Describe ec2 with boto3 and retrieve the value

I'm Wakamatsu, a beginner of Lambda (Python).

Suddenly, do you use Lambda?

The code works without a server. It's attractive, isn't it?

After all, the times are Serverless. I wish I could use about one language in the infrastructure.

In the middle of a generous generation that doesn't go against such a trend, I finally stepped into Lambda.

The introduction has become longer, but I hope that the infrastructure shop will look warmly with the feeling that they are struggling to make a joke.

Thing you want to do

I want to get the instance ID of an instance that has a specific IP.

environment

AWS Lambda Python 3.6

First form

code

For the time being, I decided to retrieve all the instance information, so I wrote the following code.

import boto3

def lambda_handler(event, context):

    ec2 = boto3.client('ec2')
    
    responce = ec2.describe_instances()

    return responce

result

Return fails with the following error

{
  "errorMessage": "An error occurred during JSON serialization of response",
  "errorType": "datetime.datetime(2017, 5, 11, 5, 15, 59, tzinfo=tzlocal()) is not JSON serializable"
}

It seems that the result itself cannot be treated as JSON.

Investigation

When I call the boto3 reference, it seems that the return value of describe_instances is of type dict (dictionary). For the time being, it is better to output with print, so I decided to change the code.

Second form

code

Change the output to a print statement for the time being

import boto3

def lambda_handler(event, context):

    ec2 = boto3.client('ec2')
    
    responce = ec2.describe_instances()

    print(responce)

    return

result

The following was output to the log. That's what you often see in the AWS CLI results.

{
    "Reservations": [
        {
            "OwnerId": "xxxxxxxxxxxx", 
            "ReservationId": "r-xxxxxxxxxxxxxxxxx", 
            "Groups": [], 
            "Instances": [
                {
                    "Monitoring": {
                        "State": "disabled"
                    }, 
                    "PublicDnsName": "ec2-xxx-xxx-xxx-xxx.ap-northeast-1.compute.amazonaws.com", 
                    "Platform": "xxxxxxx", 
                    "State": {
                        "Code": 80, 
                        "Name": "stopped"
                    }, 
                    "EbsOptimized": false, 
                    "LaunchTime": "xxxx-xx-xxxxx:xx:xx.xxxx", 
                    "PublicIpAddress": "xxx.xxx.xxx.xxx", 
                    "PrivateIpAddress": "xxx.xxx.xxx.xxx", 
                    "ProductCodes": [], 
                    "VpcId": "vpc-xxxxxxx", 
                    "StateTransitionReason": "", 
                    "InstanceId": "i-xxxxxxxxxxxxxxxxx", 
                    "EnaSupport": true, 
                    "ImageId": "ami-xxxxxxxx", 
The following is omitted

Investigation

Next, I would like to narrow down by IP. It seems that --filter in AWS CLI is also in boto3, so I decided to use it.

Third form

code

Added Filters to narrow down to instances that have a specific IP

import boto3

def lambda_handler(event, context):

    ec2 = boto3.client('ec2')
    
    responce = ec2.describe_instances(
        Filters=[{'Name':'network-interface.addresses.private-ip-address','Values':["xxx.xxx.xxx.xxx"]}]
    )

    print(responce)

    return

result

Narrowed down to instances with the specified IP address.

Investigation

Next, narrow down the return value to the instance ID. The image is --query in AWS CLI, but it doesn't seem to be in boto3. I had a hard time because I was danced by the information on the internet because I was converting to JSON here. As a result, I found that the dict type seems to be able to retrieve the value by writing ["hoge"] ["fuga"] after the object.

Final form

code

import boto3

def lambda_handler(event, context):

    ec2 = boto3.client('ec2')
    
    responce = ec2.describe_instances(
        Filters=[{'Name':'network-interface.addresses.private-ip-address','Values':["xxx.xxx.xxx.xxx"]}]
    )["Reservations"][0]["Instances"][0]["InstanceId"]

    print(responce)

    return

result

Congratulations on getting the instance ID. I want to be aware that you need to explicitly write 0 as [0] when you have a list.

• Because it can be abbreviated as [] in --query of AWS CLI.

Summary

What did you think. The content I am doing is very rudimentary, but I was addicted to it, so I summarized it as a memorandum.

It's surprisingly easy to move, so please give it a try. Lambda I'm not scared.