Session Lambda

A simple way to manage sessions for AWS Lambdas

This package simplfy the way one can use DynamoDB as a key/value presistance layer for AWS Lambda - using a single python decorator.

Install

pip install session-lambda

Prerequisites

DynamoDB Table

• A table in DynamoDB with a primary key named key of type string
• [optional] Enable TTL in your DynamoDB table with attribute named ttl

Usage

Set SESSION_LAMBDA_DYNAMODB_TABLE_NAME env var:

export SESSION_LAMBDA_DYNAMODB_TABLE_NAME=<table-name>

Run the following python code:

from session_lambda import session, set_session_data, get_session_data

@session
def lambda_handler(event, context):
    print(get_session_data())
    set_session_data((get_session_data() or 0)+1)
    return {"headers":{}}

# first client_a call 
response = lambda_handler({'headers':{}}, {})  
# get session id from response (created by the server)
session_id = response.get('headers').get('session-id')
# use session id in subsequent calls
lambda_handler({'headers':{'session-id':session_id}}, {})
lambda_handler({'headers':{'session-id':session_id}}, {})
lambda_handler({'headers':{'session-id':session_id}}, {})

# first client_b call 
lambda_handler({'headers':{}}, {})

You should get the following prints:

None
1
1
1
None

This time using the update=True mode:

from session_lambda import session, set_session_data, get_session_data

@session(update=True)
def lambda_handler(event, context):
    print(get_session_data())
    set_session_data((get_session_data() or 0)+1)
    return {"headers":{}}

# first client_a call 
response = lambda_handler({'headers':{}}, {})  
# get session id from response (created by the server)
session_id = response.get('headers').get('session-id')
# use session id in subsequent calls
lambda_handler({'headers':{'session-id':session_id}}, {})
lambda_handler({'headers':{'session-id':session_id}}, {})
lambda_handler({'headers':{'session-id':session_id}}, {})

# first client_b call 
lambda_handler({'headers':{}}, {})

Now you should see:

None
1
2
3
None

Features

@session(id_key_name='session-id', update=False, ttl=0)
def lambda_handler(event, context):
    ...

• id_key_name is the expected key name in the event[headers]. It is default to session-id. It is case-sensitive.
• update flag control weather set_sessions_data updates the data. It is default to False.
• ttl is seconds interval for the session to live (since the last update time). By default it is disabled. Any value larger then 0 will enable this feature. Make sure to set the TTL key name in your dynamodb to ttl.

Future Features

• Support Schema validation for session data

Additional Inforamtion

• Check this session-lambda-example repository for more usage examples: https://github.com/roy-pstr/session-lambda-example

• Check this medium post for general guidance: https://medium.com/@roy-pstr/a-simple-way-to-manage-sessions-with-aws-lambda-dynamodb-in-python-c7aae1aa7258