Health checks failed with these codes: [502] - Cloudformation - amazon-web-services

Question

Hi I am using cloudforamtion to create ecs cluster, service and task. In task I am simply pulling wordpress image and connecting it to rds database. The problem here is the instance in the target group goes to draining state and then turn unhealthy. Wordpress shows up in the dns of alb but when you refresh it sometime gives error 502 bad gateway. I am only attaching the template where the error can exist most probably I might be giving the port wrong. I have good connection to the database (I have checked it as I did ssh into the instance and then used mysql -umysqldb -pmysql123a -h rds.endpoint command). The targets in targetgroup shoes an error Health checks failed with these codes: [502]
Task:
---
AWSTemplateFormatVersion: 2010-09-09
Parameters:
ExRole:
Type: String
RDS:
Type: String
Resources:
Task:
Type: AWS::ECS::TaskDefinition
Properties:
Family: wordpress
Cpu: 1 vCPU
ExecutionRoleArn: !Ref ExRole
Memory: 1 GB
NetworkMode: bridge
RequiresCompatibilities:
- EC2
TaskRoleArn: !Ref ExRole
ContainerDefinitions:
- Essential: true
Image: wordpress:latest
Name: wordpress
PortMappings:
- ContainerPort: 80
HostPort: 0
Protocol: tcp
Environment:
- Name: WORDPRESS_DB_HOST
Value: !Ref RDS
- Name: WORDPRESS_DB_USER
Value: mysqldb
- Name: WORDPRESS_DB_PASSWORD
Value: mysql123a
- Name: WORDPRESS_DB_NAME
Value: mysqldb
Outputs:
Task:
Description: Contains all the task specifications
Value: !Ref Task
Export:
Name: "Task"
alb:
---
AWSTemplateFormatVersion: 2010-09-09
Parameters:
SubnetA:
Type: String
SubnetB:
Type: String
VpcID:
Type: String
Resources:
Albsg:
Type: AWS::EC2::SecurityGroup
Properties:
GroupName: alb-sg
VpcId: !Ref VpcID
SecurityGroupIngress:
- IpProtocol: tcp
FromPort: 80
ToPort: 80
CidrIp: 0.0.0.0/0
Description: For traffic from Internet
GroupDescription: Security Group for demo server
Alb:
Type: AWS::ElasticLoadBalancingV2::LoadBalancer
Properties:
IpAddressType: ipv4
Name: Alb
Scheme: internet-facing
SecurityGroups:
- !Ref Albsg
Subnets:
- Ref: "SubnetA"
- Ref: "SubnetB"
Type: application
DefaultTargetGroup:
Type: AWS::ElasticLoadBalancingV2::TargetGroup
DependsOn: Alb
Properties:
Name: alb-tg
VpcId: !Ref VpcID
Port: 80
Protocol: HTTP
LoadBalancerListener:
Type: AWS::ElasticLoadBalancingV2::Listener
Properties:
LoadBalancerArn: !Ref Alb
Port: 80
Protocol: HTTP
DefaultActions:
- Type: forward
TargetGroupArn: !Ref DefaultTargetGroup
Outputs:
Albsg:
Description: security group for application load balancer
Value: !Ref Albsg
Export:
Name: "Albsg"
Alb:
Description: application load balancer
Value: !Ref Alb
Export:
Name: "Alb"
DefaultTargetGroup:
Description: Default Target Group
Value: !Ref DefaultTargetGroup
Export:
Name: "DefaultTargetGroup"
Cluster and service
---
AWSTemplateFormatVersion: 2010-09-09
Parameters:
KeyName:
Type: AWS::EC2::KeyPair::KeyName
Default: webserver
DesiredCapacity:
Type: Number
Default: 2
MinSize:
Type: Number
Default: 1
MaxSize:
Type: Number
Default: 4
InstanceProfile:
Type: String
DefaultTargetGroup:
Type: String
Task:
Type: String
Albsg:
Type: String
VpcID:
Type: String
SubnetA:
Type: String
SubnetB:
Type: String
webserver:
Type: String
Resources:
MyCluster:
Type: AWS::ECS::Cluster
Properties: {}
Myservice:
Type: AWS::ECS::Service
Properties:
Cluster: !Ref MyCluster
DeploymentController:
Type: ECS
DesiredCount: 2
LaunchType: EC2
LoadBalancers:
- ContainerName: wordpress
ContainerPort: 80
TargetGroupArn: !Ref DefaultTargetGroup
#Role: !Ref InstanceProfile
SchedulingStrategy: REPLICA
ServiceName: wordpress
TaskDefinition: !Ref Task
ec2instance:
Type: AWS::AutoScaling::LaunchConfiguration
Properties:
UserData:
Fn::Base64: !Sub |
#!/bin/bash -xe
yum update -y && yum install -y aws-cfn-bootstrap
echo ECS_CLUSTER=${MyCluster} >> /etc/ecs/ecs.config
echo ECS_BACKEND_HOST= >> /etc/ecs/ecs.config
/opt/aws/bin/cfn-signal -e $? \
--stack ${AWS::StackName} \
--resource myASG \
--region ${AWS::Region}
BlockDeviceMappings:
- DeviceName: /dev/xvda
Ebs:
DeleteOnTermination: "true"
VolumeSize: 30
VolumeType: gp2
ImageId: ami-06e05a843071324d1
InstanceType: t2.small
IamInstanceProfile: !Ref InstanceProfile
KeyName: !Ref KeyName
SecurityGroups:
- Ref: webserver
myASG:
Type: AWS::AutoScaling::AutoScalingGroup
CreationPolicy:
ResourceSignal:
Timeout: PT5M
Count: !Ref DesiredCapacity
Properties:
#AutoScalingGroupName: myASG
MinSize: !Ref MinSize
MaxSize: !Ref MaxSize
DesiredCapacity: !Ref DesiredCapacity
HealthCheckGracePeriod: 300
LaunchConfigurationName:
Ref: ec2instance
VPCZoneIdentifier:
- !Ref SubnetA
- !Ref SubnetB
TargetGroupARNs:
- !Ref DefaultTargetGroup

Answer 1

most probably I might be giving the port wrong
In your Type: AWS::ECS::TaskDefinition you have defined port 80 for the wordpress.
But your target group is using port 8080:
Properties:
Name: alb-tg
VpcId: !Ref VpcID
Port: 8080 # <--- should be 80
Protocol: HTTP
To use 302 code for health checks:
DefaultTargetGroup:
Type: AWS::ElasticLoadBalancingV2::TargetGroup
DependsOn: Alb
Properties:
Name: alb-tg
VpcId: !Ref VpcID
Port: 80
Protocol: HTTP
Matcher:
HttpCode: 302