Azure Blob Storage に Append Block でログ追記する話

If-None-Match: *

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import urllib2
import base64
import hmac,hashlib
import datetime

def request(account_name, access_key, blob_path, content = ''):
    u'''指定の content を追記します。指定の content が空で BLOB が存在しない場合はは空の BLOB を作成します。'''
    
    content_encoding = 'UTF-8'
    content = content.encode(content_encoding)
    content_length = len(content)
    content_md5 = base64.b64encode(hashlib.md5(content).digest())
    content_type = 'text/plain'
    x_ms_blob_type = 'AppendBlob'
    x_ms_date = '{:%a, %d %b %Y %H:%M:%S GMT}'.format(datetime.datetime.utcnow())
    x_ms_version = '2015-02-21'
    request_url_format = 'https://{}.blob.core.windows.net{}'
    if content:
        request_url_format += '?comp=appendblock'
    
    string_to_sign_format = 'PUT\n{}\n\n{}\n{}\n{}\n\n\n\n{}\n\n\nx-ms-blob-type:{}\nx-ms-date:{}\nx-ms-version:{}\n/{}{}{}'
    string_to_sign = string_to_sign_format.format(
        content_encoding,
        content_length if 0 < content_length else '',
        content_md5,
        content_type,
        '*' if not content else '',
        x_ms_blob_type,
        x_ms_date,
        x_ms_version,
        account_name,
        blob_path,
        '\ncomp:appendblock' if content else ''
    )
    signature = base64.encodestring(hmac.new(base64.decodestring(access_key), string_to_sign, hashlib.sha256).digest()).rstrip('\n')
    
    req = urllib2.Request(request_url_format.format(account_name, blob_path), content)
    req.get_method = lambda: 'PUT'
    req.add_header("Authorization", 'SharedKey {}:{}'.format(account_name, signature))
    req.add_header("Content-Encoding", content_encoding)
    req.add_header("Content-Length", content_length)
    req.add_header("Content-MD5", content_md5)
    req.add_header("Content-Type", content_type)
    if not content:
        req.add_header("If-None-Match", '*')
    req.add_header("x-ms-blob-type", x_ms_blob_type)
    req.add_header("x-ms-date", x_ms_date)
    req.add_header("x-ms-version", x_ms_version)
    
    if not content:
        try:
            return urllib2.urlopen(req)
        except urllib2.HTTPError, e:
            if e.code == 409:
                # If-None-Match ヘッダにより既に BLOB がある場合は要求を受け付けない
                return e
            else:
                raise
    else:
        return urllib2.urlopen(req)

if __name__ == '__main__':
    account_name = 'STORAGE_ACCOUNT_NAME'
    access_key = 'STORAGE_ACCESS_KEY'
    blob_path = '/CONTAINER/PATH/TO/BLOB.log'
    
    # BLOB が無ければ作成する
    res = request(account_name, access_key, blob_path)
    print res.code, res.msg
    
    # 追記する
    res = request(account_name, access_key, blob_path, u'おはよう\r\n')
    print res.code, res.msg
    res = request(account_name, access_key, blob_path, u'こんにちは\r\n')
    print res.code, res.msg
    res = request(account_name, access_key, blob_path, u'こんばんは\r\n')
    print res.code, res.msg

おはよう
こんにちは
こんばんは