Elastic Container Instance:Use probes for container health checks

Overview

ECI supports liveness probes and readiness probes to check the health and status of containers.

API configuration

When creating an ECI instance with the CreateContainerGroup operation, you can configure probes using the LivenessProbe and ReadinessProbe parameters. For more information, see CreateContainerGroup.

Console configuration

When you create an ECI instance in the Elastic Container Instance console, you can select a container in the Container Configurations section, expand the container's advanced settings, enable health checks, and then configure the probes.

Example

This example shows how to create an ECI instance with a liveness probe and a readiness probe, and then simulate a service failure to see the probes in action.

1. Call the CreateContainerGroup operation to create an ECI instance.

   The following example uses the TCP socket method for health checks:

   ContainerGroupName=test-probe
   # Use the nginx image and automatically create and associate an EIP.
   Container.1.Name=container-1
   Container.1.Image=nginx
   AutoCreateEip=true
   # Liveness probe: checks port 80 every 3s, starting 5s after launch. Success threshold: 1, failure threshold: 3, timeout: 10s.
   Container.1.LivenessProbe.TcpSocket.Port=80
   Container.1.LivenessProbe.InitialDelaySeconds=5
   Container.1.LivenessProbe.PeriodSeconds=3
   Container.1.LivenessProbe.SuccessThreshold=1
   Container.1.LivenessProbe.FailureThreshold=3
   Container.1.LivenessProbe.TimeoutSeconds=10
   # Readiness probe: checks port 80 every 3s, starting 5s after launch. Success threshold: 1, failure threshold: 3, timeout: 10s.
   Container.1.ReadinessProbe.TcpSocket.Port=80
   Container.1.ReadinessProbe.InitialDelaySeconds=5
   Container.1.ReadinessProbe.PeriodSeconds=3
   Container.1.ReadinessProbe.SuccessThreshold=1
   Container.1.ReadinessProbe.FailureThreshold=3
   Container.1.ReadinessProbe.TimeoutSeconds=10

2. View the ECI instance events in the Elastic Container Instance console.

   After the ECI instance is created, click the instance ID to open its details page. On the Events tab, you can see that the container started normally.

   The event list shows four Normal events in order: Pulling image "nginx", Successfully pulled image "nginx", Created container container-1, and Started container container-1.

3. Connect to the container. For more information, see Connect to an ECI instance with Workbench.

4. Change the Nginx listening port to simulate a service failure.

   1. Modify the Nginx listening port.

      Note

      The Nginx image used in this example does not have vim installed. Before you run the vi command, run apt-get update and apt-get install vim to install vim.

      vi /etc/nginx/conf.d/default.conf

      Change the listening port from 80 to 8080, as shown in the following example:

      server {
          listen       8080;
          listen  [::]:8080;
          server_name  localhost;
          #access_log  /var/log/nginx/host.access.log  main;
          location / {
              root   /usr/share/nginx/html;
              index  index.html index.htm;
          }
          #error_page  404              /404.html;
          # redirect server error pages to the static page /50x.html
          #
          error_page   500 502 503 504  /50x.html;
          location = /50x.html {
              root   /usr/share/nginx/html;
          }
      }

   2. Reload the Nginx configuration.

      nginx -s reload

5. Check the effect of the probes.

   A few seconds after you reload Nginx, the container automatically restarts. You can view the instance events to see the container restart after the liveness and readiness probes fail.

   The event list shows that the probes failed with the message dial tcp 172.x.x.x:80: connect: connection refused, which indicates that the connection to the container port was refused. As a result, ECI automatically restarted the container-1 container.