Ansible offers two keywords for creating loops: loop and with_. Most of the packaging modules, like yum and apt, have this capability. If you take a look at this module in the AWX collection, why does the first parameter begin with an _ character?. You can create nested loops using with_nested. Tim has spent the bulk of his career in the solution architecture space, problem solving and designing solutions to meet very specific needs. Referencing variables in your templates is a great way to keep your Ansible playbook logic separate from your data. Before you look at loops in Ansible, I hope you have followed other chapters in this Ansible tutorial series. To control the time (in seconds) between the execution of each item in a task loop, use the pause directive with loop_control: To keep track of where you are in a loop, use the index_var directive with loop_control. Why? loop.index: The current iteration of the loop (1 indexed). Ansible will look for jinja2 template files in your project directory or in a directory named templates under your project directory. For example: When you use register with a loop, the data structure placed in the variable will contain a results attribute that is a list of all responses from the module. I try it like this: (% for mounts in {{ ansible_mounts }} %) Mountpoint: {{ ansible_mounts.mount }} (% endfor %) But it does not work. Basically, minimum of two parameters are required while using template module in ansible. If you get stuck … reach out! The playbook is called varloop.yml: The playbook simply uses the variable file we specified and calls the template module in a task to build a file called output.txt from a j2 template. Non-optimal yum, slower and may cause issues with interdependencies, Place the result of the current item in the variable, Retry a task until a certain condition is met, result.stdout.find("all systems go") != -1, Show all the hosts matching the pattern, ie all but the group www, Create servers, pause 3s before creating next, start=0 end=4 stride=2 format=testuser%02x, with_random_choice -> loop (No loop is needed here), Understanding privilege escalation: become, Controlling where tasks run: delegation and local actions, Working with language-specific version managers, Discovering variables: facts and magic variables, Validating tasks: check mode and diff mode, Controlling playbook execution: strategies and more, Virtualization and Containerization Guides, Controlling how Ansible behaves: precedence rules, Defining inner and outer variable names with. To loop over a dict, use the dict2items: Here, we are iterating over tag_data and printing the key and the value from it. First, I’ll describe the issue in detail (feel free to follow along on your own Ansible install). SUMMARY. So what I want to do is: In a template I want to loop over all the objects in the array and output the values of each "mount" key. (0 indexed), The number of iterations from the end of the loop (1 indexed), The number of iterations from the end of the loop (0 indexed). During a recent … Ansible loop is used to repeat any task or a part of code multiple times in an Ansible-playbook. with_indexed_items is replaced by loop, the flatten filter and loop_control.index_var. For role authors, writing roles that allow loops, instead of dictating the required loop_var value, you can gather the value via: In most cases, loops work best with the loop keyword instead of with_X style loops. It can be used to iteratively go through the values of a list, dictionary etc. (1 indexed) loop.length: The number of items in the sequence Two different examples for different files: /etc/hosts and workers.properties: /etc/hosts We want to generate the following snip… using for loops for configs of reverse proxies like HAProxy or Nginx; using variables is useful to share the same templates for prod/stg/dev environments; Important points As I explained template module is very convenient, but as long as it modifies original files at execution of Ansible, there is a possibility of miss configurations. First, add the following line to your ansible.cfg:--- [defaults] jinja2_extensions = jinja2.ext.do,jinja2.ext.i18n It includes the creation of multiple users using the user module, installing multiple packages using apt or yum module or changing permissions on several files or folders using the file module. We need to have two parameters when using the Ansible Template module, such as: src: The source of the template file. Using lists in Ansible templates. Common Ansible loops include changing ownership on several files and/or directories with the file module, creating multiple users with the user module, and repeating a polling step until a certain result is reached. [gituser@ip RTR-TEMPLATE]$ ansible-playbook site.yml PLAY ... After the template line is 'with_items:'; with_items is an iterator (it acts like a for loop where the variable 'item' will be set to equal one of with_items elements on each iteration). ansible_hostnameis just another regular variable expansion. The loop syntax is usually best expressed using filters instead of more complex use of query or lookup. Consider the playbook below where we have a list of packages that need to be installed. — http://jinja.pocoo.org/docs/2.9/templates/#assignments. The item from the previous iteration of the loop. You should know the concept of Ansible playbooks, aware of the ad-hoc commands and know the basic terminology associated with Ansible like list, dictionaries etc. Usually, the template files will have the .j2 extension, which denotes the Jinja2 templating engine used. See Basic conditionals with when for examples. For example, a loop can combine nested lists: You can use the until keyword to retry a task until a certain condition is met. Undefined during the last iteration. A significant part of this initiative was to dynamically create configuration templates for routers, based on variable input. You must set the until parameter if you want a task to retry. We could either use what Ansible package delivered or resort to things like distributing Ansible modules in roles (which we consider an ugly hack around Ansible's limitations). When you run a task with until and register the result as a variable, the registered variable will include a key called “attempts”, which records the number of the retries for the task. Behavior of failures inside of loops is inconsistent between "fatal" and "failed" outcomes. Ensuring list input for loop: using query rather than lookup, Tracking progress through a loop with index_var, Defining inner and outer variable names with loop_var. Author: Tim Fairweather. Ansible provides a very useful module named template, which give you the ability to use a template where you can make use of available variables, use conditions to generate specific case data, use filters, statements and comments to provide more information to the template user. When looping over complex data structures, the console output of your task can be enormous. You can specify the name of the variable for each loop using loop_var with loop_control: If Ansible detects that the current loop is using a variable which has already been defined, it will raise an error to fail the task. Ask Question Asked 4 years, 7 months ago. When a variable value changes, you simply reflect that change in your variables file instead of having to make any changes to your actual template. In this section, we will explore how to make practical use of loops in your Ansible playbooks. Hosts is our inventory file and is simply our localhost that we are running Ansible on. In some ways it comes down to documentation, a mixing of languages (YAML, Python, Jinja2), and variables. Multiple loop keywords were provided, which were prefixed with with_, followed by the name of an Ansible look-up plug-in (an advanced feature not covered in detail in this course). Ansible has a number of modules that can be used to modify existing files. Jinja2 can be a pain, but ultimately a very powerful tool. The loop keyword is equivalent to with_list, and is the best choice for simple loops. This enables you to use variables, such as Ansible facts, to customize a particular file for a specific server. repeating a polling step until a certain result is reached. You may need to use flatten(1) with loop to match the exact outcome. Ansible Template Module Example. Please keep in mind that it is not possible to set variables inside a block and have them show up outside of it. You can define the list directly in the task: You can define the list in a variables file, or in the ‘vars’ section of your play, then refer to the name of the list in the task: Either of these examples would be the equivalent of: You can pass a list directly to a parameter for some plugins. We are NOT able to extract the value of the colour_count variable outside of the inner loop where we are performing the count. Viewed 1k times 1. When available, passing the list to a parameter is better than looping over the task. Iterating over a simple loop. In some ways it comes down to documentation, a mixing of languages (YAML, Python, Jinja2), and variables. One containing a list of people with their favourite colours, and a second one containing a list of colours with things that happen to be of those colours. Mainly the ability to have a variable’s value accessible outside of the loop that is currently being run. Ansible offers two keywords for creating loops: loop and with_. Hope this helps you out in your template writing. To limit the displayed output, use the label directive with loop_control: The output of this task will display just the name field for each item instead of the entire contents of the multi-line {{ item }} variable. with_items is replaced by loop and the flatten filter. A much more powerful way to manage files is to template them. These examples show how to convert many common with_ style loops to loop and filters. _terms. Let’s create a templates directory to keep thing cleaner and more organized: [elliot@control plays]$ mkdir templates [elliot@control plays]$ cd templates/ In my case each iteration produced about 3k output, and it pushed full jenkins output way over 2Mb for my project. with_flattened is replaced by loop and the flatten filter. Knowing the basics of YAML is also appreciated. [ansible@controller lab2]$ mkdir templates [ansible@controller lab2]$ cd templates/ We have created a Jinja2 template file with content which is required to configure an FTP server using vsftpd. Notice how the for loop in Jinja2 mimics the syntax of Python’s for loop; again don’t forget to end the loop with {% endfor %}. This config file has a heading for each machine type, and then a series of variables. The benefit of using the template module, rather than the copy module, is that the Ansible template module can use the Jinja2 templating language.Jinja2. by Shahriar Shovon The Ansible template module is mainly used to copy files from the Ansible client (where Ansible is installed) to the Ansible hosts (managed by Ansible). Loop dictionary in ansible template. Notice in our output after running Ansible with our updated template file, the numbers are properly counted. ansible_managed (configurable via the defaults section of ansible.cfg) … The use of a well supported and powerful template library to supplement Ansible’s automation and remote control features provides a wide range of opportunities to output pretty complex files with a reasonable amount of effort. If there is sensitive data in loop, set no_log: yes on the task to prevent disclosure. Now we write a simple playbook that will call on a Jinja template we will write. (1 indexed), The current iteration of the loop. It's really important to know how Jinja2 works if you want to create powerful templates for your playbooks. The variables are all optional, so I needed a way to handle this. The loop_control keyword lets you manage your loops in useful ways. It will not modify the banner. You can use the cat command to examine the output and verify where the models exist in … That might sound confusing to the new Ansible user, so I'll break it down a bit through an example. With the release of Ansible 2.5, the recommended way to perform loops is the with_sequence is replaced by loop and the range function, and potentially the The real power of Ansible, however, is in learning how to use playbooks to run multiple, complex tasks against a set of targeted hosts in an easily repeatable manner. With the introduction of Ansible Collections, we gained a lot more control over the content we use in our Ansible playbooks. (1 indexed) loop.length: The number of items in the sequence Two different examples for different files: /etc/hosts and workers.properties: /etc/hosts We want to generate the following snip… In our example we see that because we can’t call the variable outside of the inner loop, the counting didn’t work. If until is not defined, the value for the retries parameter is forced to 1. Viewed 41k times 13. The benefit of using the template module, rather than the copy module, is that the Ansible template module can … Today we're gonna work with: loop.index: The current iteration of the loop. There are a couple of things that you need to keep in mind, a included task that has it’s own with_ loop will overwrite the value of the special item variable. Ask Question Asked 3 years, 10 months ago. with_nested and with_cartesian are replaced by loop and the product filter. with_together is replaced by loop and the zip filter. You can force lookup to return a list to loop by using wantlist=True, or you can use query instead. This is for making console output more readable, not protecting sensitive data. Generally speaking, any use of with_* covered in Migrating from with_X to loop can be updated to use loop. The bare metal machines we use as the basis for our OpenStack infrastructure have different capabilities. #we can further add more parameters as follows owner: user_name group: user_group mode: u+rw,g-wx,o-rwx See the output here: In our example we see that because we can’t call the variable outside of the inner loop, the counting didn’t work. Templating is extremely useful when creating custom configuration files for multiple servers but unique for each of them. Ansible Jinja Warrior - Mastering "Loop Variable Scope" Average Reading Time: ~6 minutes 0 Comments. This block allows us to use the update function to update an element in a dictionary variable. They can also be a leading contributor to hair loss. Ansible 2.5 introduced a new Jinja2 function named query that always returns a list, offering a simpler interface and more predictable output from lookup plugins when using the loop keyword. Why? In computer programming, this is called a loop. Active 3 years, 10 months ago. The loop keyword will not accept a string as input, see Ensuring list input for loop: using query rather than lookup. Now for the j2 template itself varloop.j2: In this j2 template we are attempting the following: looping over the list of colours and attempting to run a nested loop inside, that counts the number of people who’s favourite is the colour of the current loop iteration, listing all of the things that are of the colour of the current loop iteration. It can be a relative and absolute path. Now let’s create a full example that shows off the power of for loops in Jinja2. The for loop in the Jinja2 template file – example2_template.j2 – is as shown When the playbook is executed, the loop iterates over the car list, and prints out the car models in the destination file. Note: You can use Jinja2 loops and conditionals in Ansible templates, but not in Ansible Playbooks. Have a question? The default value for “retries” is 3 and “delay” is 5. Change to your templates directory and create the following hosts.j2 template file: So let’s move on. The loop keyword requires a list as input, but the lookup keyword returns a string of comma-separated values by default. The double curly braces will denote the variables in a template file, '{{variables}}'. In computer programming, this is called a loop. Ansible uses Jinja2 which is a modern templating engine for Python frameworks used to generate dynamic content or expressions. with_random_choice is replaced by just use of the random filter, without need of loop. Using ‘for’ loop structure inside Ansible template One of the main program expression we usually use is the ‘for’ loop. This means the inner, nested loop will overwrite the value of item from the outer loop. The item from the following iteration of the loop. Stop by the google group! Template files bear the .j2 extension, implying that Jinja2 templating is in use. Having worked across many vertical and technology areas, Tim applies this expertise to his work with Arctiq’s clients. Does the _ mean you dont have to name the parameter when using it? Last updated on Jan 12, 2021. src: source of the template file which is ./templates by default. While using loops in Ansible, by default, output contains the entire content of the item being processed. In Ansible loops you can use the conditional statement when to control the looping based on the nature of variables or system facts. Author: Tim Fairweather. It is not yet a full replacement for with_, but we recommend it for most use cases. I have also used ansible facts to get the IPv4 address from the managed node and place it in the vsftpd.conf just for reference purpose. For example, when looping through the output of the "show ip bgp sum", we want to use just an IP of the peer as an input in another task. If the result of any attempt has “all systems go” in its stdout, the task succeeds. Jinja2 provides filters which change the output format for template expressions (for example, to JSON). File: Playbook.yml - hosts: all vars: list1: ['Apple','Banana','Cat', 'Dog'] tasks: - name: Template Loop example. First add the following line to your ansible.cfg: Then modify your varloop.j2 file like this: Notice the “do” block in the updated template. I'm using for in template file {% for vhost in item %} server = {{vhost}} {% endfor %} With items use with_items in file yml ansible. This can result in a great amount of verbosity if the item is a dictionary or is otherwise long. SUMMARY late template expansion turns the lack of variable scopes into a problem under certain conditions. Variable Filters. So, let’s dive right into it. And so on. © Copyright 2019 Red Hat, Inc. Sometimes you want to repeat a task multiple times. The Ansible template module is mainly used to copy files from the Ansible client (where Ansible is installed) to the Ansible hosts (managed by Ansible). Jinja2 uses the double curly braces { {... }} to enclose a variable that has been defined. ansible Nested loops Example. with_dict can be substituted by loop and either the dictsort or dict2items filters. We have specified an array called ‘ packages ‘ that contains a list of packages that need to be installed. If you iterate over huge dictionary Ansible’s output is real mess. [student1@ansible closed_loop_incident_mgmt]$ ansible-playbook demo_setup.yml After this step, log into your tower instance and verify that the 2 “SNOW” job templates are present: SNOW-Demo-Compliance-Check - this Job Template will check for the banner being in compliance. The current iteration of the loop. This also applies to loops. It's really important to know how Jinja2 works if you want to create powerful templates for your playbooks. (we unlocked this with that extensions line in our ansible.cfg file)  In our case we are updating the colour of the current loop iteration to include a new key/value pair called people_count. Common Ansible loops include changing ownership on several files and/or directories with the file module, creating multiple users with the user module, and However, they are not always easy to use effectively and correctly. It doesn't continue past the failed item, even though "failed" outcomes do, and templating errors can be specific to the item in the loop..