lambda_function.py

#
# Retrieves and returns all movies in the 
# MovieLens database running in AWS.
#

import json
import os
import datatier

from configparser import ConfigParser

def serialize_datetime(obj):
  return obj.isoformat()

def lambda_handler(event, context):
  try:
    print("**call to lambda-in-docker-movies**")
    
    #
    # setup AWS based on config file:
    #
    config_file = 'movielens-config.ini'
    os.environ['AWS_SHARED_CREDENTIALS_FILE'] = config_file
    
    configur = ConfigParser()
    configur.read(config_file)
    
    #
    # configure for RDS access
    #
    rds_endpoint = configur.get('rds', 'endpoint')
    rds_portnum = int(configur.get('rds', 'port_number'))
    rds_username = configur.get('rds', 'user_name')
    rds_pwd = configur.get('rds', 'user_pwd')
    rds_dbname = configur.get('rds', 'db_name')

    #
    # open connection to the database:
    #
    print("**opening connection**")
    
    dbConn = datatier.get_dbConn(rds_endpoint, rds_portnum, rds_username, rds_pwd, rds_dbname)
    
    #
    # do we have any parameters for paging movies?
    #
    limit = 100  # default to first 100 movies
    offset = 0

    if "pathParameters" in event:
      limit = event["pathParameters"]["limit"]
      offset = event["pathParameters"]["offset"]
      
    print("offset:", offset)
    print("limit:", limit)
      
    #
    # now retrieve requested movies:
    #
    print("**retrieving movies**")

    sql = "SELECT * FROM movies LIMIT %s OFFSET %s;"
    
    rows = datatier.retrieve_all_rows(dbConn, sql, [limit, offset])
    
    N = len(rows)
    
    print("retrieved", N, "movies")
    
    print("first movie:", rows[0])
    print("last movie:", rows[N-1])
    
    #for row in rows:
    #  print(row)

    #
    # respond in an HTTP-like way, i.e. with a status
    # code and body in JSON format:
    #
    print("**done, returning rows**")
    
    return {
      'statusCode': 200,
      'body': json.dumps(rows, default=serialize_datetime)
    }
    
  except Exception as err:
    print("**ERROR**")
    print(str(err))
    
    return {
      'statusCode': 500,
      'body': json.dumps(str(err))
    }