It is a question about AWS.
The following error occurred between ELB and EC2(nginx).
ELB
HTTP 504: Gateway Timeout
EC2(nginx)
HTTP Error 408 Request timeout
Have someone discovered the same phenomenon? and know the cause?
Are you getting 408 in nginx error.log ? If yes, then it has nothing to do with ELB because it shows that request is going from ELB to nginx; and nginx itself is giving "Request timeout".. It is an application issue..Your application is not able to process the request.
One way to test would be to expose EC2 to public i.e. associate an Elastic IP address to EC2 and try to connect to it directly i.e. removing ELB from picture to be double sure.
Related
I have created an API that has two endpoints. I containerized that API and deployed that into the ECS Fargate container behind the Application Load Balancer.
End Points.
Get = Return the status of the API
Post = Insert data into the RDS.
api/v1/healthcheck is working
api/v1/insertRecord is not working => 502 bad Gateway
The problem I am running into is that I am able to get the HealthCheck response but I am not able to make the Post API call I am getting 502 Bad Gateway error
Target Group
My target group is directed to the healthcheck endPoint so my ecs stays up. Can someone plz tell me where am I making mistake?
The 502 (Bad Gateway) status code indicates that the server, while acting as a gateway or proxy, received an invalid response from an inbound server it accessed while attempting to fulfill the request. if the service returns an invalid or malformed response, instead of returning that nonsensical information to the client.
Possible causes: taken from
check protocol and port number during REST call
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.
The target response is malformed or contains HTTP headers that are
not valid.
The target closed the connection with a TCP RST or a TCP FIN while
the load balancer had an outstanding request to the target.
you can enable cloudWatch log for further debugging.
I have configured a http external load balancer on GCP and all my vm instances are healthy in backend.
But when i am trying to access my server(installed on VM) from frontend static IP that is reserved at load balancer it is giving me 502 status error.
As a result of which i am unable to launch my application server using load balancer. Help me fix this issue.
Thanking you in advance.
To troubleshoot 502 response from the Load Balancer due to "failed_to_connect_to_backend." I would check the followings:
Usually, "failed_to_connect_to_backend" error message indicates that the load balancer is failing to connect to backends, investigating URL map rules is also a good point to start. I would also suggest reviewing your Load Balancer's URL map to make sure that Host rules, Path matcher, and Path rules are correctly defined and comply with descriptions in this article.
Also check if the backend instances are exhausting their resources, If a backend server is overwhelmed, it will refuse incoming requests, potentially causing the load balancer to give up on it and return the specific 502 error you're experiencing. Also, check the output on how many established connections are present at any one time using 'netstat' and watch command.
I would also recommend testing again with the HTTP(S) request directly to the instance, request the same URL that reporting 502. You might do this test in another VM instance in your VPC network.
maybe you should check if the time taken for the API to return the response is exceeded the timeout that will trigger the 502. The default value is 30 seconds.
Ref: https://cloud.google.com/load-balancing/docs/backend-service#timeout-setting
We have 3 EC2 Instances(Apache Web Server) running under AWS ELB, it sharing load correctly but whenever any of Web Server down i.e. Web1 having some issue i.e. Disk Full or Apache Crash then still ELB trying to send request to that server which is already not responding or don't have capacity to respond, hence user who is connected to that server are getting error.
Question : Is there way to identify Fail server and force ELB to stop passing request to failed server?
FYI: Auto Scaling is not enabled.
You need to configure health checks for your ELB. When the checks are failing, the elb will stop forwarding traffic to the unhealthy instance.
I deployed an Application to AWS elastic beanstalk. When I try to open the application, I am getting 502 proxy error Saying following message.
Proxy Error
The proxy server received an invalid response from an upstream server.
The proxy server could not handle the request GET /.
Reason: Error reading from remote server
Apache/2.2.31 (Amazon) Server at mehe.us-west-2.elasticbeanstalk.com
Port 80
Strange part is when I run the application from localhost(Still connected to amazon database) the application is working fine, but after deloying it is not working. Here's the link to application
Any ideas how to get rid off it.
The timeout value for HTTPD is lower than the timeout value set for ELB. Change the timeout value in /etc/httpd/conf/httpd.conf
The keep the value between reboots you'll need to either create a custom AMI or use .ebextensions feature.
We are seeing a lot of 408 timeouts on our ELB access logs. Have come across this thread https://serverfault.com/questions/485063/getting-408-errors-on-our-logs-with-no-request-or-user-agent
and also https://forums.aws.amazon.com/thread.jspa?messageID=307846
These are just two sample threads I found but others suggest the same solutions with no joy.
Have set web server timeout to be < ELB idle timeout, to be = to it and to be > than it, same result, our logs are polluted with these 408s. A bigger problem though it that they also throw off the average latency response time of our ELB which is what we trigger our auto scaler with.
We use Tomcat on our back end instances. No logs appear on tomcat to indicate a request was recieved but the ELB still shows as if requests had timed out.
On our ELB access logs there is no back end IP given for the 408s so in my opinon the requests never got to an instance at all but Amazon disagree :(.
Any one had this problem and got a reliable solution for it?
Following the suggestion of milsonspt in the linked thread, I added a virtual host to my server that monitors a different thread instead of 80 so all health checks will be executed on that host (replace CUSTOM_PORT with any port you want to be used for ELB health check).
Listen CUSTOM_PORT
<VirtualHost *:CUSTOM_PORT>
CustomLog "|/usr/sbin/rotatelogs /var/log/httpd/access_log_elb_health_check_rotated_%Y-%m-%d-%H_%M_%S 10M" combined
</VirtualHost>
Make sure that the ELB does NOT have a listener on that port.
That configuration removed the 408 errors and logs all health check in a separate log so you get an uncluttered log for your regular access log, and a dedicated log for health check.
This could happen when ELB is waiting on the client for complete request. If a partial request comes in, with incomplete headers AWS ELB would just wait. AWS ELB would not do anything with the partial request headers, and eventually respond with 408 req_timeout due to idle timeout expiry on the tcp connection.