Is Ansible command module idempotent?
The principle that enables Ansible to be declarative and yet reliable is idempotence, a concept borrowed from mathematics. An idempotent operation is one that can be applied multiple times without changing the result beyond the initial application, such as multiplication by zero. Ansible modules are idempotent.Apr 28, 2014
In general, idempotence is “the property of certain operations in mathematics and computer science that can be applied multiple times without changing the result beyond the initial application”. For Ansible it means after 1 run of a playbook to set things to a desired state, further runs of the same playbook should result in 0 changes.
Is Ansible command module idempotent?
Most modules in Ansible is idempotent. Meaning you can apply it over and over again and get the same results. This concept is widely adopted for infrastructure automation across tools and services.Jul 24, 2019
How do you achieve idempotency in Ansible?
We can use lineinfile module to ensure idempotency at all times so that an Ansible task which introduces a change to your system must not report the same change when run a second time.Nov 10, 2016
What is idempotent task?
Idempotence is any function that can be executed several times without changing the final result beyond its first iteration. Idempotence is a technical word, used in mathematics and computer science, that classifies a function's behavior.May 11, 2020
How do you make shell command Idempotent Ansible?
Making tasks idempotent by using creates keyword
You can make the shell and command modules idempotent using the 'creates' keyword and 'removes' keyword. This depends on the presence or absence of a file. i.e., we can specify the task should run only if a file exists or removed.Feb 26, 2017
What is Changed_when in Ansible?
Ansible failed_when and changed_when statements are similar to ansible when statement. The only difference is that It will mark the task as failed or Success[changed], when the condition defined, is met or satisfied. ... Ansible would report it as changed as long as the command (or) script give ZERO return code.Jun 14, 2021
Why Ansible is called idempotent?
The resource models are idempotent meaning change commands are not run unless needed, and Ansible will bring the system back to a desired state regardless of the actual state – rather than you having to tell it how to get to the state.
Is Ansible template idempotent?
When a playbook is executed to configure a system, the system should always have the same, well defined state. By its nature, Ansible tasks will only change the system if there is something to do. ... Most Ansible modules provide this idempotency.Oct 11, 2020
Is terraform idempotent?
Both Terraform and Ansible support idempotent operations. Saying that an operation is idempotent means that applying it multiple times will not change the result. ... You can run terraform apply continuously for hours, and if your configuration matches what is defined in the plan, it won't actually change anything.
What is a example of idempotent?
In computing, an idempotent operation is one that has no additional effect if it is called more than once with the same input parameters. For example, removing an item from a set can be considered an idempotent operation on the set. In mathematics, an idempotent operation is one where f(f(x)) = f(x).Jul 3, 2009
Related questions
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What is Idempotence and how is it used?
Idempotency essentially means that the result of a successfully performed request is independent of the number of times it is executed. For example, in arithmetic, adding zero to a number is an idempotent operation.Sep 30, 2021
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What is Idempotence and why is it useful?
Idempotency is important in APIs because a resource may be called multiple times if the network is interrupted. In this scenario, non-idempotent operations can cause significant unintended side-effects by creating additional resources or changing them unexpectedly.Aug 19, 2020
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Is Ansible procedural?
Ansible is actually a hybrid of procedural and declarative. You could perform ad-hoc commands for procedural-style configuration. On the other hand, you have the option of using various Ansible modules that can perform declarative-style configuration.Dec 31, 2019
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What are declarative software tools?
Declarative programming is a high-level programming concept, which is the opposite of imperative programming. It is typically found in databases and configuration management software, paired with a domain-specific language (DSL).
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What is declarative configuration?
Declarative configuration management refers to the class of tools that allow operators to declare a desired state of some system (be it a physical machine, an EC2 VPC, an entire Google Cloud account, or anything else), and then allow the system to automatically compare that desired state to the present state, and then ...Nov 12, 2019
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What does idempotency mean in Ansible?
- For Ansible it means after 1 run of a playbook to set things to a desired state, further runs of the same playbook should result in 0 changes. In simplest terms, idempotency means you can be sure of a consistent state in your environment.
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What is your primary use case for Ansible?
- Ansible enables infrastructure as code. It has been a valuable tool for my [email protected] project, helping me to setup the programs Consul and Nomad, to provide DNS for nodes and services, and an Nginx endpoint.
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How to combat configuration drift with Ansible?
- There are multiple ways to combat Configuration Drift with Ansible, such as using Ansible Tower to check frequently with playbooks that detect drift, then notify the appropriate resource through chat, email, etc and/or make an appropriate modification to keep it in line with the baseline. Ansible Modules are idempotent as we mentioned above.
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Why can't Ansible read the content of a file?
- Feb 13 '15 at 6:33 1 Only if the regexpdid notmatch the content of the file, the line will be added to the file. Regarding the symlink: It might simply be Ansible is not following a link and therefore can not read the content of the file in the first place.
Related
What does idempotency mean in Ansible?What does idempotency mean in Ansible?
For Ansible it means after 1 run of a playbook to set things to a desired state, further runs of the same playbook should result in 0 changes. In simplest terms, idempotency means you can be sure of a consistent state in your environment.
Related
When to use Ansible modules to change the system?When to use Ansible modules to change the system?
If a playbook consists of 10 steps, and the system deviates in step 4 from the desired state, then only this particular step should be applied. By its nature, Ansible tasks will only change the system if there is something to do. Most Ansible modules provide this idempotency. But some modules can be used in a way that breaks this pattern.
Related
How to combat configuration drift with Ansible?How to combat configuration drift with Ansible?
There are multiple ways to combat Configuration Drift with Ansible, such as using Ansible Tower to check frequently with playbooks that detect drift, then notify the appropriate resource through chat, email, etc and/or make an appropriate modification to keep it in line with the baseline. Ansible Modules are idempotent as we mentioned above.
Related
Why can't Ansible read the content of a file?Why can't Ansible read the content of a file?
Feb 13 '15 at 6:33 1 Only if the regexpdid notmatch the content of the file, the line will be added to the file. Regarding the symlink: It might simply be Ansible is not following a link and therefore can not read the content of the file in the first place.
