CODEWITHSUNDEEP
amazon-ec2amazon-web-servicesamazon-elb
sheki
sheki

Reputation: 9349

Method of finding instances attached to ELB

I am using the Amazon AWS ELB command line tools. Is there a way of finding out the instances attached to a particular Elastic Load Balancer (ELB)?

Upvotes: 13

Views: 19104

Answers (11)

nirmal rajan
nirmal rajan

Reputation: 1

aws elb describe-load-balancers --load-balancer-name "LB_NAME" | grep "InstanceId" | awk '{print $2}' | sed 's/\"//g'

Upvotes: 0

Yordan Georgiev
Yordan Georgiev

Reputation: 5420

You can loop trough all you load balancer instance ids as follows: 

while read -r lb ; do echo -e "\n\n start lb: $lb " ; \
echo run cmd on lb: $lb ; echo " stop  lb: $lb" ; \
done < <(aws elb describe-load-balancers --query \
'LoadBalancerDescriptions[].Instances[].InstanceId' \
 --profile dev|perl -nle 's/\s+/\n/g;print')

You can loop trough your load balancers names as follows :

    # how-to loop trough all your load balancer names 
    while read -r lb ; do \
        echo -e "\n\n start lb: $lb " ; \
        echo run cmd on lb: $lb ; \
        echo " stop  lb: $lb" ; \
    done < <(aws elb describe-load-balancers --query \
    'LoadBalancerDescriptions[].LoadBalancerName' \
    --profile rnd|perl -nle 's/\s+/\n/g;print')

Provided that you have configured your aws cli : src: http://docs.aws.amazon.com/cli/latest/topic/config-vars.html cat << "EOF" > ~/.aws/config

[profile dev]
output = text
region = us-east-1
[profile dev]
output = text
region = us-east-1
[default]
output = text
region = Global

EOF

And configured your security credentials:

    # in aws admin console :
    # Services => iam => users => <<your_username>> => Security Credentials => Access Keys
    # configure the aws cli
    cat << "EOF" > ~/.aws/credentials
    [dev]
    aws_access_key_id = <<your_aws_access_key_id_in_the_dev_environment>>
    aws_secret_access_key = <<your_aws_secret_access_key_in_dev_env>>
    [dev]
    aws_access_key_id = <<your_aws_access_key_id_in_the_dev_environment>>
    aws_secret_access_key = <<your_aws_secret_access_key_in_dev_env>>
    [default]
    aws_access_key_id = <<your_aws_access_key_id_in_the_dev_environment>>
    aws_secret_access_key = <<your_aws_secret_access_key_in_dev_env>>
    EOF

Upvotes: 0

Colin MacKenzie - III
Colin MacKenzie - III

Reputation: 1393

If you want to see all your ELB's and the instances attached use JMESPath like this: 

aws elb describe-load-balancers --query "LoadBalancerDescriptions[*].{ID:LoadBalancerName,InstanceId:Instances[*].InstanceId}[*]. {ELB:ID,InstanceId:InstanceId[*]}" --output=json

Result

[
    {
        "ELB": "my_name",
        "InstanceId": [
            "i-0cc72"
        ]
    },
    {
        "ELB": "my_name2",
        "InstanceId": [
            "i-02ff5f",
            "i-09e467"
        ]
    }
]

If you know the name of the ELB and want to see what is attached use JMESPath like this: 

aws elb describe-load-balancers --load-balancer-name "my_name" --query "LoadBalancerDescriptions[].{ID:LoadBalancerName,InstanceId:Instances[].InstanceId}[].{ELB:ID,InstanceId:InstanceId[]}" --output=json

Result:

[
    {
        "ELB": "my_name",
        "InstanceId": [
            "i-02ff5f72",
            "i-09e46743"
        ]
    }
]

Upvotes: 2

Cyril Duchon-Doris
Cyril Duchon-Doris

Reputation: 13929

Because I love answers that can be used with a minimum of search/replace and copy paste

Prerequisites : aws-cli configured

pip install awscli
aws configure

Configure : your ELB name

$ELB_NAME = "Your-elb-name"

Copy-n-Paste in terminal

for ID in $(aws elb describe-load-balancers --load-balancer-name $ELB_NAME \
    --query LoadBalancerDescriptions[].Instances[].InstanceId \
    --output=text);
do
    aws ec2 describe-instances --instance-ids $ID \
        --query Reservations[].Instances[].PublicIpAddress \
        --output text
done

Will output a list of Public IPs. You could also just execute the query inside the parenthesis of the for ID in $(...) to just get the instance IDs

Want something different ?

Feel free to have a look at the structure of 

aws elb describe-load-balancers --load-balancer-name $ELB_NAME
aws ec2 describe-instances --instance-ids $INSTANCE_ID

and change the query accordingly!

Upvotes: 6

rohithpr
rohithpr

Reputation: 6330

In node.js you can do this by using aws-sdk.

var AWS = require('aws-sdk')
var options = {
  accessKeyId: 'accessKeyId',
  secretAccessKey: 'secretAccessKey',
  region: 'region'
}
var elb = new AWS.ELB(options)

elb.describeLoadBalancers({LoadBalancerNames: ['elbName']}, function(err, data) {
  if (err) {
    console.log('err: ', err)
  }
  else {
    console.log('data: ', data.LoadBalancerDescriptions)
  }
})

data.LoadBalancerDescriptions is an array and each element in the array is an object with the property Instances that has the instance id.

Upvotes: 0

Art
Art

Reputation: 11

replace INSTANCEID with actual instance id

aws elb describe-load-balancers --query "LoadBalancerDescriptions[*].{ID:LoadBalancerName,InstanceId:Instances[?InstanceId=='INSTANCEID'].InstanceId}[*].{ID:ID,InstanceId:InstanceId[0]}" --output=text | grep INSTANCEID | awk '{print $1}'

Upvotes: 1

Mike D
Mike D

Reputation: 6195

Assuming you have aws-cli and jq installed, you can use the following command to get associated ec2 instance ids:

aws elb describe-load-balancers --load-balancer-name my-elb \
  | jq -r '.LoadBalancerDescriptions[].Instances[].InstanceId'

This will return the ec2 ids associated with that ELB.

Side note: I recommend you setup aws cli profiles so you don't have to fiddle with environment variables and region params (as much).

Upvotes: 8

Alaa Qutaish
Alaa Qutaish

Reputation: 239

You can use AWS command line tools with some bash piping:

elb-describe-instance-health loadbalancer_name --region eu-west-1 | awk '{ print $2 }' | xargs ec2-describe-instances --region eu-west-1 | grep ^INSTANCE | awk '{ print $4 }'

This will give you the public DNS name for every instance attached to the ELB, you can change the awk columns respectively to get other details.

Upvotes: -2

Till
Till

Reputation: 22408

2013/12/18: To update this and since the links are dead!

I installed the new AWS cli tools:

$ pip install awscli

Then ran:

$ aws configure                                                                                                                                                
AWS Access Key ID [None]: my-key
AWS Secret Access Key [None]: my-secret
Default region name [None]: us-east-1
Default output format [None]:

This data is saved into ~/.aws/config.

Then I can find instances connected to a loadbalancer like so:

$ aws elb describe-load-balancers --load-balancer-name "my-name"
{
    "LoadBalancerDescriptions": [
        {
            "Subnets": [],
            "CanonicalHostedZoneNameID": "ID",
            "CanonicalHostedZoneName": "my-name-foo.us-east-1.elb.amazonaws.com",
            "ListenerDescriptions": [
                {
                    "Listener": {
                        "InstancePort": 80,
                        "LoadBalancerPort": 80,
                        "Protocol": "HTTP",
                        "InstanceProtocol": "HTTP"
                    },
                    "PolicyNames": []
                },
                {
                    "Listener": {
                        "InstancePort": 80,
                        "SSLCertificateId": "arn:aws:iam::x:server-certificate/x-ssl-prod",
                        "LoadBalancerPort": 443,
                        "Protocol": "HTTPS",
                        "InstanceProtocol": "HTTP"
                    },
                    "PolicyNames": [
                        "AWSConsole-SSLNegotiationPolicy-api-production"
                    ]
                }
            ],
            "HealthCheck": {
                "HealthyThreshold": 10,
                "Interval": 30,
                "Target": "HTTP:80/healthy.php",
                "Timeout": 5,
                "UnhealthyThreshold": 2
            },
            "BackendServerDescriptions": [],
            "Instances": [
                {
                    "InstanceId": "i-FIRST-INSTANCEID"
                },
                {
                    "InstanceId": "i-SECOND-INSTANCEID"
                }
            ],
            "DNSName": "my-name-foo.us-east-1.elb.amazonaws.com",
            "SecurityGroups": [],
            "Policies": {
                "LBCookieStickinessPolicies": [],
                "AppCookieStickinessPolicies": [],
                "OtherPolicies": [
                    "AWSConsole-SSLNegotiationPolicy-my-name"
                ]
            },
            "LoadBalancerName": "my-name",
            "CreatedTime": "2013-08-05T16:55:22.630Z",
            "AvailabilityZones": [
                "us-east-1d"
            ],
            "Scheme": "internet-facing",
            "SourceSecurityGroup": {
                "OwnerAlias": "amazon-elb",
                "GroupName": "amazon-elb-sg"
            }
        }
    ]
}

The data is in LoadBalancerDescriptions.Instances.

My loadbalancer is called my-name — this is the name you selected when you created it.

Old answer below!

I'm not familiar with the cli tool, but I used the API.

I'd check these two requests:

The cli tool probably has something to resemble these?

HTH!

Upvotes: 10

CharlesA
CharlesA

Reputation: 4350

If anyone arrives here from a search as to why the elb-describe-lbs command returns nothing when they have ELBs up and running, what I realised was I needed to add EC2_REGION=eu-west-1 to my environment variables (or use elb-describe-lbs --region command)

Upvotes: 2

ErJab
ErJab

Reputation: 6375

First do elb-describe-lbs to get a list of your load balancers and their names.

Then do elb-describe-instance-health <LB_NAME> to get a list of instances behind that load balancer. LB_NAME is the value of the 2nd column in the output of elb-describe-lbs.

Upvotes: -1

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