how to update the microservice on the 20000 Linux server without downtime

To update a microservice on 20000 Linux servers without downtime, you can use a rolling update strategy. Here are the general steps to follow:

1. Prepare the new version of the application: Build and test the new version of the microservice application in a staging environment. Once you're confident that the new version is ready, package it into a deployment artifact, such as a Docker image or a binary package.
2. Deploy the new version to a subset of servers: Start by deploying the new version of the application to a small subset of servers, such as 5-10% of the total servers. Use Ansible or another configuration management tool to automate the deployment process.
3. Verify the deployment: Once the new version of the application is deployed to the subset of servers, verify that it's working as expected. Use monitoring tools, such as Prometheus or Nagios, to monitor the performance and availability of the new version.
4. Incrementally roll out the new version: Once the new version of the application is verified, gradually roll it out to more servers in small batches. For example, you can deploy the new version to an additional 10% of servers every 30 minutes. Use Ansible to automate the deployment process and ensure that it's consistent across all servers.
5. Monitor the deployment: Continuously monitor the performance and availability of the new version of the application as it's rolled out to more servers. Use monitoring tools to detect any issues and quickly roll back the deployment if necessary.
6. Complete the rollout: Once the new version of the application is deployed to all servers, complete the rollout by cleaning up any temporary files or resources used during the deployment process.

By following this rolling update strategy, you can update a microservice application on 20000 Linux servers without downtime, while also ensuring that the new version is thoroughly tested and verified before it's deployed to all servers.

Updating a microservice application on 20,000 servers with Ansible requires careful planning and optimization to ensure that the update process completes as quickly and efficiently as possible. Here's an example of how you can achieve this:

1. Optimize Ansible performance: Ansible can be slow when running playbooks against a large number of servers. To optimize Ansible performance, you can do the following:

• Use Ansible in "pull" mode instead of "push" mode, which allows you to run playbooks locally on each server instead of remotely.
• Use the async and poll parameters to run tasks asynchronously and in parallel across multiple servers.
• Use the serial parameter to update servers in batches, rather than all at once.
• Use the --forks option to specify the number of parallel processes to use when running playbooks.

1. Divide servers into groups: To update 20,000 servers, you'll need to divide them into groups based on location, function, or any other relevant criteria. You can use Ansible inventory files to define these groups, and then target each group separately in your playbook.
2. Use rolling updates: To minimize the impact of the update process, you can use a rolling update strategy, as described earlier. You can update a subset of servers at a time, starting with less critical ones, and then gradually move on to more critical ones.
3. Use a dedicated update server: To avoid overloading your application servers during the update process, you can use a dedicated update server that can download and distribute the updated application to each server in a controlled manner.
4. Monitor and validate the update process: It's important to monitor the update process closely to detect any issues and ensure that the update is progressing smoothly. You can use Ansible to run health checks on each server after the update to verify that the new version of the application is running properly.

Here's an example playbook that uses the above techniques to update a microservice application on 20,000 servers:

--
- name: Update microservice application
? hosts: all
? serial: 100
? tasks:
? ? - name: Copy new version of microservice application
? ? ? copy:
? ? ? ? src: /path/to/new/microservice
? ? ? ? dest: /opt/microservice/microservice
? ? - name: Stop old version of microservice application
? ? ? systemd:
? ? ? ? name: microservice
? ? ? ? state: stopped
? ? - name: Start new version of microservice application
? ? ? systemd:
? ? ? ? name: microservice
? ? ? ? state: started
? ? - name: Verify microservice application health
? ? ? uri:
? ? ? ? url: https://localhost:8080/health
? ? ? ? method: GET
? ? ? ? return_content: yes
? ? ? register: health_check
? ? ? retries: 10
? ? ? delay: 10
? ? ? until: health_check.status == 200 and 'OK' in health_check.content
? strategy: free

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