Variable - a variable in a variable

Question

Ansible version 1.9.2.

Does Ansible support variable expansion inside a variable when evaluating it?

I have a task to download 3 zip files from Artifactory.

Instead of writing 3 separate tasks in a role, I used a listenable loop in the tutorial. In the Ansible role default / main.yml, I have all the necessary variables defined / available for the ie Jmeterplugins_extras_artifactory_url role and others (standard / webdriver) perf_tests roles are visible.

--- #- Download and install JMeterPlugins # Use get_url when Ansible is 2.0+ is available on the machine (otherwise, we can't use get_url) thus, using wget. - name: Download JMeterPlugins-* command: wget {{ jmeterplugins_{{ item.plugin }}_artifactory_url }} chdir="{{ common_download_dir }}" creates="{{ common_download_dir }}/{{ jmeterplugins_{{ item.plugin }}_file }}" with_items: - { plugin: 'extras' } - { plugin: 'standard' } - { plugin: 'webdriver' } 

But with the code above, I get an error message (as shown below):

 15:58:57 TASK: [perf_tests | Download JMeterPlugins-*] ********************************* 15:58:57 <jmeter01.super.fast.jenkins> ESTABLISH CONNECTION FOR USER: cmuser on PORT 22 TO jmeter01.super.fast.jenkins 15:58:57 fatal: [jmeter01.super.fast.jenkins] => Failed to template wget {{ jmeterplugins_{{ item.plugin }}_artifactory_url }} chdir="{{ common_download_dir }}" creates="{{ common_download_dir }}/{{ jmeterplugins_{{ item.plugin }}_file }}": template error while templating string: expected token 'variable_end', got '{' 15:58:57 15:58:57 FATAL: all hosts have already failed -- aborting 15:58:57 15:58:57 PLAY RECAP ******************************************************************** 15:58:57 to retry, use: --limit @/home/cmuser/perf_tests.retry 15:58:57 15:58:57 jmeter01.super.fast.jenkins : ok=23 changed=6 unreachable=1 failed=0 

It is not possible to support a variable extension / evaluation if the variable contains another variable (especially when I use a loop).

I just do not want to expand my simple loop task to 3 different tasks for downloading zip files for jmeterplugins_extras, jmeterplugins_standard and jmeterplugins_webdriver separately. It seems that the error is related to Jinja.

How can I use the value of var giga in another variable, that is, if var contains giga , then I should get the value of the variable special_giga_variable ({{special_ {var}} _ variable}})? where var is set by default to /main.yml as:

var: giga

Answer 1

No no. But this does not mean that you need to expand it to 3 different tasks. What you can do is actually expand your vocabulary to look something like this:

 with_items: - {"url": "https://xxxxx", "file": "/tmp/xxxxx" } - {"url": "https://yyyyy", "file": "/tmp/yyyyy" } - {"url": "https://zzzzz", "file": "/tmp/zzzzz" } 

Then in your task just call different parameters: {{ item.url }} and {{ item.file }}

Alternative options:

• Write your own filter that will expand your variable to match the {{ jmeterplugins_url | my_custom_filter(item.plugin) }} {{ jmeterplugins_url | my_custom_filter(item.plugin) }}

• Write your own module that will encapsulate all url fetching functions into a file based on your inputs

• Write a custom lookup_plugin that will lookup_plugin over the list of variables and return the correct result.

• Since you are using the command module, you can use bash to combine your url, file in the same command (this would probably be the most messy solution)

Answer 2

He does.

you can use

 set_fact: variable: '{{ vars['my_' + variablename + '_variable'] }}' 

The only drawback to this approach so far is that it will not dynamically expand variables that get the value of another variable. example:

roles/xxx/defaults/main.yml :

 var1: foo var2: '{{ var1 }}' 

This, unfortunately, will not work when trying to use the allowed value in var2 . Consequently,

 - debug: msg='{{ vars["var2"] }}' 

prints {{ var1 }} instead of foo .

Workaround:

In the vars declaration, instead of using var2: {{ var1 }} use var2: '{{ vars["var1"] }}' . So it will work.