Try running a Schedule to start and stop an instance on AWS Lambda (Python)

Introduction

I've wanted to make it for a long time, but when I thought it would be great to make it in Java, I haven't written about AWS Lambda being able to run in Python, so It's been 3 months since I decided to take on the challenge.

I tried it while various people wrote it.

Overview

Create a table in DynamoDB, tag information set for time and instance, Enter whether to start or stop.

Lambda Function (Python) runs every 10 minutes, If it matches the time of the data stored in DynamoDB, For all instances whose tag information matches Start or stop.

Preparation

Create a table "EC2" in DynamoDB. There are four items. "Id" "Time" "Tag" "Start Stop".

1. Id: Sequence number, please make sure to order
2. Time: Time, "% H:% M" format, eg "09:00"
3. Tag: Tag of the instance Enter the tag you want to start or stop
4. StartStop: Enter whether to start or stop.

Lambda settings

1. Runtime is "Python 2.7"
2. Code later ...
3. Handler is suitable
4. Role is OK if there is read / write to DynamoDB and start / stop and reference to EC2
5. I think the memory can be 128MB
6. Timeout is appropriate (10sec this time)

Lambda Function(Python)

There are some points that I personally struggled with.

1. "Filters = [{'Name':'tag-key','Values': [tableInfo ['Tag']]}]" I didn't know that there was a "[]" before and after the "tableInfo ['Tag']"
2. There must be "['Items']" in "table.scan () ['Items']" Without this, you cannot get the Item of the data acquired from DynamoDB
3. I don't know why, but it must be "boto3.client ('ec2')" It didn't work with "boto3.resource ('ec2')"
4. It seems that "from boto3.dynamodb.conditions import Key, Attr" is required

And the code is as follows.

import boto3
import datetime
from boto3.dynamodb.conditions import Key, Attr

def lambda_handler(event, context):
    # create EC2 client
    ec2 = boto3.client('ec2')
    # get the time(%H:%M)
    timeInfo = datetime.datetime.now().strftime("%H:%M")
    tableInfoList = getTableInfoList(timeInfo)
    instanceList = getInstanceStartStopList(ec2, tableInfoList)
    executeInstanceStartStop(ec2, instanceList)

# get the list of data (Id, StartEnd, Tag, Time)
#     Id       : Sequence
#     StartEnd : "start" or "stop"
#     Tag      : Tag-key
#     Time     : %H:%M  ex) 09:00
# @param timeInfo
# @return list of data(Id, StartEnd, Tag, Time)
def getTableInfoList(timeInfo):
    dynamodb = boto3.resource('dynamodb')
    #Set TableName
    table    = dynamodb.Table('EC2')
    #Send the Query
    #Query Parameter
    #   @param TimeInfo : [hh:mm]
    #TimeInfo = "09:00"
    tableInfoList = table.scan(
            FilterExpression=Attr('Time').eq(timeInfo)
        )['Items']
    return tableInfoList

# get the list of data (Start or Stop Instance Ids)
# @param ec2
# @param tableInfoList
# @return instanceList Dictionaly('start', 'stop')
def getInstanceStartStopList(ec2, tableInfoList):
    startInstanceIdList = []
    stopInstanceIdList  = []
    for tableInfo in tableInfoList:
        for reservation in ec2.describe_instances(Filters=[{'Name':'tag-key','Values':[tableInfo['Tag']]}])["Reservations"]:
            for instance in reservation["Instances"]:
                if (tableInfo['StartStop'] == 'start'):
                    startInstanceIdList.append(instance["InstanceId"])
                elif (tableInfo['StartStop'] == 'stop'):
                    stopInstanceIdList.append(instance["InstanceId"])
    instanceList = {"start":startInstanceIdList, "stop":stopInstanceIdList}
    return instanceList

# Start of Stop Instances
# @param ec2
# @param instanceList
def executeInstanceStartStop(ec2, instanceList):
    startInstanceIdList = instanceList["start"]
    stopInstanceIdList  = instanceList["stop"]

    if not len(startInstanceIdList) == 0:
        ec2.start_instances(InstanceIds=startInstanceIdList)

    if not len(stopInstanceIdList) == 0:
        ec2.stop_instances(stopInstanceIdList)

I managed to do it with trial and error.

from now on

From now on, I'm thinking of making something that accompanies this.

1. Script that can register / update / delete / view DynamoDB data
2. Register / update / delete / view DynamoDB data with static HTML + JS with S3
3. Real-time execution with API Gateway + Lambda

I don't know when it will be. .. ..