识别 ECS 实例的硬编码 DNS 记录

Question

我有一个需要部署的 docker 映像，同时保持一致的 DNS 记录。最重要的是，我想要一个硬编码的实例数量（例如，2）。我喜欢 ECS 的易用性以及 ECS 代理维护正常运行时间，但是负载均衡器对于单个实例来说是多余的。到目前为止，我只是创建了一个最小/最大/期望为 1 的 ASG，所以没有任何冲突的问题。

对于自动缩放组中的实例编号有一个非常激烈的论据（here 就是一个例子），这是有道理的，尽管我认为这是一个无法避免的非常可靠的用例。

我已成功修改 meltwater/terraform-aws-asg-dns-handler，为 ASG 中的单个 ECS 实例提供硬编码的 DNS 记录（例如 instance-1.example.com），尽管它不是很漂亮。为了让两个实例正常工作（instance-1.example.com 和 instance-2.example.com），我想我有两个选择：

• 创建一个 hacky 解决方案来读取我的 Lambda 函数中的现有 Route53 记录，以“确定性地”决定在 ASG 生命周期挂钩中分配我的实例的索引（this 可能是一个好的开始）
• 创建两个 ECS 集群，每个集群都有一个实例，并使用两个单独的 Lambda 函数

这两个选项对我来说似乎都不是非常可靠的选择，所以我想知道是否有更好的方法以类似 ECS 的方式部署单个 Docker 容器，我可以将 DNS 记录附加到。

就上下文而言，“两个 ECS 集群”方法可以正常工作，但我会这样做三到四次，所以我最终会在几个其他集群之上建立 8 个 ECS 集群，这至少可以说是不方便。

Answer 1

如果您使用 Auto Scaling 组和带有用户数据的启动配置或模板...这是我在用户数据中添加的内容，以便在任何时候自动更新 Route53 DNS 记录实例旋转起来，带有一个计数器。希望这能有所帮助！

## --------------------------------------------------------------------------------------------------------------- ##
## --- AUTO SCALING LOGIC for user-data -------------------------------------------------------------------------- ##
## --------------------------------------------------------------------------------------------------------------- ##
## --- Get ip addresses of existing app DNS Entries (that point to app nodes, not load balancer) ----- ##
## --- Get this ip address --------------------------------------------------------------------------------------- ##
## --- If this IP Address matches any in existing list, do not create a new DNS record --------------------------- ##
## --- If this IP Address does not match any in existing list, create a new DNS record --------------------------- ##
## --------------------------------------------------------------------------------------------------------------- ##

region="us-east-1"
hosted_zone="ROUTE53-HOSTED-ZONE-ID"
vpc="vpc-ID"
r53_domain="example.com"
asg_desired="2"
application="app"

echo "USING EC2 INSTANCE META DATA TO OBTAIN IP ADDRESS ..."
echo "IF YOU ARE NOT USING DEFAULT AMZN INSTANCE, USE ifconfig OR ANOTHER METHOD TO OBTAIN THIS INSTANCE IP ..."

# CHOOSE THE PRIVATE (local-ipv4) OR PUBLIC IP DEPENDING ON USE CASE 
#this_ip=`curl http://169.254.169.254/latest/meta-data/local-ipv4`
this_ip=`curl http://169.254.169.254/latest/meta-data/public-ipv4`
echo $this_ip > /tmp/this-ip.txt

# FILTER BASED ON UNIQUE TAGS FOR YOUR TARGETED INSTANCE(S)
# THIS IS USING Application Tag. 
aws --region $region ec2 describe-instances --query "Reservations[*].Instances[? Tags[? (Key=='Application') && Value=='$application']].PublicIpAddress" --output text >> /tmp/existing-ec2-ips.txt

counter=1
until [ $counter -gt $asg_desired ]
do
  aws --region $region route53 list-resource-record-sets --hosted-zone-id $hosted_zone --query "ResourceRecordSets[?Name == 'instance-$counter.$r53_domain.'].ResourceRecords" --output text >> /tmp/existing-ips.txt
  aws --region $region route53 list-resource-record-sets --hosted-zone-id $hosted_zone --query "ResourceRecordSets[?Name == 'instance-$counter.$r53_domain.']" --output text >> /tmp/existing-records.txt
  ((counter++))
done

diff /tmp/existing-ips.txt /tmp/this-ip.txt

echo "Does this instance IP exist in a $application route53 record?"
this_ip_result=`grep $this_ip /tmp/existing-ips.txt | wc -l`

if [[ $this_ip_result -gt 0 ]]
then
  echo "Yes, this instance IP already exists in a $application route53 record."
  echo "Nothing left to do"
else
  echo "No, this instance IP does not exist in a $application route53 record."
  echo "Adding route53 record... "
  counter=1
    until [ $counter -gt $asg_desired ]
    do
        grep -L instance-$counter.$r53_domain /tmp/existing-records.txt > /tmp/instance-$counter.$r53_domain.txt
        if [ -s /tmp/instance-$counter.$r53_domain.txt ]
            then
                echo "instance-$counter.$r53_domain does not exist... Adding!"
                aws --region $region route53 change-resource-record-sets --hosted-zone-id $hosted_zone --change-batch '{ "Comment": "Auto Scaling Creating Record Set", "Changes": [ { "Action": "CREATE", "ResourceRecordSet": { "Name": "instance-'$counter'.'$r53_domain'", "Type": "A", "TTL": 120, "ResourceRecords": [ { "Value": "'"$this_ip"'" } ] } } ] }'
            else
                echo "Updating Record Set!"
                echo "Updating Route53 Records with the following IPs ..."
                diff /tmp/existing-ec2-ips.txt /tmp/existing-ips.txt | grep ">" | sed 's/> //g'
                ip_update=`diff /tmp/existing-ec2-ips.txt /tmp/existing-ips.txt | grep ">" | sed 's/> //g'`
                record_update=`grep -B 1 $ip_update /tmp/existing-records.txt | grep $application | awk '{print $1}' | awk 'FNR == 1 {print}'`
                aws --region $region route53 change-resource-record-sets --hosted-zone-id $hosted_zone --change-batch '{ "Comment": "Auto Scaling Updating Record Set", "Changes": [ { "Action": "UPSERT", "ResourceRecordSet": { "Name": "'"$record_update"'", "Type": "A", "TTL": 120, "ResourceRecords": [ { "Value": "'"$this_ip"'" } ] } } ] }'
            fi
        ((counter++))
    done
fi