14-Day5-3-UnderstandingAndConfiguringExecutionStrategies

Day 5: Lab Series 3 - Understanding and Configuring Execution Strategies

Objective:

This lab introduces participants to execution strategies in Ansible. Participants will understand how forks, serial, and throttle settings affect task execution and learn to configure these strategies for optimal resource usage and control.

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Lab 3.1: Configuring Forks

Scenario:

Optimize parallel task execution by increasing the number of forks.

Steps:

1. Default Forks Setting: Run a playbook with the default forks setting.

   ---
   - name: Test Default Forks
     hosts: all
     tasks:
       - name: Ping all hosts
         ping:

   Command to run:

   ansible-playbook forks_example.yaml -i inventory

   Observe the speed of execution for multiple hosts.

2. Increase Forks:

   Set a higher forks value in the playbook execution command:

   ansible-playbook forks_example.yaml -i inventory --forks 10

3. Exercise:

   • Compare the execution time with different forks values (e.g., 1, 5, 10).

   • Test with a larger inventory file to see the impact.

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Lab 3.2: Using Serial Execution

Scenario:

Control task execution by running tasks on a limited number of hosts at a time.

Steps:

1. Playbook with serial:

   Save as serial_example.yaml:

   ---
   - name: Execute Tasks Serially
     hosts: all
     serial: 2
     tasks:
       - name: Display Hostname
         debug:
           msg: "Task running on {{ inventory_hostname }}"

2. Run the Playbook:

   ansible-playbook serial_example.yaml -i inventory

3. Exercise:

   • Modify the serial value to 1, 2, or 5, and observe the behavior.

   • Identify scenarios where serial execution might be beneficial (e.g., rolling updates).

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Lab 3.3: Using Throttle for Task Control

Scenario:

Limit concurrent execution of a specific task using the throttle keyword.

Steps:

1. Playbook with Throttling:

   Save as throttle_example.yaml:

   ---
   - name: Throttle Specific Task Execution
     hosts: all
     tasks:
       - name: Install Packages
         yum:
           name: httpd
           state: present
         throttle: 3

2. Run the Playbook:

   ansible-playbook throttle_example.yaml -i inventory

3. Exercise:

   • Experiment with different throttle values (e.g., 1, 3, 5).

   • Compare how throttling differs from serial.

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Lab 3.4: Combining Strategies

Scenario:

Use serial, throttle, and forks together to configure complex execution strategies.

Steps:

1. Playbook with Multiple Strategies:

   Save as combined_example.yaml:

   ---
   - name: Test Combined Strategies
     hosts: all
     serial: 2
     tasks:
       - name: Ping Hosts
         ping:
   
       - name: Deploy Apache
         yum:
           name: httpd
           state: present
         throttle: 1

2. Run the Playbook:

   ansible-playbook combined_example.yaml -i inventory --forks 5

3. Exercise:

   • Analyze how serial, throttle, and forks interact.

   • Test with a larger inventory file for deeper insights.

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Optional Lab: Debugging Execution Strategies

Scenario:

Test execution strategies in failure scenarios.

1. Modify a playbook to deliberately fail on a few hosts (e.g., by using incorrect package names or unreachable hosts).

2. Run the playbook with different strategies:

   • serial

   • throttle

   • forks

3. Observe the behavior and learn how each strategy handles errors.

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Key Learning Points:

1. Forks: Determine how to optimize parallel execution for large inventories.

2. Serial Execution: Control rolling updates or phased deployments with serial.

3. Throttling: Limit resource-intensive tasks to a subset of hosts.

4. Combining Strategies: Mix execution strategies to balance speed and control in complex deployments.

These exercises empower participants to effectively manage execution flow in diverse scenarios.