boto3 dynamodb 入门使用

介绍

Amazon DynamoDB 是一项快速灵活的 NoSQL 数据库服务，适合所有需要一致性且延迟低于 10 毫秒的任意规模的应用程序。它是完全托管的云数据库，支持文档和键值存储模型。灵活的数据模型和可靠的性能使其成为移动、Web、游戏、广告技术、物联网和众多其他应用的不二之选。

定价

官方网站的价格介绍：https://aws.amazon.com/cn/dynamodb/pricing/

但是我实际开发的时候一个月只有4000多写收了27RMB，我一共创建了两个表，没有搞清怎么收费，还是每个表有一个最低收费。我配置每张表的读取，写入的速度，可以根据每张表的实际使用读写和写入速度，这样可以最大的降低费用，避免不必要的浪费。

入门视频

介绍： https://aws.amazon.com/cn/dynamodb/getting-started/

上手实验营：https://aws.amazon.com/cn/dynamodb/getting-started/

代码例子

创建新表

import boto3
# Get the service resource.
dynamodb = boto3.resource('dynamodb')
# Create the DynamoDB table.
table = dynamodb.create_table(
TableName='users',
KeySchema=[
{
'AttributeName': 'username',
'KeyType': 'HASH'
},
{
'AttributeName': 'last_name',
'KeyType': 'RANGE'
}
],
AttributeDefinitions=[
{
'AttributeName': 'username',
'AttributeType': 'S'
},
{
'AttributeName': 'last_name',
'AttributeType': 'S'
},

],
ProvisionedThroughput={
'ReadCapacityUnits': 5,
'WriteCapacityUnits': 5
}
)
# Wait until the table exists.
table.meta.client.get_waiter('table_exists').wait(TableName='users')

# Print out some data about the table.
print(table.item_count)

添加新item

table.put_item(
Item={
'username': 'janedoe',
'first_name': 'Jane',
'last_name': 'Doe',
'age': 25,
'account_type': 'standard_user',
}
)

跟新item

table.update_item(
Key={
'username': 'janedoe',
'last_name': 'Doe'
},
UpdateExpression='SET age = :val1',
ExpressionAttributeValues={
':val1': 26
}
)

我写的一个项目，对象dynamodb：

# coding:utf-8
from boto3 import Session
from error import DynamodbConnectionError, DynamoDBError
from botocore.exceptions import ClientError
from boto3.dynamodb.conditions import Attr
from helper import DecimalEncoder
import logging
import json

logger = logging.getLogger(__name__)

class MyserviceDynamodb(object):
"""

"""
def __init__(self, **kwargs):
self.region = kwargs['region']
self.access_key = kwargs['access_key']
self.secret_key = kwargs['secret_key']
self.session = self.__session()

def __session(self):
try:
session = Session(aws_access_key_id=self.access_key,
aws_secret_access_key=self.secret_key,region_name=self.region)
except:
raise DynamodbConnectionError("Failed to connect session in region{0}".format(self.region))
return session

def get_table(self, table_name):
dynamodb = self.session.resource('dynamodb')
if not dynamodb:
raise DynamodbConnectionError("Failed to get resource for dynamodb!")
try:
table = dynamodb.Table(table_name)
except Exception as e:
logger.error("Failed to get table {0}, error".format(table_name, e))

return table

def put_item(self, table, item_dict=None):
try:
response = table.put_item(Item=item_dict)
except Exception as e:
logger.error("Failed to put item in to {0}:error{1}".format(table,e))
return response

def status_scan_items(self, table, event_status=None):
try:
response = table.scan(FilterExpression=Attr('event_status').eq(event_status))
except Exception as e:
logger.error('{0} failed query items , error{1}'.format(json.dumps(table, indent=4,cls=DecimalEncoder),e))
return response

def get_item(self, table, id):
try:
response = table.get_item(Key={'event_id': id})
except ClientError as e:
if e.response['Error']['Code'] == "ConditionalCheckFailedException":
logger.error(e.response['Error']['Message'])
else:
raise DynamoDBError('Failed to get item from dynamodb not by Conditional')
else:
logger.info(json.dumps(response, indent=4, cls=DecimalEncoder))
return response

def update_status_by_event_id(self, table, event_id, change_status=None):
try:
response = table.update_item(
Key = {'event_id':event_id},UpdateExpression = "SET event_status = :val1",
ExpressionAttributeValues={':val1':change_status},ReturnValues="UPDATED_NEW")
except ClientError as e:
if e.response['Error']['Code'] == "ConditionalCheckFailedException":
logger.error(e.response['Error']['Message'])
else:
raise DynamoDBError('Failed update the dynamodb by event_id,not Failed Conditional')
else:
logger.info("UpdateItem succeeded:{0}".format(json.dumps(response, indent=4, cls=DecimalEncoder)))
return response

注意：

Dynamodb的保留字段，在创建表的字段的时候不要使用一下字段不然的话，在进行表操作会报错：

Attribute name is a reserved keyword; reserved keyword: status

Dynamodb 保留字段：

http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ReservedWords.html

参考文档：

官方文档： http://boto3.readthedocs.io/en/latest/guide/dynamodb.html