I have an httpd container with ECS service along with ALB.
Container with ALB are using a dynamic port feature which means host port is set to 0.
if i try to ssh in an instance container and try to curl localhost:port number it works.
But when i try to use ALB DNS name it turns out to 504.
ALb security group allows HTTP 80 connections from anywhere and instance sg allows any connection on any port from alb sg.
Interestingly
when I try to check the target group associated with alb all the instances are unhealthy.
Update:- i tried to open a security group of ecs container to public and yet the instance were not healthy
you need to check the events of the ECS service and see what is the exact error message. If it states something like port 45675 is unhealthy then you need to check your security group configuration, it should get rid of 504 error message. If it states health check failed (this should give 502) then you should ssh into the container and check on which port the application is running and create a new service with the modification.
Assuming, you have configured the health check for traffic port and haven't modified it.
httpd service generally works on port 80. So I'll suggest use the container port as 80.
504 is Gateway Timeout error, if the above information doesn't help you can provide look at the AWS link here - https://aws.amazon.com/premiumsupport/knowledge-center/troubleshoot-http-5xx/
If you can share the error message from the ecs events that will help in narrowing down the issue.
Adding the screenshots of the changes I made to fix the issue, I hope it helps. I am assuming you are using the default httpd image -
I create ECS service and it runs 1 ecs instance and I can see the instance is registered as a target of the load balancer.
Now I trigger a Auto Scaling Group (by just incrementing desired instance count) to launch a new instance.
The instance is launched and added to the ECS cluster. (I can see it on ECS instances tab)
But the instance is not added to the ALB target. (I expect to see 2 instances in the following image, but I only see 1)
I can edit AutoScalingGroup 's target group like the following
Then I see the following .
But the health check fails. It seems the 80 port is not reachable.
Although I have port 80 open for public in the security group for the instance. (Also, instance created from ecs service uses dynamic port mapping but instance created by ALS does not)
So AutoScalingGroup can launch new instance but my load balancer never gives traffic to the new instance.
I did try https://aws.amazon.com/premiumsupport/knowledge-center/troubleshoot-unhealthy-checks-ecs/?nc1=h_ls and it shows I can connect to port 80 from host to the docker container by something like curl -v http://${IPADDR}/health.
So it must be the case that there's something wrong with host port 80 (load balancer can't connect to it).
But it is also the case the security group setting is not wrong, because the working instance and this non working instance is using the same SG.
Edit
Because I used dynamic mapping, my webserver is running on some random port.
As you can see the instance started by ecs service has registered itself to target group with random port.
However instance started by ALB has registered itself to target group with port 80.
The instance will not be added to the target group if it's not healthy. So you need to fix the health check first.
From your first instance, your mapped port is 32769 so I assume if this is the same target group and if it is the same application then the port in new instance should be 32769.
When you curl the IP endpoint curl -I -v http://${IPADDR}/health. is the HTTP status code was 200, if it is 200 then it should be healthy if it's not 200 then update the backend http-status code or you can update health check HTTP status code.
I assume that you are also running ECS in both instances, so ECS create target group against each ECS services, are you running some mix services that you need target group in AS group? if you are running dynamic port then remove the health check path to traffic port.
Now if we look the offical possible causes for 502 bad Gateway
Dynamic port mapping is a feature of container instance in Amazon Elastic Container Service (Amazon ECS)
Dynamic port mapping with an Application Load Balancer makes it easier
to run multiple tasks on the same Amazon ECS service on an Amazon ECS
cluster.
With the Classic Load Balancer, you must statically map port numbers
on a container instance. The Classic Load Balancer does not allow you
to run multiple copies of a task on the same instance because the
ports conflict. An Application Load Balancer uses dynamic port mapping
so that you can run multiple tasks from a single service on the same
container instance.
Your created target group will not work with dynamic port, you have to bind the target group with ECS services.
dynamic-port-mapping-ecs
HTTP 502: Bad Gateway
Possible causes:
The load balancer received a TCP RST from the target when attempting to establish a connection.
The load balancer received an unexpected response from the target, such as "ICMP Destination unreachable (Host unreachable)", when attempting to establish a connection. Check whether traffic is allowed from the load balancer subnets to the targets on the target port.
The target closed the connection with a TCP RST or a TCP FIN while the load balancer had an outstanding request to the target. Check whether the keep-alive duration of the target is shorter than the idle timeout value of the load balancer.
The target response is malformed or contains HTTP headers that are not valid.
The load balancer encountered an SSL handshake error or SSL handshake timeout (10 seconds) when connecting to a target.
The deregistration delay period elapsed for a request being handled by a target that was deregistered. Increase the delay period so that lengthy operations can complete.
http-502-issues
It seems you know the root cause, which is that port 80 is failing the health check and thats why it is never added to ALB. Here is what you can try
First, check that your service is listening on port 80 on the new host. You can use command like netcat
nv -v localhost 80
Once you know that the service is listening, the recommended way to allow your ALB to connect to your host is to add a Security group inbound rule for your instance to allow traffic from your ALB security group on port 80
I have set up a Docker container running on port 5566 with a small Django application. The Docker image is uploaded into the ECR and later used by Fargate container(s).
I have set up an ECS cluster with a VPC.
After creating the Task Definition and Service, the Service starts up 2 tasks (as it is supposed to):
Here's the Service's Network Access (with health check grace period on 300s):
I also set up an Application Load Balancer (with DNS) with a target group for the service, but the health checks seem to be failing:
Here's the health check configuration:
Because the health checks are failing the tasks are terminated and new ones are started after ~every 5 minutes.
Here's the container's port mapping:
As one cannot access the Fargate container (via SSH for example) and the logs are empty, how should I troubleshoot the issue?
I have tried to follow every step in the Troubleshoot Your Application Load Balancer.
Feel free to ask additional information.
can you confirm once, your application is working on port 5566 inside docker?
you can check logs in cloudwatch. you'll get the link in cluster -> service -> tasks -> your task.
Can you post your ALB configuration? your Target group port?
I am using cloud formation template to build the infrastructure (ECS fargate cluster).
Template executed successfully and stack has been created successfully. However, task has failed with the following error:
Task failed ELB health checks in (target-group arn:aws:elasticloadbalancing:eu-central-1:890543041640:targetgroup/prc-service-devTargetGroup/97e3566c8b307abf)
I am not getting what and where to look for this to troubleshoot the issue.
as it is fargate cluster, I am not getting how to login to container and execute some health check queries to debug further.
Can someone please help me to guide further on this and help me?
Due to this error, I am not even able to access my web app. As ALB won't route the traffic if it is unhealthy.
What I did
After some googling, I found this post:
https://aws.amazon.com/premiumsupport/knowledge-center/troubleshoot-unhealthy-checks-ecs/
However, I guess, this is related to EC2 compatibility in fargate. But in my case, EC2 is not there.
If you feel, I can paste the entire template as well.
please help
This is resolved.
It was the issue with the following points:
Docker container port mapping with host port were incorrect
ALB health check interval time was very short. Due to that, ALB was giving up immediately, not waiting for docker container to up and running properly.
after making these changes, it worked properly
There are quite a few of different possible reasons for this issue, not only the open ports:
Improper IAM permissions for the ecsServiceRole IAM role
Container instance security group Elastic Load Balancing load
balancer not configured for all Availability Zones Elastic Load
Balancing load balancer health check misconfigured
Unable to update the service servicename: Load balancer container name or port changed in task definition
Therefore AWS created an own website in order to address the possibilities of this error:
https://docs.aws.amazon.com/en_en/AmazonECS/latest/developerguide/troubleshoot-service-load-balancers.html
Edit: in my case the health check code of my application was different. The default is 200 but you can also add a range such as 200-499.
Let me share my experience.
In my case everything was correct, except the host on which the server listens, it was localhost which makes the server not reachable from the outside world and respectively the health check didn't work. It should be 0.0.0.0 or empty in some libraries.
I got this error message because the security group between the ECS service and the load balancer target group was only allowing HTTP and HTTPS traffic.
Apparently the health check happens over some other port and or protocol as updating the security group to allow all traffic on all ports (as suggested at https://docs.aws.amazon.com/AmazonECS/latest/userguide/create-application-load-balancer.html) made the health check work.
I had this exact same problem. I was able to get around the issue by:
navigate to EC2 service
then select Target Group in the side panel
select your target group for your load balancer
select the health check tab
make sure the health check for your EC2 instance is the same as the health check in the target group. This will tell your ELB to route its traffic to this endpoint when conducting its health check. In my case my health check path was /health.
In my case, ECS Fargate orchestration of the docker container functionality as a service and not a Web app or API. The service is that is not listening to any port (eg: Schedule corn/ActiveMQ message consumer ...etc).
In order words, it is a client and not a server node. So I made to listen to localhost for health check only...
All I added health check path in Target Group to -
And below code in index.ts -
import express from 'express';
const app = express();
const port = process.env.PORT || 8080;
//Health Check
app.get('/__health', (_, res) => res.send({ ok: 'yes' }));
app.listen(port, () => {
logger.info(`Health Check: Listening at http://localhost:${port}`);
});
As mentioned by tschumann above, check the security group around the ECS cluster. If using Terraform, allow ingress to all docker ephemeral ports with something like below:
resource "aws_security_group" "ecs_sg" {
name = "ecs_security_group"
vpc_id = "${data.aws_vpc.vpc.id}"
}
resource "aws_security_group_rule" "ingress_docker_ports" {
type = "ingress"
from_port = 32768
to_port = 61000
protocol = "-1"
cidr_blocks = ["${data.aws_vpc.vpc.cidr_block}"]
security_group_id = "${aws_security_group.ecs_sg.id}"
}
Possibly helpful for someone.. our target group health check path was set to /, which for our services pointed to Swagger and worked well. After updating to use Springfox instead of manually generating swagger.json, / now performs a 302 redirect to /swagger-ui.html, which caused the health check to fail. Since this was for a Spring Boot service we simply pointed the health check path in the target group to /health instead (OOTB Spring status page).
Solution is partial correct in response 'iravinandan', but in last part of your nodejs router just simple add status(200) and that's it. Or you can set your personal status clicking on advance tab, on end of the page.
app.get('/__health', (request, response) => response.status(200).end(""));
More info here: enter link description here
Regards
My case was a React application running on FARGATE mode.
The first issue was that the Docker image was built over NodeJS "serving" it with:
CMD npm run start # react-scripts start
Besides that's not a good practice at all, it requires a lot of resources (4GB & 2vCPU were not enough), and because of that, the checks were failing. (this article mentions this as a probable cause)
To solve the previous issue, we modify the image as a multistage build with NodeJS for the building phase + NGINX for serving the content. Locally that was working great, but we haven't realized that the default port for NGINX is 80, and you can not use a different host and container port on FARGATE with awsvpc network mode.
To troubleshoot it, I launched an EC2 instance with the right Security Groups to connect with the FARGATE targets on the same port the Load Balancer was failing to perform a Health Check. I was able to execute curl's commands against other targets, but with this unhealthy target (constantly being recycled) I received an instant Connection refused response. It wasn't a timeout, which told me that the target was not able to manage that request because it was not listening to that port. Then I realized that my container was expecting traffic on port 80 and my application was configured to work on a 3xxx port.
The solution here was to modify the default configuration of NGINX to listen to the port we wanted, re-build the image and re-launch the service.
On my case, my ECS Fargate service does not need load balancer so I've removed "Load Balancer" and "Security Group" then it works.
I had the same issue with deploying a java springboot app on ACS running as a fargate. There were 3 issues which I had to address to fix the problem, if this can help others in future.
The container was running on port 8080 (because of tomcat), so the ELB, target group and the two security groups (one with ELB and one with ECS) must allow 8080 in their inbounds rules. Also the task set up had to be revised to change the container to map at 8080.
The port on target group health check section (advance settings) had to be explicitly changed to 8080 instead of 80 as the default.
I had to create a dummy health check path in the application because pinging the root of the app at "/" was resulting in a 302 error code.
Hope this helps.
I have also faced the same issue while using the AWS Fargate.
Here are some possible solutions to try:
First Check the Security group of Service that Attached has outbound and Inbound rules in place.
If you are using the Loadbalancer and pointing out to target group then you must enable the docker container port on security group and attached the inbound traffic only coming from the ALB security group
3)Also check the healthcheck endpoint that we are assigning to target group are there any dependanies it should return only 200 status repsonse / what we have specifed in target group
In my case it was a security group rule which allowed connections only from a certain IP, and this was blocking healthchecks from LB. I added VPC's cidr as another rule to the security group and then it worked.
My ECS set-up keeps on failing in health check when I set it up with dynamic port.
Here is my set-up:
I have a spring-boot web app which uses port 10440. So in my Task Definition I use port 0 as my Host Port to enable dynamic porting and 10440 as my container port. I have two 2 ec2 instances and run 2 task in my service. But my task are keep on terminating due to failing health check.
Screenshots:
-Task event logs
-Unhealthy regitered ec2 instances in target group
Note: If change my Host port to 10440 also, the set-up works fine. But I cannot run more task than the number of ec2 instance.
Screenshot:
Health registered ec2 instance in target group
I hope someone can help so I can setup my ECS to run more task in 2 instances. Thank you!
I faced the same issue and got to know that in the ECS cluster security group, Dynamic ports (All TCP ports) not allowed to ALB sg. Once it is allowed traffic port should able to connect to EC2 instance then health check will pass
Ensure that the port for your health-check of your target group is set to "traffic port".
I just figure out the problem. Upon executing
aws elbv2 describe-target-health --target-group-arn
I have found out that health check is having a timeout error, so I just prolong the timeout in health check setting.