MultipartUpload的presign怎么使用
本篇内容介绍了“Multipart Upload的presign怎么使用”的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！
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需求背景
有项目需要在客户端上传数据，但是出于安全考虑不能在客户端本地任何位置存储secret-key的信息，同时普通的presign上传请求也有局限性，特别是当文件很大的时候整个上传效率非常低。因此需要调研Multipart Upload是否支持presign机制。（Multipart Upload是否支持presign，AWS及ceph官方都没有明确说明）
Multipart Upload基本流程
整个Multipart Upload大致分为3个阶段
1. initiate_multipart_upload:使用HTTP POST请求构建初始化数据，object的metadata、content-type这些都是在这个阶段设置，请求成功以后的response里面回返回uploadID，后续使用这个uploadID进行数据上传操作。
2. upload_part:使用HTTP PUT请求构建数据上传操作，客户端本地将大文件拆分成多个part文件，每个part使用相同的uploadID，按uploadNumber顺序依次上传数据(可以并行）。每个part文件上传成功会返回对应的etag来完成每个part文件的一致性校验。
3. compelte_upload:使用HTTP PUT请求构建最后的合并请求操作，完成各个分块的逻辑合并，注意返回的etag不具备一致性校验功能。
Multipart Upload特性总结:
1.拆分大文件到多个part文件，实现超大文件的上传。
2.拆分的part文件可以并行上传，极大地提高了上传效率。
3.Multipart Upload实现的是过程一致性校验，而非最终一致性校验。
4.metadata和content-type一类的信息必须在initiate阶段提前设置。
在upload_part阶段实现presign
流程介绍:和普通Multipart Upload一样先在client端实现文件的拆分，之后对每个part文件生成单独的PreSignURL，最后使用生成的URL完成各个part文件的上传（不再需要secret-key）。
使用python实现upload_part阶段的presign
分为两部分，server_demo.py主要实现最关键的S3Sign,代码如下
# -*- coding: utf-8 -*-
import time
import hmac
from hashlib import sha1 as sha
py3k = False
try:
from urlparse import urlparse, unquote
from base64 import encodestring
except:
py3k = True
from urllib.parse import urlparse, unquote
from base64 import encodebytes as encodestring
class S3PreSign():
def __init__(self, access_key, secret_key, service_url, bucket_name, object_name, upload_ID, expires):
self.service_url = str(service_url)
self.access_key = str(access_key)
self.secret_key = str(secret_key)
self.bucket_name = str(bucket_name)
self.object_name = str(object_name)
self.upload_ID = str(upload_ID)
self.Expires = int(time.time()) + int(expires)
def get_signature_str(self, sign_str):
if py3k:
key = self.secret_key.encode('utf-8')
msg = sign_str.encode('utf-8')
else:
key = self.secret_key
msg = sign_str
h = hmac.new(key, msg, digestmod=sha)
return (encodestring(h.digest()).strip()).replace('+', '%2b')
def build_url(self, partNumber, Signature):
url_ = "http://{bucket_name}.{service_url}/{object_name}?uploadId={uploadId}&partNumber={partNumber}&Expires={Expires}&AWSAccessKeyId={AWSAccessKeyId}&Signature={Signature}".format(
bucket_name=self.bucket_name,
service_url=self.service_url,
object_name=self.object_name,
uploadId=self.upload_ID,
partNumber=partNumber,
Expires=self.Expires,
AWSAccessKeyId=self.access_key,
Signature=Signature
)
return url_
def build_url_with_partid(self, partMd5, partNumber):
sign_str = "PUT\n{partMd5}\n\n{Expires}\n/{bucket_name}/{object_name}?partNumber={partNumber}&uploadId={uploadId}".format(
partMd5=partMd5,
Expires=self.Expires,
bucket_name=self.bucket_name,
object_name=self.object_name,
partNumber=partNumber,
uploadId=self.upload_ID)
Signature_ = self.get_signature_str(sign_str)
return self.build_url(partNumber, Signature_)最后在client_demo.py中实现对应的并行上传用例，这里只是简单的说明过程，如果需要隐藏secret-key这些信息，需要将这个生成presignURL的过程封装成一个独立的服务接口，客户端通过请求去获取这些生成的presignURL。
# -*- coding: utf-8 -*-
from server_demo import S3PreSign
import requests
from base64 import encodestring
from hashlib import md5
import os
from multiprocessing import Pool
class S3client():
def __init__(self, part_num, uploadfile_path):
self.part_num = part_num
self.uploadfile_path = uploadfile_path
def split_file(self):
filelist = []
statinfo = os.stat(self.uploadfile_path)
chunksize = statinfo.st_size / self.part_num
print "File size: %d(MB)" % (statinfo.st_size / (1024 * 1024))
print self.uploadfile_path,chunksize
with open(self.uploadfile_path, "rb") as f:
index = 1
while True:
chunk = f.read(chunksize)
if (chunk):
fn = "%s.part.%d" % (self.uploadfile_path, index)
print "creating", fn
with open(fn, "wb") as fw:
fw.write(chunk)
partMD5 = self.compute_hash(fn)
tmp_ = {}
tmp_[fn] = str(partMD5)
filelist.append(tmp_)
index = index + 1
else:
break
return filelist
def compute_hash(self, filepath, buf_size=8192, size=None, hash_algorithm=md5):
hash_obj = hash_algorithm()
with open(filepath) as fp:
spos = fp.tell()
if size and size < buf_size:
s = fp.read(size)
else:
s = fp.read(buf_size)
while s:
if not isinstance(s, bytes):
s = s.encode('utf-8')
hash_obj.update(s)
if size:
size -= len(s)
if size <= 0:
break
if size and size < buf_size:
s = fp.read(size)
else:
s = fp.read(buf_size)
base64_digest = encodestring(hash_obj.digest()).decode('utf-8')
if base64_digest[-1] == '\n':
base64_digest = base64_digest[0:-1]
return base64_digest
def make_upload_list(self,S3Sign):
upload_file_list = self.split_file()
for f in upload_file_list:
part_path = f.keys()[0]
partMD5 = f.values()[0]
partnum_ = f.keys()[0].split(".")[-1]
url_ = S3Sign.build_url_with_partid(partMD5, partnum_)
# print "Ready to upload {part_path} with URL={url_} MD5={partMD5}".format(part_path=part_path,url_=url_,partMD5=partMD5)
yield (url_, part_path, partMD5)
def multipart_upload_with_part(url_, part_file_path, partMD5):
headers = {}
headers["Content-MD5"] = partMD5
with open(part_file_path,'r') as fh:
response = requests.put(url_, headers=headers, data=fh.read())
if response.status_code == 200:
print "{} upload Sucessful !".format(part_file_path)
if __name__ == "__main__":
endpoint = 's3.ceph.work'
access_key = ''
secret_key = ''
key_name = 'cosben-0.4.2.c4.zip'
part_num = 6 #大文件切分数量
expires = 300 #生成的presignURL有效时长
bucket_name = 'multi-upload'
file_path = '/tmp/cosbench-0.4.2.c4.zip'
upload_ID = '2~EAEhzt0luJqhV4KkZDGQH3CmegO00FX' #uploadID使用boto或者其他方法生成
processes_num = 2 #并行上传进程数
s3sign = S3PreSign(access_key=access_key, secret_key=secret_key, service_url=endpoint, bucket_name=bucket_name,
object_name=key_name, upload_ID=upload_ID, expires=expires)
s3client = S3client(part_num,file_path)
# s3client.split_file()
upload_file_list = s3client.make_upload_list(s3sign)
p = Pool(processes=processes_num)
for i in upload_file_list:
# print i
p.apply_async(multipart_upload_with_part, (i[0], i[1], i[2],))
print 'Waiting for all subprocesses done...'
p.close()
p.join()
print 'All subprocesses done.'“Multipart Upload的presign怎么使用”的内容就介绍到这里了，感谢大家的阅读。如果想了解更多行业相关的知识可以关注创新互联网站，小编将为大家输出更多高质量的实用文章！
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