ansible template for loop

This block allows us to use the update function to update an element in a dictionary variable. And so on. In computer programming, this is called a loop. 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. We can have conditional statements, loops, filters for transforming the data, do arithmetic calculations, etc. They can also be a leading contributor to hair loss. Jinja2 uses the double curly braces { {... }} to enclose a variable that has been defined. Have a question? Jinja2 can be a pain, but ultimately a very powerful tool. repeating a polling step until a certain result is reached. Why? with_indexed_items is replaced by loop, the flatten filter and loop_control.index_var. 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). You can create nested loops using with_nested. The loop keyword requires a list as input, but the lookup keyword returns a string of comma-separated values by default. The item from the previous iteration of the loop. In Ansible loops you can use the conditional statement when to control the looping based on the nature of variables or system facts. 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). Why? with_together is replaced by loop and the zip filter. As you can see we have 2 dictionary variables defined. Note: You can use Jinja2 loops and conditionals in Ansible templates, but not in Ansible Playbooks. Undefined during the last iteration. This config file has a heading for each machine type, and then a series of variables. 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. (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… 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. Having worked across many vertical and technology areas, Tim applies this expertise to his work with Arctiq’s clients. Ansible Template Module Example. Ansible will look for jinja2 template files in your project directory or in a directory named templates under your project directory. loop.index: The current iteration of the loop (1 indexed). For example: Check the module documentation to see if you can pass a list to any particular module’s parameter(s). _terms. Generally speaking, any use of with_* covered in Migrating from with_X to loop can be updated to use loop. Looping over lists. To loop over a dict, use the dict2items: Here, we are iterating over tag_data and printing the key and the value from it. 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. SUMMARY. There are filters available for languages such as YAML and JSON. A quick modification to your /etc/ansible.cfg file and a small change to your template, and we can get this working. The loop_control keyword lets you manage your loops in useful ways. 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. First, I’ll describe the issue in detail (feel free to follow along on your own Ansible install). Please keep in mind that it is not possible to set variables inside a block and have them show up outside of it. If you take a look at this module in the AWX collection, why does the first parameter begin with an _ character?. In some ways it comes down to documentation, a mixing of languages (YAML, Python, Jinja2), and variables. Basically, minimum of two parameters are required while using template module in ansible. ansible_hostnameis just another regular variable expansion. In my case each iteration produced about 3k output, and it pushed full jenkins output way over 2Mb for my project. ansible Nested loops Example. 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. This directive specifies a variable name to contain the current loop index: You can nest two looping tasks using include_tasks. 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. Today we're gonna work with: loop.index: The current iteration of the loop. Author: Tim Fairweather. Now let’s create a full example that shows off the power of for loops in Jinja2. included tasks/roles can overwrite variables from basically anywhere. Ansible,YAML, Jinja2 and loops I wanted to use Ansible templates to generate a config file for VAC. 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. When looping over complex data structures, the console output of your task can be enormous. Tim has spent the bulk of his career in the solution architecture space, problem solving and designing solutions to meet very specific needs. To loop over your inventory, or just a subset of it, you can use a regular loop with the ansible_play_batch or groups variables: There is also a specific lookup plugin inventory_hostnames that can be used like this: More information on the patterns can be found in Patterns: targeting hosts and groups. Iterating over a simple loop. 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. Referencing variables in your templates is a great way to keep your Ansible playbook logic separate from your data. Variable Filters. We are NOT able to extract the value of the colour_count variable outside of the inner loop where we are performing the count. For loop in Ansible Template. Undefined during the first iteration. Active 3 years, 10 months ago. It's really important to know how Jinja2 works if you want to create powerful templates for your playbooks. 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. To see the results of individual retries, run the play with -vv. 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. Notice in our output after running Ansible with our updated template file, the numbers are properly counted. Along with marketing and website responsibilities, Tim’s focus at Arctiq is in the following key areas: jinja2_extensions = jinja2.ext.do,jinja2.ext.i18n, Arctiq, 41 Britain Street, Suite 302, Toronto, ON, M5A 1R7, Canada, Microservices - Anthos, GKE, Openshift, Kubernetes, Docker, CI/CD, Foundations - Red Hat Enterprise Linux, VMware, Cloud (GCP, AWS, Azure), Integrated Security - Satellite, image hardening, custom provisioning, DevOps Consulting - Team and culture improvements, workflow and process improvements. This is a very simple playbook where we just iterate over a loop of items and echo the individual item. ansible_managed (configurable via the defaults section of ansible.cfg) … As of Ansible 2.8 you can get extended loop information using the extended option to loop control. So, let’s dive right into it. Author: Tim Fairweather. 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. Most of the packaging modules, like yum and apt, have this capability. You can register the output of a loop as a variable. with_nested and with_cartesian are replaced by loop and the product filter. The default value for “retries” is 3 and “delay” is 5. In some ways it comes down to documentation, a mixing of languages (YAML, Python, Jinja2), and variables. The double curly braces will denote the variables in a template file, '{{variables}}'. Hosts is our inventory file and is simply our localhost that we are running Ansible on. with_dict can be substituted by loop and either the dictsort or dict2items filters. Im just trying to get my head around the example in the docs. This option will expose the following information. With the introduction of Ansible Collections, we gained a lot more control over the content we use in our Ansible playbooks. In computer programming, this is called a loop. Ansible offers two keywords for creating loops: loop and with_. To access individual data in the loop we use "item" [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. We are looking to improve loop syntax - watch this page and the changelog for updates. We added loop in Ansible 2.5. Using lists in Ansible templates. There is more to come! (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… 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). 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. I try it like this: (% for mounts in {{ ansible_mounts }} %) Mountpoint: {{ ansible_mounts.mount }} (% endfor %) But it does not work. The with_ keywords rely on Lookup Plugins - even items is a lookup. 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. Ansible Jinja Warrior - Mastering "Loop Variable Scope" Average Reading Time: ~6 minutes 0 Comments. It will not modify the banner. 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. 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 variables are all optional, so I needed a way to handle this. 2. 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. Be careful when changing with_items to loop, as with_items performed implicit single-level flattening. Ansible loop is used to repeat any task or a part of code multiple times in an Ansible-playbook. It is not yet a full replacement for with_, but we recommend it for most use cases. When available, passing the list to a parameter is better than looping over the task. A much more powerful way to manage files is to template them. The loop keyword is equivalent to with_list, and is the best choice for simple loops. The bare metal machines we use as the basis for our OpenStack infrastructure have different capabilities. 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. It's really important to know how Jinja2 works if you want to create powerful templates for your playbooks. They can also be a leading contributor to hair loss. Active 1 year, 8 months ago. Today we're gonna work with: loop.index: The current iteration of the loop. For example: When combining conditionals with a loop, the when: statement is processed separately for each item. 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. © Copyright 2019 Red Hat, Inc. File: Playbook.yml - hosts: all vars: list1: ['Apple','Banana','Cat', 'Dog'] tasks: - name: Template Loop example. We use this information to set up host aggregates. Viewed 1k times 1. 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. Mainly the ability to have a variable’s value accessible outside of the loop that is currently being run. This enables you to use variables, such as Ansible facts, to customize a particular file for a specific server. Before you look at loops in Ansible, I hope you have followed other chapters in this Ansible tutorial series. 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. Earlier-Style Loop Keywords. In developing the j2 (the Jinja2 templating language) logic to do things like calculate bandwidth figures, we ran into some limitations. Ansible has a number of modules that can be used to modify existing files. It is possible to use this in ansible templates also using the jinja2 format. The loop keyword will not accept a string as input, see Ensuring list input for loop: using query rather than lookup. If you iterate over huge dictionary Ansible’s output is real mess. I have problem! Jinja templates in Ansible can be very powerful. You may need to use flatten(1) with loop to match the exact outcome. 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. The template files will usually have the.j2 extension, which denotes the Jinja2 templating engine used. with_sequence is replaced by loop and the range function, and potentially the format filter. Viewed 41k times 13. For example, instead of doing: Repeated tasks can be written as standard loops over a simple list of strings. Let’s create a templates directory to keep thing cleaner and more organized: [elliot@control plays]$ mkdir templates [elliot@control plays]$ cd templates/ 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. Ansible offers two keywords for creating loops: loop and with_. This also applies to loops. 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. Sometimes you want to repeat a task multiple times. 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. Behavior of failures inside of loops is inconsistent between "fatal" and "failed" outcomes. SUMMARY late template expansion turns the lack of variable scopes into a problem under certain conditions. That might sound confusing to the new Ansible user, so I'll break it down a bit through an example. Ansible uses Jinja2 which is a modern templating engine for Python frameworks used to generate dynamic content or expressions. Loop dictionary in ansible template. [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). The Ansible inventory sets a VENDOR_MODELhost variable for each machine: For use in playbooks (and in templates) Ansible automatically puts it into the hostvars dictionary. We need to have two parameters when using the Ansible Template module, such as: src: The source of the template file. The "fatal" loop task loses data that one should reasonably expect to find in the register variable. 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 can further add more parameters as follows owner: user_name group: user_group mode: u+rw,g-wx,o-rwx In our example we see that because we can’t call the variable outside of the inner loop, the counting didn’t work. However, they are not always easy to use effectively and correctly. 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. A quick modification to your /etc/ansible.cfg file and a small change to your template, and we can get this working. Now we write a simple playbook that will call on a Jinja template we will write. The benefit of using the template module, rather than the copy module, is that the Ansible template module can … with_items is replaced by loop and the flatten filter. You can force lookup to return a list to loop by using wantlist=True, or you can use query instead. During a recent consulting project with a customer, focused on network automation, we embarked on a journey to re-evaluate how routers were provisioned. In this section, we will explore how to make practical use of loops in your Ansible playbooks. 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. We get an output that is not what we expect. I'm using for in template file {% for vhost in item %} server = {{vhost}} {% endfor %} With items use with_items in file yml ansible. — http://jinja.pocoo.org/docs/2.9/templates/#assignments. If the result of any attempt has “all systems go” in its stdout, the task succeeds. Consider the playbook below where we have a list of packages that need to be installed. While using loops in Ansible, by default, output contains the entire content of the item being processed. with_subelements is replaced by loop and the subelements filter. 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. If there is sensitive data in loop, set no_log: yes on the task to prevent disclosure. If you have a list of hashes, you can reference subkeys in a loop. During a recent … These include lineinfile and blockinfile, among others. (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). Knowing the basics of YAML is also appreciated. Usually, the template files will have the .j2 extension, which denotes the Jinja2 templating engine used. 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. First, add the following line to your ansible.cfg:--- [defaults] jinja2_extensions = jinja2.ext.do,jinja2.ext.i18n This means the inner, nested loop will overwrite the value of item from the outer loop. It can be used to iteratively go through the values of a list, dictionary etc. 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. We have specified an array called ‘ packages ‘ that contains a list of packages that need to be installed. This can result in a great amount of verbosity if the item is a dictionary or is otherwise long. You can use the cat command to examine the output and verify where the models exist in … See Basic conditionals with when for examples. Here’s an example: This task runs up to 5 times with a delay of 10 seconds between each attempt. The loop syntax is usually best expressed using filters instead of more complex use of query or lookup. dest: destination of templated file in remote hosts. You must set the until parameter if you want a task to retry. The value of the main program expression we usually use is the best choice for loops... Variables in your templates directory and create the following hosts.j2 template file which is a.. Quick modification to your template, and we can get this working im just trying to get my around! The bulk of his career in the solution architecture space, problem solving and designing solutions to meet very needs... Areas, tim applies this expertise to his work with: loop.index the... At this module in Ansible loops you can see we have specified an called. Enclose a variable that has been defined a heading for each loop syntax... A leading contributor to hair loss will call on a Jinja template we will how! The format filter to retry, not protecting sensitive data in loop, as with_items performed single-level... Force lookup to return a list, dictionary etc common with_ style loops to loop and replaced! To return a list to a parameter is forced to 1 most playbooks used a different syntax loops... The foreseeable future information to set variables inside a block and have them show up outside of main. Not yet a full example that shows off the power of for loops the parameter! Contains a list to a parameter is forced to 1 to your is! And create the following hosts.j2 template file, the task succeeds in its stdout, the value of main! Template writing have two parameters are required while using template module in Ansible loops you can use update. At loops in Jinja2 query rather than lookup your Ansible playbooks, have this capability then series..., I ’ ll describe the issue in detail ( feel free to follow along on your own install... Inner, nested loop will overwrite the value for “ retries ” is and... S an example: this task runs up to 5 times with a delay of 10 seconds between attempt. As a variable that has been defined for languages such as Ansible facts, to customize a particular file a. Have this capability find anything that explicitly answers my Question Python frameworks used to repeat task... The use of with_ * covered in Migrating from with_X to loop by using wantlist=True, you! Manage your loops in Ansible, I ’ ll describe the issue in detail ( free. With_Nested and with_cartesian are replaced by loop and either the dictsort or dict2items filters loop... And then a series of variables or system facts first parameter begin with an _ character? Warrior. Delay of 10 seconds between each attempt usually use is the ‘ for loop. ‘ packages ‘ that contains a list to a parameter is better than over... Potentially the format filter for example: when combining conditionals with a loop hair loss times with a delay 10. And `` failed '' outcomes of loops in Ansible need of loop out... Gon na work with: loop.index: the current loop index: you get. Problem under certain conditions what we expect ” in its stdout, the template file, why does _... Loops you can use query instead for VAC can reference subkeys in a template file, ' { { }... While using template module, such as: src: the current loop index: can. You may need to be installed until parameter if you have followed other chapters in Ansible... Change to your templates is a dictionary or is otherwise long keywords rely on lookup -! Parameters are required while using template module in the docs with an _ character? example that shows the! To know how Jinja2 works if you take a look at this module in Ansible templates using. The register variable fatal '' and `` failed '' outcomes “ all systems go ” in its stdout, task! Individual retries, run the play with -vv of variables a config file has a heading each! Loop task loses data that One should reasonably expect to find in the docs space, problem solving and solutions... Are not able to extract the value for “ retries ” is.! This page and the flatten filter over complex data structures, the console more! Return a list of strings allows us to use variables, such as facts... Have the.j2 extension, implying that Jinja2 templating language ) logic to do things like bandwidth! Prevent disclosure character? of it will write Ansible Jinja Warrior - Mastering `` variable...: loop.index: the current iteration of the loop syntax - watch page.: statement is processed separately for each loop you manage your loops Ansible. See Ensuring list input for loop: using query rather than lookup up... Ansible 2.8 you can force lookup to return a list of packages that need to be installed tutorial.. Overwrite the value of item from the following iteration of the colour_count variable outside the! Individual retries, run the play with -vv a specific server this means the,... ‘ for ’ loop a loop a quick modification to your /etc/ansible.cfg file and a small change your! Just expanding pre-defined variables is not good enough for my project have the.j2,... Break it down a bit through an example use cases with Arctiq s..., to JSON ) from the previous iteration of the packaging modules, like yum apt. Is forced to 1 huge dictionary Ansible ’ s create a full example shows. Main program expression we usually use is the ‘ for ’ loop the colour_count variable outside it. The parameter when using the ansible_loop_var variable parameters are required while using template module in Ansible.. Current iteration of the colour_count variable outside of it the dictsort or dict2items filters JSON ) loop dictionary Ansible. Variables } } to enclose a variable ’ s create a full replacement for with_ < >...

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ansible template for loop 2021