AWS Lambda Coding Session - clda.co/webinar-lambda

aws-lambda-demo1-restful-api.py

def lambda_handler(event, context):
    name = event.get('name') or 'World'
    print("Name: %s" % name)
    return "Hello %s!" % name

aws-lambda-demo1-s3-role.json

{
    "Effect": "Allow",
    "Action": [
        "s3:GetObject",
        "s3:PutObject"
    ],
    "Resource": "arn:aws:s3:::*"
}

aws-lambda-demo2-upload-s3.py

from __future__ import print_function
import os, urllib, json
import zipfile, StringIO
import boto3

s3 = boto3.client('s3')

def compress(body, key):
    data = StringIO.StringIO()
    with zipfile.ZipFile(data, 'w', zipfile.ZIP_DEFLATED) as f:
        f.writestr(os.path.basename(key), body)
    data.seek(0)
    return data.read()

def lambda_handler(event, context):

    # read bucket and key from event data
    bucket = event['Records'][0]['s3']['bucket']['name']
    key = urllib.unquote_plus(event['Records'][0]['s3']['object']['key']).decode('utf8')

    # generate new key name
    new_key = "compressed/%s.zip" % os.path.basename(key)

    # read the source obj content
    body = s3.get_object(Bucket=bucket, Key=key)['Body'].read()

    # create new obj with compressed data
    s3.put_object(
        Body=compress(body, key),
        Key=new_key,
        Bucket=bucket,
    )

    return "OK"

aws-lambda-demo3-ddb-role.json

{
    "Effect":"Allow",
    "Action":["dynamodb:*"],
    "Resource":["arn:aws:dynamodb:eu-central-1:582636008125:table/notifications"]
}

aws-lambda-demo3-sns-message.py

import boto3

DDB = boto3.resource('dynamodb').Table('notifications')

def lambda_handler(event, context):
    # read message from event data
    sns = event['Records'][0]['Sns']
    message = sns['Message']
    message_id = sns['MessageId']
    topic_arn = sns['TopicArn']
    subject = sns['Subject']

    # build new DDB item
    item = {
        'Item': {
            'MessageId': message_id,
            'Message':  message,
            'Topic': topic_arn,
            'Subject': subject,
        }
    }

    # log it
    print("Item: %s" % item)

    # write into db
    DDB.put_item(**item)

    return item

aws-lambda-demo4-scheduled-ddb.py

import time
from datetime import datetime
import boto3

DDB = boto3.resource('dynamodb').Table('logtime')

def lambda_handler(event, context):
    # generate current timestamp (UTC)
    now = datetime.utcnow()
    timestamp = int(time.mktime(now.timetuple()))

    # build new DDB item
    item = {
        'Item': {
            'timestamp': timestamp,
            'datetime': now.isoformat(),
        }
    }

    # log it
    print("Item: %s" % item)

    # write into db 
    DDB.put_item(**item)

    return item

aws-lambda-demo4_5-ddb-role.json

{
    "Effect":"Allow",
    "Action":["dynamodb:*"],
    "Resource":["arn:aws:dynamodb:eu-central-1:582636008125:table/logtime"]
}

aws-lambda-demo5-ddb-insert.py

import boto3

DDB = boto3.resource('dynamodb').Table('logtime')

def lambda_handler(event, context):
    # read records from event data (batch)
    records = event['Records']

    for record in records:
        # log each record
        print(record)

        event_name = record['eventName'].upper()

        # do something only if INSERT (new record)
        if event_name == 'INSERT':

            # retrieve the primary key
            timestamp = record['dynamodb']['Keys']['timestamp']['N']

            # update the item by adding a new field (static value)
            item = DDB.update_item(
                Key={'timestamp': int(timestamp)},
                UpdateExpression='SET newfield = :val',
                ExpressionAttributeValues={':val': "hello"},
            )

    # log how many records have been processed
    print("Processed %s records" % len(records))