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[Aws] - Adding a Ec2 Node to an Elastic Load Balancer

* source: codeforfoods

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Installing

  • Install Python

              brew install python

  • Install AWS CLI - AWS CLI (http://aws.amazon.com/cli/) is command line tool for working with Amazon Web Service. In this project, we used it for checking the Elastic Load Balancer (ELB) is existed or not, creating an ELB, adding the Health check for ELB, retrieving the EC2 instance information registering EC2 instances to ELB.

      pip install awscli

  • Create config for aws at ~/.aws/config and add below content

Config filelink
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[profile default]
output = json
region = us-east-1
aws_access_key_id = <access key id>
aws_secret_access_key = <secret access key>

Coding

add-node-2-elb.sh
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#!/bin/bash
#

# ask to add the node to load balancer

node=$1;
role=$2;
env=$3;
lbName="MyLoadBalancer"
if [ "$node" != "" ] && [ "$role" != "" ]; then

if [ "$role" == "web" ]; then
  if [ "$env" == "prod" ]; then
      lbName="MyLoadBalancerProd"
  else
      lbName="MyLoadBalancerStaging"
  fi   
else   
  printf "Please enter a valid role ('web') \n";
fi 

# http://docs.aws.amazon.com/cli/latest/reference/elb/describe-load-balancers.html
MyLoadBalancer=$(
  aws elb describe-load-balancers \
      --load-balancer-name $lbName \
  );

# the load balancer is node existed, create the ELB first
if [ "$MyLoadBalancer" == '' ]; then
  
  # http://docs.aws.amazon.com/cli/latest/reference/elb/create-load-balancer.html 
  aws elb create-load-balancer \
      --load-balancer-name $lbName \
      --listeners Protocol=HTTP,LoadBalancerPort=80,InstanceProtocol=HTTP,InstancePort=80 \
      --availability-zones us-east-1a \
      --security-groups sg-bac6eddf \

  #http://docs.aws.amazon.com/cli/latest/reference/elb/configure-health-check.html
  aws elb configure-health-check \
      --load-balancer-name $lbName \
      --health-check Target=HTTP:80/index.php,Interval=30,UnhealthyThreshold=2,HealthyThreshold=2,Timeout=3

else
  printf "$MyLoadBalancer\n";
fi

# http://docs.aws.amazon.com/cli/latest/reference/ec2/describe-instances.html
# http://xmodulo.com/how-to-parse-json-string-via-command-line-on-linux.html
# MAC - brew install jq

nodeId=$(aws ec2 describe-instances --filters "Name=ip-address,Values=$node" | jq ".Reservations[0].Instances[0].InstanceId")
nodeId="${nodeId%\"}";
# http://docs.aws.amazon.com/cli/latest/reference/elb/register-instances-with-load-balancer.html
aws elb register-instances-with-load-balancer \
  --load-balancer-name $lbName \
  --instances "${nodeId#\"}"
else
printf "Please enter the node and role adding to ELB.\n";
fi

Usage

./add-node-2-elb.sh 123.456.789.910 web staging

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