Boto3 examples(SGs,DynamoDB,EC2 and Cloudwatch)

 Create a new Dynamo table using 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)

This method will return a Dynamodb.Table

Once you have a DynamoDB.Table resource you can add new items to the table using DynamoDB.Table.put_item():
table.put_item(
   Item={
        'username': 'janedoe',
        'first_name': 'Jane',
        'last_name': 'Doe',
        'age': 25,
        'account_type': 'standard_user',
    }
)
You can then retrieve the object using DynamoDB.Table.get_item():

response = table.get_item(
    Key={
        'username': 'janedoe',
        'last_name': 'Doe'
    }
)
item = response['Item']
print(item)
You can then update attributes of the item in the table:

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

You can also delete the item using DynamoDB.Table.delete_item():

table.delete_item(
    Key={
        'username': 'janedoe',
        'last_name': 'Doe'
    }
)
With the table full of items, you can then query or scan the items in the table using the DynamoDB.Table.query() or DynamoDB.Table.scan() methods respectively. To add conditions to scanning and querying the table, you will need to import the boto3.dynamodb.conditions.Key and boto3.dynamodb.conditions.Attr classes. The boto3.dynamodb.conditions.Key should be used when the condition is related to the key of the item. The boto3.dynamodb.conditions.Attr should be used when the condition is related to an attribute of the item:

from boto3.dynamodb.conditions import Key, Attr
This queries for all of the users whose username key equals johndoe:

response = table.query(
    KeyConditionExpression=Key('username').eq('johndoe')
)
items = response['Items']
print(items)
Similarly you can scan the table based on attributes of the items. For example, this scans for all the users whose age is less than 27:

response = table.scan(
    FilterExpression=Attr('age').lt(27)
)
items = response['Items']
print(items)
Describing instances
import boto3
ec2 = boto3.client('ec2')
response = ec2.describe_instances()
print(response)

Monitor and unmonitor instances
import sys
import boto3


ec2 = boto3.client('ec2')
if sys.argv[1] == 'ON':
    response = ec2.monitor_instances(InstanceIds=['INSTANCE_ID'])
else:
    response = ec2.unmonitor_instances(InstanceIds=['INSTANCE_ID'])
print(response)

Start and stop instances

import boto3
from botocore.exceptions import ClientError

instance_id = sys.argv[2]
action = sys.argv[1].upper()

ec2 = boto3.client('ec2')


if action == 'ON':
    # Do a dryrun first to verify permissions
    try:
        ec2.start_instances(InstanceIds=[instance_id], DryRun=True)
    except ClientError as e:
        if 'DryRunOperation' not in str(e):
            raise

    # Dry run succeeded, run start_instances without dryrun
    try:
        response = ec2.start_instances(InstanceIds=[instance_id], DryRun=False)
        print(response)
    except ClientError as e:
        print(e)
else:
    # Do a dryrun first to verify permissions
    try:
        ec2.stop_instances(InstanceIds=[instance_id], DryRun=True)
    except ClientError as e:
        if 'DryRunOperation' not in str(e):
            raise

    # Dry run succeeded, call stop_instances without dryrun
    try:
        response = ec2.stop_instances(InstanceIds=[instance_id], DryRun=False)
        print(response)
    except ClientError as e:
        print(e)
		
Reboot instances
import boto3
from botocore.exceptions import ClientError


ec2 = boto3.client('ec2')

try:
    ec2.reboot_instances(InstanceIds=['INSTANCE_ID'], DryRun=True)
except ClientError as e:
    if 'DryRunOperation' not in str(e):
        print("You don't have permission to reboot instances.")
        raise

try:
    response = ec2.reboot_instances(InstanceIds=['INSTANCE_ID'], DryRun=False)
    print('Success', response)
except ClientError as e:
    print('Error', e)
Describe Regions and Availability Zones

ec2 = boto3.client('ec2')

# Retrieves all regions/endpoints that work with EC2
response = ec2.describe_regions()
print('Regions:', response['Regions'])

# Retrieves availability zones only for region of the ec2 object
response = ec2.describe_availability_zones()
print('Availability Zones:', response['AvailabilityZones'])

Create a security group and rules
import boto3
from botocore.exceptions import ClientError

ec2 = boto3.client('ec2')

response = ec2.describe_vpcs()
vpc_id = response.get('Vpcs', [{}])[0].get('VpcId', '')

try:
    response = ec2.create_security_group(GroupName='SECURITY_GROUP_NAME',
                                         Description='DESCRIPTION',
                                         VpcId=vpc_id)
    security_group_id = response['GroupId']
    print('Security Group Created %s in vpc %s.' % (security_group_id, vpc_id))

    data = ec2.authorize_security_group_ingress(
        GroupId=security_group_id,
        IpPermissions=[
            {'IpProtocol': 'tcp',
             'FromPort': 80,
             'ToPort': 80,
             'IpRanges': [{'CidrIp': '0.0.0.0/0'}]},
            {'IpProtocol': 'tcp',
             'FromPort': 22,
             'ToPort': 22,
             'IpRanges': [{'CidrIp': '0.0.0.0/0'}]}
        ])
    print('Ingress Successfully Set %s' % data)
except ClientError as e:
    print(e)
	
Delete a security group
import boto3
from botocore.exceptions import ClientError

# Create EC2 client
ec2 = boto3.client('ec2')

# Delete security group
try:
    response = ec2.delete_security_group(GroupId='SECURITY_GROUP_ID')
    print('Security Group Deleted')
except ClientError as e:
    print(e)

SNS with lambda

SNS with lambda

SNS: Simple Notification Service.

This is useful to create push notifications to the customer based on the topic which customer subscribed.For ex: Banking alerts , Promotional offers etc.

Topic: Intended subject which customer selected to get an update/alert.

For ex: If we have uploaded or modified any object which is stored in S3, you have to get an alarm/alert , to execute this kind of feature AWS provides Simple Notification Service feature to achieve it.

Also if there is modifications in Database where your external servers/customers should have to get an update , to achieve this as well , SNS will be utilized.

Steps to to create a topic in SNS

1.Search for services in AWS dashboard, select SNS

2.Create a topic by giving topic name

3.If you want to encrypt your message use the section:Encryption - optional

4.Access policy: This is the policy where we can provide the subscription on various categories like only to the owner, Everyone , Only with certain accounts or only with certain end points Under Basic Policy.

Advanced Plan:  An access policy will be created by using the JSON object.

5. Delivery retrieve policy:

When we configure a SNS topic , the server will push a notification with number of retrieves and with minimum and maximum delays .

6.Delivery status logging:

This will give us the delivery status of the messages which we sent , this log will be stored in Cloud watch.

7.Tags: This will allow you to filter a topic which will allow you to identify when you have number of topics.

So for now we just entered topic name and selected default values and clicked on create topic.

ARN: AWS Resource Number, which is the unique key created by AWS.

So to create a subscription , we are using Lambda . 

Click on "Create a Function" --> click on SNS with python --> fill as below

In above screen, select topic which we created earlier under SNS trigger

Then no need to modify python code and click on "Create function".

Once after Lambda function created , we can go to SNS and we can see function is associated with SNS as a subscription topic. Now click on publish message.

Now the Clodwatch having logs of your Lambda function  , you can see log messages there.