ansible template for loop

We use this information to set up host aggregates. For example, to get the same output as: Any with_* statement that requires using lookup within a loop should not be converted to use the loop keyword. 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). 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. 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. Viewed 1k times 1. I try it like this: (% for mounts in {{ ansible_mounts }} %) Mountpoint: {{ ansible_mounts.mount }} (% endfor %) But it does not work. Note: You can use Jinja2 loops and conditionals in Ansible templates, but not in Ansible Playbooks. 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. Templating is extremely useful when creating custom configuration files for multiple servers but unique for each of them. So, let’s dive right into it. Jinja2 can be a pain, but ultimately a very powerful tool. 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. Does the _ mean you dont have to name the parameter when using it? Ask Question Asked 4 years, 7 months ago. The loop_control keyword lets you manage your loops in useful ways. Knowing the basics of YAML is also appreciated. So let’s move on. 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. Here’s an example: This task runs up to 5 times with a delay of 10 seconds between each attempt. The template module also copies a file to a remote server, but it allows you to use Jinja2 to render a template to a file dynamically. The loop keyword is equivalent to with_list, and is the best choice for simple loops. Undefined during the first iteration. Common Ansible loops include changing ownership on several files and/or directories with the file module, creating multiple users with the user module, and In some ways it comes down to documentation, a mixing of languages (YAML, Python, Jinja2), and variables. They can also be a leading contributor to hair loss. _terms. Viewed 41k times 13. with_flattened is replaced by loop and the flatten filter. The template files will usually have the.j2 extension, which denotes the Jinja2 templating engine used. SUMMARY late template expansion turns the lack of variable scopes into a problem under certain conditions. This is a very simple playbook where we just iterate over a loop of items and echo the individual item. Be careful when changing with_items to loop, as with_items performed implicit single-level flattening. Most of the packaging modules, like yum and apt, have this capability. The loop keyword will not accept a string as input, see Ensuring list input for loop: using query rather than lookup. First, I’ll describe the issue in detail (feel free to follow along on your own Ansible install). I'm using for in template file {% for vhost in item %} server = {{vhost}} {% endfor %} With items use with_items in file yml ansible. (1 indexed), The current iteration of the loop. First, add the following line to your ansible.cfg:--- [defaults] jinja2_extensions =,jinja2.ext.i18n Generally speaking, any use of with_* covered in Migrating from with_X to loop can be updated to use loop. Why? SUMMARY. For example: Check the module documentation to see if you can pass a list to any particular module’s parameter(s). 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. A much more powerful way to manage files is to template them. 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 %}. We are looking to improve loop syntax - watch this page and the changelog for updates. © Copyright 2019 Red Hat, Inc. The with_ keywords rely on Lookup Plugins - even items is a lookup. For example: When combining conditionals with a loop, the when: statement is processed separately for each item. This differs from the data structure returned when using register without a loop: Subsequent loops over the registered variable to inspect the results may look like: During iteration, the result of the current item will be placed in the variable: You can use Jinja2 expressions to iterate over complex lists. 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. They can also be a leading contributor to hair loss. We added loop in Ansible 2.5. Ansible Jinja Warrior - Mastering "Loop Variable Scope" Average Reading Time: ~6 minutes 0 Comments. When available, passing the list to a parameter is better than looping over the task. 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). 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. 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. Let’s create a templates directory to keep thing cleaner and more organized: [elliot@control plays]$ mkdir templates [elliot@control plays]$ cd templates/ If the result of any attempt has “all systems go” in its stdout, the task succeeds. The variables are all optional, so I needed a way to handle this. 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. So in each loop iteration of the colours variable, we are able to now add a new element that contains the number of people who deem this their favourite colour. 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. In my case each iteration produced about 3k output, and it pushed full jenkins output way over 2Mb for my project. It's really important to know how Jinja2 works if you want to create powerful templates for your playbooks. In computer programming, this is called a loop. Ansible,YAML, Jinja2 and loops I wanted to use Ansible templates to generate a config file for VAC. The loop syntax is usually best expressed using filters instead of more complex use of query or lookup. The current iteration of the loop. Apart from that, you can perform conditional statements such as loops and if-else statements, and transform the data using filters and so much more. In some ways it comes down to documentation, a mixing of languages (YAML, Python, Jinja2), and variables. Hi all, I think I'm just being dumb here, but I cant find anything that explicitly answers my question. Usually, the template files will have the .j2 extension, which denotes the Jinja2 templating engine used. We need to have two parameters when using the Ansible Template module, such as: src: The source of the template file. Before Ansible 2.5, most playbooks used a different syntax for loops. — While using loops in Ansible, by default, output contains the entire content of the item being processed. (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. 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. In most cases, Jinja2 template files are used for creating files or replacing configuration files on servers. repeating a polling step until a certain result is reached. 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. Ansible offers two keywords for creating loops: loop and with_. dest: destination of templated file in remote hosts. with_nested and with_cartesian are replaced by loop and the product filter. I have problem! You may need to use flatten(1) with loop to match the exact outcome. Have a question? Ansible loop is used to repeat any task or a part of code multiple times in an Ansible-playbook. Undefined during the last iteration. During a recent consulting project with a customer, focused on network automation, we embarked on a journey to re-evaluate how routers were provisioned. Author: Tim Fairweather. In computer programming, this is called a loop. If there is sensitive data in loop, set no_log: yes on the task to prevent disclosure. 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. Hosts is our inventory file and is simply our localhost that we are running Ansible on. The bare metal machines we use as the basis for our OpenStack infrastructure have different capabilities. Active 1 year, 8 months ago. Jinja2 provides filters which change the output format for template expressions (for example, to JSON). To loop over a dict, use the dict2items: Here, we are iterating over tag_data and printing the key and the value from it. 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. During a recent … 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). ansible_hostnameis just another regular variable expansion. This also applies to loops. If you get stuck … reach out! When looping over complex data structures, the console output of your task can be enormous. Jinja templates in Ansible can be very powerful. Last updated on Jan 12, 2021. The item from the following iteration of the loop. There are filters available for languages such as YAML and JSON. ansible Nested loops Example. This means the inner, nested loop will overwrite the value of item from the outer loop. This is for making console output more readable, not protecting sensitive data. Now we write a simple playbook that will call on a Jinja template we will write. It can be a relative and absolute path. This option will expose the following information. Using ‘for’ loop structure inside Ansible template One of the main program expression we usually use is the ‘for’ loop. src: source of the template file which is ./templates by default. In Ansible loops you can use the conditional statement when to control the looping based on the nature of variables or system facts. 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. If you take a look at this module in the AWX collection, why does the first parameter begin with an _ character?. (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). with_subelements is replaced by loop and the subelements filter. with_items is replaced by loop and the flatten filter. It is possible to use this in ansible templates also using the jinja2 format. with_random_choice is replaced by just use of the random filter, without need of loop. A quick modification to your /etc/ansible.cfg file and a small change to your template, and we can get this working. If until is not defined, the value for the retries parameter is forced to 1. 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. Today we're gonna work with: loop.index: The current iteration of the loop. If you have a list of hashes, you can reference subkeys in a loop. Today we're gonna work with: loop.index: The current iteration of the loop. with_sequence is replaced by loop and the range function, and potentially the format filter. As of Ansible 2.8 you can get the name of the value provided to loop_control.loop_var using the ansible_loop_var variable. Before you look at loops in Ansible, I hope you have followed other chapters in this Ansible tutorial series. 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. Basically, minimum of two parameters are required while using template module in ansible. For loop in Ansible Template. loop.index: The current iteration of the loop (1 indexed). The item from the previous iteration of the loop. For example, a loop can combine nested lists: You can use the until keyword to retry a task until a certain condition is met. Ask Question Asked 3 years, 10 months ago. It can be used to iteratively go through the values of a list, dictionary etc. with_indexed_items is replaced by loop, the flatten filter and loop_control.index_var. 2. Change to your templates directory and create the following hosts.j2 template file: For example, instead of doing: Repeated tasks can be written as standard loops over a simple list of strings. #we can further add more parameters as follows owner: user_name group: user_group mode: u+rw,g-wx,o-rwx Notice in our output after running Ansible with our updated template file, the numbers are properly counted. Tim has spent the bulk of his career in the solution architecture space, problem solving and designing solutions to meet very specific needs. Jinja2 uses the double curly braces { {... }} to enclose a variable that has been defined. (1 indexed) loop.length: The number of items in the sequence Two different examples for different files: /etc/hosts and /etc/hosts We want to generate the following snip… It's really important to know how Jinja2 works if you want to create powerful templates for your playbooks. In the next example, I’ll be using the template module to print all the items present in a list using the for the loop. And so on. However, they are not always easy to use effectively and correctly. A significant part of this initiative was to dynamically create configuration templates for routers, based on variable input. Variable Filters. Jinja templates in Ansible can be very powerful. We have specified an array called ‘ packages ‘ that contains a list of packages that need to be installed. You can use the cat command to examine the output and verify where the models exist in … This can result in a great amount of verbosity if the item is a dictionary or is otherwise long. Author: Tim Fairweather. Iterating over a simple loop. Why? These examples show how to convert many common with_ style loops to loop and filters. The default value for “retries” is 3 and “delay” is 5. You can force lookup to return a list to loop by using wantlist=True, or you can use query instead. 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. This enables you to use variables, such as Ansible facts, to customize a particular file for a specific server. Hope this helps you out in your template writing. Sometimes, though, just expanding pre-defined variables is not good enough. Stop by the google group! We get an output that is not what we expect. 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.

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