Here is fairly generic example:
We have N zookeepers in our datacenter, if we want more redundancy, we add
a new instance with a tag indicating it is has a "zookeeper" role. Now I
can re-run my playbook which will build configurations to list all those
zookeepers where needed. Lets assume one configuration file requires the
format to be "1.2.3.4, 4.5.6.7" yet another requires
"1.2.3.4:8080,4.5.6.7:8080". Also depending on my environment these address
may be private or public. I want to per environment set the list of hosts
and then in the lower level playbooks format it properly.
If I put all this logic in the lower level playbooks/tempates that generate
the configs, I will need to put a condition to use the private or public
addresses also tying the playbook to ec2 as an example. All my lower level
playbooks are generic, give them a list of hosts and that is it, complexity
is at the top. If I switch to another cloud provider I can modify the top
level variables and I am done.
Anyways I figured out how to do this by using "do", these are in my
"group_vars" for my production and staging environments
Production AWS environment
zookeeper:
hosts: "{% set hosts = [] %}{% for host in groups['zookeeper_master']
%}{% do hosts.append(hostvars[host].ec2_private_ip_address) %}{% endfor
%}{{hosts}}"
Staging Environment
zookeeper:
hosts: "{% set hosts = [] %}{% for host in groups['zookeeper_master']
%}{host}{% endfor %}"
I am very interested/scared of your comment that ansible is not meant to be
a programming language, and that is un-ansbile-like. The world we have
today is very dynamic, clusters grow and shrink and need to be reconfigured
any time that happens. I personally like the simplicity of ansbile
compared to things like chef or salt, but there are days when trying to
debug jinja, makes me want to jump out a window. I personally have 20
years of programming behind me so doing things programmatically is a
concept that I cannot shake easily.
Thanks for your input
Kristopher
On Tuesday, April 29, 2014 11:42:08 PM UTC-4, Michael DeHaan wrote:
>
> This seems to be a very un-ansible-like bad idea and you shouldn't do it.
>
>
> In general, Ansible is not meant to be a programming language, and
> inventory is meant to be something edited by humans or pulled from a source
> of authority -- I'm probably not understanding why you want to do this
> though.
>
> Let's step back here -- what's the use case for needing to do something
> like this?
>
> Give us more info about the real world thing you are trying to model, and
> we can likely share some more Ansible-like suggestions.
>
> --Michael
>
>
> On Tue, Apr 29, 2014 at 10:30 PM, Kristopher Cieplak
> <[email protected]<javascript:>
> > wrote:
>
>> I am wondering if this is possible I have a group_vars file with some
>> variables in it, and I need to set, the list is generated from the
>> inventory and a mapping to the ec2 private ip address.
>>
>> For example in my group_vars file:
>> cassandra: {keyspace: default, log_time: false, hosts: [ "{% for host in
>> groups['tag_role_cassandra_true']
>> %}{{hostvars[host].ec2_private_ip_address}}{% if not loop.last %},{% endif
>> %}{% endfor %}" ]}
>>
>> This ends up being the following if I dump it using the "debug" directive:
>> "msg": "cassandra {'keyspace': 'default', 'log_time': False, 'hosts':
>> [u'172.31.2.85,172.31.2.84,172.31.2.86,172.31.2.83']}"
>>
>> As you can see that is a list of one string. I want a list of all hosts,
>> in this case four hosts, i.e it should be:
>> 'hosts': ['172.31.2.85', '172.31.2.84' ,'172.31.2.86', '172.31.2.83']
>>
>> Does anyone know anyway to loop over all the hosts do the conversion to
>> private ip and append to the "list".
>>
>> My fallback is to generate it as a string, then use that lower down , but
>> would be nice to have the list, as I can output it in various templates
>> differently.
>>
>> Thanks
>>
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