) {
this.prospectId = prospectId;
}
public String getBusinessName() {
return businessName;
}
public void setBusinessName(final String businessName) {
this.businessName = businessName;
}
}
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。
答案 0 :(得分：3)
UploadInput结构的Body字段只是io.Reader。所以传递你想要的任何io.Reader - 它不需要是一个文件。
答案 1 :(得分：0)
在此答案中，我将发布与该问题相关的所有对我有用的内容。非常感谢@ThunderCat和@Flimzy，它们使我意识到上载请求的主体参数已经是io.Reader。我将发布一些示例代码，以评论从该问题中学到的内容以及它如何帮助我解决该问题。也许这会对像我和@AlokKumarSingh这样的人有所帮助。
情况1：您已经在内存中存储了数据（例如，从Kafka，Kinesis或SQS等流/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：您已经有一个永久文件，并且想要上传它，但是您不想将整个文件保存在内存中：
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：这是我在系统的最终版本中实现它的方法，但是要理解为什么这样做，我必须给您一些背景知识。
我的用例有所发展。上传代码将成为Lambda的功能，并且文件很大。这意味着什么：如果我通过连接到Lambda函数的API网关中的入口点上传文件，则必须等待整个文件在Lambda中完成上传。由于lambda是根据调用的持续时间和内存使用量定价的，因此这可能是一个很大的问题。
因此，为了解决此问题，我使用了预签名的帖子URL进行上传。这如何影响架构/工作流程？
我不是从后端代码上载到S3，而是创建并验证将对象发布到后端中的S3的URL并将其发送到前端。这样，我就实现了对该URL的分段上传。我知道这比问题要具体得多，但是要找到这种解决方案并不容易，因此我认为在这里为其他人提供文档是个好主意。
这里是如何在 nodejs 中创建该预签名URL的示例。
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,
})
}
});
};
如果您想使用 go ，这是相同的想法，则只需更改de sdk。
答案 2 :(得分：0)
这是我写的一个利用管道并结合超时的小实现。
package example
import (
"context"
"fmt"
"io"
"sync"
"time"
"github.com/aws/aws-sdk-go/service/s3/s3manager"
)
func FileWriter(ctx context.Context, uploader *s3manager.Uploader, wg *sync.WaitGroup, bucket string, key string, timeout time.Duration) (writer *io.PipeWriter) {
// create a per-file flush timeout
fileCtx, cancel := context.WithTimeout(ctx, timeout)
// pipes are open until one end is closed
pr, pw := io.Pipe()
wg.Add(1)
go func() {
params := &s3manager.UploadInput{
Bucket: aws.String(bucket),
Key: aws.String(key),
Body: pr,
}
// blocking
_, err := uploader.Upload(params)
if err != nil {
fmt.Printf("Unable to upload, %v. Bucket: %s", err, bucket)
}
// always call context cancel functions!
cancel()
wg.Done()
}()
// when context is cancelled, close the pipe
go func() {
<-fileCtx.Done()
// should check fileCtx.Err() here
if err := pw.Close(); err != nil {
fmt.Printf("Unable to close")
}
}()
return pw
}
答案 3 :(得分：-1)
这就是我最后写的东西
func (s *S3Sink) upload() {
now := time.Now()
key := s.getNewKey(now)
_, err := s.uploader.Upload(&s3manager.UploadInput{
Bucket: aws.String(s.bucket),
Key: aws.String(key),
Body: s.bodyBuf,
})
if err != nil {
glog.Errorf("Error uploading %s to s3, %v", key, err)
}
glog.Infof("Uploaded at %s", key)
s.lastUploadTimestamp = now.UnixNano()
s.bodyBuf.Truncate(0)
}